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The next big breakthrough occured in 1996 when K7PRS came across a pair of Granger-Telettra HR-2 tranceivers. These were much more modern synthesized 2GHz tranceivers. We were able to obtain a service manual and set out learning about the radios. It seems that they were designed to work in frequency bands located either above or below the amateur 2GHz allocation. Upon further examination we found that the micro-stripline circuit boards were identical for either tuning range. The manufacturer simply tuned the striplines with some silver paint. Now all we had to do was learn to tune micro-striplines!
Microwave filters and circulator
Once we recovered from the trip, it was time to begin making things work. First we tuned up 5 pairs of radios, but we couldn't use them without filters and duplexers. The filters were a big problem. We needed filters and circulators to make the radios full duplex into one antenna. We had to start disassembling the older SS-2000 radios we had. We found there were two types of filters and the ones that were most plentiful required machining to make them tune in the ham band. KB7RFI came to the rescue and prepared all the filters we would need for our original project. This involved shortening the tuning elements, mounting them on rack panels with the circulators and cabling up the panels to make duplexers.
The microwave construction story continues on Page 3
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