Rick,
I agree with Phil regarding the 250 Hz filter. You will definitely need this
selectivity on 20m when a full-fledged contest is running! In the past I would
turn this narrow filter on occasionally, only when I needed it. During the 2006
ARRL RTTY I don't think I ever turned it off! RTTY contesting really seems to
have caught on recently!
Regarding the external audio filters, this depends on your RTTY demodulator.
Using a KAM, AEA, or MFJ (hardware) TNC, an external unit might help. But if
you're using MMTTY, the filters available in that product do an excellent job.
You can customize them to whatever bandwidth you desire. And to top it off, you
can preview the audio bandwidth characteristics on a graph.
The downside to the MMTTY internal audio filters is YOU do not benefit from
their steep skirts. With your speaker connected to the transceiver audio
output, you will continue to hear the normal rubbish on a crowded band. I
suppose you could drive your speakers from the soundcard output, but I haven't
tried that so I don't know if that would work or not.
73 de Bob - K0RC
* * * * * * ORIGINAL MESSAGE FOLLOWS * * * * * *
Message: 7
Date: Tue, 23 May 2006 10:35:37 +0100
From: "pcooper" <pcooper@guernsey.net>
Subject: Re: [RTTY] 250 hz filter on RTTY
To: Rmintz@Rochester.rr.com
Cc: RTTY@contesting.com
Message-ID: <1148376937.864ccf00pcooper@guernsey.net>
Content-Type: text/plain; charset="UTF-8"
Hi Rick and the group,
I am sure you will find the 250Hz filter just fine, and maybe even a little
wide at times.
OK, I know the filtering on a 756Pro is a little different, but I frequently
set my filters down to 100Hz. Whilst that may seem very narrow, I don't use the
built in RTTY filters, as I prefer to change mine according to needs at the
time.
The filtering in this way is a little SSB-like, in that the skirts flare out
enough to give copy on a RTTY signal when set to 100Hz.
It will even cope with those signals that are slightly wider than usual, but
you do have to tune in the signal very accurately.
So, I am sure you will find 250Hz just fine!
It may also pay you to look out for one of the external audio filters that sit
between the rig and the soundcard. These can clean up a lot of hash, and make
copy a little more reliable.
Cheers for now
Phil GU0SUP
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