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Re: K3/100 input voltage and TX IMD

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Rick Shindley

Re: K3/100 input voltage and TX IMD

A solid state linear RF PA will generate more IMD if the supply voltage sags on current peaks. How much distortion vs voltage change depends on the amplifier design and components used.

Someone reported here that he increased the supply voltage a bit and noted a 1 to 2 dB reduction in TX IMD. He also reported a 400 mV drop in the supply at the back of his K3/100 during Tx. Increasing the supply voltage but still having a 400mV “droop” and yet seeing a slight reduction in TX IMD hints at the sensitivity of the relationship between supply voltage and TX IMD.

I measured the voltage drop at the Power Pole connector at the back of my K3/100 while transmitting 100W CW out on 14.350 MHz into a dummy load. I found a 270mV drop due to the standard length power cable from Elecraft (IR loss) and 20mV due to the supply (Astron RM-35) load regulation capability for a total “droop” of 290mV.

So on SSB voice peaks or CW at 100W there is at least a 290 mV (and some say 400mV) drop in the supply voltage to the radio. It may even be a bit more inside the rig at the PA due to connector contact resistance and trace routing on the PCB. The slight drop in voltage will contribute to the amount of distortion in the output. Could this be the cause of the reported variations in measured TX IMD among rigs?

Rick

KC0OV

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Don Wilhelm-4

Re: K3/100 input voltage and TX IMD

Rick,

It sounds like you have a good low resistance connection with each
connection as tight as it can be.

That voltage drop is about the best you can do. If I calculate the
resistance of a 12 gauge cable 5 feet long, it is 8.1 mv for each
conductor. The APP connector contact resistance is a maximum of 578
microohms. So the total resistance in the cable and APP connector is
17.4 milliohms. That would be a voltage drop of 313 millivolts maximum
at 18 amperes. That is as measured inside the K3. The voltage drop
measured outside the K3 at 18 amps would be 292 millivolts due to the
cable alone.

Bottom line, a voltage drop of 0.3 to 0.35 volts can be blamed on the
cable and the APP connector resistance. Anything more than that can be
blamed on something else - insufficiently tight connection to the power
supply terminals, power supply 'droop', bad connection to the cable and
the terminations (both the APP connector barrels and the power supply
lugs if any are used), or any fuses used between the power supply and
the K3. Fuses are good and should be used, but they have contacts too,
and each contact adds its own contact resistance.

73,
Don W3FPR

Rick Shindley wrote:

>
> A solid state linear RF PA will generate more IMD if the supply
> voltage sags on current peaks. How much distortion vs voltage change
> depends on the amplifier design and components used.
>
> Someone reported here that he increased the supply voltage a bit and
> noted a 1 to 2 dB reduction in TX IMD. He also reported a 400 mV drop
> in the supply at the back of his K3/100 during Tx. Increasing the
> supply voltage but still having a 400mV “droop” and yet seeing a
> slight reduction in TX IMD hints at the sensitivity of the
> relationship between supply voltage and TX IMD.
>
> I measured the voltage drop at the Power Pole connector at the back of
> my K3/100 while transmitting 100W CW out on 14.350 MHz into a dummy
> load. I found a 270mV drop due to the standard length power cable from
> Elecraft (IR loss) and 20mV due to the supply (Astron RM-35) load
> regulation capability for a total “droop” of 290mV.
>
> So on SSB voice peaks or CW at 100W there is at least a 290 mV (and
> some say 400mV) drop in the supply voltage to the radio. It may even
> be a bit more inside the rig at the PA due to connector contact
> resistance and trace routing on the PCB. The slight drop in voltage
> will contribute to the amount of distortion in the output. Could this
> be the cause of the reported variations in measured TX IMD among rigs?
>
> Rick
>
> KC0OV
>
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alsopb

Re: K3/100 input voltage and TX IMD

In reply to this post by Rick Shindley

I rearranged things to shorten up the K3 supplied cable to 3'.

The difference between just the RX ON (1.11 amps) and 100 watts (18.77 amps) ended up being 0.6 volts. Supply is an Astron 20A.

Previously with a 6' cable the difference was 1 Volt.

Interesting thing is the current draw at each power level was not what I expected. I expected the higher voltage to lower the current at each power level. It did but a miniscule amount. At 10 watts the difference was 0.03 amps. At 100 watts the difference was 0.02 amps. I expected a lot more.
The endpoint voltage for the long cable was 12.7 V. For the short cable is was 13.9 volts. I kind of expected the 100 watt amperage to decrease as the ratio of these two voltages. Doing the math, the expected current draw would have been 1.6 amps versu the 20 milliamps.

Can someone explain this anomoly?
Brian/K3KO

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Jan Erik Holm

Re: K3/100 input voltage and TX IMD

In reply to this post by Rick Shindley

Rick, and others

Just to clarify things a bit.
First of all when I did get the "bad IMD" report on the
air I was at a different QTH and used a another PS, in
this case I do not know exactly what voltage K3 got or
voltage drop.
Then I did bring K3 home to a PS that had 13.9V RX and
13.5V at TX, didn´t reflect much about this. I then started
to measure IMD on the K3 and it didn´t look all that
bad up to 80W but at 120W it was much worse.
After that I started to "rant" about different things here
on the reflector, did get more or less zilch help from
Elecraft sorry to say.
Received some good ideas from some nice people here on the
reflector. That together with some studies of my own
led to bias adjustment on the KPA100 and also I did
turn up PS voltage to 14.9V at RX. Also made area of cable
between PS and K3 much much larger, at TX I now have
14.6V at the K3 display. My IMD measurements now looks
very good up to 100W and at 120W only slightly slightly
worse.
Since I didn´t get much help from Elecraft I don´t feel I owe
them anything but still to be fair to Elecraft it actually
looks slightly better now compared to the "known good"
FT-1000D. You can look at these analyzer pictures,
Ft-1000D at 200W and K3 at 100W. It actually looks very
good.
http://sk3w.se/sm2ekm/view_photo.php?set_albumName=SM2EKM-pictures&id=FT_1000D
http://sk3w.se/sm2ekm/view_photo.php?set_albumName=SM2EKM-pictures&id=P1010014
Sorry but it´s difficult to hold the camera still.
Now I have to test it on the air. Thanks a lot to the
individuals that gave a helping hand, I appreciate it.
I hope this is the end of the story.

73 Jim SM2EKM
--------------------
Rick Shindley wrote:

> A solid state linear RF PA will generate more IMD if the supply voltage
> sags on current peaks. How much distortion vs voltage change depends on
> the amplifier design and components used.
>
>
>
> Someone reported here that he increased the supply voltage a bit and
> noted a 1 to 2 dB reduction in TX IMD. He also reported a 400 mV drop
> in the supply at the back of his K3/100 during Tx. Increasing the
> supply voltage but still having a 400mV “droop” and yet seeing a slight
> reduction in TX IMD hints at the sensitivity of the relationship between
> supply voltage and TX IMD.
>
>
>
> I measured the voltage drop at the Power Pole connector at the back of
> my K3/100 while transmitting 100W CW out on 14.350 MHz into a dummy
> load. I found a 270mV drop due to the standard length power cable from
> Elecraft (IR loss) and 20mV due to the supply (Astron RM-35) load
> regulation capability for a total “droop” of 290mV.
>
>
>
> So on SSB voice peaks or CW at 100W there is at least a 290 mV (and some
> say 400mV) drop in the supply voltage to the radio. It may even be a
> bit more inside the rig at the PA due to connector contact resistance
> and trace routing on the PCB. The slight drop in voltage will contribute
> to the amount of distortion in the output. Could this be the cause of
> the reported variations in measured TX IMD among rigs?
>
>
>
> Rick
>
> KC0OV
>

David Cutter

Re: K3/100 input voltage and TX IMD

Jan

Perhaps you could share with us all the ideas and adjustments you made.

David
G3UNA

Rick, and others

Received some good ideas from some nice people here on the
reflector. That together with some studies of my own
led to bias adjustment on the KPA100 ........
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Don Wilhelm-4

Re: K3/100 input voltage and TX IMD

In reply to this post by Jan Erik Holm

Jim,

You mention that the TX IMD gets worse when run at 120 watts.
The K3 is specified at 100 watts. If you run at 120 watts, it is
entirely possible that the TX IMD will then not be as specified.

I don't understand why hams expect performance when a transmitter is
pushed beyond it specifications.

Why should I expect a transmitter specified for 100 watts to operate
within its other specs at 120 watts? I don't because that is
unreasonable! Trying to squeeze the last drop of power from a
transmitter has long been known to create splatter and distortion
products. Please don't do that.

73,
Don W3FPR

Jan Erik Holm wrote:

> Rick, and others
>
> Just to clarify things a bit.
> First of all when I did get the "bad IMD" report on the
> air I was at a different QTH and used a another PS, in
> this case I do not know exactly what voltage K3 got or
> voltage drop.
> Then I did bring K3 home to a PS that had 13.9V RX and
> 13.5V at TX, didn´t reflect much about this. I then started
> to measure IMD on the K3 and it didn´t look all that
> bad up to 80W but at 120W it was much worse.
> After that I started to "rant" about different things here
> on the reflector, did get more or less zilch help from
> Elecraft sorry to say.
> Received some good ideas from some nice people here on the
> reflector. That together with some studies of my own
> led to bias adjustment on the KPA100 and also I did
> turn up PS voltage to 14.9V at RX. Also made area of cable
> between PS and K3 much much larger, at TX I now have
> 14.6V at the K3 display. My IMD measurements now looks
> very good up to 100W and at 120W only slightly slightly
> worse.
> Since I didn´t get much help from Elecraft I don´t feel I owe
> them anything but still to be fair to Elecraft it actually
> looks slightly better now compared to the "known good"
> FT-1000D. You can look at these analyzer pictures,
> Ft-1000D at 200W and K3 at 100W. It actually looks very
> good.
>
>

Ian Maude

Re: K3/100 input voltage and TX IMD

Don Wilhelm wrote:

> Jim,
>
> You mention that the TX IMD gets worse when run at 120 watts.
> The K3 is specified at 100 watts. If you run at 120 watts, it is
> entirely possible that the TX IMD will then not be as specified.
>
> I don't understand why hams expect performance when a transmitter is
> pushed beyond it specifications.
>
> Why should I expect a transmitter specified for 100 watts to operate
> within its other specs at 120 watts? I don't because that is
> unreasonable! Trying to squeeze the last drop of power from a
> transmitter has long been known to create splatter and distortion
> products. Please don't do that.
>

This was what I was saying in my post the other day Don. If the rig
does not have good IMD over 100W and Elecraft say we should not run it
over 100W, why does the radio allow me to turn it up? IMHO, the power
level on SSB should stop at 100W. It is fine probably on CW to run 120W
but on SSB and possibly datamodes, it should stop at 100W. It is only
software.

73 Ian

> 73,
> Don W3FPR
>
> Jan Erik Holm wrote:
>
>> Rick, and others
>>
>> Just to clarify things a bit.
>> First of all when I did get the "bad IMD" report on the
>> air I was at a different QTH and used a another PS, in
>> this case I do not know exactly what voltage K3 got or
>> voltage drop.
>> Then I did bring K3 home to a PS that had 13.9V RX and
>> 13.5V at TX, didn´t reflect much about this. I then started
>> to measure IMD on the K3 and it didn´t look all that
>> bad up to 80W but at 120W it was much worse.
>> After that I started to "rant" about different things here
>> on the reflector, did get more or less zilch help from
>> Elecraft sorry to say.
>> Received some good ideas from some nice people here on the
>> reflector. That together with some studies of my own
>> led to bias adjustment on the KPA100 and also I did
>> turn up PS voltage to 14.9V at RX. Also made area of cable
>> between PS and K3 much much larger, at TX I now have
>> 14.6V at the K3 display. My IMD measurements now looks
>> very good up to 100W and at 120W only slightly slightly
>> worse.
>> Since I didn´t get much help from Elecraft I don´t feel I owe
>> them anything but still to be fair to Elecraft it actually
>> looks slightly better now compared to the "known good"
>> FT-1000D. You can look at these analyzer pictures,
>> Ft-1000D at 200W and K3 at 100W. It actually looks very
>> good.
>>
>>
>>
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> Elecraft web page: http://www.elecraft.com
>
>

--

Ian J Maude, G0VGS
SysOp GB7MBC DX Cluster
Member RSGB, GQRP, FISTS
K2 #4044 |K3 #455
http://www.amateurradiotraining.org

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Don Wilhelm-4

Re: K3/100 input voltage and TX IMD

Ian,

Your comment is worthy of consideration, but OTOH, I am of the 'old
school' - amateur radio operators traditionally have not been bound by
power limits imposed by the firmware, and many would be quite displeased
if it were limited in the K3.

We are supposed to share the bands as gentlemen and operate our
equipment in such a manner as not to annoy our fellow hams. That does
require a knowledge of our equipment, especially its limitations.

I am fully aware that there are more and more 'appliance operators' on
the ham bands who do not know the limits of their transmitters, and the
only thing they seem to understand is the upper limit of the power
knob. There is a name for those operators - I call them "LIDS". While
that term is usually applied to those who practice bad operating
protocol, I choose to apply it also to those who operate their equipment
improperly. RTFM is a requirement to know your equipment, but then I
was schooled as a young engineer and made to understand that is a VERY
important task

73,
Don W3FPR

Ian Maude wrote:

> Don Wilhelm wrote:
>
>> Jim,
>>
>> You mention that the TX IMD gets worse when run at 120 watts.
>> The K3 is specified at 100 watts. If you run at 120 watts, it is
>> entirely possible that the TX IMD will then not be as specified.
>>
>> I don't understand why hams expect performance when a transmitter is
>> pushed beyond it specifications.
>>
>> Why should I expect a transmitter specified for 100 watts to operate
>> within its other specs at 120 watts? I don't because that is
>> unreasonable! Trying to squeeze the last drop of power from a
>> transmitter has long been known to create splatter and distortion
>> products. Please don't do that.
>>
>>
> This was what I was saying in my post the other day Don. If the rig
> does not have good IMD over 100W and Elecraft say we should not run it
> over 100W, why does the radio allow me to turn it up? IMHO, the power
> level on SSB should stop at 100W. It is fine probably on CW to run 120W
> but on SSB and possibly datamodes, it should stop at 100W. It is only
> software.
>
> 73 Ian
>
>

Ian Maude

Re: K3/100 input voltage and TX IMD

Don Wilhelm wrote:
> Ian,
>
> Your comment is worthy of consideration, but OTOH, I am of the 'old
> school' - amateur radio operators traditionally have not been bound by
> power limits imposed by the firmware, and many would be quite displeased
> if it were limited in the K3.
>
With respect Don, it is already limited :) It is limited to 120W. What
is the point of doing that if the radio should not be used at that power?
> We are supposed to share the bands as gentlemen and operate our
> equipment in such a manner as not to annoy our fellow hams. That does
> require a knowledge of our equipment, especially its limitations.
>
I do not disagree with that at all, in fact I applaud it!

73 Ian

--

Ian J Maude, G0VGS
SysOp GB7MBC DX Cluster
Member RSGB, GQRP, FISTS
K2 #4044 |K3 #455
http://www.amateurradiotraining.org

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Bill Johnson-9

Re: K3/100 input voltage and TX IMD

In reply to this post by Ian Maude

I thought as HAMs we would know how to operate a rig within specs and not
rely on manufacturing. I have been an amateur for 49 years and I learned
early on that is was my responsibility to know how to operate and control my
own signals regardless of rigs. That is why we learn theory. We have a mic
gain control... just turn up your mic gain beyond its recommended settings
and splatter all over the band... there's no difference than operating at
120 watts for a rig that is designed to operate at 100. (Do we buy an amp
capable of 2500 w and operate it there? I hope not.) Besides, what good is
it to run at 120 watts anyway? No noticeable difference at the receiving
end. Let me control my rig, not Elecraft.

73,

Bill
K9YEQ
K2 #35; KX1 #35; K3 #1744; mini mods

-----Original Message-----

>
> Why should I expect a transmitter specified for 100 watts to operate
> within its other specs at 120 watts? I don't because that is
> unreasonable! Trying to squeeze the last drop of power from a
> transmitter has long been known to create splatter and distortion
> products. Please don't do that.
>
This was what I was saying in my post the other day Don. If the rig
does not have good IMD over 100W and Elecraft say we should not run it
over 100W, why does the radio allow me to turn it up? IMHO, the power
level on SSB should stop at 100W. It is fine probably on CW to run 120W
but on SSB and possibly datamodes, it should stop at 100W. It is only
software.

73 Ian

> 73,
> Don W3FPR
>
> Jan Erik Holm wrote:
>
>> Rick, and others
>> Then I did bring K3 home to a PS that had 13.9V RX and
>> 13.5V at TX, didn´t reflect much about this. I then started
>> to measure IMD on the K3 and it didn´t look all that
>> bad up to 80W but at 120W it was much worse.

--

Ian J Maude, G0VGS
SysOp GB7MBC DX Cluster
Member RSGB, GQRP, FISTS
K2 #4044 |K3 #455

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n7ws

Re: K3/100 input voltage and TX IMD

In reply to this post by Ian Maude

--- On Wed, 1/28/09, Ian Maude <[hidden email]> wrote:

> This was what I was saying in my post the other day Don.
If the rig does not have good IMD over 100W and Elecraft say we should not run it over 100W, why does the radio allow me to turn it up?

> IMHO, the power level on SSB should stop at 100W. It is fine probably on CW to run 120W but on SSB and possibly datamodes, it should stop at 100W.

> It is only software.
>
> 73 Ian

Precisely.

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ac0h

Re: K3/100 input voltage and TX IMD

In reply to this post by Don Wilhelm-4

It's simple,

The manual says this.

"Note: The K3 is capable of up to 120 W output on some bands. However,
IMD and spurious products are specified at 100 W. This is the
recommended maximum."

You run your rig out of spec don't complain to Elecraft about it's
performance. Maybe that particular sentence should be in a bigger font
and bold. Obviously it isn't getting read.

Of course that wouldn't do a thing about those folks who run their rigs
"all knobs full right".

Don Wilhelm wrote:

> Ian,
>
> Your comment is worthy of consideration, but OTOH, I am of the 'old
> school' - amateur radio operators traditionally have not been bound by
> power limits imposed by the firmware, and many would be quite displeased
> if it were limited in the K3.
>
> We are supposed to share the bands as gentlemen and operate our
> equipment in such a manner as not to annoy our fellow hams. That does
> require a knowledge of our equipment, especially its limitations.
>
> I am fully aware that there are more and more 'appliance operators' on
> the ham bands who do not know the limits of their transmitters, and the
> only thing they seem to understand is the upper limit of the power
> knob. There is a name for those operators - I call them "LIDS". While
> that term is usually applied to those who practice bad operating
> protocol, I choose to apply it also to those who operate their equipment
> improperly. RTFM is a requirement to know your equipment, but then I
> was schooled as a young engineer and made to understand that is a VERY
> important task
>
> 73,
> Don W3FPR

>

--
R. Kevin Stover, ACØH
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Bill W4ZV

Re: K3/100 input voltage and TX IMD

In reply to this post by Don Wilhelm-4

Don Wilhelm-4 wrote

You mention that the TX IMD gets worse when run at 120 watts.
The K3 is specified at 100 watts. If you run at 120 watts, it is
entirely possible that the TX IMD will then not be as specified.

I don't understand why hams expect performance when a transmitter is
pushed beyond it specifications.

Typical Citizen Band mentality ("knobs fully to the right") plus some on this list are well known QRO types (i.e. VERY big amps need more drive than legal amps).

73, Bill

Simon (HB9DRV)

Re: K3/100 input voltage and TX IMD

----- Original Message -----
From: "Bill W4ZV" <[hidden email]>
>
> Typical Citizen Band mentality ("knobs fully to the right") plus some on
> this list are well known QRO types (i.e. VERY big amps need more drive
> than
> legal amps).
>

... a remark tossed off by Ian Gillan of Deep Purple during a concert in
Japan: "Could we have everything louder than everything else?"

Probably an RTTY contester?

Simon Brown, HB9DRV
www.ham-radio-deluxe.com

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P.B. Christensen

Re: K3/100 input voltage and TX IMD

In reply to this post by Ian Maude

> With respect Don, it is already limited :) It is limited to 120W. What
> is the point of doing that if the radio should not be used at that power?

I can't speak for the K3 designer(s), but not all modes elevate or produce
IM at the upper end of the output power curve. CW is one such mode,
although other non-IM artifacts may be possible above 100W.

There are times when driving a low-gain, GG amplifier (e.g., 3CX1200 w/
untuned input) when the operator wants to drive it to its maximum capability
but in order to do so, something a bit more than 100W is required. It's not
worth getting into a discussion as to whether the added power increase from
the extra drive is worth it -- but some ops want to utilize their amps to
the fullest capability when conditions permit.

But that same op needs to understand that in IMD-generating modes like SSB,
the K3's power needs to be throttled back to specified limits. When running
an amp, s/he may safely achieve 1500W in CW, but must then settle for
something less (e.g., 1300W) in SSB mode.

Paul, W9AC

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Gilbert Cross

Re: K3/100 input voltage and TX IMD

In reply to this post by Rick Shindley

It would be interesting to check the voltage drop from the APP on the K3 to the cathode of D11 ( component of KPA3) when under a 100 watt load.

73 Gil K8EAG

----- Original Message -----

From: [hidden email]

To: [hidden email]

Sent: Tuesday, January 27, 2009 11:09 PM

Subject: Re: [Elecraft] K3/100 input voltage and TX IMD

A solid state linear RF PA will generate more IMD if the supply voltage sags on current peaks. How much distortion vs voltage change depends on the amplifier design and components used.

Someone reported here that he increased the supply voltage a bit and noted a 1 to 2 dB reduction in TX IMD. He also reported a 400 mV drop in the supply at the back of his K3/100 during Tx. Increasing the supply voltage but still having a 400mV droop and yet seeing a slight reduction in TX IMD hints at the sensitivity of the relationship between supply voltage and TX IMD.

I measured the voltage drop at the Power Pole connector at the back of my K3/100 while transmitting 100W CW out on 14.350 MHz into a dummy load. I found a 270mV drop due to the standard length power cable from Elecraft (IR loss) and 20mV due to the supply (Astron RM-35) load regulation capability for a total droop of 290mV.

So on SSB voice peaks or CW at 100W there is at least a 290 mV (and some say 400mV) drop in the supply voltage to the radio. It may even be a bit more inside the rig at the PA due to connector contact resistance and trace routing on the PCB. The slight drop in voltage will contribute to the amount of distortion in the output. Could this be the cause of the reported variations in measured TX IMD among rigs?

Rick

KC0OV

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P.B. Christensen

Re: K3/100 input voltage and TX IMD

In reply to this post by P.B. Christensen

> "It would be interesting to check the voltage drop from the APP on the K3
> to the cathode of D11 ( component of KPA3) when under a 100 watt load. 73
> Gil K8EAG"

Cascading APP connectors can add up to relevant IR loss. For example, in
my installation, the power supply and a 55-AH gel-cell battery (back-up) are
routed to West Mountain PowerGate. The PowerGate feeds an 8-port APP
manifold. One manifold port feeds the K3. That's 5 (count 'em) APP
connector sets in the power supply path.

At ~ 20A, the voltage drop at the K3 is nearly one volt when using #10 AWG
wire -- and the reason why I am now using an industrial-grade power supply
with remote sensing terminals that makes up for the IR loss on demand. The
other devices on the manifold can easily withstand the variation.

Paul, W9AC

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David Cutter

Re: K3/100 input voltage and TX IMD

Have you measured the transient response time? Should be easy to see a 1V
transient with a modest scope.

David
G3UNA

>> "It would be interesting to check the voltage drop from the APP on the K3
>> to the cathode of D11 ( component of KPA3) when under a 100 watt load. 73
>> Gil K8EAG"
>
> Cascading APP connectors can add up to relevant IR loss. For example, in
> my installation, the power supply and a 55-AH gel-cell battery (back-up)
> are
> routed to West Mountain PowerGate. The PowerGate feeds an 8-port APP
> manifold. One manifold port feeds the K3. That's 5 (count 'em) APP
> connector sets in the power supply path.
>
> At ~ 20A, the voltage drop at the K3 is nearly one volt when using #10 AWG
> wire -- and the reason why I am now using an industrial-grade power supply
> with remote sensing terminals that makes up for the IR loss on demand.
> The
> other devices on the manifold can easily withstand the variation.
>
> Paul, W9AC
>
>

Nick Kennedy

Re: K3/100 input voltage and TX IMD

I did my own little unscientific IMD check yesterday. I connected the
K3 to my Cantenna and monitored with my IC-706IIg on the same desk and
same power supply. I used a bit of wire in the 706's antenna terminal
sufficient to give an S9 or higher received signal strength. Had the K3
at 100 watts and mic gain to hit 100W on peaks. Then tuned up and down
from my signal several kHz each way on the 706 listening for splatter as
I transmitted. Didn't hear any, unless it was faint. Of course, I hear
my signal changing in pitch and diminishing in strength as I moved the
receiver away, but I hope I know what that sounds like.

I did this on 40 meters and 15 meters, and with CMP on and off. I did
it again at 50 and 80 watts and didn't notice any difference. Also
checked at 13.8V and 14.5V supply voltage and didn't notice a difference.

I checked my voltage drop on the K3's internal meter. From receive to
100 watts CW key down, I got 0.7 VDC drop. I note that the MFJ switcher
provided 0.19V of that. Today I soldered my crimped lugs at the P/S end
and noticed no difference when I did the measurement check again.

73-Nick, WA5BDU

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Alan Bloom

Re: K3/100 input voltage and TX IMD

In reply to this post by Ian Maude

If they do that (limit SSB power to 100W) they really should vary the
limit based on power supply voltage. For example, the K3 is specified
down to 11V, but you can't get 100W at that voltage. If you try you'll
get horrible distortion. It's up to the operator to be aware of these
limitations and set the power accordingly.

I think Elecraft's philsophy is to assume the operator is competent and
not to limit any capabilities unnecessarily.

Al N1AL

On Wed, 2009-01-28 at 06:25, Ian Maude wrote:

> Don Wilhelm wrote:
> > Ian,
> >
> > Your comment is worthy of consideration, but OTOH, I am of the 'old
> > school' - amateur radio operators traditionally have not been bound by
> > power limits imposed by the firmware, and many would be quite displeased
> > if it were limited in the K3.
> >
> With respect Don, it is already limited :) It is limited to 120W. What
> is the point of doing that if the radio should not be used at that power?
> > We are supposed to share the bands as gentlemen and operate our
> > equipment in such a manner as not to annoy our fellow hams. That does
> > require a knowledge of our equipment, especially its limitations.
> >
> I do not disagree with that at all, in fact I applaud it!
>
> 73 Ian