Eugene,

The Russians had a system (1960-70s ?) known as DFSK that used 4 tones.  I'm not sure if it was two channels or one channel with redundancy.  AN/FRA-86 was used to demodulate it.

Duncan
K2OEQ


On 1/12/2025 5:22 PM, W2HX wrote:
Has anyone ever tried combining two different shift streams into one? In other words, four tones in one audio stream? Would it allow one stream to work for two different audiences (say 170 shift audience and 850 shift audience)?


73 Eugene W2HX
My Youtube Channel: https://www.youtube.com/@w2hx/videos
 

-----Original Message-----
From: [email protected] <[email protected]> On Behalf Of Harold Hallikainen via GreenKeys
Sent: Saturday, January 11, 2025 10:14 PM
To: Green Keys <[email protected]>
Subject: [GreenKeys] Selective Fading Experiment

I ran an experiment comparing signal levels and fading with 850 and 170 Hz shift by transmitting four frequencies at once and seeing if they all faded together. My notes are at https://w6iwi.org/rtty/SelectiveFading/ .

Harold
https://w6iwi.org




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