RCA PTT Out Reading

Ei4gyb
Posts: 4
Joined: Fri Apr 14, 2017 11:19 pm

RCA PTT Out Reading

Postby Ei4gyb » Fri Jan 12, 2018 8:24 pm

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
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w-u-2-o
Posts: 1144
Joined: Fri Mar 10, 2017 1:47 pm

Re: RCA PTT Out Reading

Postby w-u-2-o » Fri Jan 12, 2018 10:28 pm

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.
Ei4gyb
Posts: 4
Joined: Fri Apr 14, 2017 11:19 pm

Re: RCA PTT Out Reading

Postby Ei4gyb » Sat Jan 13, 2018 12:29 am

Thank you Scott.
That’s what I wanted to hear... Perfect !

73

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