[Elecraft] PSK31 on the K2

[Igor Sokolov]

> >Has it
> >something to do with VFO stability of phase shift in the filters - I do
not
> >know. But weak signals coming from my IC765 get easyly decoded by the
> >program while if I use K2 the same program can decode only solid signals.
>
> I agree with others that it is probably a filter alignment issue. There
are
> excellent resources in the Elecraft community to help you fix that.

I do not think so. I did filter calibration with Spectrogram.

>
> >I am not pleased with SSB performance of K2 either.
>
> First, you must remember that the K2 started out life as a QRP CW rig. As
> that, it's spectacularly good. The K2/100 is also a very good CW
contesting
> rig, but for the excessive wideband phase noise that makes you very
> unpopular with your neighbors if you use it to drive an amp.
> I agree. The widest RX filter is the TX filter. It has very good magnitude
> and phase response, and it sounds great. But the "stagger-tuning" of the
CW
> RX filters to provide narrower SSB RX produce a VERY bumpy audio response
> (both magnitude and phase) that only the programmer's mother could love.
It
> sounds awful, and it degrades intelligibility.
>
> >Especially on TX.

When I mentioned PSK31 I should have state that I am trying to use just
those narrow filters for RX. On Spectrogram they look reasonably good
provided the bandwidth is less then 1 kHz. With more then 1Khz settings  the
ripple in the passband makes them of very little use.

> I agree with you, but there are some very good fixes that can improve it
> significantly. Many of them are written up on user websites, with links
from
> the Elecraft webpage. The fundamental problem is that the K2 audio path is
> low on gain. The gain is also a bit lacking further on in the signal
chain.
>
> I developed a simple mod that helps a lot. On the SSB board, change R14 to
> 2K, change C34 to 0.22 uF, and add 2.2 uF in series with R15. This
provides

I have actually removed R14 all together. It gives me some extra gain but
still not enough to compensate for the losses caused by RC chain wich I put
at the mike input trying to boost high frequencies a bit. Besides the noise
gate which is build into the mike IC started to be noticable. My
correspondents report "step type" distortions on my signal. Then AF
compression is not as efficient as RF compression. All together that make
SSB signal dull and not as penetrative as one needs for SSB contesting. I am
now thinking of additional mike amp to improve the situation.

> 6 dB additional gain for the mic, which allows you to hit the compressor
> harder and increase the average loudness. It also rolls off the low end a
> bit, which prevents "pops" from activating the compressor, making the
> compressor work better.

I will try your mode  but I feel it may not be enough at least with the
present cheep computer grade electret microphon. Still this very mike works
pretty well with my main IC-765 radio.


73, Igor UA9CDC

>
> >Having said that it is pretty good as CW contest rig and is almost on the
> >par with my main radio.
>
> Yep!
>
> Jim Brown K9YC
>
>
>
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