Juma PA 100D PTT Connection

[KK5DB]

I am building a special cable for the PTT input on my PA 100D. I would like to confirm that the tip of the 3.5mm "stereo" (3 conductor) plug should be pulled to ground for the PTT to operate. I plan to make the cable with only a connection to the tip and ground (sleeve) of the plug. There will be no connection to the ring on the plug.

Thanks
Dennis
KK5DB

[5B4AIY]

Yes, that is correct, the tip of the 3.5mm TIP/RING/SLEEVE plug has to be pulled to ground to put the linear amplifier into transmit. Note that you MUST use a standard stereo plug, that is TIP/RING/SLEEVE, because the sleeve connection repeats the PTT signal, and a mono plug would short this to ground.

The PTT line is pulled up to +12V via a 10K resistor in series with a 1K resistor. (I am attaching the schematic if you do not already have it.) Make sure that your PTT line does not have more than +12V on it when in the RX mode. An open-collector or dry relay contact is ideal.

Adrian, 5B4AIY