Date   

Re: Dirty Transmitters

Joe Subich, W4TV
 

(c) I also added a ground terminal to the back of the supply. Again
making sure the terminal is connected and not being insulated by the
paint. This is my common point ground for the entire station. Each
piece of equipment uses a dedicated jumper to this terminal.
Not a good idea! If the negative lead of your power cable is already
bonded to the case of the equipment and the power supply, you have
just created a loop that will radiate any noise from the supply.

In addition, cables connected between the transmitter (high current
load) and accessories will provide parallel ground returns that allow
the high current to "pump" the ground reverence in the accessory. If
the accessory is handling low level signals (e.g., dynamic mic audio)
that "pumping" ground reference can be easily coupled into the audio
and produce what appears to be common mode RFI.

You are far better served to dedicate a 30A power supply to the
transceiver and use a separate 1-10A supply (depending on total
load) for any accessories (including VHF/UHF rigs, etc.). Connect
the station common point ground at a truly common point independent
of any one piece of equipment (or use the LAST RF device - one
connected directly to the antenna system if the feedline(s) have
an effective "entry window" ground that is tied to the power line
entry ground as required by NEC).

Having a station "common point ground" tied directly to the power
line "safety" ground - as you do when you tie the "green wire" of
your power supply *and* station common point to the power supply
chassis is begging for lightning damage if the common point and
antenna entry window are not tied tightly to the power entry ground.

73,

... Joe, W4TV


On 2019-11-06 11:43 AM, Bob McGraw - K4TAX wrote:
Yes, the small footprint, the lower physical weight,  the lack of transformer humm, the excellent regulation, the low noise.
I have 3 of these supplies.  In each case I do not find them to generate any RFI on any band including 160M - 2M.  There are a couple of points I will stress and that is to check the individual supply to find the following:
(a) open the supply and make sure the AC 3rd pin ground green wire is electrically connected to the chassis.  I have found instances where the nice paint job actually insulates the connection.   Scrape away the paint and re-attach the wire.
(b) the outer shell is sometimes insulated from the bottom pan by paint.   I removed the screws and sanded the area around the screw holes and the mating areas on the shell, then put the screws back in place.
(c) I also added a ground terminal to the back of the supply. Again making sure the terminal is connected and not being insulated by the paint.  This is my common point ground for the entire station.  Each piece of equipment uses a dedicated jumper to this terminal.
As to switching supplies and their reputation, I think this comes from hams recovering supplies from various sources with out regard for any filtering.  In many cases, the EMI filtering is done outside of the supply and is not removed when the supply is removed {as in computer suplies} .  And some supplies are just pure crap.   I purchased a 12V 20A switching supply off of Amazon.  It is intended to supply voltage to LED illumination strips.  It is very noisy in terms of EMI and RFI.  If a ham gets and uses one of these then they will likely brand all switching supplies as noisy.    All switching supplies are NOT created equal.
73
Bob, K4TAX


Re: Dirty Transmitters

Richard Smith <ku4nz01@...>
 

This thread caused me to adjust output on my RS-35M. Thanks all. 

RAS



On Nov 6, 2019, at 12:33, Rob Sherwood <rob@...> wrote:

 The Astron power supplies I own have an internal pot to set the voltage. I would adjust it with nothing connected.  The can likely go over 16 volts. I have 3 RS-35Ms, but have never used a 50. For some reason removing the top covers are a pain.  Rob, NC0B


On Nov 6, 2019, at 8:41 AM, HB via Groups.Io <hbjr@...> 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.


Re: Dirty Transmitters

Rob Sherwood
 

The Astron power supplies I own have an internal pot to set the voltage. I would adjust it with nothing connected.  The can likely go over 16 volts. I have 3 RS-35Ms, but have never used a 50. For some reason removing the top covers are a pain.  Rob, NC0B


On Nov 6, 2019, at 8:41 AM, HB via Groups.Io <hbjr@...> 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.


Re: Dirty Transmitters

Al N1AL
 

All switching supplies are NOT created equal.
Right.  HP/Agilent/Keysight measurement instruments mostly use switching power supplies these days.  That includes spectrum analyzers designed to measure low-level signals from audio to microwave.  So it is certainly possible to design low-noise switching power supplies.

Alan N1AL


On 11/6/19 8:43 AM, Bob McGraw - K4TAX wrote:
... As to switching supplies and their reputation, I think this comes from hams recovering supplies from various sources with out regard for any filtering.  In many cases, the EMI filtering is done outside of the supply and is not removed when the supply is removed {as in computer suplies} .  And some supplies are just pure crap.   I purchased a 12V 20A switching supply off of Amazon.  It is intended to supply voltage to LED illumination strips.  It is very noisy in terms of EMI and RFI.  If a ham gets and uses one of these then they will likely brand all switching supplies as noisy.    All switching supplies are NOT created equal.


Re: Dirty Transmitters

Edward McCann
 

Thanks for comprehensive reply!
73,
Ed McCann
AG6CX


On Nov 6, 2019, at 8:43 AM, Bob McGraw - K4TAX <rmcgraw@...> wrote:

Yes, the small footprint, the lower physical weight,  the lack of transformer humm, the excellent regulation, the low noise.   

I have 3 of these supplies.  In each case I do not find them to generate any RFI on any band including 160M - 2M.  There are a couple of points I will stress and that is to check the individual supply to find the following:

(a) open the supply and make sure the AC 3rd pin ground green wire is electrically connected to the chassis.  I have found instances where the nice paint job actually insulates the connection.   Scrape away the paint and re-attach the wire.

(b) the outer shell is sometimes insulated from the bottom pan by paint.   I removed the screws and sanded the area around the screw holes and the mating areas on the shell, then put the screws back in place. 

(c) I also added a ground terminal to the back of the supply.  Again making sure the terminal is connected and not being insulated by the paint.  This is my common point ground for the entire station.  Each piece of equipment uses a dedicated jumper to this terminal.

As to switching supplies and their reputation, I think this comes from hams recovering supplies from various sources with out regard for any filtering.  In many cases, the EMI filtering is done outside of the supply and is not removed when the supply is removed {as in computer suplies} .  And some supplies are just pure crap.   I purchased a 12V 20A switching supply off of Amazon.  It is intended to supply voltage to LED illumination strips.  It is very noisy in terms of EMI and RFI.  If a ham gets and uses one of these then they will likely brand all switching supplies as noisy.    All switching supplies are NOT created equal.

73

Bob, K4TAX


On 11/6/2019 9:52 AM, Edward McCann wrote:
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.


Re: Dirty Transmitters

Bob McGraw - K4TAX
 

Yes, the small footprint, the lower physical weight,  the lack of transformer humm, the excellent regulation, the low noise.   

I have 3 of these supplies.  In each case I do not find them to generate any RFI on any band including 160M - 2M.  There are a couple of points I will stress and that is to check the individual supply to find the following:

(a) open the supply and make sure the AC 3rd pin ground green wire is electrically connected to the chassis.  I have found instances where the nice paint job actually insulates the connection.   Scrape away the paint and re-attach the wire.

(b) the outer shell is sometimes insulated from the bottom pan by paint.   I removed the screws and sanded the area around the screw holes and the mating areas on the shell, then put the screws back in place. 

(c) I also added a ground terminal to the back of the supply.  Again making sure the terminal is connected and not being insulated by the paint.  This is my common point ground for the entire station.  Each piece of equipment uses a dedicated jumper to this terminal.

As to switching supplies and their reputation, I think this comes from hams recovering supplies from various sources with out regard for any filtering.  In many cases, the EMI filtering is done outside of the supply and is not removed when the supply is removed {as in computer suplies} .  And some supplies are just pure crap.   I purchased a 12V 20A switching supply off of Amazon.  It is intended to supply voltage to LED illumination strips.  It is very noisy in terms of EMI and RFI.  If a ham gets and uses one of these then they will likely brand all switching supplies as noisy.    All switching supplies are NOT created equal.

73

Bob, K4TAX


On 11/6/2019 9:52 AM, Edward McCann wrote:
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.


Re: Dirty Transmitters

Rick 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.


Re: Dirty Transmitters

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.


Re: Dirty Transmitters

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.


Re: Dirty Transmitters

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.


Re: Dirty Transmitters

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.


Re: Dirty Transmitters

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.


Re: Dirty Transmitters

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.


Re: Dirty Transmitters

southdaleus
 

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.


Re: Dirty Transmitters

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.


Re: Dirty Transmitters

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.


Re: Join elecraft group

GRANT YOUNGMAN <ghyoungman@...>
 

On Nov 4, 2019, at 9:45 PM, Robin Kidd <w4ien@comcast.net> wrote:

What is the address of the Schulman site?

7


Re: Join elecraft group

Robin Kidd <w4ien@...>
 

What is the address of the Schulman site?

72/73,
EM73vx
Robin
G-QRP #12386
SKCC #7294
W4IEN 
w4ien@...


On Nov 4, 2019, at 21:43, Larry <telegrapher@q.com> wrote:


Paolo, there is a nice K3 selling on the Schulman auction site.  You just have to be the top bidder.  
Larry  W0OGH



Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------
From: Paolo NERVI <Iu1cyf@...>
Date: 11/3/19 1:09 AM (GMT-07:00)
To: elecraft-k3@groups.io
Subject: [Elecraft-K3] Join elecraft group

Hi,
I'd like to join this group.
I own a elecraft KX3 and i love to buy a K3 or a K3S.
73 de Paolo.

IU1CYF
Eng. Paolo Nervi
Turin Italy


Re: Join elecraft group

Larry
 

Paolo, there is a nice K3 selling on the Schulman auction site.  You just have to be the top bidder.  
Larry  W0OGH



Sent from my Verizon, Samsung Galaxy smartphone

-------- Original message --------
From: Paolo NERVI <Iu1cyf@...>
Date: 11/3/19 1:09 AM (GMT-07:00)
To: elecraft-k3@groups.io
Subject: [Elecraft-K3] Join elecraft group

Hi,
I'd like to join this group.
I own a elecraft KX3 and i love to buy a K3 or a K3S.
73 de Paolo.

IU1CYF
Eng. Paolo Nervi
Turin Italy


Re: Dirty Transmitters

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

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