Topics

Dirty Transmitters

Bob McGraw - K4TAX
 

The nice thing,  the K3S which contains the new synthesizers and a K3 updated with new synthesizers will be cleaner due to lower phase noise and amplitude noise.   Otherwise, lower composite noise which does and will affect any receiver.   Receiver filtering will not reduce the type of  noise which exists in the passband of the receiver.    If the transmitter is dirty, everybody suffers.   It it is fed through an amplifier, everybody suffers more.

Please read Rob Sherwood's article in QST, November 2019, pp 38 - 41.  "It's Time to Clean Up our Transmitters".   You may discover that the wonderful radio you just purchased may not be so wonderful after all. 

73

Bob, K4TAX


On 11/3/2019 11:32 AM, Wes wrote:
If TX IMD is the issue, K3 and K3S transmitters are a real mixed bag.  My old K3 at 30 watts is fantastic, with IMD at all frequencies better than -40 dBc (ARRL method).  The same radio at 10W is the worst of my two radios, except at 24 MHz where the K3 and K3S tie at -22 dBc.

It's been hard to keep up with these measurements since the KLPA3A in the K3S has been replaced twice and the KPA3A is IIRC, on the fourth version.

Wes  N7WS



On 11/3/2019 8:16 AM, Martin Sole wrote:
I suspect the quality of the transmitter particularly with regard to its composite noise spectrum to be a large player. Some radios with high end receiver performance have rudimentary (I'm being kind) transmitter composite noise performance.

See what NK7Z, NC0B and K9YC have written about this.


Martin, HS0ZED



On 03/11/2019 21:30, Mark Morin wrote:
My experience is that the type of rig does make a difference for close coexistence. We’ve found on DxPeditions that an upgraded K3 with KPA500 and a Kenwood TS-590s also with KPA500, can coexist quite well with antennas about 300 ft apart. On most bands, we can operate SSB and CW simultaneously with tolerable QRM. Other times we have tried different high-end rigs in similar setup and found that opposite end of same-band operation was nearly impossible due to QRM. I suspect it’s mostly the receivers that makes the difference. 

Mark VA2MM

dalej
 

I should think or believe my K3/K3s is pretty clean at 35 watts into my KPA500?

Dale, K9VUJ


On 03, Nov 2019, at 13:23, Bob McGraw - K4TAX <rmcgraw@...> wrote:

The nice thing,  the K3S which contains the new synthesizers and a K3 updated with new synthesizers will be cleaner due to lower phase noise and amplitude noise.   Otherwise, lower composite noise which does and will affect any receiver.   Receiver filtering will not reduce the type of  noise which exists in the passband of the receiver.    If the transmitter is dirty, everybody suffers.   It it is fed through an amplifier, everybody suffers more.

Please read Rob Sherwood's article in QST, November 2019, pp 38 - 41.  "It's Time to Clean Up our Transmitters".   You may discover that the wonderful radio you just purchased may not be so wonderful after all. 

73

Bob, K4TAX


On 11/3/2019 11:32 AM, Wes wrote:
If TX IMD is the issue, K3 and K3S transmitters are a real mixed bag.  My old K3 at 30 watts is fantastic, with IMD at all frequencies better than -40 dBc (ARRL method).  The same radio at 10W is the worst of my two radios, except at 24 MHz where the K3 and K3S tie at -22 dBc.

It's been hard to keep up with these measurements since the KLPA3A in the K3S has been replaced twice and the KPA3A is IIRC, on the fourth version.

Wes  N7WS



On 11/3/2019 8:16 AM, Martin Sole wrote:
I suspect the quality of the transmitter particularly with regard to its composite noise spectrum to be a large player. Some radios with high end receiver performance have rudimentary (I'm being kind) transmitter composite noise performance.

See what NK7Z, NC0B and K9YC have written about this.


Martin, HS0ZED



On 03/11/2019 21:30, Mark Morin wrote:
My experience is that the type of rig does make a difference for close coexistence. We’ve found on DxPeditions that an upgraded K3 with KPA500 and a Kenwood TS-590s also with KPA500, can coexist quite well with antennas about 300 ft apart. On most bands, we can operate SSB and CW simultaneously with tolerable QRM. Other times we have tried different high-end rigs in similar setup and found that opposite end of same-band operation was nearly impossible due to QRM. I suspect it’s mostly the receivers that makes the difference. 

Mark VA2MM


Bob McGraw - K4TAX
 

In my case, my K3S at 35 watts will overdrive my KPA500.   In fact 19 to 22 watts produces 500 watts output on all bands.   Your 35 watts may be clean, but I doubt the KPA500 driven with 35 watts is clean.    Just my experience and measurements with my radio and amp.

73

Bob, K4TAX

On 11/3/2019 4:21 PM, dalej via Groups.Io wrote:
I should think or believe my K3/K3s is pretty clean at 35 watts into my KPA500?

Dale, K9VUJ


On 03, Nov 2019, at 13:23, Bob McGraw - K4TAX <rmcgraw@...> wrote:

The nice thing,  the K3S which contains the new synthesizers and a K3 updated with new synthesizers will be cleaner due to lower phase noise and amplitude noise.   Otherwise, lower composite noise which does and will affect any receiver.   Receiver filtering will not reduce the type of  noise which exists in the passband of the receiver.    If the transmitter is dirty, everybody suffers.   It it is fed through an amplifier, everybody suffers more.

Please read Rob Sherwood's article in QST, November 2019, pp 38 - 41.  "It's Time to Clean Up our Transmitters".   You may discover that the wonderful radio you just purchased may not be so wonderful after all. 

73

Bob, K4TAX


On 11/3/2019 11:32 AM, Wes wrote:
If TX IMD is the issue, K3 and K3S transmitters are a real mixed bag.  My old K3 at 30 watts is fantastic, with IMD at all frequencies better than -40 dBc (ARRL method).  The same radio at 10W is the worst of my two radios, except at 24 MHz where the K3 and K3S tie at -22 dBc.

It's been hard to keep up with these measurements since the KLPA3A in the K3S has been replaced twice and the KPA3A is IIRC, on the fourth version.

Wes  N7WS



On 11/3/2019 8:16 AM, Martin Sole wrote:
I suspect the quality of the transmitter particularly with regard to its composite noise spectrum to be a large player. Some radios with high end receiver performance have rudimentary (I'm being kind) transmitter composite noise performance.

See what NK7Z, NC0B and K9YC have written about this.


Martin, HS0ZED



On 03/11/2019 21:30, Mark Morin wrote:
My experience is that the type of rig does make a difference for close coexistence. We’ve found on DxPeditions that an upgraded K3 with KPA500 and a Kenwood TS-590s also with KPA500, can coexist quite well with antennas about 300 ft apart. On most bands, we can operate SSB and CW simultaneously with tolerable QRM. Other times we have tried different high-end rigs in similar setup and found that opposite end of same-band operation was nearly impossible due to QRM. I suspect it’s mostly the receivers that makes the difference. 

Mark VA2MM


dalej
 

On the 75 meter band it takes fewer watts to drive the KPA500 to 500 watts, much fewer.  On 20 the amp needs 35 to drive it to 500.  I use a three element SteppIR  on the upper bands.  My KPA is an early version, maybe that’s the difference.  

Dale, K9VUJ



On 03, Nov 2019, at 18:33, Bob McGraw - K4TAX <rmcgraw@...> wrote:

In my case, my K3S at 35 watts will overdrive my KPA500.   In fact 19 to 22 watts produces 500 watts output on all bands.   Your 35 watts may be clean, but I doubt the KPA500 driven with 35 watts is clean.    Just my experience and measurements with my radio and amp.

73

Bob, K4TAX

On 11/3/2019 4:21 PM, dalej via Groups.Io wrote:
I should think or believe my K3/K3s is pretty clean at 35 watts into my KPA500?

Dale, K9VUJ


On 03, Nov 2019, at 13:23, Bob McGraw - K4TAX <rmcgraw@...> wrote:

The nice thing,  the K3S which contains the new synthesizers and a K3 updated with new synthesizers will be cleaner due to lower phase noise and amplitude noise.   Otherwise, lower composite noise which does and will affect any receiver.   Receiver filtering will not reduce the type of  noise which exists in the passband of the receiver.    If the transmitter is dirty, everybody suffers.   It it is fed through an amplifier, everybody suffers more.

Please read Rob Sherwood's article in QST, November 2019, pp 38 - 41.  "It's Time to Clean Up our Transmitters".   You may discover that the wonderful radio you just purchased may not be so wonderful after all. 

73

Bob, K4TAX


On 11/3/2019 11:32 AM, Wes wrote:
If TX IMD is the issue, K3 and K3S transmitters are a real mixed bag.  My old K3 at 30 watts is fantastic, with IMD at all frequencies better than -40 dBc (ARRL method).  The same radio at 10W is the worst of my two radios, except at 24 MHz where the K3 and K3S tie at -22 dBc.

It's been hard to keep up with these measurements since the KLPA3A in the K3S has been replaced twice and the KPA3A is IIRC, on the fourth version.

Wes  N7WS



On 11/3/2019 8:16 AM, Martin Sole wrote:
I suspect the quality of the transmitter particularly with regard to its composite noise spectrum to be a large player. Some radios with high end receiver performance have rudimentary (I'm being kind) transmitter composite noise performance.

See what NK7Z, NC0B and K9YC have written about this.


Martin, HS0ZED



On 03/11/2019 21:30, Mark Morin wrote:
My experience is that the type of rig does make a difference for close coexistence. We’ve found on DxPeditions that an upgraded K3 with KPA500 and a Kenwood TS-590s also with KPA500, can coexist quite well with antennas about 300 ft apart. On most bands, we can operate SSB and CW simultaneously with tolerable QRM. Other times we have tried different high-end rigs in similar setup and found that opposite end of same-band operation was nearly impossible due to QRM. I suspect it’s mostly the receivers that makes the difference. 

Mark VA2MM



Drew Vonada-Smith K3PA
 

The K3 has nice low phase noise, but no SS transmitter running at 12 V has great IMD.  So no, the K3 is not an especially clean TX on SSB.  By no means the worst either, of course.

73,

Drew K3PA

Joe Subich, W4TV
 

On 2019-11-04 12:06 PM, Drew Vonada-Smith K3PA wrote:
The K3 has nice low phase noise, but no SS transmitter running at 12 V has great IMD.
The issue is that 12V transistors are simply not capable of providing
the "clean" voltage swings necessary to generate 100 - 120W peak power.

A typical transistor/FET has a series output impedance of around 1 - 1.5
Ohms. Thus if the peak current is ~10A per device, the transistor is
operating from cut-off to saturated - with the unavoidable distortion
(clipping/saturation) at each end of that range.

Simply put, insistence on more than about 60 W PEP from a pair of 12V
devices is *asking for IMD* and "precorrection" only masks that issue.
Equipment designers should give up on 12V devices for "base station"
radios and go to 48V devices - even at 200 W PEP output levels, They should stick to 60 W output for 12V devices. 60 W output level is more
than enough to drive an amplifier in the KPA-500 class to rated output
and close (if not sufficient) for even a KPA-1500.

Redesigned with bias levels and transformers optimized for the lower
power levels, the K3/K3S could exhibit *much* - at least 10 dB - better
IMD at 50 - 60 W PEP output (although efficiency would probably suffer
for those who just absolutely need to run the rig from a battery pack
on a picnic table).

73,

... Joe, W4TV


On 2019-11-04 12:06 PM, Drew Vonada-Smith K3PA wrote:
The K3 has nice low phase noise, but no SS transmitter running at 12 V has great IMD.  So no, the K3 is not an especially clean TX on SSB.  By no means the worst either, of course.
73,
Drew K3PA

Bob Novas
 

Is there any difference between 12V and 13.8V or 14.1V, e.g., does it matter if you’re running off a run down battery?  Should you run the voltage up to the max if you’re running on AC?  Just curious if a volt or two makes a significant difference. If it does, maybe it’d be worth running as high a voltage as you can safely. Bob - W3DK

 

From: Elecraft-K3@groups.io [mailto:Elecraft-K3@groups.io] On Behalf Of Drew Vonada-Smith K3PA
Sent: Monday, November 04, 2019 12:07 PM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] Dirty Transmitters

 

The K3 has nice low phase noise, but no SS transmitter running at 12 V has great IMD.  So no, the K3 is not an especially clean TX on SSB.  By no means the worst either, of course.

73,

Drew K3PA

Roger N1RJ
 

Why not just parallel two 50 watt modules? A common technique in
high power amplifiers.

73, Roger

On 11/4/2019 3:27 PM, Joe Subich, W4TV wrote:
On 2019-11-04 12:06 PM, Drew Vonada-Smith K3PA wrote:
The K3 has nice low phase noise, but no SS transmitter running at 12 V has great IMD.
The issue is that 12V transistors are simply not capable of providing
the "clean" voltage swings necessary to generate 100 - 120W peak power.
A typical transistor/FET has a series output impedance of around 1 - 1.5
Ohms. Thus if the peak current is ~10A per device, the transistor is
operating from cut-off to saturated - with the unavoidable distortion
(clipping/saturation) at each end of that range.
Simply put, insistence on more than about 60 W PEP from a pair of 12V
devices is *asking for IMD* and "precorrection" only masks that issue.
Equipment designers should give up on 12V devices for "base station"
radios and go to 48V devices - even at 200 W PEP output levels, They should stick to 60 W output for 12V devices. 60 W output level is more
than enough to drive an amplifier in the KPA-500 class to rated output
and close (if not sufficient) for even a KPA-1500.
Redesigned with bias levels and transformers optimized for the lower
power levels, the K3/K3S could exhibit *much* - at least 10 dB - better
IMD at 50 - 60 W PEP output (although efficiency would probably suffer
for those who just absolutely need to run the rig from a battery pack
on a picnic table).
73,
... Joe, W4TV
On 2019-11-04 12:06 PM, Drew Vonada-Smith K3PA wrote:
The K3 has nice low phase noise, but no SS transmitter running at 12 V has great IMD. So no, the K3 is not an especially clean TX on SSB. By no means the worst either, of course.

73,

Drew K3PA

 

Amplifier "headroom" increases with supply voltage, so the answer to all four of your questions is Yes.

73,
Wayne
N6KR

On Nov 4, 2019, at 9:53 AM, Bob Novas via Groups.Io <bob.novas=verizon.net@groups.io> wrote:

Is there any difference between 12V and 13.8V or 14.1V, e.g., does it matter if you’re running off a run down battery? Should you run the voltage up to the max if you’re running on AC? Just curious if a volt or two makes a significant difference. If it does, maybe it’d be worth running as high a voltage as you can safely. Bob - W3DK

From: Elecraft-K3@groups.io [mailto:Elecraft-K3@groups.io] On Behalf Of Drew Vonada-Smith K3PA
Sent: Monday, November 04, 2019 12:07 PM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] Dirty Transmitters

The K3 has nice low phase noise, but no SS transmitter running at 12 V has great IMD. So no, the K3 is not an especially clean TX on SSB. By no means the worst either, of course.

73,

Drew K3PA

Rob Sherwood
 

Yes it makes a difference as to the voltage, and voltage drop in some long cables, plus the fuses and holders, can exacerbate the issue.  I set my Astrons at 14.3 volts to compensate for a typical voltage drop of 0.5 volts.  I haven’t seen a night and day difference between 13.8 at the radio and a half to a full volt higher (within the +/- 15% typical spec), but as one goes much lower than 13.8 IMD can measurably degrade.  

 

I guess the question is what is significant, and would anyone on the receive end notice?  13.8 to 14.3 volts, I doubt it.  At 12.0 volts, maybe so since the degradation might be several dB. (5 dB?) Who knows without an actual measurement on an individual rig.  Of course the IMD varies band by band, and tests in the lab are done into a resistive power attenuator, not an real antenna.

 

Rob, NC0B 

 

From: Elecraft-K3@groups.io [mailto:Elecraft-K3@groups.io] On Behalf Of Bob Novas via Groups.Io
Sent: Monday, November 04, 2019 10:54 AM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] Dirty Transmitters

 

Is there any difference between 12V and 13.8V or 14.1V, e.g., does it matter if you’re running off a run down battery?  Should you run the voltage up to the max if you’re running on AC?  Just curious if a volt or two makes a significant difference. If it does, maybe it’d be worth running as high a voltage as you can safely. Bob - W3DK

 

From: Elecraft-K3@groups.io [mailto:Elecraft-K3@groups.io] On Behalf Of Drew Vonada-Smith K3PA
Sent: Monday, November 04, 2019 12:07 PM
To: Elecraft-K3@groups.io
Subject: Re: [Elecraft-K3] Dirty Transmitters

 

The K3 has nice low phase noise, but no SS transmitter running at 12 V has great IMD.  So no, the K3 is not an especially clean TX on SSB.  By no means the worst either, of course.

73,

Drew K3PA

Steve
 

I remember a comment from Elecraft saying that the K3 will transmit a cleaner signal with voltage around 13.8 to 14 volts.   I don't remember the exact comment.

Bob McGraw - K4TAX
 

This has been stated and confirmed several times.  

A suggestion:   If you have a power supply with good regulation, no load to rated load, and you use power leads with very low resistance between the power supply and radio, you can run the power supply at 14.5 volts.  This will certainly improve the transmit IMD. 

Power leads should be of minimum length required, use #10 AWG wire, crimp on the correct terminals required for each end.   If in doubt crimp and solder terminals.  AND do connect the radio power cable direct to the power supply.  DO NOT use a DC power distribution strip.  Every connection adds resistance and results in voltage drop.  

73

Bob, K4TAX


On 11/5/2019 3:40 PM, Steve wrote:
I remember a comment from Elecraft saying that the K3 will transmit a cleaner signal with voltage around 13.8 to 14 volts.   I don't remember the exact comment.

dalej
 

Also if you have the KPA500 you only need around 30 watts to drive it and that is in the good area for IMD from 12 volt amps.  That’s were I run mine, maybe a little more 35 watts driving the KPA.  That also helps with the amp draw from a power supply.  

Dale k9vuj



On 06, Nov 2019, at 6:45, Bob McGraw - K4TAX <rmcgraw@...> wrote:

This has been stated and confirmed several times.  

A suggestion:   If you have a power supply with good regulation, no load to rated load, and you use power leads with very low resistance between the power supply and radio, you can run the power supply at 14.5 volts.  This will certainly improve the transmit IMD. 

Power leads should be of minimum length required, use #10 AWG wire, crimp on the correct terminals required for each end.   If in doubt crimp and solder terminals.  AND do connect the radio power cable direct to the power supply.  DO NOT use a DC power distribution strip.  Every connection adds resistance and results in voltage drop.  

73

Bob, K4TAX


On 11/5/2019 3:40 PM, Steve wrote:
I remember a comment from Elecraft saying that the K3 will transmit a cleaner signal with voltage around 13.8 to 14 volts.   I don't remember the exact comment.

Bob McGraw - K4TAX
 

I find that my KPA500 {s/n 3519} drives to 500 watts output on all bands with 19 to 23 watts.   I find that driving power of over 25 watts will push my KPA500 to over 500 watts.   All measurements were made with my Bird 43 into a 50.5 ohm resistive load.  {Please do not use an antenna for this measurement even if the SWR is 1:1.}  

The LED bargraph and the LCD display were correctly calibrated using the Menu / Edit and PWR ADJ feature of the KPA500.    The PWR ADJ feature DOES NOT affect the output of the amplifier.  It only affects the displayed or indicated values of both the LED display and the LCD display.  The FAULT power function is also affected by the PWR ADJ setting.

Based on earlier discussions, some amps may require more power to attain 500 watts output.

73

Bob, K4TAX


On 11/6/2019 7:09 AM, dalej via Groups.Io wrote:
Also if you have the KPA500 you only need around 30 watts to drive it and that is in the good area for IMD from 12 volt amps.  That’s were I run mine, maybe a little more 35 watts driving the KPA.  That also helps with the amp draw from a power supply.  

Dale k9vuj



On 06, Nov 2019, at 6:45, Bob McGraw - K4TAX <rmcgraw@...> wrote:

This has been stated and confirmed several times.  

A suggestion:   If you have a power supply with good regulation, no load to rated load, and you use power leads with very low resistance between the power supply and radio, you can run the power supply at 14.5 volts.  This will certainly improve the transmit IMD. 

Power leads should be of minimum length required, use #10 AWG wire, crimp on the correct terminals required for each end.   If in doubt crimp and solder terminals.  AND do connect the radio power cable direct to the power supply.  DO NOT use a DC power distribution strip.  Every connection adds resistance and results in voltage drop.  

73

Bob, K4TAX


On 11/5/2019 3:40 PM, Steve wrote:
I remember a comment from Elecraft saying that the K3 will transmit a cleaner signal with voltage around 13.8 to 14 volts.   I don't remember the exact comment.

David Bunte
 

Bob -

I am not posting this to the list, as I don't think it will add anything of value... but I was surprised to see K9VUJ talk about up to 35 watts drive power to his KPA500. Your numbers are FAR more like mine. I have never bothered to adjust the digital display and the bar graph on my KPA500 as you described... so thanks for the reminder that I can do that.

I appreciate many of your posts. I do not have a technical background (my career was on the microphone side of Public Radio). After 62 years of hamming, and at age 76 I am glad I can still learn.

73 de Dave - K9FN

On Wed, Nov 6, 2019 at 8:49 AM Bob McGraw - K4TAX <rmcgraw@...> wrote:

I find that my KPA500 {s/n 3519} drives to 500 watts output on all bands with 19 to 23 watts.   I find that driving power of over 25 watts will push my KPA500 to over 500 watts.   All measurements were made with my Bird 43 into a 50.5 ohm resistive load.  {Please do not use an antenna for this measurement even if the SWR is 1:1.}  

The LED bargraph and the LCD display were correctly calibrated using the Menu / Edit and PWR ADJ feature of the KPA500.    The PWR ADJ feature DOES NOT affect the output of the amplifier.  It only affects the displayed or indicated values of both the LED display and the LCD display.  The FAULT power function is also affected by the PWR ADJ setting.

Based on earlier discussions, some amps may require more power to attain 500 watts output.

73

Bob, K4TAX


On 11/6/2019 7:09 AM, dalej via Groups.Io wrote:
Also if you have the KPA500 you only need around 30 watts to drive it and that is in the good area for IMD from 12 volt amps.  That’s were I run mine, maybe a little more 35 watts driving the KPA.  That also helps with the amp draw from a power supply.  

Dale k9vuj



On 06, Nov 2019, at 6:45, Bob McGraw - K4TAX <rmcgraw@...> wrote:

This has been stated and confirmed several times.  

A suggestion:   If you have a power supply with good regulation, no load to rated load, and you use power leads with very low resistance between the power supply and radio, you can run the power supply at 14.5 volts.  This will certainly improve the transmit IMD. 

Power leads should be of minimum length required, use #10 AWG wire, crimp on the correct terminals required for each end.   If in doubt crimp and solder terminals.  AND do connect the radio power cable direct to the power supply.  DO NOT use a DC power distribution strip.  Every connection adds resistance and results in voltage drop.  

73

Bob, K4TAX


On 11/5/2019 3:40 PM, Steve wrote:
I remember a comment from Elecraft saying that the K3 will transmit a cleaner signal with voltage around 13.8 to 14 volts.   I don't remember the exact comment.

Rob Sherwood
 

I think Wayne said as high as 15.5 volts, which approaches the upper end of spec. In spec is within spec, which would be 15.87 volts.  The low side spec would be below 12 volts, which would not be ideal. Rob, NC0B


On Nov 6, 2019, at 5:28 AM, Steve <99sunset@...> wrote:

I remember a comment from Elecraft saying that the K3 will transmit a cleaner signal with voltage around 13.8 to 14 volts.   I don't remember the exact comment.

HB
 

What is the upper limit of say an Astron Linear 35 or 50 amp supply?

On Nov 6, 2019, at 10:21 AM, Rob Sherwood <rob@...> wrote:

 I think Wayne said as high as 15.5 volts, which approaches the upper end of spec. In spec is within spec, which would be 15.87 volts.  The low side spec would be below 12 volts, which would not be ideal. Rob, NC0B


On Nov 6, 2019, at 5:28 AM, Steve <99sunset@...> wrote:

I remember a comment from Elecraft saying that the K3 will transmit a cleaner signal with voltage around 13.8 to 14 volts.   I don't remember the exact comment.

Bob McGraw - K4TAX
 

My Astron 30 amp linear supply on the bench will adjust to about 16 volts and maintain good regulation, no load to 20 amps.  On the other hand, I no longer use a linear supply with my station as I find my Astron SS-30M to be superior.

73

Bob, K4TAX


On 11/6/2019 9:40 AM, HB via Groups.Io wrote:
What is the upper limit of say an Astron Linear 35 or 50 amp supply?

On Nov 6, 2019, at 10:21 AM, Rob Sherwood <rob@...> wrote:

 I think Wayne said as high as 15.5 volts, which approaches the upper end of spec. In spec is within spec, which would be 15.87 volts.  The low side spec would be below 12 volts, which would not be ideal. Rob, NC0B


On Nov 6, 2019, at 5:28 AM, Steve <99sunset@...> wrote:

I remember a comment from Elecraft saying that the K3 will transmit a cleaner signal with voltage around 13.8 to 14 volts.   I don't remember the exact comment.

Edward McCann
 

Bob:

Re:

 I no longer use a linear supply with my station as I find my Astron SS-30M to be superior

could you be a bit more specific on what features make it “superior”?

And could you comment on the notion that the linear Astron version might be quieter in spurious emissions claims traditionally linked to SS supplies?

Would be helpful, as I was about to buy one.

Thanks,

Ed McCann
AG6CX



On Nov 6, 2019, at 7:45 AM, Bob McGraw - K4TAX <rmcgraw@...> wrote:

My Astron 30 amp linear supply on the bench will adjust to about 16 volts and maintain good regulation, no load to 20 amps.  On the other hand, I no longer use a linear supply with my station as I find my Astron SS-30M to be superior.

73

Bob, K4TAX


On 11/6/2019 9:40 AM, HB via Groups.Io wrote:
What is the upper limit of say an Astron Linear 35 or 50 amp supply?

On Nov 6, 2019, at 10:21 AM, Rob Sherwood <rob@...> wrote:

 I think Wayne said as high as 15.5 volts, which approaches the upper end of spec. In spec is within spec, which would be 15.87 volts.  The low side spec would be below 12 volts, which would not be ideal. Rob, NC0B


On Nov 6, 2019, at 5:28 AM, Steve <99sunset@...> wrote:

I remember a comment from Elecraft saying that the K3 will transmit a cleaner signal with voltage around 13.8 to 14 volts.   I don't remember the exact comment.

Rick Bates, NK7I
 

From 2015:

On Apr 15, 2015, at 7:48 AM, Edward R Cole <kl7uw@...> wrote:

One question is how low voltage can be adjusted.  Amps are designed for 12.0 volts.
Ed,

All Elecraft 100-W amplifiers are designed for optimal performance at about 14 V (as measured at the DC jack on key-down). This includes the K3's and K2's internal 100-W amps as well as the KXPA100. They will certainly run from lower voltages -- down to about 10.5 to 11 V -- but for home use, we recommend setting the DC supply to 14.0-14.2 V. They'll run from as high as 15 V, though again, around 14 V optimizes power output, IMD levels, and efficiency.

73,
Wayne
N6KR

de Rick NK7I
On 11/5/2019 1:40 PM, Steve wrote:
I remember a comment from Elecraft saying that the K3 will transmit a cleaner signal with voltage around 13.8 to 14 volts.   I don't remember the exact comment.