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

[Trevor Jacobs]

Hi Don,

No, I know that you can use a wide band noise generator to peak the filters
with the BFO. The problem is once you have done this to each filter, they
are not listening to the same frequency any longer. Since you use OPB1 the
SSB board filter for transmit, they kind of all need to be matched to that
one or your little 31 Hz PSK signal is going to be on a different RX and TX
frequency. Not to mention that trying to narrow down on a weak station is
next to impossible if the signals shift all over the place. Ideally you want
to have a common center passband frequency, so that if you tune the rig so
that the signal is centered say on 1000 Hz in the waterfall, it stays there
as you narrow down. This is the problem I was having, and I don't see an
easy solution. You have to use a single tone source to align it this way.

73's Trev - KG6CYN
http://www.qsl.net/kg6cyn
----- Original Message ----- 
From: "Don Wilhelm" <W3FPR@peoplepc.com>
To: "Trevor Jacobs" <kg6cyn@softhome.net>; "Elecraft Mailing List"
<elecraft@mailman.qth.net>
Sent: Saturday, February 07, 2004 7:28 AM
Subject: Re: [Elecraft] K2 Filters - RTTY Mode PSK31...Problem...


> 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
>