want to do it myself

My brother drives a Volvo. He got the "perch" mount that replaces a bolt in the mirror. Attached a regular mirror arm mount, 4 1/2 ft Francis, 9ft coax to his tuned up Cobra 29/ RK 56 mic, and regularly gets accused of running a "big" radio.

P.S. lol...... We get off topic a lot here, but it all usually works out.

 

Title and author.....?????

(Just finished reading a book by Mark Levin, "Men in Black", but he didn't say anything about coax length!!! lol)

 

Yikes, A bunch of nonsense on this board.

You have a bone stock radio?
Any time you buy a new cb, it has to be opened upped and peaked and tuned. ALL new radios are set at 4 watts, a FCC rule. A cb shop should be able to turn your Cobra up to 25 watts.

Now I'll leave so you can discuss ohms.

 

It is not a FCC rule that all new CB radios must be set at 4 watts. The rule is not over 4 watts. Most are more like 2-3 1/2 watts out of the box. I've seen a new CB come out at a little less than 2 watts. If a CB shop can turn a Cobra 29 up to 25 watts they must really know magic. When it only has a 16 watt final.

 

No need to know magic, all you need is a "magical meter" and a "golden screwdriver".

 

You have that right

 

18ft coax is 1/2 wavelength on 11 meters. With a 1/2 wave length coax, the impedance at the antenna end will be the same at the radio end. If the impedance at the antenna is reasonably close to 50 ohm, the same impedance at the radio end will make its finals happy.

 

Well that depends on the coax 18 foot about 210 inches in free space is 1/2 wave in coax it would be about 12 foot ....

 

Oops, you're right - I forgot about the coax velocity factor.

 

Coax length makes NO difference in the REAL world. It only makes the meter read what the operator WANTS it to. The only time it makes a difference is 1) when the vehicle body is "plastic", 2) there's no grounding available, or 3) the design of the antenna is such that the coax is part of the antenna itself.

50 ohm coax is 50 ohm coax. What people are trying to say is, the coax is ONLY 50 ohms at certain places along its length, and that's just silly. What are you gonna do if you use something OTHER than coax: there ARE such things, ya know!!!!

GF