In Article <4b35uo$egm@fountain.mindlink.net> "andrew_taylor@mindlink.bc.ca (Andrew Taylor)" says:
> Just wondering if anybody has made a phone Patch (with
> DTMF encode/decoder!)...If you can point me in the right
> direction Id appreciate it!...Im going to be using it
> with VHF radio!.
>
> Andrew T.
> andrew_taylor@mindlink.bc.ca
>
>
PHONE PATCH FOR HANDHELD RADIOS
This circuit was published in _73_ magazine ~10 years ago. I've built
lots of them. Push-to-talk circuit as shown works with most
handhelds, which key their transmitters when a dc path through the
microphone is completed. Base/mobile rigs use a separate push-to-talk
line.
to radio earphone jack
^ ^
| |
| /
T1 | \ R2 (optional)
C1 | / _____
o-----||---)| | | |( |
)| ______|__.______ |( \ R1 | PTT
phone 1k )|(8 ohm | 8 ohm)|( 1k / ---
line )|(______._________)|( \<------o o---o to radio mike input
)| |( / (use shielded wire.)
o----------)| |(_____|_____________o
C1 1 uf 200 volt non-electrolytic.
R1 ~5k screwdriver-adjust pot to set microphone input level.
R2 resistance to equalize speaker and patch levels.
T1, T2 Audio-output transformer: Radio Shack part # 273-1330
(center taps not used).
--
Frank reid@indiana.edu W9MKV
Date: Mon, 18 Dec 1995 10:23 EST
Original Subject: Re: Phone Patch