[Elecraft] Peculiar problem on 80 M

[Stephen W. Kercel]

Don:

Thanks very much for your various suggestions.

I have made no mods at all. R98 is the original value.

I did not think that there was anything band dependent about the 
power level. That has led me to wonder if the problem might be a 
software glitch.

The phenomenon does depend on exact steps, but is repeatable if I do 
those steps.

I verify the level of requested power by tweaking the power knob very 
slightly. If I was at 10 watts and tweak it down a bit the display 
momentarily shows a numerical 9.5 watts. I can then tweak it back up 
and get the 10 watt reading. However, when the anomalous behavior is 
occurring the bar graph shows 4 or 5 watts on key down.

Running the rig from the low power jack as a diagnostic is a good 
idea. However, I'll need to make up a new power supply lead before I 
try it. I've never used anything but the Anderson lead thus far.

Thanks again,

Steve


At 07:28 AM 9/25/2006, Don Wilhelm wrote:
>Steve,
>
>Have you perhaps increased the value of R98 on the bottom of the RF Board to
>give you a more stable power control at high power?  If so, it will make the
>power control at lower power more sluggish.  That is the only thing I can
>think of which would make a difference.
>
>There is nothing band dependent about the power control that I am aware of,
>but the overall gain of the transmitter does vary from band to band, and
>that combined with the granularity of the power control may be causing the
>effect. The K2 remembers the power setting unless the power request is
>changed or the band is changed.  So the real power output that you are
>observing may be dependent on the exact steps that you are using to observe
>this phenonomon.
>
>You did say that you verify the power output level on the K2 display?  Can
>you provide the sequence you are using to do that?  The normal transmit
>display does not show the power output level, so you must be doing something
>other than a keydown.
>
>It would also be of interest to know if the same thing happens with the
>wider range QRP levels - power the K2 through the low power jack only
>(disconnect or turn off the power to the KPA100).
>
>73,
>Don W3FPR
>
>
> > -----Original Message-----
> >
> > I have a strange problem with my K2/100 on 80 meters.
> >
> > The situation is as follows:
> >
> > I work QRP DX at the low end of 80 M, (say 3508 kHz or thereabouts)
> > with a requested power of 4.5 watts, and get an indicated 5 watts out.
> >
> > I then check into the Pine Tree Net on 3596 kHz and crank up the
> > requested power to 10 watts (this is before the relay clicks; I'm
> > still in QRP mode), and I get about 10 watts out. So far so good, right?
> >
> > Then I go back to 3508 kHz, without resetting the power request level
> > knob, but the rig puts out 5 watts, even though the display
> > acknowledges my ten watt request. If I go back to 3596 the output
> > goes back to 10 watts in agreement with the requested level.
> >
> > Note the essential point, when I make a big excursion in frequency,
> > the radio is putting out a level of power substantially different
> > from the requested level.
> >
> > I can correct the output level at the low end by sweeping the
> > requested level either low (near 0) or high enough to make the QRO
> > relay click, and then adjust it down to and desired QRP level, and
> > the rig will put out approximately the requested level of power.
> >
> > The phenomenon occurs whether I change frequency by switching VFOs
> > preset to the two frequencies, or if I retune one VFO using the
> > tuning knob.
> >
> > This is not an issue of varying antenna impedance. I get this effect
> > with a commercial dry dummy load as well as a real (very well
> > matched) antenna.
> >
> > I can also create the effect the other way around. If I request 5
> > watts at the 3596 then go to the low end and request 10 watts, then
> > go back to 3596 with the knob in the 10 watt position, I still get 5
> > watts until I jigger the power level request knob.
> >
> > I have tried to reproduce this effect on 40 meters, requesting 5 and
> > 10 watt levels at frequencies differing by about 100 kHz. In that
> > case I get what I would regard as normal behavior. The rig always
> > puts out the approximately the requested level of power irrespective
> > of when I set the power level request knob.
> >
> > Has anyone else run into this phenomenon?
> >
> > Is it a quirk in the software?
> >
> > Is something wrong with the radio?
> >
> > 73,
> >
> > Steve Kercel
> > AA4AK
> >
> >
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