Simple HardWare VOX?

[Skyler]

Hello,

I was going to build a quick SIMPLEX repeater, but I realized that my new (actually old, but just got it) rig doesn't have VOX. It is a kenwood tm-241a.

I was wondering if there was any SIMPLE transistor/relay/capacitor/resistor etc. circuit that could achieve VOX from my computers sound card output without any special hard-ware.

I would like to use general purpose transistors like 2N3904 etc....

I would like a 2-3 second delay just in case someone pauses a bit between words


Thanks

Skyler KDØWHB

 

[Captain Kilowatt]

A regular audio amp feeding into a resistor load with a diode off the output for rectifying the voltage and a smoothing capacitor to store the charge. Use this derived voltage to feed the base of a 2N2222A or similar transistor that switches a relay. We used to make up all kinds of these using an LM384 amplifier IC. We used them as "silence detectors" in program and off air circuits to trip an alarm if the program line went dead for a predetermined amount of time.

 

[Skyler]

Is there any way I can control it with a bit less audio, I would like not to use an amp, just my computers sound card output, and I have no transformer to make the voltage larger.

 

[Captain Kilowatt]

It may be able without an amp but that depends on the volume out of the computer. However an amp isolates the computer from the rest of the circuit in the event something shorts and feeds voltage back into the sound card.