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FM radio antenna questions

Throckmorton

Lifer
Aug 23, 2007
16,830
1
0
Since my Mustang is in the body shop for deer accident repairs, I'm having them fill the antenna hole on the fender (the 05-09 Mustangs have an UGLY front mounted antenna), so I need to buy or build an interior antenna. The trunk is another option because I have unused holes from my spoiler delete.


I've been Googling, but there isn't much info out there on this topic. Most people interested in custom antennas don't seem to know anything about radio theory and just buy whatever Crutchfield sells. So here are my questions:

1) Do I need an amplified antenna? Every windshield mount antenna I find is amplified. Why? Is it required to get the signal down the length of cable to the head unit?

2) Does the resistance of a custom antenna have to be a certain number of ohms? How do you measure that?

3) Can I use antenna foil tape like this to draw an antenna on the rear window? Is there a thinner version of this product? http://www.aircraftspruce.com/catalog/avpages/copperTape.php

4) How do you prevent the wire from acting as part of the antenna, messing up the optimal length and adding electrical interference from car systems? Shielded wire?
 

NutBucket

Lifer
Aug 30, 2000
26,430
268
126
IMHO on-glass antennas suck. I would much rather have a mast. I guess I'm just different like that. If you notice, lots of new cars use the little roof mounted fins. Not only is it trendy it really does work a lot better than other "slick" options.
 

JulesMaximus

No Lifer
Jul 3, 2003
74,182
632
126
IMHO on-glass antennas suck. I would much rather have a mast. I guess I'm just different like that. If you notice, lots of new cars use the little roof mounted fins. Not only is it trendy it really does work a lot better than other "slick" options.
Those are for satellite radio and, of course, the government tracking device is in there too. :sneaky:
 

Zenmervolt

Elite member
Oct 22, 2000
24,510
11
81
Do I need an amplified antenna? Every windshield mount antenna I find is amplified. Why? Is it required to get the signal down the length of cable to the head unit?
It's because the signal is attenuated fairly significantly by having the antenna placed inside the vehicle and windshield mount antennas don't have the same natural dBi as exterior mount mast antennas. Mast antennas also have the advantage of being omnidirectional, whereas most windshield mount antennas are, to some degree, directional, so the amplifier helps when the antenna's not aligned with the station's transmitting tower as well.

The amplifier's not about "getting the signal down the wire," it's about compensating for the low inherent gain for the antenna. The little "fin" shaped antennas on modern cars, and the stock antennas embedded into the window glass of some cars also have amplifiers from the factory.

ZV
 

Meghan54

Diamond Member
Oct 18, 2009
9,996
2,942
136
After more than a few years spent with both types, I'll take the "horrible" look of a mast over in-glass or on-glass every time.
 

JulesMaximus

No Lifer
Jul 3, 2003
74,182
632
126
After more than a few years spent with both types, I'll take the "horrible" look of a mast over in-glass or on-glass every time.
Does anyone really listen to radio anymore? I haven't owned a car with a mast antenna in more than 10 years. Can't believe any car manufacturer still uses them quite frankly.
 

Throckmorton

Lifer
Aug 23, 2007
16,830
1
0
Does anyone really listen to radio anymore? I haven't owned a car with a mast antenna in more than 10 years. Can't believe any car manufacturer still uses them quite frankly.
Some places have good radio stations, other places just have Clearchannel garbage.
 

nerp

Diamond Member
Dec 31, 2005
9,843
93
91
I listen to NPR on FM. I refuse to pay for satelite radio. I had it for free for a year in my new car and it was not worth the money, unless, of course, you can't get enough of CNN with no video or right wing nonsense or the most mainstream and generic of all music genres.
 

Throckmorton

Lifer
Aug 23, 2007
16,830
1
0
I ordered the Tune Trapper with the wire coming out of the end. Planning to mount it on the rear window, I'll just have to figure out where to run the wire
 

Throckmorton

Lifer
Aug 23, 2007
16,830
1
0
I got my car back and I got my antenna, but I don't think the cable is long enough to reach to the rear window. Can I use an extension for the cable or will it mess up the impedance? I still don't understand what the "ohms" of an antenna means
 

Throckmorton

Lifer
Aug 23, 2007
16,830
1
0
I got the Tune Trapper and wired it in with a 3ft extension (13 ft of cable total) and the reception is great. It even works lying on the back seat. Now I just need to figure out where to mount it. Routing wires is difficult in the Mustang. I have it tucked under the console but from there I don't know where to run the wire... Maybe along the edge of the rear seat and then up the right side (it's a side feed wire)
 

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