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FM composite

R

radiorob2.0

I have a station rebuild project on the horizon. They are upgrading processing but would like the old box on line as a back up. Is it possible to use a high isolation antenna A/B switch with to select which processor feeds the exciter?
 
I had a similar problem at one time when I needed to switch between a local studio and the main studio, both coming in on composite STL's at the transmitter site. I used a low-power coaxial relay that could be remotely switched by applying 12 volts, and rigged a latching circuit that could be turned on by the remote control. Latching the relay "on" switched the local studio on line, normally off was the main studio feed. These little low power coax relays used to be common, but I just checked Surplus Sales and their selection seem very slim. Check some of the other amateur radio supply outfits--many are made with BNC in/out which makes hook-up simple.

Most modern processors will tolerate a little extra coax between the processor and exciter.
 
Besides using a composite DA, have succesfully done this. Parallel the feeds from the STL/Processor to the main and backup. BUT put a relay in the backup transmitter feed that turns on when the backup's on. Have a short lead between the STL/Processor and the relay. One less thing in the main composite path to go bad.
 
TomT said:
I had a similar problem at one time when I needed to switch between a local studio and the main studio, both coming in on composite STL's at the transmitter site. I used a low-power coaxial relay that could be remotely switched by applying 12 volts, and rigged a latching circuit that could be turned on by the remote control. Latching the relay "on" switched the local studio on line, normally off was the main studio feed. These little low power coax relays used to be common, but I just checked Surplus Sales and their selection seem very slim. Check some of the other amateur radio supply outfits--many are made with BNC in/out which makes hook-up simple.

Most modern processors will tolerate a little extra coax between the processor and exciter.
Click to expand...

There's a Broadcast Tools switcher that has BNC connectors that could be used to switch composite feeds.
 
Besides using a composite DA, have successfully done this. Parallel the feeds from...
Click to expand...
Wow. How did THAT post? I re-read the question (a good idea at that hour) than re-wrote a reply that DIDN"T post. Sloppy clicking I guess.

Anyway, try to keep it simple with the fewest active devices. I've never had any problems with a good quality coax relay. They've used them for years in the Moseley & TFT auto-changeover panels.
 
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