[GreenKeys] RTTY - High tones - Low tones?

[Harold Hallikainen]

When I started (late 1960s), it was 2125, 2975. These were on both HF and
VHF. We directly shifted the transmitter VFO (Viking Ranger for me). When
I came back (maybe 10 years ago), standard shift was 170 Hz and tones into
an SSB transceiver were standard. It looks like in the US, 2125 Hz was
kept and space was up 170 Hz. But in Europe, 2125 Hz was kept, and MARK
was moved down 170 Hz. Then there are the HAL low tones (Mark 1.275 kHz,
Space 1.445 kHz), Navy MMM (Mark tone 1.615 kHz, Space 1.785 kHz), and the
Navy LF LSB (Mark tone 915 Hz, Space 1085 Hz). All this is listed in the
autostart table at https://w6iwi.org/rtty/ .

In my DSP TU ( https://w6iwi.org/rtty/DspTU2/) I have user configurable
center frequency and shift for both narrow and wide shift. The software
calculates the tone frequencies from these. There is also a "Mark High"
switch that puts the mark frequency above the space frequency (reverse
normal). The default values result in 2125, 2975 for narrow shift, and 2
kHz +/- 425 Hz for wide shift.

I'm sure glad I'm able to do this in software instead of having a ton of
retunable hardware filters and tone generators!

Harold
https://w6iwi.org