Passive Relay's


Nick Gregory G0HIK
 

Living in a valley, I've been interested in using a passive relay and have talked about them several times over the years with local amateurs.

When I was working, on one of the sites we had tanks that were refurbished WWII fuel dumps with chambers underground. To enable the UHF radios to work we had a folded dipole in the chamber with LDF4-50 feeding and 18 ele jaybeam. This gave comms back to the control room (Less than a mile).

While working on the rigs, we had a blind spot, I installed a system with two folded dipoles back to back. This was not perfect, but was a great improvement.

As I walk on the Fells around here there, I often come across community TV repeaters. They are always been powered, not sure if they are simply a pre-amplifier or they frequency shift.

I have been told that you cant have the passive repeater anywhere near the middle of the link and has to be right at one end of it. Not sure how the logic works, as several of the communities fed by these are not that close to them, say up to 2 to 5 miles away.

Finding a site locally that I could use that is on a hill and secure was a problem. But recently a radio friend who lives the other side of the valley, around 5 miles away said I could install one on the roof of his shack for me to try out. I was thinking of 144MHz because I was talking about this with another chap in the club whom I would like to communicate with who has Two metres. But it could be any band, maybe 23cm's might be a good one to try out.

Nick G0HIK

 

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