K3 TX Power

[Ray Coles]

For the last few months I have been focussing on datamode operation, and
putting a lot of hitherto unobtainable DX in the log as a result.

I have noticed a problem with my K3 on all bands related to TX power. My rig
is a K3/100 plus a KPA500/KAT500 combo which remain on STBY for digital
modes of course.

My problem is: I dial in a power-setting on the K3 and for the first (let's
say JT65) transmission the actual transmitted power as measured by: the K3
itself, the KPA500 and my inline MFJ duelling banjo wattmeter is always much
less. If I dial in 100W I would get 20-30W during my first transmission,
30-50W on the second, and 75-80W on the third. On the 4th or 5th minute of
transmission it will reach the dialled in power setting. The SWRs are all in
the 1 to 1.5 range and I can see no external problems.

This is not good because I would really prefer it the other way around, once
someone has responded they will stick with you, but if they don't hear you
on the first call, you're toast.

To offset the problem I turn the power up to 100W and cross my fingers that
they will hear my first (weak) transmission. Unfortunately by the time I am
done, I am putting out more power than is healthy for other users who may
find that the weak signal they are working is pushed down by their AGC due
to my strong signal in the same window.

Attempts to adjust the power during a QSO fail, with a minor downward
adjustment (say from 100 to 80W) resulting in the true output power
plummeting to 20W and the cycle starting over.

This doesn't seem to be any kind of "warm-up" issue (my first suspicion) but
maybe some kind of logic or control feedback issue.

Has anybody else experienced this? Is it me?

 

Ray Coles, C.Eng. M0XDL

10 Littlemoor Road,

Weymouth DT3 6AA

Tel: [phone]

Mob: [phone]

 

 

 

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[Nicklas Johnson]

I can't comment on the K3 specifically, but I once had something very
similar happen with an Icom rig, and the problem turned out to be leaky
gates in the finals, unfortunately (they had to be replaced)... though in
my case the power output was a little more random compared to what you're
seeing.

I also observed a quirk of ALC in my KX3 which I haven't spent much time on
trying to reproduce yet, but maybe you can play with and see. It *appeared*
as though having the ALC kick in would actually reduce power to below the
point just before ALC took effect.  To give a more concrete example, say
setting the output volume of the PC to "9" would not trigger ALC, and the
KX3 would transmit 4 watts; turning the volume up to "10" on the PC would
trigger ALC, and the KX3 would transmit 3.8 watts, suggesting that ALC,
once activated, limits to something less than 100% of its threshold value.
 Again, I haven't played with this much, it's just something that *seemed*
to be happening.

(I don't think that would explain the behavior you're seeing though.)

I know I'm being sort of vague and nonspecific, but maybe some ideas to
play with.

   Nick



On 16 August 2013 09:33, Ray Coles <[hidden email]> wrote:

> For the last few months I have been focussing on datamode operation, and
> putting a lot of hitherto unobtainable DX in the log as a result.
>
> I have noticed a problem with my K3 on all bands related to TX power. My
> rig
> is a K3/100 plus a KPA500/KAT500 combo which remain on STBY for digital
> modes of course.
>
> My problem is: I dial in a power-setting on the K3 and for the first (let's
> say JT65) transmission the actual transmitted power as measured by: the K3
> itself, the KPA500 and my inline MFJ duelling banjo wattmeter is always
> much
> less. If I dial in 100W I would get 20-30W during my first transmission,
> 30-50W on the second, and 75-80W on the third. On the 4th or 5th minute of
> transmission it will reach the dialled in power setting. The SWRs are all
> in
> the 1 to 1.5 range and I can see no external problems.
>
> This is not good because I would really prefer it the other way around,
> once
> someone has responded they will stick with you, but if they don't hear you
> on the first call, you're toast.
>
> To offset the problem I turn the power up to 100W and cross my fingers that
> they will hear my first (weak) transmission. Unfortunately by the time I am
> done, I am putting out more power than is healthy for other users who may
> find that the weak signal they are working is pushed down by their AGC due
> to my strong signal in the same window.
>
> Attempts to adjust the power during a QSO fail, with a minor downward
> adjustment (say from 100 to 80W) resulting in the true output power
> plummeting to 20W and the cycle starting over.
>
> This doesn't seem to be any kind of "warm-up" issue (my first suspicion)
> but
> maybe some kind of logic or control feedback issue.
>
> Has anybody else experienced this? Is it me?
>
>
>
> Ray Coles, C.Eng. M0XDL
>
> 10 Littlemoor Road,
>
> Weymouth DT3 6AA
>
> Tel: [phone]
>
> Mob: [phone]
>
>
>
>
>
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

--
*N6OL*
Saying something doesn't make it true.  Belief in something doesn't make it
real. And if you have to lie to support a position, that position is not
worth supporting.
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[Iain MacDonnell - N6ML-2]

A couple of basic things...

1) Perform the TX gain calibration (see the Owner's manual)

2) Adjust the audio level from the sound card (if applicable) and the
line-in level on the K3 until you see 5 bars on the ALC meter when
transmitting JT65.

73,

    ~iain / N6ML


On Fri, Aug 16, 2013 at 9:33 AM, Ray Coles <[hidden email]> wrote:

> For the last few months I have been focussing on datamode operation, and
> putting a lot of hitherto unobtainable DX in the log as a result.
>
> I have noticed a problem with my K3 on all bands related to TX power. My rig
> is a K3/100 plus a KPA500/KAT500 combo which remain on STBY for digital
> modes of course.
>
> My problem is: I dial in a power-setting on the K3 and for the first (let's
> say JT65) transmission the actual transmitted power as measured by: the K3
> itself, the KPA500 and my inline MFJ duelling banjo wattmeter is always much
> less. If I dial in 100W I would get 20-30W during my first transmission,
> 30-50W on the second, and 75-80W on the third. On the 4th or 5th minute of
> transmission it will reach the dialled in power setting. The SWRs are all in
> the 1 to 1.5 range and I can see no external problems.
>
> This is not good because I would really prefer it the other way around, once
> someone has responded they will stick with you, but if they don't hear you
> on the first call, you're toast.
>
> To offset the problem I turn the power up to 100W and cross my fingers that
> they will hear my first (weak) transmission. Unfortunately by the time I am
> done, I am putting out more power than is healthy for other users who may
> find that the weak signal they are working is pushed down by their AGC due
> to my strong signal in the same window.
>
> Attempts to adjust the power during a QSO fail, with a minor downward
> adjustment (say from 100 to 80W) resulting in the true output power
> plummeting to 20W and the cycle starting over.
>
> This doesn't seem to be any kind of "warm-up" issue (my first suspicion) but
> maybe some kind of logic or control feedback issue.
>
> Has anybody else experienced this? Is it me?
>
>
>
> Ray Coles, C.Eng. M0XDL
>
> 10 Littlemoor Road,
>
> Weymouth DT3 6AA
>
> Tel: [phone]
>
> Mob: [phone]
>
>
>
>
>
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

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[Don Wilhelm-4]

Ray,

That is the behavior that results from insufficient audio drive to the K3 -
Use TX TEST so you do not bother others with a signal on the air, then
adjust the audio drive until the ALC meter indicates 4 bars solid with
the 5th bar flickering.  Don't be concerned about the "NO ALC" rule - on
the K3 in DATA mode, the onset of ALC is indicated by the 5th bar - the
bars below that are to aid you in setting the correct level.

Then set the desired power using the power knob.

The reason is the way the K3 controls power - in a closed loop.  If the
power level is not up to the power requested by the power knob, the K3
will attempt to increase the drive to make up for it.

73,
Don W3FPR

On 8/16/2013 12:33 PM, Ray Coles wrote:

> For the last few months I have been focussing on datamode operation, and
> putting a lot of hitherto unobtainable DX in the log as a result.
>
> I have noticed a problem with my K3 on all bands related to TX power. My rig
> is a K3/100 plus a KPA500/KAT500 combo which remain on STBY for digital
> modes of course.
>
> My problem is: I dial in a power-setting on the K3 and for the first (let's
> say JT65) transmission the actual transmitted power as measured by: the K3
> itself, the KPA500 and my inline MFJ duelling banjo wattmeter is always much
> less. If I dial in 100W I would get 20-30W during my first transmission,
> 30-50W on the second, and 75-80W on the third. On the 4th or 5th minute of
> transmission it will reach the dialled in power setting. The SWRs are all in
> the 1 to 1.5 range and I can see no external problems.
>
> This is not good because I would really prefer it the other way around, once
> someone has responded they will stick with you, but if they don't hear you
> on the first call, you're toast.
>
> To offset the problem I turn the power up to 100W and cross my fingers that
> they will hear my first (weak) transmission. Unfortunately by the time I am
> done, I am putting out more power than is healthy for other users who may
> find that the weak signal they are working is pushed down by their AGC due
> to my strong signal in the same window.
>
> Attempts to adjust the power during a QSO fail, with a minor downward
> adjustment (say from 100 to 80W) resulting in the true output power
> plummeting to 20W and the cycle starting over.
>
> This doesn't seem to be any kind of "warm-up" issue (my first suspicion) but
> maybe some kind of logic or control feedback issue.
>
> Has anybody else experienced this? Is it me?
>
>

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Post: mailto:[hidden email]

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[AD6XY]

Yes - back in the early days of the K3 it did the opposite, it would transmit more power than requested which was a nightmare for those of us using linear amplifiers. Some new ALC software was developed which had this effect, but it was not as marked as you are experiencing. There might be a biasing problem which could cause this sort of slow build effect, but from what you say happens when you adjust the power control it looks like it is directly related to the power setting algorithm. The first thing to do is repeat the calibration. That may well fix it.

If not, JT65 might be confusing the ALC algorithm, it may expect a waveform with some modulation to operate but JT65 has a constant amplitude. If you key CW does it do the same? I.e. initial Key down, sits at low power, sending dots goes to high power? What is it like on SSB?

Mike

[dainiux]

Hello

Have you found the reason? I have exactly the same situation on ssb - when I start transmit, output is about 20W and output rises step by step till 90w within 10-15 seconds. Second TX is in full power etc, until I change the band or freaquency. SWR is good. No ALC in external amplfier used. No problem with CW, only on SSB....  

Dan
ly4oo