[Elecraft] K2 Filters - RTTY Mode PSK31...Problem...

[Don Wilhelm]

Trev,

Good plan - but your trouble is using a single frequency signal source for
the filter alignment - it is very difficult to do it that way because you
can only tell that the signal is in the passband - you want it to be in the
center of the passband.

Use a wideband noise source and you will obtain better results.  View the
audio output on the computer running Spectrogram or SpectrumLab (freeware)
or the waterfall display on your PSK31 program.
I find the spectrum line display to be much easier to use than deciphering
the subtle color changes in a waterfall display, but you can do it either
way.

If you don't have a real wideband noise generator, try the noise on a dead
band (make certain there are no signals), or if you need more amplitude,
turn on an flourescent lamp and route an antenna wire near it - makes lots
of RF wideband noise.

73,
Don W3FPR

----- Original Message ----- 
.
>
> I was using a signal generator (yep you know the one) to inject a signal
750
> Hz (center of the passband) above my operating frequency on upper
sideband.
> This should generate a 750 Hz tone in a receiver or show a marker at 750
Hz
> on a waterfall display. Well, you can make that happen, but when you have
> adjusted the BFO frequencies for each filter accordingly and it's all set
up
> great, now if you go back and check everything you're not set in the
middle
> of the filter passband any longer!!!! I'm really starting to pull my hair
> out on this one! By the time I got everything set up so that I could
narrow
> down (250 Hz) on a PSK station and be on the same basic frequency, half of
> my waterfall display had disappeared on the wide setting!  The filter
center
> passband seems to shift up and down and not just narrow down on a center
> frequency....
>