At 07:39 PM 08/27/07, you wrote: >Larry, Gord VE3HKE used subaudible tones to limit access to the >autopatch on VE3TTY. I still have mine! It was a Ferrotronics unit >that was adjusted with a pot, definitely not programmable! > >I seem to remember that was around 1972/73, not much later because the >autopatch went into VE3RPT in 1974 and I know TTY's was on first. > >We made limited use of CTCSS on VE3RPT at times in the early >seventies, but it was for command station access, not general use. > >73 >Nigel >ve3id
Ditto - my first subaudible tone encoder was a twin-T oscillator using polystyrene caps and metal film resistors and a 2N2222 as the osc and a second one as a buffer. It all fit inside a high band HT200 along with 6 sets of crystals. Later on I did some numerical playing around with a Data General Nova computer at NASA/JPL and discovered that if you divide 103.477khz by integer numbers you will hit all the 32 standard PL tones very very closely. I gave that info to Spence Porter at Com-Spec and about 6 months later the TS-32 came out. Mike WA6ILQ
