ZL1NC’s Information Pages

Now you could just take a COS signal from the transistor driving the green receive LED. BUT if you are using CTCSS (PL tone) on receive, the UV series radio will still light the green LED whilst signal is present - even though the audio is muted.

UV series radios achieve COS from P65/AURX supplying a signal to switching transistors that supply power to the final audio driver chip when the squelch is to be opened. When a valid signal (or PL tone / DCS) is detected, P65 goes high. Q18 is forward biased, pulling down the base of Q19 (which was held high by R90). Q19 is now forward biased and conducts BAT1 to pin 2 of the TDA2282 amplifier.

Aha! Pin 2 of the TDA2282 is the perfect place to pick off a +Ve going COS (PL) trigger.






So, where IS the audio chip?
Why HERE it is!



I used a header-pin "jumper" as found on old computer bits, to make a socket for the COS output of the radio. Worked out quite tidily. I am eying up the space under the belt-clip holder... If I can I will fit a PS2 socket in the side, to take ALL the connections MIC, SP, PTT, COS in a single plug!