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A little afternoon project
Darren:
--- Quote from: John Hill on November 08, 2009, 03:23:30 AM ---
--- Quote from: kvom on November 06, 2009, 08:05:08 PM ---For offroad use you don't need as big a range as a truck driver does. Mainly you're just talking with people within a few hundred yards at most
--- End quote ---
The size of the aerial is determined more by the wavelength being used than the working distance.
--- End quote ---
I think he was referring to the advantage of roof mounting instead of side mounting and having a box metal box in the way of the signals.
Because of the short distances the effective power loss wouldn't matter.
SKIPRAT:
all points noted Darren what i was trying to say is that having a transmitting part of an antenna close to metal objects makes tuning the antenna difficult (SWR problems) when off roading you usually only need a range
of a few hundred yards or so i just thought i would add my little bit on the subject . My other hobby is amateur radio and has been for quite a few years.
Cheers Paul 73 G6FOW
75Plus:
The advantage of roof mounting is that the roof becomes a "Ground Plane" and tends to radiate the signal evenly in all directions. Compared to the side mount pictured which will have the stronger signal in the direction AWAY from the vehicle.
I have used roof mounts for VHF/UHF antennas since they tend to be short. I use rear mount for HF antennas and try to point the vehicle toward the location I am in contact with. Turning away can cause a 3 or 4 DB drop in signal.
73's n0fnf
Joe
John Hill:
No doubt about it the centre of the roof is the ideal spot for a VHF whip antenna but if that is impractical because of bushes, trees, low garage roof etc (or if the roof is fibreglass) another really good spot is smack bang in the middle of the bonnet ('hood' for those rebel colonists) but you will need a wire braid to ground the bonnet to the rest of the body and of course good shielded cable within the engine compartment.
kvom:
The Jeep has no roof, but rather a DOM tubing roll cage.
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