Re: FM radio antenna height for car... ?

[NeilH011]

>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.

If it's a screw-in type why not replace it? You can find aftermarket ones that
are much shorter (right at about a foot long) that have the requisite length
of wire wrapped in a coil around the shorter antenna shaft. I've seen 'em in
different colors too, so you can get a plain black one or a flourescent lime
green one if you want : )

NeilH

[Scott Dorsey]

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.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[dt king]

"Scott Dorsey" > wrote in message
...
> WideGlide > wrote:
> >
> 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.

Good chance to pick up a new CB radio, extra large belt buckle, ball cap,
and one of those salted pecan rolls, too.

Love those nut rolls.

dtk

[Kurt Albershardt]

dt king wrote:

> "Scott Dorsey" > wrote in message
> ...
>
>> WideGlide > wrote:
>>
>> 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.
>
>
> Good chance to pick up a new CB radio, extra large belt buckle, ball cap,
> and one of those salted pecan rolls, too.
>
> Love those nut rolls.


I got a really nice DC microwave (and one for a friend) there a couple
years back. Saved me buying an inverter and kept me 60Hz-free in my
camper. Of course most popup truck campers can't handle the 72A draw
very well, but I've got batteries taking up the space where I left out
propane.