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Re: PSK-31 Satellite



Bob, I don't know if I could volunteer for this (probably not), but
I can tell you that you will need fundamental mode crystals for that
(most 29 MHz xtals are 3rd OT) and you will need to either characterize them 
(JAN Xtals will do that for $10/xtal) or simply experiment with 3-pole, 
3-xtals, and set the BW of the filter with
the same set of 4 coupling capacitors, and use an adjustable matching
network "L" on both sides and tune until the shape is good.  If that
is done, several iterations can eventually give you the BW you want
with the crystal filter.  The bad thing is the only really good way
of doing this is with the help of a network analyzer.

For more info on this, check out my http://www.w0fms.org site, and
click on the "30m WARCbler" project.

Getting the driver stage to work on 30m has been a BEAR.. but the
receiver perked right up.  Although at the higher HF frequencies, a
little more gain is nice, so I'd advise the possibility of adding
a preamp at 29 MHz to the circuit.

Fred W0FMS



>From: Bob Bruninga <bruninga@usna.edu>
>To: amsat-bb@AMSAT.Org
>CC: psk31@bipt106.bi.ehu.es
>Subject: [amsat-bb] PSK-31 Satellite
>Date: Thu, 19 Apr 2001 21:16:57 -0400 (EDT)
>
>I am still reserving space on our satellite for a 10m "warbler" class
>PSK-31 uplink receiver.  There is a cheap set of 29.4 MHz crystals listed
>in most catalogs, so presumably a cheap modification can be done.
>
>I now find I am totally snowed under trying to get all the rest of the
>satellite built, so I'm just not going to get around to developing and
>testing this aux payload.
>
>But, again, I can make no promises, but if someone who is "good" at
>RF and construction and will make up just the receiver side of a "warbler"
>or whatever it takes to get a 10m (29.4 MHz) 2 Khz wide SSB receiver
>working,  I think I might be able to get it on board.  When activated, as
>many as 10? 20? PSK-31 users uplinking on SSB on 10m will all come down in
>the single (no doppler) 2m FM downlink....
>
>As we discussed before, with only about a max of 1 Hz per second doppler
>on 10m and nothing on the FM downlink, this mode is entirely possible...
>
>de WB4APR, Bob
>
>
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