Best antenna

OK from everything I have read, I have come to he opinion... coax length should m mmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmmm39.+
not matter when it comes to SWR. If you have a perfect !:! SWR It should, in a perfect world be the same at any reasonable length. When your SWR is less than perfect the SWR's appear to change due to the slight change in resistance or loss across the cable. This is my personal conclusion, after reading all I could find. Rather yhan quite a loy of info... here are some relevant links:

http://www.jeepforum.com/forum/f20/coax-length-swr-exposed-1256187/
http://www.eham.net/ehamforum/smf/index.php?topic=12116.0;wap2
http://www.hamuniverse.com/testingswr.html

It has been a hotly debated issue as long as I can remember. In theory, from what I read, is that a shorter coax will provide less loss thereby providing the most accurate reading. As someone mentioned coils, They are a definite no-no. Don't eatly coil a lot of extra coa... trim it or route it a different way.

 

You are very close on your analysis. With a properly matched antenna (1:1 SWR), the length of the coax will have no effect. (Assuming a 50Ω system.) If the antenna isn't matched, the coax length will have an effect on the impedance that the transmitter "sees". However, it's not the resistance of the coax that has the effect; it's the inductive and capacitive reactances that do, as well as the phase angle of the reflected wave.

Side note regarding the 18' myth: (And yes, I do mean myth.)

A half wavelength of feedline does have a few unique properties. One of these is that the SWR measured at 1/2λ (or integer multiples) will be exactly the same as it is at the antenna connector. However, this is 1/2 ELECTRICAL wavelength, not physical wavelength. (The physical length of 1/2λ electrical wavelength of most common coax is a bit under 12 feet.)

As for coiling the coax... I found that making a coil of 5-6 turns of coax *at the antenna* does a great job of keeping RF out of the cab. The coil forms a choke, and keeps RF from flowing down the shield of the antenna. Some poorly designed antennas (which may not be cheap!) actually rely on the loss of this shield current to make a reasonable match. I will say that the antenna I'm using a choke with is not one you're going to find at a truck stop...


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18 feet of coax is a myth. The halfwave length of the cb frequency is 18 feet ONLY when the signal is traveling through air. Your signal is traveling through coax between the radio and the antenna not air. The halfwave length of the cb frequency traveling through metal -- like the center conductor of your coax cable-- is 11 feet 10 inches. Now 18 feet of coax will infact work. But at more than 50% longer than the halfwave length of the coax you are using, this proves that the halfwave length of the cb frequency is irrelevent to the length of coax you need to use.
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If you need 18 feet to connect your radio to the antenna, then okay use 18 feet.
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.If you can get away with a shorter length by all means use the shorter length. Shorter lengths have less signal loss. Shorter lengths have less excessive cable that needs to be stored. Improperly stored coax can cause inductance that screws up your tuning of the antenna. I recommend that excessive cable be stored in the shape of a figure 8 that is approximately 12 inches in length. Maintain the figure 8 shape by using tape.

 

Everyone has an opinion on this subject. Mine is I have used 18ft since forever just because that has been the common wisdom forever. I have always been able to get a good swr match on singles and duals with 18ft of coax. Therefore if it is not broke don't fix it.

 

At CB frequencies, whichever is cheaper. Seriously. RG8X ("mini 8") is lower loss, but the difference is so slight that you can't tell.

 

I agree, I used to run Francis fiberglass whips and loved them, but after breaking 3 over the years went for the Wilson 2000 Trucker it performs well and is durable. The only thing I lost was I had greater NOAA weather Alert reception with the fiberglass whips, not a biggie to me.

 

I agree, I use 9' of coax to minimize signal loss. Whenever I change out coax (which is about every 2-3 years max weather it looks good or not), I figure 8 the excess and check my SWRs BEFORE I start sawing on my antenna. I have had good results lowering my SWRs by shortening or lengthening the figure 8 loops.

 

Best CHEAP antenna for me: Francis

 

Fikstick any good?