Here's what we have been using for decades. Got tired of hand wiring the parts and 'flying' them on the transistor's leads. The pc board does reduce the labor to build them.
A resistor goes from the "RF In" hole to the center pin of the amplifier's input socket. Low drive levels call for a 2.2k 2 Watt resistor. A 4.7k 2 Watt is okay up to around 200 Watt peaks.
The cold side of the relay coil goes to the "Out" hole. The transistor tab just bolts to the chassis for the ground connection. This assumes a positive DC voltage on the relay. Older boxes that use a negative DC voltage to run the relay require that the thing be mounted with the transistor tab isolated from ground and the "out" side grounded. The "Gnd" side would then go to the cold side of the relay coil.
Just one problem. It's too cheap to sell one at a time. My overhead to make a sale transaction is about equal to what we sell it for on a customer's repair bill.
But I'll make you a proposition. Mail me 15 bucks and I'll pack one into an envelope and send it to you.
We're at:
Nomad Radio
1615 Bardstown Road
Louisville, KY 40205
The snail-mail addy is on our web site, too.\
Thought about putting them on Ebay, but a price high enough to cover the overhead would make it at least thirty bucks. Just doesn't seem worth that much.
Not a big deal to build. Found a schemo on file.
Works every time.
(edit) Found a pic showing the steps to just "twist" one up the old way.
73