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Mobile antennas with a coil

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#1
It was recommended to me that I would get better recieve and send if my top of cab (metal cab), mag mounted, antenna had a coil. At present I have an older, 30", mag. mount antenna. Would I get any noticable gain with a coiled antenna?

BTW, the antenna is on a Ford Ranger (a wanna be a truck).
 
Joined
Jul 12, 2016
Messages
118
Location
Rossland, BC
#2
It was recommended to me that I would get better recieve and send if my top of cab (metal cab), mag mounted, antenna had a coil. At present I have an older, 30", mag. mount antenna. Would I get any noticable gain with a coiled antenna?

BTW, the antenna is on a Ford Ranger (a wanna be a truck).

I forgot to mention, this is for a CB radio.
 

ofd8001

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#3
Antennas function best when their length is with respect to the frequency it deals with. For example a 1/4 wave antenna is one fourth the height of the radio wave.

Base loaded or coiled antennas have things inside which make the antenna function as if it was the certain length.

Putting it on the roof as you intend will give you the best possible reception.

Generally reception is secondary to transmitting. One wants to avoid as much reflected power back. This is measured by a watt meter and some fine tuning of the antenna length may be needed to minimize reflected power.

This is true for all bands and not just CB.
 
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#4
It was recommended to me that I would get better recieve and send if my top of cab (metal cab), mag mounted, antenna had a coil. At present I have an older, 30", mag. mount antenna. Would I get any noticable gain with a coiled antenna?

BTW, the antenna is on a Ford Ranger (a wanna be a truck).
If you have a CB antenna that is only 30 inches tall, then it already has a "coil". The coils make up for the short length. The coil is in the antenna base.

As OFD said, it's all about wavelength. 1/4 wavelength antennas are often used for mobile radios. On VHF, it's about 18 inches tall, and works well.
Trouble with CB is that 1/4 wavelength is 108 inches tall, and that gets to be an issue on larger vehicles. A true 1/4 wave antenna on the roof of your truck would work well, but then you run into mounting issues, especially with a mag mount, and the actual "running into things".
Most mobile CB antennas are shortened 1/4 wave antennas. The coil in the base, center or top makes up for the shorter length. Coils in antenna bases can also be used to change the feed point impeadance.

30 inches is pretty short for a CB antenna. Replacing that with something a bit more efficient would help things.
I've always had good luck with the Larsen NMO27 antennas. They use the industry standard NMO mount. They are about 48 inches long and have a slender flexible whip. You'd likely have to replace your mag mount, but that's a small price to pay.
I know others have their favorites....
 
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