[Elecraft] KPA100 - Problems on 15m

[Ken Alexander]

Hi Don, 

I tried the same tests with my dummy load connected and got the same lower output on 15m when transmitting versus pressing Tune.

I increased the output from the audio interface to the rig and the transmitter output can be adjusted to give normal output.  So maybe it just needed a little extra drive on 15 for some reason.  The problem is that the audio level that gives good output on 15 gives me one solid ALC bar on 20m, so I'll have to be careful when going from band to band.

I can't think of a reason why the drive required on one band wouldn't be the same as all bands.

Ken



--- On Sun, 2/14/10, Don Wilhelm <w3fpr at embarqmail.com> wrote:

> From: Don Wilhelm <w3fpr at embarqmail.com>
> Subject: Re: [Elecraft] KPA100 - Problems on 15m
> To: "Ken Alexander" <k.alexander at rogers.com>
> Cc: elecraft at mailman.qth.net
> Date: Sunday, February 14, 2010, 3:08 AM
> Ken,
> 
> That does not make sense.  The Power output for RTTY
> is no different than CW (or TUNE) except that the audio
> input to the K2 is different from CW.  There is no band
> to band difference for the K2 - AFSK modulation is AFSK
> modulation no matter which band it is on.
> 
> I would be looking for RF Feedback problems on 15
> meters.  Try it into a dummy load and see if things are
> normal - if so, look at your antenna system or the
> solution.
> 
> OTOH, if all bands behave the same way when operated into a
> dummy load, then look to your RTTY driving software and
> whatever interface you are using.
> 
> Actually, RTTY AFSK is more related to SSB transmission
> than CW, so try SSB as well.  If SSB transmission os
> OK, then your RTTY driving system is suspect (but would be
> the same on all bands).  If your problems are confined
> to only 15 meters, then look at the possibility of RF
> Feedback on 15 meters.
> 
> 73,
> Don W3FPR
> 
> Ken Alexander wrote:
> > I completed building my KPA100 a few weeks ago. 
> It passed all tests and checks all the way through. 
> However, today I noticed something strange.
> > 
> > I'm operating in the CQ WPX RTTY contest this weekend
> and spent most of the day on 20m with the Power set to
> 50W.  I went to 15m to try it out.  With the Power
> control still set to 50W I hit the Tune button to get my
> remote autotuner to tune to 15m.  The K2 and my
> external power meter indicated the normal 20W, as it should
> in Tune mode when the power is set higher than 20W.
> > 
> > When I went to transmit RTTY (without touching the
> Power control), my external power meter barely indicated 10
> watts.  This only happens on 15m.
> > 
> > As an experiment, I went to the CW portion of the
> band.  Tune gives you 20W.  Keying the transmitter
> with my paddles give me 50W.
> > 
> > Any ideas would be appreciated.
> > 
> > 73,
> > 
> > Ken Alexander
> > VE3HLS
> > 
> > 
> >
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