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Old September 9th 03, 06:52 PM
Scott Dorsey
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Posts: n/a
Default FM radio antenna height for car... ?

WideGlide > wrote:
>The height of the stock FM radio antenna on a new car I bought is about 31"
>high. It hits some things that hang from the garage ceiling so I'd love to
>be able to shorten the antenna. I realize that doing so will most likely
>decrease the quality of reception etc. Someone mentioned that if I shorten
>the antenna I would need to keep it at a certain specific length... a
>multiple of something... in order for it to work effectively...? Is this
>true? I was just going to hack off maybe 6"... thus the total height would
>now be 26" as opposed to 31"... but, is there some formula or rule about
>antenna height that I need to pay attention to? I don't mind if I reduce
>the overall effectiveness of the antenna by a little bit. If I cut 20% of
>the length off the antenna, will I simply loose 20% of the antenna's
>effectiveness? Thanks.

Most car antennae aren't resonant anyway. They are shorter than a quarter
wave and go into a high-z input rather than have a normal antenna system
where the antenna resonates in the band and feeds a low-Z input.

This is part of why car radio reception is so crappy.

Anyway, you could trim it down. Or you could stop at your local truckstop
and get a wound fibreglass FM antenna that will be shorter AND give you
better reception.
"C'est un Nagra. C'est suisse, et tres, tres precis."