I occasionally drive by one of the old Bell System microwave radio relay towers here in Michigan and always wondered if it was still active. Does anyone know if any of the original microwave relays are still being used (i.e. the original 4GHz systems)?

I found that the transmitter still has an active FCC license, so that is what led me to believe they might still be in use. The particular link that still has active call signs runs from Traverse City, Mich to Perkins, Michigan. For reference, the Allenville tower that I've been past has the call sign WHR249. If they are still active, are they just used for backup, or do they regularly carry calls? What is their capacity?

With all the knowledgeable and experienced folks on this site, I'm sure someone will know!

-Nelson

I did a lot of Microwave work, just not for the Bell System and not in Michigan,

Microwave is still used regularly for locations where it's too expensive or too difficult to get fiber into. Or, if it's got to be in NOW (you can get a link in pretty quickly if conditions are right).

Any link in the spectrum below 38 ghz requires FCC approval, which can take a little time to get, so if there's an approved 4 gig link whoever owns is probably keeping it up - even if they're not using it now- just in case.

A 4 GHZ link is probably good for 15-20 miles and could easily carry a T-3 (45 mbs) circuit.

These days I see them used very often for feeding cell sites, but very often they're in there for backup.

Hope that helps,

Sam

Thanks for the info, Sam. That supports my suspicions. I didn't think AT&T would maintain the FCC license if they weren't using the links in some way.

-Nelson