Will this work? Two FETs in parallel, two inputs

[Terry Judkins]

**broken link removed**

This is for a 40 year old Heathkit transceiver that I am experimenting with a bit..

 

[MikeMl]

Are you trying to ADD the two inputs, or are you trying to MIX the two signals?

 

[Terry Judkins]

Neither. The signals will not be present at the same time. However both share the crystal filter and some following circuitry. At present the signals are dot ored together. The one being of 2K source impedance and the other very high by comparison. I was hoping to improve the match to the filter in receive mode and isolate the two signal sources..

 

[MikeMl]

Dot Oring with two switching diodes sharing a common pull-up resistor would be a lot simpler. You could still buffer/equalize the levels upstream of the diode gate.

 

[mneary]

The two MPF102's aren't likely to have the same threshold, resulting in one being on and the other off all of the time.