The Microwave Project
Page 3

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Microwave pg. 1
Microwave pg. 2
Microwave pg. 4


Other Sites

Mt. Lemmon
Mount Bigelow
Mule Mountain
Heliograph Peak
Elephant Head
Tucson
Dragoon
Dark Canyon

Now was the time to begin building our new microwave hub on Mt. Bigelow. We planned to have at least five links tie together at the site. We began by building the links to Pinal Peak and Elephant Head. We did these two first so that we could make a kind of 'bypass' around the existing links, enabling us to disconnect the Oracle links once the Pinal/Elephant Head link was working. We installed the first two dishes on Mt. Bigelow and a second dish on Pinal Peak.

It points to Elephant Head thru the plywood
The dish was assembled from sections

The construction on Mt. Bigelow proved a real challenge as we had to haul everything we needed up a 12 foot ladder to a third story attic of the transmitter building. The ladder poked through a three foot square opening in the floor of the attic. Our biggest challenge was to get a six foot dish antenna through this hole. Luckily we found a surplus home satellite dish that came apart in sections, so we were able to disassemble and reassemble the dish in its new home. We also mounted an eight foot grid dish on the exterior of the building to point toward Pinal Peak. Getting the RF to work was fairly straightforward. It was a matter of running heliax to the dishes and hooking them up to the filters. The hard part was getting the Granger mux to work. The radios we had were part of a whole shelf and we were missing many of the baseband components.
Interface card
Homebrew interface card
We found we had to homebrew some audio pads and high pass filters to make the mux work with the radios. We learned a lot about terminations, measurements, Bessel functions and the need to get test equipment calibrated. All in all, we found out that getting mux to work was a matter of getting the levels set very accurately. There is not much room for error. In the end, we had the bypass running by the time CARBA hosted the Cactus meeting in February of 1999.

The microwave construction story continues on Page 4

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