[GreenKeys] Getting RTTY on the air

[Ralph Mowery]

There are several ways the frequency is specified.  I would not worry about
that and just tune to the demodulator is happy.

Most ham rtty that uses audio into the ssb transceivers usually use the dial
frequency and you will have the 2125 hz tone for the mark.

Set your transceiver for LSB and 170 hz shift.  The common frequencies will
be around 14.08 to 14.1 MHz on 20 meters.  Go to arrl.org and look for the
rtty bulliten times and frequencies.  This should get you started.  Probably
not too many now, but at one time there were some hams using 200 hz shift.
I think that had to do with some computer type saving to tape programs.

As some pointed out there are some military type transmissions in the ham
bands that use 850 hz shift. 



Ralph ku4pt
 

-----Original Message-----
From: greenkeys-bounces at mailman.qth.net
[mailto:greenkeys-bounces at mailman.qth.net] On Behalf Of Harold Hallikainen
Sent: Tuesday, November 10, 2020 10:00 PM
To: Green Keys
Subject: [GreenKeys] Getting RTTY on the air

I've finished connecting my model 15 to the TU-170 to my radio (
https://w6iwi.org/SEA245/ ). I added an audio transformer and a reed relay
to the TU-170 to drive the SEA245 tri-state audio bus. For testing, I'm
trying to get the RTTY decoder on a KiwiSDR ( http://rx.linkfanel.net/ )
to decode my signal. So, here are some questions.

1. I remember from MANY years ago, that LSMFT, or Low Space Makes Fine
Teletype. That, as I recall, is on RF, and it's reversed on AFSK. So, the
TU-170 uses 2.125 kHz for mark and shifts up 170 Hz for space. That
indicates that the transceiver should be set for LSB to get the signal
right side up. Is this correct?

2. How is the transmit frequency normally specified? I can think of
several ways:

a - Mark frequency
b - Center frequency (Mark frequency minus 135 Hz)
c - LSB "carrier frequency" (Mark frequency + 2.125 kHz

Is one of these correct? If so, which one?

3. What are common frequencies on the HF bands for RTTY? From many years
ago, I think I remember 3.635 MHz for the mark frequency.

4. Anything special in the FSK settings on a KiwiSDR? Should the signal be
inverted?

THANKS!

Harold