Elad DUO ART 120 - How to select power setting?


gcoxuk@googlemail.com
 

Greetings,

I’m a novice doing the learning curve to my Duo Art set. Ummm nothing much in the ops manual about output except ~5w in yeilds ~120w. Nothing is said about its response to lesser input power to reduce output power.

Am I missing something or is this a ~120w output only???

Thanks in advance.
Geoff
Stansted UK


Kevin Larcombe
 

Hi Geoff,

You can reduce the drive from the radio, (I assume you are using the Duo) or in the menu on the DUO ART you can select attenuation of 2, 3 & 5dB (from my memory)

My Duo/ART and all my radios are packed away at present during the shack rebuild, so sorry I can't look and tell you which menu. It easy to find in the manual though. (you can also set it  per band in the profiles)

Regards

Kevin


From: EladSDR@groups.io <EladSDR@groups.io> on behalf of gcoxuk@... via groups.io <gcoxuk@...>
Sent: 13 April 2021 00:06
To: EladSDR@groups.io <EladSDR@groups.io>
Subject: [EladSDR] Elad DUO ART 120 - How to select power setting?
 
Greetings,

I’m a novice doing the learning curve to my Duo Art set.  Ummm nothing much in the ops manual about output except ~5w in yeilds ~120w.  Nothing is said about its response to lesser input power to reduce output power.

Am I missing something or is this a ~120w output only???

Thanks in advance.
Geoff
Stansted UK






gcoxuk@googlemail.com
 

Thanks Kevin.

I’ve tried reducing the elad FMD output power with very small effect.
Forgive my ignorance, but what db setting effects this?
😃


On 13 Apr 2021, at 15:53, Kevin Larcombe <kevlarcombe@...> wrote:


Hi Geoff,

You can reduce the drive from the radio, (I assume you are using the Duo) or in the menu on the DUO ART you can select attenuation of 2, 3 & 5dB (from my memory)

My Duo/ART and all my radios are packed away at present during the shack rebuild, so sorry I can't look and tell you which menu. It easy to find in the manual though. (you can also set it  per band in the profiles)

Regards

Kevin


From: EladSDR@groups.io <EladSDR@groups.io> on behalf of gcoxuk@... via groups.io <gcoxuk@...>
Sent: 13 April 2021 00:06
To: EladSDR@groups.io <EladSDR@groups.io>
Subject: [EladSDR] Elad DUO ART 120 - How to select power setting?
 
Greetings,

I’m a novice doing the learning curve to my Duo Art set.  Ummm nothing much in the ops manual about output except ~5w in yeilds ~120w.  Nothing is said about its response to lesser input power to reduce output power.

Am I missing something or is this a ~120w output only???

Thanks in advance.
Geoff
Stansted UK






Kevin Larcombe
 

Geoff,

I'm just having a quick look at the manual, the 2nd button from the left on the Art120 is "In-Att" this sets the input attenuator, which I think is 0 , 2, 3 or 5dB.

In the memory bank you can set the attenuator per band, and you can set which antenna port it uses per band. You get into this with a long press on the MEN button.

The manual explains it, just need to remember there are a number of memory banks. The number of memory banks available can also be user changed. I set mine all the same to avoid confusion if I mistakenly pressed the button and selected another.

Kevin GW0PUH

On 13 Apr 2021, at 16:39, "gcoxuk@... via groups.io" <googlemail.com@groups.io target=_blank>gcoxuk=googlemail.com@groups.io> wrote:
Thanks Kevin.

I’ve tried reducing the elad FMD output power with very small effect.
Forgive my ignorance, but what db setting effects this?
😃


On 13 Apr 2021, at 15:53, Kevin Larcombe <kevlarcombe@...> wrote:


Hi Geoff,

You can reduce the drive from the radio, (I assume you are using the Duo) or in the menu on the DUO ART you can select attenuation of 2, 3 & 5dB (from my memory)

My Duo/ART and all my radios are packed away at present during the shack rebuild, so sorry I can't look and tell you which menu. It easy to find in the manual though. (you can also set it  per band in the profiles)

Regards

Kevin


From: EladSDR@groups.io <EladSDR@groups.io> on behalf of gcoxuk@... via groups.io <gcoxuk@...>
Sent: 13 April 2021 00:06
To: EladSDR@groups.io <EladSDR@groups.io>
Subject: [EladSDR] Elad DUO ART 120 - How to select power setting?
 
Greetings,

I’m a novice doing the learning curve to my Duo Art set.  Ummm nothing much in the ops manual about output except ~5w in yeilds ~120w.  Nothing is said about its response to lesser input power to reduce output power.

Am I missing something or is this a ~120w output only???

Thanks in advance.
Geoff
Stansted UK






Klaus Brosche
 

A setting of 3dB RF input attenuation at the ART-120 means that the input RF power from the DUO
is being reduced by 50%. 3 dB attenuation equals half power.

E.g., if your DUO is set for 5 watts output, the input attenuator of the ART-120 will dissipate 2.5 watts
into an RF resistor and will pass only 2.5 watts to the ART-120 final stage.

If the ART-120 puts out 120 watts with DUOs output set to 5 watts, you'll see around 60 watts output
on the ART-120, IF engaging its 3 dB input attenuator.

The same or nearly the same effect can be achieved if you set the DUO output to 2.5 watts and have
the ART-120 input anttenuator set at 0 dB attenuation.

As the gain factor of an amplifier is not exactly equal across its frequency range - it may vary by a few
dB - depending on the frequency band of operation, the output of the amp may vary from band to band,
even if the driver power (DUO) is set to a certain level, e.g. 2.5 watts.

73, Klaus, DK3QN



Am 13.04.2021 um 17:39 schrieb gcoxuk@... via groups.io:

Thanks Kevin.

I’ve tried reducing the elad FMD output power with very small effect.
Forgive my ignorance, but what db setting effects this?
😃


On 13 Apr 2021, at 15:53, Kevin Larcombe <kevlarcombe@...> wrote:


Hi Geoff,

You can reduce the drive from the radio, (I assume you are using the Duo) or in the menu on the DUO ART you can select attenuation of 2, 3 & 5dB (from my memory)

My Duo/ART and all my radios are packed away at present during the shack rebuild, so sorry I can't look and tell you which menu. It easy to find in the manual though. (you can also set it  per band in the profiles)

Regards

Kevin


From: EladSDR@groups.io <EladSDR@groups.io> on behalf of gcoxuk@... via groups.io <gcoxuk@...>
Sent: 13 April 2021 00:06
To: EladSDR@groups.io <EladSDR@groups.io>
Subject: [EladSDR] Elad DUO ART 120 - How to select power setting?
 
Greetings,

I’m a novice doing the learning curve to my Duo Art set.  Ummm nothing much in the ops manual about output except ~5w in yeilds ~120w.  Nothing is said about its response to lesser input power to reduce output power.

Am I missing something or is this a ~120w output only???

Thanks in advance.
Geoff
Stansted UK







gcoxuk@googlemail.com
 

Most awesome Klaus
73
Geoff M7COX


On 13 Apr 2021, at 21:15, Klaus Brosche <klaus.brosche@...> wrote:


A setting of 3dB RF input attenuation at the ART-120 means that the input RF power from the DUO
is being reduced by 50%. 3 dB attenuation equals half power.

E.g., if your DUO is set for 5 watts output, the input attenuator of the ART-120 will dissipate 2.5 watts
into an RF resistor and will pass only 2.5 watts to the ART-120 final stage.

If the ART-120 puts out 120 watts with DUOs output set to 5 watts, you'll see around 60 watts output
on the ART-120, IF engaging its 3 dB input attenuator.

The same or nearly the same effect can be achieved if you set the DUO output to 2.5 watts and have
the ART-120 input anttenuator set at 0 dB attenuation.

As the gain factor of an amplifier is not exactly equal across its frequency range - it may vary by a few
dB - depending on the frequency band of operation, the output of the amp may vary from band to band,
even if the driver power (DUO) is set to a certain level, e.g. 2.5 watts.

73, Klaus, DK3QN



Am 13.04.2021 um 17:39 schrieb gcoxuk@... via groups.io:
Thanks Kevin.

I’ve tried reducing the elad FMD output power with very small effect.
Forgive my ignorance, but what db setting effects this?
😃


On 13 Apr 2021, at 15:53, Kevin Larcombe <kevlarcombe@...> wrote:


Hi Geoff,

You can reduce the drive from the radio, (I assume you are using the Duo) or in the menu on the DUO ART you can select attenuation of 2, 3 & 5dB (from my memory)

My Duo/ART and all my radios are packed away at present during the shack rebuild, so sorry I can't look and tell you which menu. It easy to find in the manual though. (you can also set it  per band in the profiles)

Regards

Kevin


From: EladSDR@groups.io <EladSDR@groups.io> on behalf of gcoxuk@... via groups.io <gcoxuk@...>
Sent: 13 April 2021 00:06
To: EladSDR@groups.io <EladSDR@groups.io>
Subject: [EladSDR] Elad DUO ART 120 - How to select power setting?
 
Greetings,

I’m a novice doing the learning curve to my Duo Art set.  Ummm nothing much in the ops manual about output except ~5w in yeilds ~120w.  Nothing is said about its response to lesser input power to reduce output power.

Am I missing something or is this a ~120w output only???

Thanks in advance.
Geoff
Stansted UK







T.W.H. Fockens
 

That is why you need an Automatic Level Control (ALC).
IMHO that is lack in the Elad equiment.

Koos Fockens,
PA0KDF

On 13 Apr, gcoxuk@googlemail.com via groups.io <gcoxuk=googlemail.com@groups.io> wrote:
Most awesome Klaus
73
Geoff M7COX
On 13 Apr 2021, at 21:15, Klaus Brosche <klaus.brosche@mail.de> wrote:

#
A setting of 3dB RF input attenuation at the ART-120 means that the input RF power from the DUO
is being reduced by 50%. 3 dB attenuation equals half power.

E.g., if your DUO is set for 5 watts output, the input attenuator of the ART-120 will dissipate 2.5 watts
into an RF resistor and will pass only 2.5 watts to the ART-120 final stage.

If the ART-120 puts out 120 watts with DUOs output set to 5 watts, you'll see around 60 watts output
on the ART-120, IF engaging its 3 dB input attenuator.

The same or nearly the same effect can be achieved if you set the DUO output to 2.5 watts and have
the ART-120 input anttenuator set at 0 dB attenuation.

As the gain factor of an amplifier is not exactly equal across its frequency range - it may vary by a few
dB - depending on the frequency band of operation, the output of the amp may vary from band to band,
even if the driver power (DUO) is set to a certain level, e.g. 2.5 watts.

73, Klaus, DK3QN



Am 13.04.2021 um 17:39 schrieb gcoxuk@googlemail.com via groups.io:
Thanks Kevin.

I've tried reducing the elad FMD output power with very small effect.
Forgive my ignorance, but what db setting effects this?
#


On 13 Apr 2021, at 15:53, Kevin Larcombe <kevlarcombe@hotmail.com> wrote:

#
Hi Geoff,

You can reduce the drive from the radio, (I assume you are using the Duo) or in the menu on the DUO ART you can select attenuation of 2, 3 & 5dB (from my memory)

My Duo/ART and all my radios are packed away at present during the shack rebuild, so sorry I can't look and tell you which menu. It easy to find in the manual though. (you can also set it per band in the profiles)

Regards

Kevin

From: EladSDR@groups.io <EladSDR@groups.io> on behalf of gcoxuk@googlemail.com via groups.io <gcoxuk=googlemail.com@groups.io>
Sent: 13 April 2021 00:06
To: EladSDR@groups.io <EladSDR@groups.io>
Subject: [EladSDR] Elad DUO ART 120 - How to select power setting?

Greetings,

I'm a novice doing the learning curve to my Duo Art set. Ummm nothing much in the ops manual about output except ~5w in yeilds ~120w. Nothing is said about its response to lesser input power to reduce output power.

Am I missing something or is this a ~120w output only???

Thanks in advance.
Geoff
Stansted UK





--
Ir. T.W.H. Fockens
Kieftweg 1
7165BR Rietmolen

Onze democratie is gebaat bij een kiesdrempel.


Kevin Larcombe
 

I don't see how ALC would help, ALC only stops the output level from exceeding a set limit.

What is required is integration of the Elad software, so that the ART120 can be controlled by the same software as the FDM DUO. If that were the case, they could simply provide a slider in the software to set the required output power also status monitoring of the ART120 could be provided in the software. 

Unfortunately, although the individual components perform very well, Elad has failed to integrate them. (I guess their design is flawed in this area, perhaps not enough attention to the requirements) This is my main gripe with the ART120, I have to have it in view and the buttons in reach instead of being able to put it in the rack adjacent to my operating desk and being able to control it from SW2 the same as the radio.

I think Elad missed a big trick with this oversight.

Kevin GW0PUH 


From: EladSDR@groups.io <EladSDR@groups.io> on behalf of T.W.H. Fockens <koos@...>
Sent: 14 April 2021 10:03
To: EladSDR@groups.io <EladSDR@groups.io>
Subject: Re: [EladSDR] Elad DUO ART 120 - How to select power setting?
 
That is why you need an Automatic Level Control (ALC).
IMHO that is lack in the Elad equiment.

Koos Fockens,
PA0KDF


On 13 Apr, gcoxuk@... via groups.io <gcoxuk@...> wrote:
> Most awesome Klaus
> 73
> Geoff M7COX
> > On 13 Apr 2021, at 21:15, Klaus Brosche <klaus.brosche@...> wrote:
> >
> > #
> > A setting of 3dB RF input attenuation at the ART-120 means that the input RF power from the DUO
> > is being reduced by 50%. 3 dB attenuation equals half power.
> >
> > E.g., if your DUO is set for 5 watts output, the input attenuator of the ART-120 will dissipate 2.5 watts
> > into an RF resistor and will pass only 2.5 watts to the ART-120 final stage.
> >
> > If the ART-120 puts out 120 watts with DUOs output set to 5 watts, you'll see around 60 watts output
> > on the ART-120, IF engaging its 3 dB input attenuator.
> >
> > The same or nearly the same effect can be achieved if you set the DUO output to 2.5 watts and have
> > the ART-120 input anttenuator set at 0 dB attenuation.
> >
> > As the gain factor of an amplifier is not exactly equal across its frequency range - it may vary by a few
> > dB - depending on the frequency band of operation, the output of the amp may vary from band to band,
> > even if the driver power (DUO) is set to a certain level, e.g. 2.5 watts.
> >
> > 73, Klaus, DK3QN
> >
> >
> >
> > Am 13.04.2021 um 17:39 schrieb gcoxuk@... via groups.io:
> >> Thanks Kevin.
> >>
> >> I've tried reducing the elad FMD output power with very small effect.
> >> Forgive my ignorance, but what db setting effects this?
> >> #
> >>
> >>
> >>> On 13 Apr 2021, at 15:53, Kevin Larcombe <kevlarcombe@...> wrote:
> >>>
> >>> #
> >>> Hi Geoff,
> >>>
> >>> You can reduce the drive from the radio, (I assume you are using the Duo) or in the menu on the DUO ART you can select attenuation of 2, 3 & 5dB (from my memory)
> >>>
> >>> My Duo/ART and all my radios are packed away at present during the shack rebuild, so sorry I can't look and tell you which menu. It easy to find in the manual though. (you can also set it  per band in the profiles)
> >>>
> >>> Regards
> >>>
> >>> Kevin
> >>>
> >>> From: EladSDR@groups.io <EladSDR@groups.io> on behalf of gcoxuk@... via groups.io <gcoxuk@...>
> >>> Sent: 13 April 2021 00:06
> >>> To: EladSDR@groups.io <EladSDR@groups.io>
> >>> Subject: [EladSDR] Elad DUO ART 120 - How to select power setting?
> >>>
> >>> Greetings,
> >>>
> >>> I'm a novice doing the learning curve to my Duo Art set.  Ummm nothing much in the ops manual about output except ~5w in yeilds ~120w.  Nothing is said about its response to lesser input power to reduce output power.
> >>>
> >>> Am I missing something or is this a ~120w output only???
> >>>
> >>> Thanks in advance.
> >>> Geoff
> >>> Stansted UK
> >>>
> >>>
> >>>
> >>>
> >>>
> >
> >


>

--
Ir. T.W.H. Fockens
Kieftweg 1
7165BR Rietmolen

Onze democratie is gebaat bij een kiesdrempel.






T.W.H. Fockens
 

No, that is a misconception. The ALC prevents you from overdriving your
PA, and so preventing IM and splatter. It also controls the power match
between the output of your driving trx and the PA.

This is a serious aspect of transmitter design and should never be
neglected.

Koos PA0KDF

On 14 Apr, Kevin Larcombe <kevlarcombe@hotmail.com> wrote:
I don't see how ALC would help, ALC only stops the output level from exceeding a set limit.
What is required is integration of the Elad software, so that the ART120 can be controlled by the same software as the FDM DUO. If that were the case, they could simply provide a slider in the software to set the required output power also status monitoring of the ART120 could be provided in the software.
Unfortunately, although the individual components perform very well, Elad has failed to integrate them. (I guess their design is flawed in this area, perhaps not enough attention to the requirements) This is my main gripe with the ART120, I have to have it in view and the buttons in reach instead of being able to put it in the rack adjacent to my operating desk and being able to control it from SW2 the same as the radio.
I think Elad missed a big trick with this oversight.
Kevin GW0PUH
________________________________
From: EladSDR@groups.io <EladSDR@groups.io> on behalf of T.W.H. Fockens <koos@pa0kdf.nl>
Sent: 14 April 2021 10:03
To: EladSDR@groups.io <EladSDR@groups.io>
Subject: Re: [EladSDR] Elad DUO ART 120 - How to select power setting?
That is why you need an Automatic Level Control (ALC).
IMHO that is lack in the Elad equiment.
Koos Fockens,
PA0KDF

On 13 Apr, gcoxuk@googlemail.com via groups.io <gcoxuk=googlemail.com@groups.io> wrote:
Most awesome Klaus
73
Geoff M7COX
On 13 Apr 2021, at 21:15, Klaus Brosche <klaus.brosche@mail.de> wrote:

#
A setting of 3dB RF input attenuation at the ART-120 means that the input RF power from the DUO
is being reduced by 50%. 3 dB attenuation equals half power.

E.g., if your DUO is set for 5 watts output, the input attenuator of the ART-120 will dissipate 2.5 watts
into an RF resistor and will pass only 2.5 watts to the ART-120 final stage.

If the ART-120 puts out 120 watts with DUOs output set to 5 watts, you'll see around 60 watts output
on the ART-120, IF engaging its 3 dB input attenuator.

The same or nearly the same effect can be achieved if you set the DUO output to 2.5 watts and have
the ART-120 input anttenuator set at 0 dB attenuation.

As the gain factor of an amplifier is not exactly equal across its frequency range - it may vary by a few
dB - depending on the frequency band of operation, the output of the amp may vary from band to band,
even if the driver power (DUO) is set to a certain level, e.g. 2.5 watts.

73, Klaus, DK3QN



Am 13.04.2021 um 17:39 schrieb gcoxuk@googlemail.com via groups.io:
Thanks Kevin.

I've tried reducing the elad FMD output power with very small effect.
Forgive my ignorance, but what db setting effects this?
#


On 13 Apr 2021, at 15:53, Kevin Larcombe <kevlarcombe@hotmail.com> wrote:

#
Hi Geoff,

You can reduce the drive from the radio, (I assume you are using the Duo) or in the menu on the DUO ART you can select attenuation of 2, 3 & 5dB (from my memory)

My Duo/ART and all my radios are packed away at present during the shack rebuild, so sorry I can't look and tell you which menu. It easy to find in the manual though. (you can also set it per band in the profiles)

Regards

Kevin

From: EladSDR@groups.io <EladSDR@groups.io> on behalf of gcoxuk@googlemail.com via groups.io <gcoxuk=googlemail.com@groups.io>
Sent: 13 April 2021 00:06
To: EladSDR@groups.io <EladSDR@groups.io>
Subject: [EladSDR] Elad DUO ART 120 - How to select power setting?

Greetings,

I'm a novice doing the learning curve to my Duo Art set. Ummm nothing much in the ops manual about output except ~5w in yeilds ~120w. Nothing is said about its response to lesser input power to reduce output power.

Am I missing something or is this a ~120w output only???

Thanks in advance.
Geoff
Stansted UK





--
Ir. T.W.H. Fockens
Kieftweg 1
7165BR Rietmolen
Onze democratie is gebaat bij een kiesdrempel.






--
Ir. T.W.H. Fockens
Kieftweg 1
7165BR Rietmolen

Onze democratie is gebaat bij een kiesdrempel.


Kevin Larcombe
 

I agree with your comment about the general use of ALC so that an amplifier is not over driven, in instances where the exciter is capable of overdriving the amplifier. 

But in the case of the FDM DUO & ART120 setup, the radio is not capable of overdriving the amplifier. So presumably the best way to reduce power is by applying attenuation to the input of the amplifier. 

This solution will also prevent any chance of overshoot of the signal when ALC is used and the circuit doesn't act quick enough.

Kevin GW0PUH


From: EladSDR@groups.io <EladSDR@groups.io> on behalf of T.W.H. Fockens <koos@...>
Sent: 14 April 2021 11:11
To: EladSDR@groups.io <EladSDR@groups.io>
Subject: Re: [EladSDR] Elad DUO ART 120 - How to select power setting?
 
No, that is a misconception. The ALC prevents you from overdriving your
PA, and so preventing IM and splatter. It also controls the power match
between the output of your driving trx and the PA.

This is a serious aspect of transmitter design and should never be
neglected.

Koos PA0KDF

On 14 Apr, Kevin Larcombe <kevlarcombe@...> wrote:
> I don't see how ALC would help, ALC only stops the output level from exceeding a set limit.

> What is required is integration of the Elad software, so that the ART120 can be controlled by the same software as the FDM DUO. If that were the case, they could simply provide a slider in the software to set the required output power also status monitoring of the ART120 could be provided in the software.

> Unfortunately, although the individual components perform very well, Elad has failed to integrate them. (I guess their design is flawed in this area, perhaps not enough attention to the requirements) This is my main gripe with the ART120, I have to have it in view and the buttons in reach instead of being able to put it in the rack adjacent to my operating desk and being able to control it from SW2 the same as the radio.

> I think Elad missed a big trick with this oversight.

> Kevin GW0PUH

> ________________________________
> From: EladSDR@groups.io <EladSDR@groups.io> on behalf of T.W.H. Fockens <koos@...>
> Sent: 14 April 2021 10:03
> To: EladSDR@groups.io <EladSDR@groups.io>
> Subject: Re: [EladSDR] Elad DUO ART 120 - How to select power setting?

> That is why you need an Automatic Level Control (ALC).
> IMHO that is lack in the Elad equiment.

> Koos Fockens,
> PA0KDF


> On 13 Apr, gcoxuk@... via groups.io <gcoxuk@...> wrote:
> > Most awesome Klaus
> > 73
> > Geoff M7COX
> > > On 13 Apr 2021, at 21:15, Klaus Brosche <klaus.brosche@...> wrote:
> > >
> > > #
> > > A setting of 3dB RF input attenuation at the ART-120 means that the input RF power from the DUO
> > > is being reduced by 50%. 3 dB attenuation equals half power.
> > >
> > > E.g., if your DUO is set for 5 watts output, the input attenuator of the ART-120 will dissipate 2.5 watts
> > > into an RF resistor and will pass only 2.5 watts to the ART-120 final stage.
> > >
> > > If the ART-120 puts out 120 watts with DUOs output set to 5 watts, you'll see around 60 watts output
> > > on the ART-120, IF engaging its 3 dB input attenuator.
> > >
> > > The same or nearly the same effect can be achieved if you set the DUO output to 2.5 watts and have
> > > the ART-120 input anttenuator set at 0 dB attenuation.
> > >
> > > As the gain factor of an amplifier is not exactly equal across its frequency range - it may vary by a few
> > > dB - depending on the frequency band of operation, the output of the amp may vary from band to band,
> > > even if the driver power (DUO) is set to a certain level, e.g. 2.5 watts.
> > >
> > > 73, Klaus, DK3QN
> > >
> > >
> > >
> > > Am 13.04.2021 um 17:39 schrieb gcoxuk@... via groups.io:
> > >> Thanks Kevin.
> > >>
> > >> I've tried reducing the elad FMD output power with very small effect.
> > >> Forgive my ignorance, but what db setting effects this?
> > >> #
> > >>
> > >>
> > >>> On 13 Apr 2021, at 15:53, Kevin Larcombe <kevlarcombe@...> wrote:
> > >>>
> > >>> #
> > >>> Hi Geoff,
> > >>>
> > >>> You can reduce the drive from the radio, (I assume you are using the Duo) or in the menu on the DUO ART you can select attenuation of 2, 3 & 5dB (from my memory)
> > >>>
> > >>> My Duo/ART and all my radios are packed away at present during the shack rebuild, so sorry I can't look and tell you which menu. It easy to find in the manual though. (you can also set it  per band in the profiles)
> > >>>
> > >>> Regards
> > >>>
> > >>> Kevin
> > >>>
> > >>> From: EladSDR@groups.io <EladSDR@groups.io> on behalf of gcoxuk@... via groups.io <gcoxuk@...>
> > >>> Sent: 13 April 2021 00:06
> > >>> To: EladSDR@groups.io <EladSDR@groups.io>
> > >>> Subject: [EladSDR] Elad DUO ART 120 - How to select power setting?
> > >>>
> > >>> Greetings,
> > >>>
> > >>> I'm a novice doing the learning curve to my Duo Art set.  Ummm nothing much in the ops manual about output except ~5w in yeilds ~120w.  Nothing is said about its response to lesser input power to reduce output power.
> > >>>
> > >>> Am I missing something or is this a ~120w output only???
> > >>>
> > >>> Thanks in advance.
> > >>> Geoff
> > >>> Stansted UK
> > >>>
> > >>>
> > >>>
> > >>>
> > >>>
> > >
> > >


> >

> --
> Ir. T.W.H. Fockens
> Kieftweg 1
> 7165BR Rietmolen

> Onze democratie is gebaat bij een kiesdrempel.







>

--
Ir. T.W.H. Fockens
Kieftweg 1
7165BR Rietmolen

Onze democratie is gebaat bij een kiesdrempel.






Klaus Brosche
 

ALC as a means of preventing amp overdrive is the second best solution (at best).

It basically is just a voltage feedback loop from an amp back to the TRX, i.e. to an amplification stage in that TRX,
which reduces the amplification factor of that TRX stage so that the the power amp doesn't get overdriven.

Being based on a feedback loop means: the TRX TX gain / power output is only decreased *after* an overdrive
condition at the power amp has been detected, which then triggers the ALC feedback loop voltage.
Typically there is some sort of time constant implemented to the ALC feedback loop, so that the amount of
ALC voltage is averaged over the transmitting period, thus preventing the ALC voltage from fast alterations/
voltage jumps depending on voice/modulation characteristics (different sound levels with respect to sound
frequencies in the human voice). This is true for SSB modulation.

For CW, FM etc. modes the principle is the same, with the exception that there is a more or less constant
carrier level present and due to the ALC circuit time constant, that also is valid for keyed CW.

A way better way of preventing a power amp from getting overdriven is to adjust the TRX RF output to
a level at which the power amp is not faced with an overdrive situation. Imho "best practice" and no need
for an ALC feedback loop.

ALC dates back to times when Transceivers/Transmitters in general had no provision for adjusting the
RF output power of a transceiver in SSB mode by means of a front panel control being effective at some
intermediate TX RF amplification stage. E.g. tube era Heathkit SB and HW transceivers, Collins KWM-2 and 32s-,
Drake T4 and TR4, etc., but also semiconductor radios like TS-430/440, FT-757, IC-730, etc.

In conclusion, ALC with such kind of radios was/is the only way to go, IF the power amps design was such that
the required driver power for max. output was significantly lower than what a typical 100 watt transceiver
would provide in SSB mode.

Klaus, DK3QN


Am 14.04.2021 um 12:29 schrieb Kevin Larcombe:

I agree with your comment about the general use of ALC so that an amplifier is not over driven, in instances where the exciter is capable of overdriving the amplifier. 

But in the case of the FDM DUO & ART120 setup, the radio is not capable of overdriving the amplifier. So presumably the best way to reduce power is by applying attenuation to the input of the amplifier. 

This solution will also prevent any chance of overshoot of the signal when ALC is used and the circuit doesn't act quick enough.

Kevin GW0PUH


From: EladSDR@groups.io <EladSDR@groups.io> on behalf of T.W.H. Fockens <koos@...>
Sent: 14 April 2021 11:11
To: EladSDR@groups.io <EladSDR@groups.io>
Subject: Re: [EladSDR] Elad DUO ART 120 - How to select power setting?
 
No, that is a misconception. The ALC prevents you from overdriving your
PA, and so preventing IM and splatter. It also controls the power match
between the output of your driving trx and the PA.

This is a serious aspect of transmitter design and should never be
neglected.

Koos PA0KDF

On 14 Apr, Kevin Larcombe <kevlarcombe@...> wrote:
> I don't see how ALC would help, ALC only stops the output level from exceeding a set limit.

> What is required is integration of the Elad software, so that the ART120 can be controlled by the same software as the FDM DUO. If that were the case, they could simply provide a slider in the software to set the required output power also status monitoring of the ART120 could be provided in the software.

> Unfortunately, although the individual components perform very well, Elad has failed to integrate them. (I guess their design is flawed in this area, perhaps not enough attention to the requirements) This is my main gripe with the ART120, I have to have it in view and the buttons in reach instead of being able to put it in the rack adjacent to my operating desk and being able to control it from SW2 the same as the radio.

> I think Elad missed a big trick with this oversight.

> Kevin GW0PUH

> ________________________________
> From: EladSDR@groups.io <EladSDR@groups.io> on behalf of T.W.H. Fockens <koos@...>
> Sent: 14 April 2021 10:03
> To: EladSDR@groups.io <EladSDR@groups.io>
> Subject: Re: [EladSDR] Elad DUO ART 120 - How to select power setting?

> That is why you need an Automatic Level Control (ALC).
> IMHO that is lack in the Elad equiment.

> Koos Fockens,
> PA0KDF


> On 13 Apr, gcoxuk@... via groups.io <gcoxuk@...> wrote:
> > Most awesome Klaus
> > 73
> > Geoff M7COX
> > > On 13 Apr 2021, at 21:15, Klaus Brosche <klaus.brosche@...> wrote:
> > >
> > > #
> > > A setting of 3dB RF input attenuation at the ART-120 means that the input RF power from the DUO
> > > is being reduced by 50%. 3 dB attenuation equals half power.
> > >
> > > E.g., if your DUO is set for 5 watts output, the input attenuator of the ART-120 will dissipate 2.5 watts
> > > into an RF resistor and will pass only 2.5 watts to the ART-120 final stage.
> > >
> > > If the ART-120 puts out 120 watts with DUOs output set to 5 watts, you'll see around 60 watts output
> > > on the ART-120, IF engaging its 3 dB input attenuator.
> > >
> > > The same or nearly the same effect can be achieved if you set the DUO output to 2.5 watts and have
> > > the ART-120 input anttenuator set at 0 dB attenuation.
> > >
> > > As the gain factor of an amplifier is not exactly equal across its frequency range - it may vary by a few
> > > dB - depending on the frequency band of operation, the output of the amp may vary from band to band,
> > > even if the driver power (DUO) is set to a certain level, e.g. 2.5 watts.
> > >
> > > 73, Klaus, DK3QN
> > >
> > >
> > >
> > > Am 13.04.2021 um 17:39 schrieb gcoxuk@... via groups.io:
> > >> Thanks Kevin.
> > >>
> > >> I've tried reducing the elad FMD output power with very small effect.
> > >> Forgive my ignorance, but what db setting effects this?
> > >> #
> > >>
> > >>
> > >>> On 13 Apr 2021, at 15:53, Kevin Larcombe <kevlarcombe@...> wrote:
> > >>>
> > >>> #
> > >>> Hi Geoff,
> > >>>
> > >>> You can reduce the drive from the radio, (I assume you are using the Duo) or in the menu on the DUO ART you can select attenuation of 2, 3 & 5dB (from my memory)
> > >>>
> > >>> My Duo/ART and all my radios are packed away at present during the shack rebuild, so sorry I can't look and tell you which menu. It easy to find in the manual though. (you can also set it  per band in the profiles)
> > >>>
> > >>> Regards
> > >>>
> > >>> Kevin
> > >>>
> > >>> From: EladSDR@groups.io <EladSDR@groups.io> on behalf of gcoxuk@... via groups.io <gcoxuk@...>
> > >>> Sent: 13 April 2021 00:06
> > >>> To: EladSDR@groups.io <EladSDR@groups.io>
> > >>> Subject: [EladSDR] Elad DUO ART 120 - How to select power setting?
> > >>>
> > >>> Greetings,
> > >>>
> > >>> I'm a novice doing the learning curve to my Duo Art set.  Ummm nothing much in the ops manual about output except ~5w in yeilds ~120w.  Nothing is said about its response to lesser input power to reduce output power.
> > >>>
> > >>> Am I missing something or is this a ~120w output only???
> > >>>
> > >>> Thanks in advance.
> > >>> Geoff
> > >>> Stansted UK
> > >>>
> > >>>
> > >>>
> > >>>
> > >>>
> > >
> > >


> >

> --
> Ir. T.W.H. Fockens
> Kieftweg 1
> 7165BR Rietmolen

> Onze democratie is gebaat bij een kiesdrempel.







>

--
Ir. T.W.H. Fockens
Kieftweg 1
7165BR Rietmolen

Onze democratie is gebaat bij een kiesdrempel.







Chris Bartram
 

I'm sorry Koos, I'm afraid the misconception is yours.

In a linear transmitter system, it is always to better to match the output level of a linear transmitter to that required to drive a subsequent amplifier within its linear power input range. If you are seeing ALC operation every time you talk, you are adding to the non-linearity of the system, and probably provoking splatter!

The use of ALC came about in the days of tube-based transmitters - I blame Collins Radio! - when the gain of the transmitter strip was unpredictable due to device aging and other effects. An automatic gain control loop had to be implemented to counter the gain changes. This came to be used by radio amateurs as a de facto speech processing process.

The problem with using a gain control loop is that it takes time to respond. In that time the overall gain is usually sufficient to cause the PA to saturate, resulting in transient excess intermodulation components being generated ie. splatter! Measuring the transmitter with ALC in operation with a two-tone test doesn't show this effect, as the loop has stabilised. With the right test equipment, it's instructive to do this.

With modern digital transmitter design, such as that employed in the ELAD FDM-DUO, the output level is essentially determined by the DAC actually generating the signal. The effects of gain changes in a well designed solid-state amplifier chain are small enough to eliminate any need for ALC.

73

Chris G4DGU

No, that is a misconception. The ALC prevents you from overdriving your
PA, and so preventing IM and splatter. It also controls the power match
between the output of your driving trx and the PA.

This is a serious aspect of transmitter design and should never be
neglected.

Koos PA0KDF
--
Chris Bartram G4DGU


gcoxuk@googlemail.com
 

Again, thanks fir your efforts on this.

One related question come to mind fro reading this regarding CW.  I see the amp triggering on each contact of the CW key.  Is this ok??  Thought best practice is turning in the the Carrier Wave, generating the message code, and then switching off the amp.
So I’ve set the delay to the max 1 sec (presumably during which time the carrier continues until 1 sec following the last bit of code sent).  Is this correct or a concern?
Again, I’m a code novice making observations at this point!

73 to all
Kr
Geoff M7COX


On 14 Apr 2021, at 12:40, Klaus Brosche <klaus.brosche@...> wrote:


ALC as a means of preventing amp overdrive is the second best solution (at best).

It basically is just a voltage feedback loop from an amp back to the TRX, i.e. to an amplification stage in that TRX,
which reduces the amplification factor of that TRX stage so that the the power amp doesn't get overdriven.

Being based on a feedback loop means: the TRX TX gain / power output is only decreased *after* an overdrive
condition at the power amp has been detected, which then triggers the ALC feedback loop voltage.
Typically there is some sort of time constant implemented to the ALC feedback loop, so that the amount of
ALC voltage is averaged over the transmitting period, thus preventing the ALC voltage from fast alterations/
voltage jumps depending on voice/modulation characteristics (different sound levels with respect to sound
frequencies in the human voice). This is true for SSB modulation.

For CW, FM etc. modes the principle is the same, with the exception that there is a more or less constant
carrier level present and due to the ALC circuit time constant, that also is valid for keyed CW.

A way better way of preventing a power amp from getting overdriven is to adjust the TRX RF output to
a level at which the power amp is not faced with an overdrive situation. Imho "best practice" and no need
for an ALC feedback loop.

ALC dates back to times when Transceivers/Transmitters in general had no provision for adjusting the
RF output power of a transceiver in SSB mode by means of a front panel control being effective at some
intermediate TX RF amplification stage. E.g. tube era Heathkit SB and HW transceivers, Collins KWM-2 and 32s-,
Drake T4 and TR4, etc., but also semiconductor radios like TS-430/440, FT-757, IC-730, etc.

In conclusion, ALC with such kind of radios was/is the only way to go, IF the power amps design was such that
the required driver power for max. output was significantly lower than what a typical 100 watt transceiver
would provide in SSB mode.

Klaus, DK3QN


Am 14.04.2021 um 12:29 schrieb Kevin Larcombe:
I agree with your comment about the general use of ALC so that an amplifier is not over driven, in instances where the exciter is capable of overdriving the amplifier. 

But in the case of the FDM DUO & ART120 setup, the radio is not capable of overdriving the amplifier. So presumably the best way to reduce power is by applying attenuation to the input of the amplifier. 

This solution will also prevent any chance of overshoot of the signal when ALC is used and the circuit doesn't act quick enough.

Kevin GW0PUH


From: EladSDR@groups.io <EladSDR@groups.io> on behalf of T.W.H. Fockens <koos@...>
Sent: 14 April 2021 11:11
To: EladSDR@groups.io <EladSDR@groups.io>
Subject: Re: [EladSDR] Elad DUO ART 120 - How to select power setting?
 
No, that is a misconception. The ALC prevents you from overdriving your
PA, and so preventing IM and splatter. It also controls the power match
between the output of your driving trx and the PA.

This is a serious aspect of transmitter design and should never be
neglected.

Koos PA0KDF

On 14 Apr, Kevin Larcombe <kevlarcombe@...> wrote:
> I don't see how ALC would help, ALC only stops the output level from exceeding a set limit.

> What is required is integration of the Elad software, so that the ART120 can be controlled by the same software as the FDM DUO. If that were the case, they could simply provide a slider in the software to set the required output power also status monitoring of the ART120 could be provided in the software.

> Unfortunately, although the individual components perform very well, Elad has failed to integrate them. (I guess their design is flawed in this area, perhaps not enough attention to the requirements) This is my main gripe with the ART120, I have to have it in view and the buttons in reach instead of being able to put it in the rack adjacent to my operating desk and being able to control it from SW2 the same as the radio.

> I think Elad missed a big trick with this oversight.

> Kevin GW0PUH

> ________________________________
> From: EladSDR@groups.io <EladSDR@groups.io> on behalf of T.W.H. Fockens <koos@...>
> Sent: 14 April 2021 10:03
> To: EladSDR@groups.io <EladSDR@groups.io>
> Subject: Re: [EladSDR] Elad DUO ART 120 - How to select power setting?

> That is why you need an Automatic Level Control (ALC).
> IMHO that is lack in the Elad equiment.

> Koos Fockens,
> PA0KDF


> On 13 Apr, gcoxuk@... via groups.io <gcoxuk@...> wrote:
> > Most awesome Klaus
> > 73
> > Geoff M7COX
> > > On 13 Apr 2021, at 21:15, Klaus Brosche <klaus.brosche@...> wrote:
> > >
> > > #
> > > A setting of 3dB RF input attenuation at the ART-120 means that the input RF power from the DUO
> > > is being reduced by 50%. 3 dB attenuation equals half power.
> > >
> > > E.g., if your DUO is set for 5 watts output, the input attenuator of the ART-120 will dissipate 2.5 watts
> > > into an RF resistor and will pass only 2.5 watts to the ART-120 final stage.
> > >
> > > If the ART-120 puts out 120 watts with DUOs output set to 5 watts, you'll see around 60 watts output
> > > on the ART-120, IF engaging its 3 dB input attenuator.
> > >
> > > The same or nearly the same effect can be achieved if you set the DUO output to 2.5 watts and have
> > > the ART-120 input anttenuator set at 0 dB attenuation.
> > >
> > > As the gain factor of an amplifier is not exactly equal across its frequency range - it may vary by a few
> > > dB - depending on the frequency band of operation, the output of the amp may vary from band to band,
> > > even if the driver power (DUO) is set to a certain level, e.g. 2.5 watts.
> > >
> > > 73, Klaus, DK3QN
> > >
> > >
> > >
> > > Am 13.04.2021 um 17:39 schrieb gcoxuk@... via groups.io:
> > >> Thanks Kevin.
> > >>
> > >> I've tried reducing the elad FMD output power with very small effect.
> > >> Forgive my ignorance, but what db setting effects this?
> > >> #
> > >>
> > >>
> > >>> On 13 Apr 2021, at 15:53, Kevin Larcombe <kevlarcombe@...> wrote:
> > >>>
> > >>> #
> > >>> Hi Geoff,
> > >>>
> > >>> You can reduce the drive from the radio, (I assume you are using the Duo) or in the menu on the DUO ART you can select attenuation of 2, 3 & 5dB (from my memory)
> > >>>
> > >>> My Duo/ART and all my radios are packed away at present during the shack rebuild, so sorry I can't look and tell you which menu. It easy to find in the manual though. (you can also set it  per band in the profiles)
> > >>>
> > >>> Regards
> > >>>
> > >>> Kevin
> > >>>
> > >>> From: EladSDR@groups.io <EladSDR@groups.io> on behalf of gcoxuk@... via groups.io <gcoxuk@...>
> > >>> Sent: 13 April 2021 00:06
> > >>> To: EladSDR@groups.io <EladSDR@groups.io>
> > >>> Subject: [EladSDR] Elad DUO ART 120 - How to select power setting?
> > >>>
> > >>> Greetings,
> > >>>
> > >>> I'm a novice doing the learning curve to my Duo Art set.  Ummm nothing much in the ops manual about output except ~5w in yeilds ~120w.  Nothing is said about its response to lesser input power to reduce output power.
> > >>>
> > >>> Am I missing something or is this a ~120w output only???
> > >>>
> > >>> Thanks in advance.
> > >>> Geoff
> > >>> Stansted UK
> > >>>
> > >>>
> > >>>
> > >>>
> > >>>
> > >
> > >


> >

> --
> Ir. T.W.H. Fockens
> Kieftweg 1
> 7165BR Rietmolen

> Onze democratie is gebaat bij een kiesdrempel.







>

--
Ir. T.W.H. Fockens
Kieftweg 1
7165BR Rietmolen

Onze democratie is gebaat bij een kiesdrempel.







T.W.H. Fockens
 

Hello Chris and Klaus,

Of course the ALC circuit needs to be well-designed. Overshoot is not
neccessarely.

The rise time of the driving signal is always limited by the filter
bandwidth of the SSB filter, or equivalent filtering in the software.
That means that the risetime is about the inverse of the bandwidth. It
is not difficult to design the ALC circuit so that it controlls the
feedback in time. What helps is that there should not be a hard limit,
but a partly soft control range.
I see that the PA that I use has a very soft control behaviour. That
means I can do everything that is needed in the exciter.

Second point is that the fall-time of the ALC must be long: 10 seconds
or more.

It goes wrong in those situations wherein people try to combine the
compressor working with the ALC: you should not do that.

A speech compressor should be designed according different design
philosophy, using a logaritmic detector and fast fall-back.

I can really advise you to study the book "Single Sideband Systems and
Circuits, Ed. II" from Sabin and Schoenike, indeed old Collins people.

Of course, you can fine tune the gain of the exciter and amount of drive
by hand. For digital modes that works fine, the only problem is you keep
controlling it on and on, and forget it at crucial moments.

For phone there are two extra problem:
1. The output from the microphone is not constant, but varying by the
way you speak, the distance between your mouth and the microphone, etc.
So your output from the exciter varies. You could think of an
speechcompressor or limitter, but that has the next problem:

2. the amplitude of the SSB modulated signal is not proportional with
the amplitude of the complicated microphone audio. So using an audio
speechprocessor, or even an audio limitter, is not enough to limit the
SSB signal correctly. See above mentioned book. 2.

Helas, I see very often amateur designs of exciters without any
amplitude controlling...

I see also this: For Elad and the other digital boys there is a penalty
for using an ALC circuit: you need an extra ADC to digitize the ALC
voltage, and feed the data back into the DSP software. This complicates
the hardware as well as the software. And so the costs. But be open
about that.

One thing is absolute sure for me: A PA without an ALC output, I would
never buy, and I find it a pity that the FDM-DUO has no ALC input.

Koos
PA0KDF

On 14 Apr, Chris Bartram <chris@chris-bartram.co.uk> wrote:
I'm sorry Koos, I'm afraid the misconception is yours.
In a linear transmitter system, it is always to better to match the
output level of a linear transmitter to that required to drive a
subsequent amplifier within its linear power input range. If you are
seeing ALC operation every time you talk, you are adding to the
non-linearity of the system, and probably provoking splatter!
The use of ALC came about in the days of tube-based transmitters - I
blame Collins Radio! - when the gain of the transmitter strip was
unpredictable due to device aging and other effects. An automatic gain
control loop had to be implemented to counter the gain changes. This
came to be used by radio amateurs as a de facto speech processing process.
The problem with using a gain control loop is that it takes time to
respond. In that time the overall gain is usually sufficient to cause
the PA to saturate, resulting in transient excess intermodulation
components being generated ie. splatter! Measuring the transmitter with
ALC in operation with a two-tone test doesn't show this effect, as the
loop has stabilised. With the right test equipment, it's instructive to
do this.
With modern digital transmitter design, such as that employed in the
ELAD FDM-DUO, the output level is essentially determined by the DAC
actually generating the signal. The effects of gain changes in a well
designed solid-state amplifier chain are small enough to eliminate any
need for ALC.
73
Chris G4DGU

No, that is a misconception. The ALC prevents you from overdriving your
PA, and so preventing IM and splatter. It also controls the power match
between the output of your driving trx and the PA.

This is a serious aspect of transmitter design and should never be
neglected.

Koos PA0KDF
--
Ir. T.W.H. Fockens
Kieftweg 1
7165BR Rietmolen

Onze democratie is gebaat bij een kiesdrempel.


Klaus Brosche
 

Hi Geoff,

In CW mode the FDM-DUO - as per ARRL QST review in QST issue May 2016 - has an RF onset delay
of about 7 milliSeconds after the key line (morse key) is closed.
After opening the key line, the delay until RF is completely finished (transmitted) is about 9 milliSeconds.
This is the "technical" situation which is as it is and cannot be changed.

"Operational" options

In DUO menu item #38 ("CW Delay") you can set the "CW Delay" to any value between 0 and 9000
milliSeconds. This setting refers to the time gap in switching from TX to RX between a dit or dah and
the subsequent dit or dah.

If you send your CW characters at very low speed, the DUO would switch over after a single dit or
dah of a morse code letter or number. This relates to a "CW Delay" setting of 0 or a very small single
digit delay setting.

If sending at high speed, the switch over (TX to RX) may only happen between a morse code letter
or number, due to the fast transmitting speed.

If you set the "CW Delay" to something like a couple of hundred mS, depending on CW speed,
the switch over may happen only between words.
-------
Brief morse code related comments:

A morse code sequence is divided into "elements", where a
dit = 1 element
dah = 3 elements
the gap between each dit or dah = 1 element.

Additionally, there is
a gap between 2 subsequent morse code characters of 3 elements (a "dahs" length), and
a gap between words of 7 elements.

This is to make letters and numbers distinct from each other as well as making it distinct
that a word is separated from a subsequent word or number sequence.

Following that distinct "spacing" sequence makes reading your morse code transmission
much easier for your fellow QSO partner.
------
Back to "CW Delay" setting and why and when I personally choose different settings
for certain operational situations:

For rag chewing QSOs, I typically set my setting to a value that allows switch over
only between words. If my QSO partner wants to interrupt me for any reason, I would
hear his "interrupt" after having fully transmitted my CW word.

You may of course extend this delay to a value which allows for sending a complete
sentence and leave a short pause after having transmitted that sentence and thus
allowing your partner to interrupt.

For contest operation I would set "CW Delay" to zero or a low milliSecond number
in order to be able to hear what is going on the frequency during my transmission
(QRM etc.).
-------
For the latter situation it needs to be pointed out that that very frequent and fast
switching over process may not be appropriate for certain kinds of Transceivers
and Amplifiers. Namely those ones where a electro-mechanical relay provides the
task of the switching over process.

Because these kind of relays are relatively slow in switching (typically about
10 to 30 or so milliSeconds) plus they are getting physically stressed by such an
action and thus are wearing out earlier.

In the case of the DUO plus ART-120 my assumption is that the switching over
is done by means of an RF diode switching technique which is a) fast and
b) does not involve mechanical parts.

Please double check this yourself or maybe someone out of this community may
comment on my assumption.
-------
Finally, the "CW Delay" setting is a matter of your personal liking and whether
or not you typically want to hear band noise in between morse code characters,
words or even sequences of words/numbers.

73 and stay safe!

Klaus, DK3QN


Am 14.04.2021 um 15:01 schrieb gcoxuk@... via groups.io:

Again, thanks fir your efforts on this.

One related question come to mind fro reading this regarding CW.  I see the amp triggering on each contact of the CW key.  Is this ok??  Thought best practice is turning in the the Carrier Wave, generating the message code, and then switching off the amp.
So I’ve set the delay to the max 1 sec (presumably during which time the carrier continues until 1 sec following the last bit of code sent).  Is this correct or a concern?
Again, I’m a code novice making observations at this point!

73 to all
Kr
Geoff M7COX


On 14 Apr 2021, at 12:40, Klaus Brosche <klaus.brosche@...> wrote:


ALC as a means of preventing amp overdrive is the second best solution (at best).

It basically is just a voltage feedback loop from an amp back to the TRX, i.e. to an amplification stage in that TRX,
which reduces the amplification factor of that TRX stage so that the the power amp doesn't get overdriven.

Being based on a feedback loop means: the TRX TX gain / power output is only decreased *after* an overdrive
condition at the power amp has been detected, which then triggers the ALC feedback loop voltage.
Typically there is some sort of time constant implemented to the ALC feedback loop, so that the amount of
ALC voltage is averaged over the transmitting period, thus preventing the ALC voltage from fast alterations/
voltage jumps depending on voice/modulation characteristics (different sound levels with respect to sound
frequencies in the human voice). This is true for SSB modulation.

For CW, FM etc. modes the principle is the same, with the exception that there is a more or less constant
carrier level present and due to the ALC circuit time constant, that also is valid for keyed CW.

A way better way of preventing a power amp from getting overdriven is to adjust the TRX RF output to
a level at which the power amp is not faced with an overdrive situation. Imho "best practice" and no need
for an ALC feedback loop.

ALC dates back to times when Transceivers/Transmitters in general had no provision for adjusting the
RF output power of a transceiver in SSB mode by means of a front panel control being effective at some
intermediate TX RF amplification stage. E.g. tube era Heathkit SB and HW transceivers, Collins KWM-2 and 32s-,
Drake T4 and TR4, etc., but also semiconductor radios like TS-430/440, FT-757, IC-730, etc.

In conclusion, ALC with such kind of radios was/is the only way to go, IF the power amps design was such that
the required driver power for max. output was significantly lower than what a typical 100 watt transceiver
would provide in SSB mode.

Klaus, DK3QN


Am 14.04.2021 um 12:29 schrieb Kevin Larcombe:
I agree with your comment about the general use of ALC so that an amplifier is not over driven, in instances where the exciter is capable of overdriving the amplifier. 

But in the case of the FDM DUO & ART120 setup, the radio is not capable of overdriving the amplifier. So presumably the best way to reduce power is by applying attenuation to the input of the amplifier. 

This solution will also prevent any chance of overshoot of the signal when ALC is used and the circuit doesn't act quick enough.

Kevin GW0PUH


From: EladSDR@groups.io <EladSDR@groups.io> on behalf of T.W.H. Fockens <koos@...>
Sent: 14 April 2021 11:11
To: EladSDR@groups.io <EladSDR@groups.io>
Subject: Re: [EladSDR] Elad DUO ART 120 - How to select power setting?
 
No, that is a misconception. The ALC prevents you from overdriving your
PA, and so preventing IM and splatter. It also controls the power match
between the output of your driving trx and the PA.

This is a serious aspect of transmitter design and should never be
neglected.

Koos PA0KDF

On 14 Apr, Kevin Larcombe <kevlarcombe@...> wrote:
> I don't see how ALC would help, ALC only stops the output level from exceeding a set limit.

> What is required is integration of the Elad software, so that the ART120 can be controlled by the same software as the FDM DUO. If that were the case, they could simply provide a slider in the software to set the required output power also status monitoring of the ART120 could be provided in the software.

> Unfortunately, although the individual components perform very well, Elad has failed to integrate them. (I guess their design is flawed in this area, perhaps not enough attention to the requirements) This is my main gripe with the ART120, I have to have it in view and the buttons in reach instead of being able to put it in the rack adjacent to my operating desk and being able to control it from SW2 the same as the radio.

> I think Elad missed a big trick with this oversight.

> Kevin GW0PUH

> ________________________________
> From: EladSDR@groups.io <EladSDR@groups.io> on behalf of T.W.H. Fockens <koos@...>
> Sent: 14 April 2021 10:03
> To: EladSDR@groups.io <EladSDR@groups.io>
> Subject: Re: [EladSDR] Elad DUO ART 120 - How to select power setting?

> That is why you need an Automatic Level Control (ALC).
> IMHO that is lack in the Elad equiment.

> Koos Fockens,
> PA0KDF


> On 13 Apr, gcoxuk@... via groups.io <gcoxuk@...> wrote:
> > Most awesome Klaus
> > 73
> > Geoff M7COX
> > > On 13 Apr 2021, at 21:15, Klaus Brosche <klaus.brosche@...> wrote:
> > >
> > > #
> > > A setting of 3dB RF input attenuation at the ART-120 means that the input RF power from the DUO
> > > is being reduced by 50%. 3 dB attenuation equals half power.
> > >
> > > E.g., if your DUO is set for 5 watts output, the input attenuator of the ART-120 will dissipate 2.5 watts
> > > into an RF resistor and will pass only 2.5 watts to the ART-120 final stage.
> > >
> > > If the ART-120 puts out 120 watts with DUOs output set to 5 watts, you'll see around 60 watts output
> > > on the ART-120, IF engaging its 3 dB input attenuator.
> > >
> > > The same or nearly the same effect can be achieved if you set the DUO output to 2.5 watts and have
> > > the ART-120 input anttenuator set at 0 dB attenuation.
> > >
> > > As the gain factor of an amplifier is not exactly equal across its frequency range - it may vary by a few
> > > dB - depending on the frequency band of operation, the output of the amp may vary from band to band,
> > > even if the driver power (DUO) is set to a certain level, e.g. 2.5 watts.
> > >
> > > 73, Klaus, DK3QN
> > >
> > >
> > >
> > > Am 13.04.2021 um 17:39 schrieb gcoxuk@... via groups.io:
> > >> Thanks Kevin.
> > >>
> > >> I've tried reducing the elad FMD output power with very small effect.
> > >> Forgive my ignorance, but what db setting effects this?
> > >> #
> > >>
> > >>
> > >>> On 13 Apr 2021, at 15:53, Kevin Larcombe <kevlarcombe@...> wrote:
> > >>>
> > >>> #
> > >>> Hi Geoff,
> > >>>
> > >>> You can reduce the drive from the radio, (I assume you are using the Duo) or in the menu on the DUO ART you can select attenuation of 2, 3 & 5dB (from my memory)
> > >>>
> > >>> My Duo/ART and all my radios are packed away at present during the shack rebuild, so sorry I can't look and tell you which menu. It easy to find in the manual though. (you can also set it  per band in the profiles)
> > >>>
> > >>> Regards
> > >>>
> > >>> Kevin
> > >>>
> > >>> From: EladSDR@groups.io <EladSDR@groups.io> on behalf of gcoxuk@... via groups.io <gcoxuk@...>
> > >>> Sent: 13 April 2021 00:06
> > >>> To: EladSDR@groups.io <EladSDR@groups.io>
> > >>> Subject: [EladSDR] Elad DUO ART 120 - How to select power setting?
> > >>>
> > >>> Greetings,
> > >>>
> > >>> I'm a novice doing the learning curve to my Duo Art set.  Ummm nothing much in the ops manual about output except ~5w in yeilds ~120w.  Nothing is said about its response to lesser input power to reduce output power.
> > >>>
> > >>> Am I missing something or is this a ~120w output only???
> > >>>
> > >>> Thanks in advance.
> > >>> Geoff
> > >>> Stansted UK
> > >>>
> > >>>
> > >>>
> > >>>
> > >>>
> > >
> > >


> >

> --
> Ir. T.W.H. Fockens
> Kieftweg 1
> 7165BR Rietmolen

> Onze democratie is gebaat bij een kiesdrempel.







>

--
Ir. T.W.H. Fockens
Kieftweg 1
7165BR Rietmolen

Onze democratie is gebaat bij een kiesdrempel.








Neil Smith G4DBN
 

I set the CW delay on my DUO to 150 ms for general use or 250 ms when using a transverter with a waveguide relay or other slow element. For sending extremely slow CW under 10 wpm for weak signal troposcatter, or even slower when the other op doesn't read MorseI have a PTT footswitch that I engage while I'm sending to prevent the relays getting stressed.

I don't find that a zero delay is pleasant to use on the DUO, I used to have a radio which could do QSK full break-in with recovery to normal sensitivity between dots at 30 wpm, which was brilliant, but I don't operate much on HF any more, so QSK isn't really important to me now. Being able to listen between dots is transformative when you are chasing DX in pileups, as you can stop sending as soon as you hear the DX station sending , so you don't cause interference to others, and you don't end up doubling if they start their reply early.

At a typical contest or DX-chasing speed around 30 wpm, the dot period is 40 ms, so you lose a fair proportion of the inter-dot space with the on and off delay of the DUO and the tx/rx recovery time.

On 14/04/2021 17:31, Klaus Brosche wrote:
Hi Geoff,

In CW mode the FDM-DUO - as per ARRL QST review in QST issue May 2016 - has an RF onset delay
of about 7 milliSeconds after the key line (morse key) is closed.
After opening the key line, the delay until RF is completely finished (transmitted) is about 9 milliSeconds.
This is the "technical" situation which is as it is and cannot be changed.

"Operational" options

In DUO menu item #38 ("CW Delay") you can set the "CW Delay" to any value between 0 and 9000
milliSeconds. This setting refers to the time gap in switching from TX to RX between a dit or dah and
the subsequent dit or dah.

If you send your CW characters at very low speed, the DUO would switch over after a single dit or
dah of a morse code letter or number. This relates to a "CW Delay" setting of 0 or a very small single
digit delay setting.

If sending at high speed, the switch over (TX to RX) may only happen between a morse code letter
or number, due to the fast transmitting speed.

If you set the "CW Delay" to something like a couple of hundred mS, depending on CW speed,
the switch over may happen only between words.
-------
Brief morse code related comments:

A morse code sequence is divided into "elements", where a
dit = 1 element
dah = 3 elements
the gap between each dit or dah = 1 element.

Additionally, there is
a gap between 2 subsequent morse code characters of 3 elements (a "dahs" length), and
a gap between words of 7 elements.

This is to make letters and numbers distinct from each other as well as making it distinct
that a word is separated from a subsequent word or number sequence.

Following that distinct "spacing" sequence makes reading your morse code transmission
much easier for your fellow QSO partner.
------
Back to "CW Delay" setting and why and when I personally choose different settings
for certain operational situations:

For rag chewing QSOs, I typically set my setting to a value that allows switch over
only between words. If my QSO partner wants to interrupt me for any reason, I would
hear his "interrupt" after having fully transmitted my CW word.

You may of course extend this delay to a value which allows for sending a complete
sentence and leave a short pause after having transmitted that sentence and thus
allowing your partner to interrupt.

For contest operation I would set "CW Delay" to zero or a low milliSecond number
in order to be able to hear what is going on the frequency during my transmission
(QRM etc.).
-------
For the latter situation it needs to be pointed out that that very frequent and fast
switching over process may not be appropriate for certain kinds of Transceivers
and Amplifiers. Namely those ones where a electro-mechanical relay provides the
task of the switching over process.

Because these kind of relays are relatively slow in switching (typically about
10 to 30 or so milliSeconds) plus they are getting physically stressed by such an
action and thus are wearing out earlier.

In the case of the DUO plus ART-120 my assumption is that the switching over
is done by means of an RF diode switching technique which is a) fast and
b) does not involve mechanical parts.

Please double check this yourself or maybe someone out of this community may
comment on my assumption.
-------
Finally, the "CW Delay" setting is a matter of your personal liking and whether
or not you typically want to hear band noise in between morse code characters,
words or even sequences of words/numbers.

73 and stay safe!

Klaus, DK3QN


Am 14.04.2021 um 15:01 schrieb gcoxuk@... via groups.io:
Again, thanks fir your efforts on this.

One related question come to mind fro reading this regarding CW.  I see the amp triggering on each contact of the CW key.  Is this ok??  Thought best practice is turning in the the Carrier Wave, generating the message code, and then switching off the amp.
So I’ve set the delay to the max 1 sec (presumably during which time the carrier continues until 1 sec following the last bit of code sent).  Is this correct or a concern?
Again, I’m a code novice making observations at this point!

73 to all
Kr
Geoff M7COX


On 14 Apr 2021, at 12:40, Klaus Brosche <klaus.brosche@...> wrote:


ALC as a means of preventing amp overdrive is the second best solution (at best).

It basically is just a voltage feedback loop from an amp back to the TRX, i.e. to an amplification stage in that TRX,
which reduces the amplification factor of that TRX stage so that the the power amp doesn't get overdriven.

Being based on a feedback loop means: the TRX TX gain / power output is only decreased *after* an overdrive
condition at the power amp has been detected, which then triggers the ALC feedback loop voltage.
Typically there is some sort of time constant implemented to the ALC feedback loop, so that the amount of
ALC voltage is averaged over the transmitting period, thus preventing the ALC voltage from fast alterations/
voltage jumps depending on voice/modulation characteristics (different sound levels with respect to sound
frequencies in the human voice). This is true for SSB modulation.

For CW, FM etc. modes the principle is the same, with the exception that there is a more or less constant
carrier level present and due to the ALC circuit time constant, that also is valid for keyed CW.

A way better way of preventing a power amp from getting overdriven is to adjust the TRX RF output to
a level at which the power amp is not faced with an overdrive situation. Imho "best practice" and no need
for an ALC feedback loop.

ALC dates back to times when Transceivers/Transmitters in general had no provision for adjusting the
RF output power of a transceiver in SSB mode by means of a front panel control being effective at some
intermediate TX RF amplification stage. E.g. tube era Heathkit SB and HW transceivers, Collins KWM-2 and 32s-,
Drake T4 and TR4, etc., but also semiconductor radios like TS-430/440, FT-757, IC-730, etc.

In conclusion, ALC with such kind of radios was/is the only way to go, IF the power amps design was such that
the required driver power for max. output was significantly lower than what a typical 100 watt transceiver
would provide in SSB mode.

Klaus, DK3QN


Am 14.04.2021 um 12:29 schrieb Kevin Larcombe:
I agree with your comment about the general use of ALC so that an amplifier is not over driven, in instances where the exciter is capable of overdriving the amplifier. 

But in the case of the FDM DUO & ART120 setup, the radio is not capable of overdriving the amplifier. So presumably the best way to reduce power is by applying attenuation to the input of the amplifier. 

This solution will also prevent any chance of overshoot of the signal when ALC is used and the circuit doesn't act quick enough.

Kevin GW0PUH


From: EladSDR@groups.io <EladSDR@groups.io> on behalf of T.W.H. Fockens <koos@...>
Sent: 14 April 2021 11:11
To: EladSDR@groups.io <EladSDR@groups.io>
Subject: Re: [EladSDR] Elad DUO ART 120 - How to select power setting?
 
No, that is a misconception. The ALC prevents you from overdriving your
PA, and so preventing IM and splatter. It also controls the power match
between the output of your driving trx and the PA.

This is a serious aspect of transmitter design and should never be
neglected.

Koos PA0KDF

On 14 Apr, Kevin Larcombe <kevlarcombe@...> wrote:
> I don't see how ALC would help, ALC only stops the output level from exceeding a set limit.

> What is required is integration of the Elad software, so that the ART120 can be controlled by the same software as the FDM DUO. If that were the case, they could simply provide a slider in the software to set the required output power also status monitoring of the ART120 could be provided in the software.

> Unfortunately, although the individual components perform very well, Elad has failed to integrate them. (I guess their design is flawed in this area, perhaps not enough attention to the requirements) This is my main gripe with the ART120, I have to have it in view and the buttons in reach instead of being able to put it in the rack adjacent to my operating desk and being able to control it from SW2 the same as the radio.

> I think Elad missed a big trick with this oversight.

> Kevin GW0PUH

> ________________________________
> From: EladSDR@groups.io <EladSDR@groups.io> on behalf of T.W.H. Fockens <koos@...>
> Sent: 14 April 2021 10:03
> To: EladSDR@groups.io <EladSDR@groups.io>
> Subject: Re: [EladSDR] Elad DUO ART 120 - How to select power setting?

> That is why you need an Automatic Level Control (ALC).
> IMHO that is lack in the Elad equiment.

> Koos Fockens,
> PA0KDF


> On 13 Apr, gcoxuk@... via groups.io <gcoxuk@...> wrote:
> > Most awesome Klaus
> > 73
> > Geoff M7COX
> > > On 13 Apr 2021, at 21:15, Klaus Brosche <klaus.brosche@...> wrote:
> > >
> > > #
> > > A setting of 3dB RF input attenuation at the ART-120 means that the input RF power from the DUO
> > > is being reduced by 50%. 3 dB attenuation equals half power.
> > >
> > > E.g., if your DUO is set for 5 watts output, the input attenuator of the ART-120 will dissipate 2.5 watts
> > > into an RF resistor and will pass only 2.5 watts to the ART-120 final stage.
> > >
> > > If the ART-120 puts out 120 watts with DUOs output set to 5 watts, you'll see around 60 watts output
> > > on the ART-120, IF engaging its 3 dB input attenuator.
> > >
> > > The same or nearly the same effect can be achieved if you set the DUO output to 2.5 watts and have
> > > the ART-120 input anttenuator set at 0 dB attenuation.
> > >
> > > As the gain factor of an amplifier is not exactly equal across its frequency range - it may vary by a few
> > > dB - depending on the frequency band of operation, the output of the amp may vary from band to band,
> > > even if the driver power (DUO) is set to a certain level, e.g. 2.5 watts.
> > >
> > > 73, Klaus, DK3QN
> > >
> > >
> > >
> > > Am 13.04.2021 um 17:39 schrieb gcoxuk@... via groups.io:
> > >> Thanks Kevin.
> > >>
> > >> I've tried reducing the elad FMD output power with very small effect.
> > >> Forgive my ignorance, but what db setting effects this?
> > >> #
> > >>
> > >>
> > >>> On 13 Apr 2021, at 15:53, Kevin Larcombe <kevlarcombe@...> wrote:
> > >>>
> > >>> #
> > >>> Hi Geoff,
> > >>>
> > >>> You can reduce the drive from the radio, (I assume you are using the Duo) or in the menu on the DUO ART you can select attenuation of 2, 3 & 5dB (from my memory)
> > >>>
> > >>> My Duo/ART and all my radios are packed away at present during the shack rebuild, so sorry I can't look and tell you which menu. It easy to find in the manual though. (you can also set it  per band in the profiles)
> > >>>
> > >>> Regards
> > >>>
> > >>> Kevin
> > >>>
> > >>> From: EladSDR@groups.io <EladSDR@groups.io> on behalf of gcoxuk@... via groups.io <gcoxuk@...>
> > >>> Sent: 13 April 2021 00:06
> > >>> To: EladSDR@groups.io <EladSDR@groups.io>
> > >>> Subject: [EladSDR] Elad DUO ART 120 - How to select power setting?
> > >>>
> > >>> Greetings,
> > >>>
> > >>> I'm a novice doing the learning curve to my Duo Art set.  Ummm nothing much in the ops manual about output except ~5w in yeilds ~120w.  Nothing is said about its response to lesser input power to reduce output power.
> > >>>
> > >>> Am I missing something or is this a ~120w output only???
> > >>>
> > >>> Thanks in advance.
> > >>> Geoff
> > >>> Stansted UK
> > >>>
> > >>>
> > >>>
> > >>>
> > >>>
> > >
> > >


> >

> --
> Ir. T.W.H. Fockens
> Kieftweg 1
> 7165BR Rietmolen

> Onze democratie is gebaat bij een kiesdrempel.







>

--
Ir. T.W.H. Fockens
Kieftweg 1
7165BR Rietmolen

Onze democratie is gebaat bij een kiesdrempel.







-- 
Neil
http://g4dbn.uk


Klaus Brosche
 

Hi Koos,

Thanks for your comments.

And just a side note: I have never installed an ALC feedback voltage
line from the PA to the TRX during my ham radio lifetime
which is now more than 50 years ;-)

The possible "problems" with ALC are not only related to the co-operation
between an Amp and its Driver/TRX.

They quite often are intrinsic to the TRX ALC itself!

Effects as "ALC overshoot", which survived almost decades before getting
finally eliminated by a manufacturer.

Reason is that manufacturers most of the time sort of re-used parts of
a TRX design as a "building block" already there and existing and thus
the issues extended into their next generation of radios, and the next...

If you ever used one of these "ALC overshooter" radios, which in reality
are "ALC undershooters", my experience is that the Power Amp has no
way of correcting such TRX behavior, no matter how "good" or "bad"
its ALC circuitry is designed! It's just too late in the TRX to PA chain to
correct this.

All of the famous 3 (IKY) brands had issues with "ALC overshoot" in their
TRX product lines for years and across their platforms.

The web was full of people complaining about tube damage caused by
"spiky" TRXs, especially with high gain Grid-driven Tetrode Amps even
though they had the ALC connected between PA and TRX.
Driven with a 2x or more RF power spike relative to what the Amp Grid
can tolerate, these tubes go south in milliSeconds.

For those who are not familiar with this matter:

Imagine an Power Amp that needs max. Drive of 40 to 50 watts, typical
for a Grid driven ceramic Tetrode Amp or low drive power MosFET/LDMos
Amps.

Then you set your TRX power output to 40 watts, e.g.
Keying your TRX you will see a settled output power of 40 watts.
What you will quite likely not see, is, that there is a very brief full power
(or more) "spike" in power that is present for a few milliSeconds until
the output power is "corrected" to the selected level by the TRX internal
ALC.

Game over!

Klaus, DK3QN




Am 14.04.2021 um 17:26 schrieb T.W.H. Fockens:

Hello Chris and Klaus,

Of course the ALC circuit needs to be well-designed. Overshoot is not
neccessarely.

The rise time of the driving signal is always limited by the filter
bandwidth of the SSB filter, or equivalent filtering in the software.
That means that the risetime is about the inverse of the bandwidth. It
is not difficult to design the ALC circuit so that it controlls the
feedback in time. What helps is that there should not be a hard limit,
but a partly soft control range.
I see that the PA that I use has a very soft control behaviour. That
means I can do everything that is needed in the exciter.

Second point is that the fall-time of the ALC must be long: 10 seconds
or more.

It goes wrong in those situations wherein people try to combine the
compressor working with the ALC: you should not do that.

A speech compressor should be designed according different design
philosophy, using a logaritmic detector and fast fall-back.

I can really advise you to study the book "Single Sideband Systems and
Circuits, Ed. II" from Sabin and Schoenike, indeed old Collins people.

Of course, you can fine tune the gain of the exciter and amount of drive
by hand. For digital modes that works fine, the only problem is you keep
controlling it on and on, and forget it at crucial moments.

For phone there are two extra problem:
1. The output from the microphone is not constant, but varying by the
way you speak, the distance between your mouth and the microphone, etc.
So your output from the exciter varies. You could think of an
speechcompressor or limitter, but that has the next problem:

2. the amplitude of the SSB modulated signal is not proportional with
the amplitude of the complicated microphone audio. So using an audio
speechprocessor, or even an audio limitter, is not enough to limit the
SSB signal correctly. See above mentioned book. 2.

Helas, I see very often amateur designs of exciters without any
amplitude controlling...

I see also this: For Elad and the other digital boys there is a penalty
for using an ALC circuit: you need an extra ADC to digitize the ALC
voltage, and feed the data back into the DSP software. This complicates
the hardware as well as the software. And so the costs. But be open
about that.

One thing is absolute sure for me: A PA without an ALC output, I would
never buy, and I find it a pity that the FDM-DUO has no ALC input.

Koos
PA0KDF


On 14 Apr, Chris Bartram <chris@chris-bartram.co.uk> wrote:
I'm sorry Koos, I'm afraid the misconception is yours.
In a linear transmitter system, it is always to better to match the
output level of a linear transmitter to that required to drive a
subsequent amplifier within its linear power input range. If you are
seeing ALC operation every time you talk, you are adding to the
non-linearity of the system, and probably provoking splatter!
The use of ALC came about in the days of tube-based transmitters - I
blame Collins Radio! - when the gain of the transmitter strip was
unpredictable due to device aging and other effects. An automatic gain
control loop had to be implemented to counter the gain changes. This
came to be used by radio amateurs as a de facto speech processing process.
The problem with using a gain control loop is that it takes time to
respond. In that time the overall gain is usually sufficient to cause
the PA to saturate, resulting in transient excess intermodulation
components being generated ie. splatter! Measuring the transmitter with
ALC in operation with a two-tone test doesn't show this effect, as the
loop has stabilised. With the right test equipment, it's instructive to
do this.
With modern digital transmitter design, such as that employed in the
ELAD FDM-DUO, the output level is essentially determined by the DAC
actually generating the signal. The effects of gain changes in a well
designed solid-state amplifier chain are small enough to eliminate any
need for ALC.
73
Chris G4DGU
No, that is a misconception. The ALC prevents you from overdriving your
PA, and so preventing IM and splatter. It also controls the power match
between the output of your driving trx and the PA.

This is a serious aspect of transmitter design and should never be
neglected.

Koos PA0KDF


Kevin Larcombe
 

I have never used ALC with a linear amplifier either, I prefer to run everything well within its rating. With the Elad I generally run the FDM-DUO at 4w and have 2dB of attenuation on the ART120, admittedly I haven't undertaken any measurements.

At one place of work, I saw an interesting ALC fault with a linear amplifier when used in a configuration with a manpack radio. The radio in this configuration was powered via a battery pack, and it worked perfectly until there was a change of manufacturer and technology for the battery. We found that the replacement battery pack was able to supply a lot more instantaneous current compared with the original battery pack with which the ALC worked satisfactory.

Kevin GW0PUH


From: EladSDR@groups.io <EladSDR@groups.io> on behalf of Klaus Brosche <klaus.brosche@...>
Sent: 14 April 2021 18:29
To: EladSDR@groups.io <EladSDR@groups.io>
Subject: Re: [EladSDR] Elad DUO ART 120 - How to select power setting?
 
Hi Koos,

Thanks for your comments.

And just a side note: I have never installed an ALC feedback voltage
line from the PA to the TRX during my ham radio lifetime
which is now more than 50 years ;-)

The possible "problems" with ALC are not only related to the co-operation
between an Amp and its Driver/TRX.

They quite often are intrinsic to the TRX ALC itself!

Effects as "ALC overshoot", which survived almost decades before getting
finally eliminated by a manufacturer.

Reason is that manufacturers most of the time sort of re-used parts of
a TRX design as a "building block" already there and existing and thus
the issues extended into their next generation of radios, and the next...

If you ever used one of these "ALC overshooter" radios, which in reality
are "ALC undershooters", my experience is that the Power Amp has no
way of correcting such TRX behavior, no matter how "good" or "bad"
its ALC circuitry is designed! It's just too late in the TRX to PA chain to
correct this.

All of the famous 3 (IKY) brands had issues with "ALC overshoot" in their
TRX product lines for years and across their platforms.

The web was full of people complaining about tube damage caused by
"spiky" TRXs, especially with high gain Grid-driven Tetrode Amps even
though they had the ALC connected between PA and TRX.
Driven with a 2x or more RF power spike relative to what the Amp Grid
can tolerate, these tubes go south in milliSeconds.

For those who are not familiar with this matter:

Imagine an Power Amp that needs max. Drive of 40 to 50 watts, typical
for a Grid driven ceramic Tetrode Amp or low drive power MosFET/LDMos
Amps.

Then you set your TRX power output to 40 watts, e.g.
Keying your TRX you will see a settled output power of 40 watts.
What you will quite likely not see, is, that there is a very brief full
power
(or more) "spike" in power that is present for a few milliSeconds until
the output power is "corrected" to the selected level by the TRX internal
ALC.

Game over!

Klaus, DK3QN




Am 14.04.2021 um 17:26 schrieb T.W.H. Fockens:
> Hello Chris and Klaus,
>
> Of course the ALC circuit needs to be well-designed. Overshoot is not
> neccessarely.
>
> The rise time of the driving signal is always limited by the filter
> bandwidth of the SSB filter, or equivalent filtering in the software.
> That means that the risetime is about the inverse of the bandwidth. It
> is not difficult to design the ALC circuit so that it controlls the
> feedback in time. What helps is that there should not be a hard limit,
> but a partly soft control range.
> I see that the PA that I use has a very soft control behaviour. That
> means I can do everything that is needed in the exciter.
>
> Second point is that the fall-time of the ALC must be long: 10 seconds
> or more.
>
> It goes wrong in those situations wherein people try to combine the
> compressor working with the ALC: you should not do that.
>
> A speech compressor should be designed according different design
> philosophy, using a logaritmic detector and fast fall-back.
>
> I can really advise you to study the book "Single Sideband Systems and
> Circuits, Ed. II" from Sabin and Schoenike, indeed old Collins people.
>
> Of course, you can fine tune the gain of the exciter and amount of drive
> by hand. For digital modes that works fine, the only problem is you keep
> controlling it on and on, and forget it at crucial moments.
>
> For phone there are two extra problem:
> 1. The output from the microphone is not constant, but varying by the
> way you speak, the distance between your mouth and the microphone, etc.
> So your output from the exciter varies. You could think of an
> speechcompressor or limitter, but that has the next problem:
>
> 2. the amplitude of the SSB modulated signal is not proportional with
> the amplitude of the complicated microphone audio. So using an audio
> speechprocessor, or even an audio limitter, is not enough to limit the
> SSB signal correctly. See above mentioned book. 2.
>
> Helas, I see very often amateur designs of exciters without any
> amplitude controlling...
>
> I see also this: For Elad and the other digital boys there is a penalty
> for using an ALC circuit: you need an extra ADC to digitize the ALC
> voltage, and feed the data back into the DSP software. This complicates
> the hardware as well as the software. And so the costs. But be open
> about that.
>
> One thing is absolute sure for me: A PA without an ALC output, I would
> never buy, and I find it a pity that the FDM-DUO has no ALC input.
>
> Koos
> PA0KDF
>
>
> On 14 Apr, Chris Bartram <chris@...> wrote:
>> I'm sorry Koos, I'm afraid the misconception is yours.
>> In a linear transmitter system, it is always to better to match the
>> output level of a linear transmitter to that required to drive a
>> subsequent amplifier within its linear power input range. If you are
>> seeing ALC operation every time you talk, you are adding to the
>> non-linearity of the system, and probably provoking splatter!
>> The use of ALC came about in the days of tube-based transmitters - I
>> blame Collins Radio! - when the gain of the transmitter strip was
>> unpredictable due to device aging and other effects. An automatic gain
>> control loop had to be implemented to counter the gain changes. This
>> came to be used by radio amateurs as a de facto speech processing process.
>> The problem with using a gain control loop is that it takes time to
>> respond. In that time the overall gain is usually sufficient to cause
>> the PA to saturate, resulting in transient excess intermodulation
>> components being generated ie. splatter! Measuring the transmitter with
>> ALC in operation with a two-tone test doesn't show this effect, as the
>> loop has stabilised. With the right test equipment, it's instructive to
>> do this.
>> With modern digital transmitter design, such as that employed in the
>> ELAD FDM-DUO, the output level is essentially determined by the DAC
>> actually generating the signal. The effects of gain changes in a well
>> designed solid-state amplifier chain are small enough to eliminate any
>> need for ALC.
>> 73
>> Chris G4DGU
>
>>> No, that is a misconception. The ALC prevents you from overdriving your
>>> PA, and so preventing IM and splatter. It also controls the power match
>>> between the output of your driving trx and the PA.
>>>
>>> This is a serious aspect of transmitter design and should never be
>>> neglected.
>>>
>>> Koos PA0KDF








Simon
 

Hi all

For the record..all my homebrew amps have alc facility.
But i never use or ever will.only made into them because i could.
I have built into the amps an attenuator of suitable db so as NEVER to overdrive the amps. + gives rig perfect 50r in.( a bonus sometimes overlooked?)
The tube amp is just for the 100w rig so has one attenuator...(3db)
The ldmos amp has two attenuators of differing db depending upon rig input.ie elad / hl2 or 100w rig..( different input sockets..sma or 239 so one cannot by mistake wire up wrong rig.)

Simon g0zen


Klaus Brosche
 

Hi Simon,

Exactly, fully agreed.

The matter of producing a very clean SSB signal (or similar mode) for an SDR TRX is not so much related to the
traditional, old-school "ALC", which from its implementation is a second to third choice. At least imho.

With an SDR, it is much more related to the "pure signal/pre-distortion" technique.

A brief intro on the results of this technique can be found here:
https://sites.google.com/view/vk1hw/radios/anan-100d/puresignal

And that requires you to either set your TRX power in accordance with your Amps max needed driver power
or insert an RF power attenuator resistor into the input circuitry of your Power Amp.

Klaus, DK3QN



Am 14.04.2021 um 21:35 schrieb Simon:

Hi all

For the record..all my homebrew amps have alc facility.
But i never use or ever will.only made into them because i could.
I have built into the amps an attenuator of suitable db so as NEVER to overdrive the amps. + gives rig perfect 50r in.( a bonus sometimes overlooked?)
The tube amp is just for the 100w rig so has one attenuator...(3db)
The ldmos amp has two attenuators of differing db depending upon rig input.ie elad / hl2 or 100w rig..( different input sockets..sma or 239 so one cannot by mistake wire up wrong rig.)

Simon g0zen