[Elecraft] K3 TX Power

[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 <raycoles96 at gmail.com> 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: +44 (0) 1305 833699
>
> Mob: 07831 516517
>
>
>
>
>
>
>
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