Back when I built my Twin Cities and HAL ST-6 TUs, transmitters with FSK FM'd the transmit frequency back and forth between Mark and Space. A very few transmitters had FSK. You usually had to dig into the VFO and use a diode and capacitor to shift the frequency.
Later, as a shortcut to getting on the air with RTTY, some hams started using AFSK generators from VHF RTTY into SSB transmitters to generate a pseudo-FSK signal on HF. AFSK is not legal on HF. If they were strong, or their carrier suppression was not good, you could hear the third frequency of their carrier. And, sometimes other signals as well, especially if they had the mic gain cranked up. Definitely not a legal FSK signal. Then came "low-tone" AFSK generators that had a lower pair than the 2125/2975, because a lot of SSB transmitters couldn't pass the 2975. Then 170 Hertz shift. If you are transmitting RTTY, what frequency are you transmitting on? The Mark or Space? Or some offset where a SSB carrier should be? The problem we have is third party software that assumes we are using a SSB transmitter and uses AFSK tones to generate pseudo-FSK. Mike - AA8K Jim Dunstan wrote: > > No disrespect, but how can you tell the difference between an FSK RTTY > signal and AFSK RTTY signal, other than examining or inquiring the method > used to generate the signals? _______________________________________________ FlexRadio mailing list FlexRadio@flex-radio.biz http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archive Link: http://www.mail-archive.com/flexradio%40flex-radio.biz/ FlexRadio Knowledge Base: http://kb.flex-radio.com/ FlexRadio Homepage: http://www.flex-radio.com/
