Michael, The most simple way was to use a diode and variable capcitor in the VFO tank circuit connected to the Teletype Keyboard contacts. Some noise filtering with RF chokes and capcitor were used to keep the keying spikes down. Some used a "Polar Relay" in a 60 millamp "loop" in turn keying the diode/capacitor in the VFO tank. One had to use other hams to advise how far your shift was off and adjust accordingly. The standard went from 850 Hz shift to 170 Hz shift, with the later being easier to achive.
AM was only allowed on two meters and above for "AFSK". It still may be that way. Hams built audio oscillators for operating on two meter AM and later two meter FM. When SSB transmitters had good carrier suppresion, then hams were allowed to use audio for RTTY on HF. One who was quite active in the old RTTY days was Wayne Green, of 73 magazine. He and a few other hams went to the FCC to modernize FSK for hams. Early "RTTY" was on and off keying, no shift, can you imagine how good that was, HI. Take a look at this site: http://www.rtty.com/ Has a lot of info on RTTY operation. Look at the "History" quite interesting reading. I used a Johnson Viking II with Johnson VFO for RTTY back in the 60's. Ran the filments on the VFO 24/7 in order to keep the drift down when I wanted to operate RTTY. --- In digitalradio@yahoogroups.com, "Michael" <[EMAIL PROTECTED]> wrote: > > Hi, Folks, > > Let's cast our minds back to the days of AM (Advanced Modulation, for > those who are unfamiliar with the abbreviation <G>) rigs and RTTY. > > Now I know that simple AFSK would work - and provide both sidebands > and the carrier and really torture any SSB or true FSK rig going. > Not that I'm actually above such things but let's discount that for a > moment and look at shifting the transmit carrier as it's supposed to > be. Which is kind of where I'm having a small but measurable > problem. That problem is that I cannot for the life of me remember > how the old FSK exciters worked. And, of course, everything I've > found on the web relates to all those new fangled SSB thingies and > AFSK and all. > > So how, for example, did the MD-203 manage the T-195 to make it a > RTTY transmitter (as in the AN/GRC-46)? > > The derisive laughter may now commence. I'm used to it ... *sigh* > > BEst regards, > > Michael > Need a Digital mode QSO? Connect to Telnet://cluster.dynalias.org Other areas of interest: The MixW Reflector : http://groups.yahoo.com/group/themixwgroup/ DigiPol: http://groups.yahoo.com/group/Digipol (band plan policy discussion) Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/digitalradio/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
