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FM antenna length on cars

2

2longinbiz

Guest
I wonder if anyone can answer this for me. I always thought the optimum length for an FM receive antenna is 31 inches. Most new cars use "stubby" types only a few inches long, as on my new Mazda. Is there anything different about these, or have car makers sacrificed reception for aesthetics? Thanks.
 
> I wonder if anyone can answer this for me. I always thought
> the optimum length for an FM receive antenna is 31 inches.
> Most new cars use "stubby" types only a few inches long, as
> on my new Mazda. Is there anything different about these, or
> have car makers sacrificed reception for aesthetics? Thanks.
>
A 1/4wave vertical on FM band would be about 2.34ft @100Mhz (which is close enough to 31 inches which is actually best at the low end of the band)....it is the easiest to do but a 1/2wave of 54-60 inches would be a little better with gain; just not as easy or pretty

As to the studdy antennas, unless they have an active preamp to make up for loss, YES they have sacrified reception strength.
 
> I wonder if anyone can answer this for me. I always thought
> the optimum length for an FM receive antenna is 31 inches.
> Most new cars use "stubby" types only a few inches long, as
> on my new Mazda. Is there anything different about these, or
> have car makers sacrificed reception for aesthetics? Thanks.

Mine is bigger - GM's CB antennas were huge.....

FM on my Caddy is great - AM sucks because the electrical system is effed up....

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CBS-FM lives at http://67.83.115.5:8010
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> > I wonder if anyone can answer this for me. I always
> thought
> > the optimum length for an FM receive antenna is 31 inches.
>
> > Most new cars use "stubby" types only a few inches long,
> as
> > on my new Mazda. Is there anything different about these,
> or
> > have car makers sacrificed reception for aesthetics?
> Thanks.
> >
> A 1/4wave vertical on FM band would be about 2.34ft @100Mhz
> (which is close enough to 31 inches which is actually best
> at the low end of the band)....it is the easiest to do but a
> 1/2wave of 54-60 inches would be a little better with gain;
> just not as easy or pretty
>
> As to the studdy antennas, unless they have an active preamp
> to make up for loss, YES they have sacrified reception
> strength.
>
Wouldn't the extra length be more prone to overload as the old telescoping AM car antennas did when used for FM?
 
> > > I wonder if anyone can answer this for me. I always
> > thought
> > > the optimum length for an FM receive antenna is 31
> inches.
> >
> > > Most new cars use "stubby" types only a few inches long,
>
> > as
> > > on my new Mazda. Is there anything different about
> these,
> > or
> > > have car makers sacrificed reception for aesthetics?
> > Thanks.
> > >
> > A 1/4wave vertical on FM band would be about 2.34ft
> @100Mhz
> > (which is close enough to 31 inches which is actually best
>
> > at the low end of the band)....it is the easiest to do but
> a
> > 1/2wave of 54-60 inches would be a little better with
> gain;
> > just not as easy or pretty
> >
> > As to the studdy antennas, unless they have an active
> preamp
> > to make up for loss, YES they have sacrified reception
> > strength.
> >
> Wouldn't the extra length be more prone to overload as the
> old telescoping AM car antennas did when used for FM?
>
I just noticed that my last post was dated 7/20 @ 6:41AM instead of 7/19 @ 10:41PM!
 
> As to the studdy antennas, unless they have an active preamp
> to make up for loss, YES they have sacrified reception
> strength.

Yes, the new stubby antennas have preamps (RF boosters). The stubby antennas are useless without them.

I hear that those antenna preamps cost a small fortune to replace when they die, which happens often (but usually not until after the car goes out of warranty). It's another modern-day moneymaking scam.
 
> Wouldn't the extra length be more prone to overload as the
> old telescoping AM car antennas did when used for FM?

Actually, No.....a preamp is more likely to overload...thus being a bigger issue....a 1/2wave vs a 1/4 wave antenna will not cause overload in the rcvr front end...putting an active preamp at the base of any antenna will be a bigger threat to overload and intermod!
 
Yes reception IS compromised. Many new cars don't even have an antenna that I can see at all. Maybe they have gone back to the old wires in windshield approach or something. UGH! I rented a car a while back when my car was in the shop - the reception was crap. The local stations here in town are on big sticks about 60 miles away. Picket fencing, dropouts, mono blends. My old Pioneer car radio with a 31 inch whip hangs in there with no problems. It makes me wonder how the IBOC crowd ever expects to avoid constant analog switchovers with these crappy car antennas.

In the car before this one, I had the same Pioneer car radio and an old 60 inch telescopic whip. FM reception was MUCH improved over a 31 inch whip, with all of the rim shots strong and in stereo with many fewer dropouts and mono blends than I get now. AM, of course, was absolutely fantastic - but with the old KOMA going to talk, I didn't need an AM DX setup any more so I didn't transplant the 60 inch whip. I wish I had - for FM reception because like everybody else I though 31 inch was better. Its NOT.
 
> Yes reception IS compromised. Many new cars don't even have
> an antenna that I can see at all. Maybe they have gone back
> to the old wires in windshield approach or something. UGH!
> I rented a car a while back when my car was in the shop -
> the reception was crap. The local stations here in town are
> on big sticks about 60 miles away. Picket fencing,
> dropouts, mono blends. My old Pioneer car radio with a 31
> inch whip hangs in there with no problems. It makes me
> wonder how the IBOC crowd ever expects to avoid constant
> analog switchovers with these crappy car antennas.
>
> In the car before this one, I had the same Pioneer car radio
> and an old 60 inch telescopic whip. FM reception was MUCH
> improved over a 31 inch whip, with all of the rim shots
> strong and in stereo with many fewer dropouts and mono
> blends than I get now. AM, of course, was absolutely
> fantastic - but with the old KOMA going to talk, I didn't
> need an AM DX setup any more so I didn't transplant the 60
> inch whip. I wish I had - for FM reception because like
> everybody else I though 31 inch was better. Its NOT.
>
Was the 60 inches one solid piece or telescoping?
 
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