Topics

FDM-DUO ALC


Tony EI8JK
 

Am I right in thinking that it's not possible to access the Duo's ALC?
In fact I can't find any reference to ALC in any Elad documentation.
Or is it a case of carefully setting the Windows audio drive levels, which is fraught with problems as every Windows update seems to reset the audio out to whatever MS thinks fit.
Thanks
Tony, EI8JK


 

Hi Tony

you are correct on both accounts, No alc meter, and yes u would need to adjust windows drive .

I asked the same question couple weeks ago, and was given a workaround for wsjtx, 

if u go back a few pages on forum, you will find the question from me
andbthe answer from Neil

regards

Iain


Tony EI8JK
 

Thanks for that Iain.
Not really the answer I had hoped for ;-)
What I wanted was an ALC connection to run/control a non-Elad linear.
I thought that was a non runner though, so not unexpected.
Regards & 73
Tony...


On 04/11/2019 16:50, MM6IXE wrote:
Hi Tony

you are correct on both accounts, No alc meter, and yes u would need to adjust windows drive .

I asked the same question couple weeks ago, and was given a workaround for wsjtx, 

if u go back a few pages on forum, you will find the question from me
andbthe answer from Neil

regards

Iain


Neil Smith G4DBN
 

Hi Tony, I think the point is that ALC should have been left to wither on the vine back in the days of the thermionic valve, and we should be running linear systems and controlling the levels and gains to achieve the output level required.  Sadly, somewhere along the way, Microsoft decided they knew better, and that wantonly changing levels was an acceptable way to behave. (Pro-tip:  it is not)

ALC is definitely the spawn of Beelzebub though, and should have no place in any radio made since 1980.

Neil G4DBN


On 04/11/2019 16:59, Tony EI8JK wrote:
Thanks for that Iain.
Not really the answer I had hoped for ;-)
What I wanted was an ALC connection to run/control a non-Elad linear.
I thought that was a non runner though, so not unexpected.
Regards & 73
Tony...


On 04/11/2019 16:50, MM6IXE wrote:
Hi Tony

you are correct on both accounts, No alc meter, and yes u would need to adjust windows drive .

I asked the same question couple weeks ago, and was given a workaround for wsjtx, 

if u go back a few pages on forum, you will find the question from me
andbthe answer from Neil

regards

Iain

-- 
Neil
<a href="http://g4dbn.uk/"><small>g4dbn.uk</small></a>


Klaus Brosche, DK3QN <dk3qn@...>
 

Might be a bit 'blunt', excuse me for that, but IMHO ALC-feedback
from an Amp into an Exciter/TRX is just about the very last thing
I would consider to make an TRX/Amp combination 'work'.

It's a backward feedback loop with all kinds of implications
included!

I'd rather set the DUOs RF output level such that the Final Amplifier
is running within it's desired linear amplification range/IMD range.

You do not need a high-spec SDR for checking the quality of your
transmitted signal. A simple RTL-stick will do, as long as you'll keep
it's RF input level (monitoring your TRX signal) within the units
dynamic range.

You'll then literally 'see' (waterfall) any changes of TRX drive power
into the Amp and what this does to the quality of your transmitted
RF signal.

I have done this kind of 'exercise' on the air with quite a couple of
my local club mates and they all were quite surprised in the end
about what they've sent-out before and after this exercise.
'After' = a non-offensive RF signal transmitted w/o losing any
signal strength at the receivers side.

Klaus, DK3QN


Am 04.11.2019 um 17:59 schrieb Tony EI8JK:

Thanks for that Iain.
Not really the answer I had hoped for ;-)
What I wanted was an ALC connection to run/control a non-Elad linear.
I thought that was a non runner though, so not unexpected.
Regards & 73
Tony...


On 04/11/2019 16:50, MM6IXE wrote:
Hi Tony

you are correct on both accounts, No alc meter, and yes u would need to adjust windows drive .

I asked the same question couple weeks ago, and was given a workaround for wsjtx, 

if u go back a few pages on forum, you will find the question from me
andbthe answer from Neil

regards

Iain



Josh Murray <josh@...>
 

My Mentor/Elmer told me not to bother connecting the ALC line, so I never have.  Always had a nice clean signal through not over-driving the amp and taking care to ask for regular feedback on my received signal quality.

Josh de M0JMO


On Mon, 4 Nov 2019 at 19:51, Klaus Brosche, DK3QN <dk3qn@...> wrote:
Might be a bit 'blunt', excuse me for that, but IMHO ALC-feedback
from an Amp into an Exciter/TRX is just about the very last thing
I would consider to make an TRX/Amp combination 'work'.

It's a backward feedback loop with all kinds of implications
included!

I'd rather set the DUOs RF output level such that the Final Amplifier
is running within it's desired linear amplification range/IMD range.

You do not need a high-spec SDR for checking the quality of your
transmitted signal. A simple RTL-stick will do, as long as you'll keep
it's RF input level (monitoring your TRX signal) within the units
dynamic range.

You'll then literally 'see' (waterfall) any changes of TRX drive power
into the Amp and what this does to the quality of your transmitted
RF signal.

I have done this kind of 'exercise' on the air with quite a couple of
my local club mates and they all were quite surprised in the end
about what they've sent-out before and after this exercise.
'After' = a non-offensive RF signal transmitted w/o losing any
signal strength at the receivers side.

Klaus, DK3QN


Am 04.11.2019 um 17:59 schrieb Tony EI8JK:
Thanks for that Iain.
Not really the answer I had hoped for ;-)
What I wanted was an ALC connection to run/control a non-Elad linear.
I thought that was a non runner though, so not unexpected.
Regards & 73
Tony...


On 04/11/2019 16:50, MM6IXE wrote:
Hi Tony

you are correct on both accounts, No alc meter, and yes u would need to adjust windows drive .

I asked the same question couple weeks ago, and was given a workaround for wsjtx, 

if u go back a few pages on forum, you will find the question from me
andbthe answer from Neil

regards

Iain


--
Many Thanks

Best Regards

Josh Murray


 

Your welcome Tony, maybe their is another way, lots of smart people on here
Maybe someone can help u out
Good luck
Iain

On 4 Nov 2019, at 16:59, Tony EI8JK <ei8jk@...> wrote:

 Thanks for that Iain.
Not really the answer I had hoped for ;-)
What I wanted was an ALC connection to run/control a non-Elad linear.
I thought that was a non runner though, so not unexpected.
Regards & 73
Tony...


On 04/11/2019 16:50, MM6IXE wrote:
Hi Tony

you are correct on both accounts, No alc meter, and yes u would need to adjust windows drive .

I asked the same question couple weeks ago, and was given a workaround for wsjtx, 

if u go back a few pages on forum, you will find the question from me
andbthe answer from Neil

regards

Iain


G8DQX list
 

Tony,

it may help to think of it this way. A Duo does not have ALC, nor does it have a slow-start heater supply, nor a thermionic valve output stage. The traditional reasons for needing ALC in a transceiver no longer apply. Nor do the reasons which required back-coupling of a so-called ALC voltage from an external amplifier to a transceiver.

A digital transceiver, such as the Duo, which generates RF directly from a D/A converter at the output frequency can, in essence, run open-loop, because the gain of the PA stage(s) post D/A is relatively small, in dB terms, and relatively unvarying. Thus any needed control may be applied in the DSP, rather than the analogue, domain. A similar argument applies if the transceiver drives an external amplifier of modern, solid-state, design.

So why did we ever use ALC? It was a bodge which worked using '60's technology. It allowed for both a degree of speech compression and avoidance of overdriving PAs (or external amplifiers). But note that speech compression and avoidance of overdriving are incompatible given a common mechanism. How do we know that it was a bodge? Just try finding a specification for what a given ALC voltage means, in terms of gain reduction or power output or even IMD. It's not there, merely a phono socket labelled ALC, but more accurately identified by Neil earlier!

The 2018 ARRL handbook puts it more prosaically in section 14.1.2:

"…Since we have absolute control over the sig-
nal level by altering samples in the radio, it
is generally better to set a maximum power
out in the radio and allow the signal chain to
make the appropriate adjustments than to rely
on ALC to adjust the levels when they are too
high for an amplifier.
"An ALC subsystem that is too active can
modulate the transmit signal. This results in
distortion that could be prevented by adjusting
the proper levels in the signal chain to start
with. This is why many digital mode guide-
lines specify that the ALC system be switched
off — to avoid unintentional distortion of the
signal by power control systems."
73,

Robin, G8DQX


On 04/11/2019 12:30, Tony EI8JK wrote:
Am I right in thinking that it's not possible to access the Duo's ALC?
In fact I can't find any reference to ALC in any Elad documentation.
Or is it a case of carefully setting the Windows audio drive levels, which is fraught with problems as every Windows update seems to reset the audio out to whatever MS thinks fit.
Thanks
Tony, EI8JK


Paul Jones
 

Same as Josh here, I’ve never run ALC on any of my radios, and also had/have a clean signal, driving the Duo into the DuoArt never a problem, and then using he DuoART to drive my old Alpha78, neve a problem, running 1500w, if you put a clean signal out of the Duo you should not have any need for it, I’ve run WSJT-X here with the Duo and Duo/DuoART and not had any complaints…

 

Tony: What are you trying to drive

 

Have a Radiolutionary Day!
Paul

--

Paul Jones - Elad USA Sales & Technical Support (USA)
emailsigfile
FDM-Duo, Duo-Art, FDM-DUOR,  FDM-S3, FDM-S2, FDM-S2, FDM-SW2, T-Mate

Visit http://www.eladit.com for the full range of Elad Products or USA Sales : https://shop.elad-usa.com/

Email Support Group - https://groups.io/g/EladSDR

Sales Phone: 312.320.8160

Support Email: support@... Sales Email: sales@...
Personal Email: Paul@...
 
 

 

 

From: EladSDR@groups.io <EladSDR@groups.io> On Behalf Of Josh Murray
Sent: Monday, November 4, 2019 15:23
To: EladSDR@groups.io
Subject: Re: [EladSDR] FDM-DUO ALC

 

My Mentor/Elmer told me not to bother connecting the ALC line, so I never have.  Always had a nice clean signal through not over-driving the amp and taking care to ask for regular feedback on my received signal quality.

 

Josh de M0JMO

 

 

On Mon, 4 Nov 2019 at 19:51, Klaus Brosche, DK3QN <dk3qn@...> wrote:

Might be a bit 'blunt', excuse me for that, but IMHO ALC-feedback
from an Amp into an Exciter/TRX is just about the very last thing
I would consider to make an TRX/Amp combination 'work'.

 

It's a backward feedback loop with all kinds of implications
included!

 

I'd rather set the DUOs RF output level such that the Final Amplifier
is running within it's desired linear amplification range/IMD range.

You do not need a high-spec SDR for checking the quality of your
transmitted signal. A simple RTL-stick will do, as long as you'll keep
it's RF input level (monitoring your TRX signal) within the units
dynamic range.

 

You'll then literally 'see' (waterfall) any changes of TRX drive power
into the Amp and what this does to the quality of your transmitted
RF signal.

 

I have done this kind of 'exercise' on the air with quite a couple of
my local club mates and they all were quite surprised in the end
about what they've sent-out before and after this exercise.
'After' = a non-offensive RF signal transmitted w/o losing any
signal strength at the receivers side.

 

Klaus, DK3QN

 

 

Am 04.11.2019 um 17:59 schrieb Tony EI8JK:

Thanks for that Iain.
Not really the answer I had hoped for ;-)
What I wanted was an ALC connection to run/control a non-Elad linear.
I thought that was a non runner though, so not unexpected.
Regards & 73
Tony...

On 04/11/2019 16:50, MM6IXE wrote:

Hi Tony

you are correct on both accounts, No alc meter, and yes u would need to adjust windows drive .

I asked the same question couple weeks ago, and was given a workaround for wsjtx, 

if u go back a few pages on forum, you will find the question from me
andbthe answer from Neil

regards

Iain

 

 

--

Many Thanks

Best Regards

Josh Murray


Tony EI8JK
 

Thanks for all the replies and advice, guys.
All noted and I have most definitely learned something by asking the question.
That's the beauty of this forum.
73,
Tony.

On 04/11/2019 22:17, G8DQX list wrote:
Tony,

it may help to think of it this way. A Duo does not have ALC, nor does it have a slow-start heater supply, nor a thermionic valve output stage. The traditional reasons for needing ALC in a transceiver no longer apply. Nor do the reasons which required back-coupling of a so-called ALC voltage from an external amplifier to a transceiver.

A digital transceiver, such as the Duo, which generates RF directly from a D/A converter at the output frequency can, in essence, run open-loop, because the gain of the PA stage(s) post D/A is relatively small, in dB terms, and relatively unvarying. Thus any needed control may be applied in the DSP, rather than the analogue, domain. A similar argument applies if the transceiver drives an external amplifier of modern, solid-state, design.

So why did we ever use ALC? It was a bodge which worked using '60's technology. It allowed for both a degree of speech compression and avoidance of overdriving PAs (or external amplifiers). But note that speech compression and avoidance of overdriving are incompatible given a common mechanism. How do we know that it was a bodge? Just try finding a specification for what a given ALC voltage means, in terms of gain reduction or power output or even IMD. It's not there, merely a phono socket labelled ALC, but more accurately identified by Neil earlier!

The 2018 ARRL handbook puts it more prosaically in section 14.1.2:

"…Since we have absolute control over the sig-
nal level by altering samples in the radio, it
is generally better to set a maximum power
out in the radio and allow the signal chain to
make the appropriate adjustments than to rely
on ALC to adjust the levels when they are too
high for an amplifier.
"An ALC subsystem that is too active can
modulate the transmit signal. This results in
distortion that could be prevented by adjusting
the proper levels in the signal chain to start
with. This is why many digital mode guide-
lines specify that the ALC system be switched
off — to avoid unintentional distortion of the
signal by power control systems."
73,

Robin, G8DQX


On 04/11/2019 12:30, Tony EI8JK wrote:
Am I right in thinking that it's not possible to access the Duo's ALC?
In fact I can't find any reference to ALC in any Elad documentation.
Or is it a case of carefully setting the Windows audio drive levels, which is fraught with problems as every Windows update seems to reset the audio out to whatever MS thinks fit.
Thanks
Tony, EI8JK