At 8/27/2007 08:58, you wrote: >I do remember that the Icom 02AT had subaudiable tone as an encode >(TX) function over 20 years ago. As to the repeaters, it has and >continues to be an owner option in most areas of the US. I don't >there is a real date as to when it was introduced in repeaters. > >Mark KS4VT
I know it was used extensively on closed repeaters here in SoCal in the 70's, maybe even 60's. But as far as open CTCSS repeaters go, I believe the first one was the CLARA repeater, WR6AQD (now N6SLD) on 145.22 on Santiago Peak in the late 70's. Back then, CTCSS or "PL" as it was commonly called, was synonymous with "closed". But Harvey Brownstein WB6YNQ pushed the concept of the "PL'd open" repeater, & eventually other systems followed, the next one IIRC being N6BWE on 145.20 in Monterey Park/Alhambra. Some didn't go 100% CTCSS right away, but rather used the decoder to open a tight carrier squelch. This allowed weak stations with CTCSS to get in while the strong base & mobile stations could continue to use the repeater without tone. W.r.t. early homebrew encoders, I never really liked the 555 version because of the non-sinewave output. Since the encoder need to cover more than an octave, fixed filtering of any kind couldn't be used to clean it up. So I went with the XR2206 function generator which put out a nice clean sine wave. Only other problem was frequency stability: only many years later after spending much time & effort looking for the most stable Rs & Cs did I discover when trying to build a 1000 Hz sine generator that the chip temperature affects the operating frequency. Bob NO6B
