Stupid question here

[CATI]

Antenna on vehicle roof already installed.
If someone were to place an aluminum wheel on top of that where the antenna pokes through the wheel spokes and half the antenna was below the wheel and half above the wheel what is the signal loss?

 

[ToddDubya]

2 fars

 

[ToddDubya]

My previous snarky answer should have included a snarky wink. I don't think anybody can know. If I had to guess I'd say it wouldn't improve the signal any, but you never know.

If you have say a 1/4 wavelength antenna, the free space radiation pattern will look like the picture below. The bulk of that radiation is going directly into the aluminum wheel. Now will that wheel couple and just radiate it out? Will it reflect it back in? Will it kind of bend around the wheel? I couldn't say.

If that's your vehicle, I'd say try it out. Listening on an HT without an antenna (do not transmit on the HT without an antenna) you'll lose the signal quicker than if it had an antenna. See how far you can get before it drops out, then take the wheel off and repeat. Personally I'd run the radio in the vehicle at low power so you don't have to go as far.

 

[Uzi2]

You will be changing the entire tuning parameters of the antenna and raising the standing wave ratio (SWR) of the antenna and may render it almost useless, and also possibly damaging the radio.

Put an SWR meter in line and see how the metal wheel affects it. My well educated guess is, it will be unacceptable.

 

[timbo]

Could you mount it semi-permanently to one of the lug nut holes on the wheel of the spare? If the wheel is electrically bonded to the carrier which is electrically affixed to the body of the car. it may work OK.

 

[ToddDubya]

Or move the spare?

 

[CATI]

Or move the spare?

Going to have to move the antenna and cap the hole

 

[Coyote33]

Can you use the hole for the cable, and just mount antenna on top of the spare? You'd need to have a good weather-proof grommet or whatever. That, or go out a window up to on top of the spare. Can a top plate for that tire mounting stud be made? Out of steel, so you could use a magnetic mount antenna?