Ham Radio

Thursday, October 29, 2009
Roof Mounted Mobile Antennas
I have always used fixed mounts on my vehicles for both HF and VHF antennas which are the boot mounted grub screw type to ensure a good ground is obtained. The only snag is the corrosion that an take place beneath the mount and not forgetting the wibble wobble whenever I opened or shut the back door.

I decided to fabricate my own mounts which would bolt to the roof bars giving an extra 5” (127mm) height above the existing mounts.
To prevent any further corrosion problems I decided to use 3mm stainless steel as the material which took a bit of drilling but easy enough at a very low RPM using a radial drill. Once I removed any burs I bent the mounts into a right angle and mounted the stainless plates as far apart as possible on the roof bar. Each of the mounts is drilled in line to match holes in the roof bar (2 holes each mount) which I bolted up tight.

The antenna mounts went on to the stainless mounts nice and straight, I fixed a short grounding wire to the locking nut on the antenna mount which I fed to a close by bolt that was connected to the vehicles chassis. The SWR was 1:1 on 20M and whilst mobile earlier this morning I made QSO with Roy – VK6MV beaming long path. Roy was 5/9 at times from Cuballing, in Western Australia coming in very well to Yaesu’s original Field Commander more commonly known as the FT-100. I recieved a 5/5 report which was excellent as I was actually mobile. I also made QSO with Estonia and Italy whilst operating /mobile with the new antenna mounts. The final result looks a lot better than the commercial mounts you see, the new mounts are solid, well grounded, neat, as well as very strong.

The Antennas pictured are 145/433MHz and 14MHz, The Vehicle is a Toyota Rav-4
Mount Is Grounded To Chassis With Short Wire
posted by Simon Davison @ 5:54 pm  
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