Batboard

I think I may have already asked this, but I can't find it in a search. What is the part number for the tuning probe used for aligning the MSFs, and does anyone have a ballpark guess as to whether or not it's still available from the big M?

I've seen them on eBay from time to time. The cable is also used on Quantars and probably a few other stations. I don't think it's available all by itself but is only part of the tuning tool kit, p/n TRN7794A. I bought one a couple of years ago for $45. It includes the 5mm Allen wrench, a couple of plastic alignment tools, the tuning cable, and a plastic pouch.

I have another tuning tool kit, p/n TRN5525A, that has the same parts in it. There are no markings on the tuning cables that I have.

You can make your own cable rather easily. One end is a BNC male, the other end is about 5/8 inch of exposed center conductor with a spring clip device that holds the coax in the tuning hole. I find that the tuning cable injects a signal into the front end that's about 30dB lower than if you connect a signal directly to the receiver input.

Bob M.

D'OH. Off to FSWT/Greedbay I go.

Given the nature of the problem I'm having with the repeater in question, I'm kinda leery of trying anything homebrew. I'd probably cut the thing .000625 inches too short/long and end up with a completely dead repeater.

There's no electrical connection from the tuning cable to anything in the station. They just use the exposed center conductor (it's still insulated, just the jacket/braid is removed) to leak signal into the casting. The length can't be critical as long as it doesn't get too close to the tuning slug.

Take three feet of RG58 or RG174, put a BNC connector on one end, strip about 1/2 inch of outer insulation off the other end, fold the braid back so it fits into the hole and actually makes a good connection there, and push the insulated center conductor into the hole. Connect your signal generator to the BNC cable and tune away. It really is not critical and there's nothing active inside the RF tray casting.

I could take a photo of one next to a ruler and post it or send it to you so you can see there's really no magic in it. Don't give up so soon.

Bob M.