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School me on FM antenna

WaterH

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I'm installing a stereo in my project truck. I was under the impression that antennas were for AM radio, but I see it has an antenna jack. I really don't want an antenna sticking out the truck. Is there any chance it will work under thin aluminum sheet metal? What about these "shark fin" antennas? Do they work good? I also saw "stubby" antenna. Are they any good?
 
interested as well.
I guess not many radio guys here. I was at a car show the other day and a guy had an old truck fixed up nice. He had a full size antenna sideways under the dash mounted in rubber. He said it works good when he's stopped. But it's shit when he's driving. Of course the (Chevy) truck was heavy steel construction. (68' vintage)
 
4x4toyotatyler can you lend some of your radio experience on this?

WaterH there's some info online about building an under-dash antenna or using the vehicle itself through the ground circuit, but I haven't tried anything. In my experience without something plugged into the RF plug on the back of the radio, nothing is coming in unless you are right next to the transmitter.
 
Several manufacturers embed the antenna in the glass.

Can you put this or something like it someplace discreet?

 
in my sons car he mounted his under the package shelf in the trunk rather than using the hole in the rear fender and he had no issues. seemed to get decent reception.
 
The shark fin on the wifemobile sucks. No antenna doesn't work for FM well at all in my experience. I have used the wire thread on scotch tape on windshield antenna setup before, not sure if that's still a thing (it was a JC Whitney thing in the 90's when I last did it), but it worked pretty well back in the day when I couldn't mount the fender mount back on due to swapping to fiberglass fenders with a different flare angle/height. Back in Radio Shack days, you could get a 12"-ish rubberduck FM antenna that worked pretty well, looks like Crutchfield has some similar options in the $25 neighborhood that would probably work decently for what you're after.

Universal Antenna
Dual MANT16B (Black)
 
And now, coming over from the hosting thread, we get into radio, which is the other large part of my career, lol. Though my radio expertise is in the form of 2 way radio (think police radio type things), a lot of it transfers to AM/FM reception as well.

There's a lot that goes in to a proper antenna design, though a receive only antenna is a hell of a lot easier to deal with and is much more tolerant of bad design or installation.

In short, just about anything metallic will work as a radio antenna. This is why shoving a paperclip or screwdriver in the antenna jack will pick up radio stations. To work well, especially in areas with weak signals, you need an antenna specifically designed for whatever frequency you're trying to receive, and bigger isn't always better. This is why trying to use the old 102" CB antenna often works poorly compared to the whip that comes on most cars.

However, metal is also very good at blocking radio signals (Google Faraday cage). All things being equal, an antenna outside a metal body car will work better than one inside. Something under a steel dash can be just about useless.

No, it doesn't have to be an ugly whip on the fender. Think 70s/80s GMs with the wire embedded in the windshield. Yes, using the car body as the antenna works surprisingly well, but you may also end up picking up a lot of electrical noise as well. I did this on my Scout in the 90s when I was a dipshit teenager that didn't know any better. Now I'm just an experienced dipshit adult, lol.
 
I got the stick on windshield antenna. I haven’t stuck it on yet, but it works great just hanging there. It’s about a foot long. Would it be better to orientate it horizontally or verticall?
 
Fyi AM varies the height, but has a constant width. This is why a long antenna can get lots of stations. FM has a constant height, but varying width. This is why most antennas on cars are ~29" long
Who the hell listens to the radio anymore? I'm all mp3 or streaming

fmamcompare.gif
 
My 58TRUK has the FM antenna zip tied under the door step well. It worked when I installed it. I did stick the antenna into plastic tubing, you don't want the mast grounded out
 
Fyi AM varies the height, but has a constant width. This is why a long antenna can get lots of stations. FM has a constant height, but varying width. This is why most antennas on cars are ~29" long
Who the hell listens to the radio anymore? I'm all mp3 or streaming

fmamcompare.gif
Tell us more about how you don't really understand how RF works...hint - modulation type has absolutely zero to do with why antennas are different lengths.
 
You'll likely notice slightly better reception with it horizontal. FM broadcaster's antennas typically are set up as horizontally polarized, or circular polarized, which is a horiztonal hybrid designed to improve reception on a vehicle's vertical antenna.

Vertical antennas are largely a holdover from the days when AM dominated, and packaging of cars. It's just simpler and cheaper to have a whip sticking up from a fender than anything else.

Though in reality, modern receivers & transmitters are so good that combined with the stupid amount of power run by most FM stations that it won't be a huge difference either way.
 
It’s mounted horizontal. But it is a square zig zag shape. So I guess that is both vertical and horizontal. It works, but it worked much better when the wire to it was hanging down. When I coiled the extra wire up to tuck it in the cover, the reception went down. I guess some reception comes from the wire.
 
I had mine removed from fender but had it fit along side the inner fender rail where hood lays. Still works good when in city limit.
 
It should/might.

With cb radios and tuned length cables, twisting the coil prevents a standing wave build up. Basically, it stops physics.
The science behind not looping transmission cable into a loop or coil, is due to the large amount of current moving through the cable WHEN TRANSMITTING.
A coil, is a choke. It blocks high frequencies and allows lower frequencies to pass.

No need to worry about how the coax is dressed on a recieve only installation. We are dealing with mincrovolt range.... ( like your stereo)

You do want to avoid running in the engine bay, or across an ECU.

FM antennas at one quarter wave like to be 30ish inches.
 
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