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HAM Antenna Placement. Height vs Coax Length?
- Thread starter Brit55
- Start date
All good stuff. A couple of things that I don't think have been covered:
Antenna *location* is more important than height in this case, in that radio waves don't go through vans well. So in general the higher the better - roof, gutter, mirror, hood all better than bumper.
You've picked antenna length already, maybe because you've already got the antenna. But past 1/4 length, on a vehicle, length doesn't matter much if any, IMHO. For sure, location is more important than length. I would probably even go so far as to say a sub 1/4 wave antenna, even 6" long, in the middle of the roof would be better than a 5/8 wave on the bumper, overall.
Everybody is right, coax length doesn't matter much for the size of a van. But keep in mind the UHF (259) connectors for the extension will lose more signal than the coax itself...something like 3dB for a pair, if my memory is right, at 2m. So don't chain more than one of those things together.
If the extended top is fiberglass all the way around, like a 2' raised roof or something over the normal van shell, what about a 2m antenna *inside* the van. Radio goes through fiberglass pretty well, unless you've got metalic paint on it. Or outside, beside the top, where the metal and fiberglass meet.
If the antenna, especially that 1/2 wave one, is close to anything metal or plastic it'll affect the tuning. Check the SWR with a separate meter or the radios to avoid the reflections and associated problems, which include power loss, power foldback from the radio, noise and with some radios potentially some damage.
Tom
Antenna *location* is more important than height in this case, in that radio waves don't go through vans well. So in general the higher the better - roof, gutter, mirror, hood all better than bumper.
You've picked antenna length already, maybe because you've already got the antenna. But past 1/4 length, on a vehicle, length doesn't matter much if any, IMHO. For sure, location is more important than length. I would probably even go so far as to say a sub 1/4 wave antenna, even 6" long, in the middle of the roof would be better than a 5/8 wave on the bumper, overall.
Everybody is right, coax length doesn't matter much for the size of a van. But keep in mind the UHF (259) connectors for the extension will lose more signal than the coax itself...something like 3dB for a pair, if my memory is right, at 2m. So don't chain more than one of those things together.
If the extended top is fiberglass all the way around, like a 2' raised roof or something over the normal van shell, what about a 2m antenna *inside* the van. Radio goes through fiberglass pretty well, unless you've got metalic paint on it. Or outside, beside the top, where the metal and fiberglass meet.
If the antenna, especially that 1/2 wave one, is close to anything metal or plastic it'll affect the tuning. Check the SWR with a separate meter or the radios to avoid the reflections and associated problems, which include power loss, power foldback from the radio, noise and with some radios potentially some damage.
Tom
Last edited:
CaliMobber
Adventurer
What about a clamp mount for the back door? Look at my install on my 4runner. something like that could mount to your back doors and still get the antenna at roof height!
The bumper is about as bad as you can get it unless you can't have a riser to get the antenna starting at the hood lvl. the antenna needs a little room next to it for proper propagation to get a clean output.
The bumper is about as bad as you can get it unless you can't have a riser to get the antenna starting at the hood lvl. the antenna needs a little room next to it for proper propagation to get a clean output.
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