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RCA PTT Out Reading

Posted: Fri Jan 12, 2018 8:24 pm
by Ei4gyb
Hi folks,
Belated happy New Year.
Wondering if anyone has measured the resistance of the RCA PTT out on the rear of the radio (200D) whilst in TX and then..... in RX ?
Any idea as to what readings can be expected? Should they vary from band to band?

Not sure but think it’s making the amp act a bit weird

73

Re: RCA PTT Out Reading

Posted: Fri Jan 12, 2018 10:28 pm
by w-u-2-o
Here's the schematic for the PTT out circuit on the Orion board. It is similar on the other boards.

Image

It's just a simple FET switch to ground with no internal pull-up. Therefore with PTT not asserted there will be near infinite resistance (an open circuit), and with PTT asserted it will be almost a short.

Re: RCA PTT Out Reading

Posted: Sat Jan 13, 2018 12:29 am
by Ei4gyb
Thank you Scott.
That’s what I wanted to hear... Perfect !

73