[GreenKeys] Getting RTTY on the air

[Nick England]

How is frequency specified? All of the above!
I think hams generally specify the Mark frequency, but evidently different
rigs display either the LSB suppressed frequency or the actual Mark
frequency.
Some of us are operating military RATT (850 shift, Mark low) and the
military specifies FSK center frequency, or USB suppressed carrier
frequency (AFSK tone 2000 +/-425 Hz). Most military rigs only tune in 1kHz
or 100 Hz steps so cannot land on an arbitrary Mark frequency. My Navy TU
will run 170 shift (AFSK tone 1000 Hz +/-85) but again the transmitted
center must be on 100Hz steps.

Nick England K4NYW
www.navy-radio.com


On Tue, Nov 10, 2020 at 10:01 PM Harold Hallikainen <harold at w6iwi.org>
wrote:

> 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
>
>
>
> --
> FCC Rules Updated Daily at http://www.hallikainen.com
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