Hello The Net: I am also pondering adding a commercial GPS antenna on the roof at a height to locate the bottom of the antenna to just clear the ridge line.
Choices I have addressed for my sloped and shingled roof: 1. Secure the antenna to an existing roof penetration, like a drain pipe vent for the shack bathroom. Snake the coaxial cable down the vent pipe, cut the drain pipe inside the attic and add a PVC tee section, allowing the coax to come out the horizontal "tee" outlet. Seal as needed to keep vent gasses outside. I do not suspect the vent gasses from the septic system to be corrosive to a GPS antenna rated for outside installation. The coaxial cable can be a "poke thru" the "tee" and sealed or a connector could be applied and sealed. 2. Use a separate vent pipe penetration fitting exclusively for the GPS antenna and stub mast of non corrosive piping. Put the penetration near the ridge line, but not on the ridge line, with a stub mast, maybe 2' long. Any roofer could do the watertight installation. Penetration flanges are available in a wide variety of sizes, 1" thru 4" and sized for PVC DWV (drain, waste, vent) piping. Inside the attic I would use wooden blocks secured to the rafters to support the stub mast from moving and to keep it centered in the rubber gasketed flange. I would locate the roof penetration just above where I wanted to penetrate the shack ceiling. Could use a plastic electrical wall plate at the ceiling penetration, and a bulkhead RF coaxial connector. 3. I have a continuous ridge vent of fibrous material with shingle material, applied over it. It would be possible to sneak (snake) a cable thru this material and still maintain weatherproof integrity. The GPS antenna could be mounted on corrosion resistant sheet metal, bent to compensate for the roof pitch. The cable would be mounted on a direct path to the shack. 4. Right now the GPS antenna is on a ground mounted tripod, at about the height of the top of the gutter and roof drip edge. I use a continuous vented aluminum drip edge, so I could also poke thru that with a coaxial cable. The GPS antenna could then be mounted on sheet metal. The existing performance on the tripod is good for my Trimble Thunderbolt. The ridge line is about 10' higher, Putting the GPS antenna on the roof would give me some lightning protection, being within the "zone of protection" of the towers near the house. 5. Could put the GPS antenna and larger coaxial cable on the nearby tower, mounting it on a side arm. Minimum of 70' to the house and another 15' after the bulkhead penetration point, into the shack. I do not expect any significant improvement in capture performance by having the antenna at the ridge line height vs. the gutter height. There are nearby deciduous trees to the east thru north and NW. Stan, W1LE Cape Cod, FN41sr ZZZZz _______________________________________________ time-nuts mailing list -- time-nuts@febo.com To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.