[CQ-Contest] RTTY contesting; filters

[Ed Muns]

An IF bandwidth of 600 Hz is ideal with our modern software decoders.
(Narrower bandwidth introduces phase shift that degrades copy error rate.)
Older radios often don't allow narrow filtering in SSB mode.  Yes, you want
to shift such that the bandpass is centered on whatever tone pair you use. 

 

I do like lower tones and typically use 915/1085 which is less fatiguing
over long periods.  OTOH, their TX audio harmonic is still within the normal
2 kHz bandwidth for SSB transmitters when transmitting AFSK.  Not a problem
for those of us using FSK.

 

73,

Ed W0YK

 

From: Mike Smith VE9AA <ve9aa at nbnet.nb.ca> 
Sent: 16 February, 2021 13:16
To: cq-contest at contesting.com
Subject: RTTY contesting; filters

 

Not really a RTTY contester, but when I do play, I am constantly bothered by
my rx filtering setup.

I currently run a pair of IC7410's in LSB (AFSK) mode.    On RTTY I am
currently SO1R, but I know how to go about

doing SO2R if I can ever get the filters setup better.

N1MM+

MMTTY

What "seems" to work best (by randomly flailing about) doesn't work very
well.

 

I don't believe using the RTTY mode (and thus the twin peak filters) will
work, as that is designed for FSK and I would prefer to stick with AFSK, as
I have that working and I don't wish to change any settings or wiring when
going over to SSB.

 

What works best as a SSB filter and how I do I select that and tailor it?

 

I tried using a 1.8kHz filter and doing an IF shift totally to the right to
capture the 2125Hz tone, but I think I am going about this all wrong.
Someone said there's a way to select a lower "note" to listen to in MTTY and
filter on that, but I am lost, so reaching out to the experts.

 

Been on HF, VHF and contesting CW/SSB a long time, but barely dabble in
RTTY.  Feel I could possibly be a little more active if I had some idea how
to set the filters up in these rigs so I don't get clobbered on RX.

 

 

Tnx guys

 

Mike VE9AA

Mike, Coreen & Corey

Keswick Ridge, NB