Coax facts

I noticed the last Wilson antenna i bought stated in the directions to use 18 ft...
I only needed about 12 to get the radio wired and it tuned just fine.
I cut the end off of an 18ft run,made it 12 ft and soldered a new end on.
The 18ft rule is BS.......lol!

 

yes you are correct. the 18 foot myth is just that. a myth.

 

Ok now you got me curious. If you're not suppose to connect the SWR meter at the radio end of the coax, how the heck do you check with the meter connected to the antenna? I mean especially for the antenna on the right mirror? Do you zip tie the meter to the antenna? I may not be understanding you correctly.

 

And because it was the average length it took to get from antenna to radio in the days of full sized cars. People picked up on the 18 feet thing (omitting the real reason... and not technically important) to have a certain length. If it were important, then I'd have to have 120 or 240 feet for my HF radio on 3923 KHZ
depending on one's version of antenna theory! Now WHERE, or how could I store, 120 feet of coax in a mid-sized pickup truck?

GF

 

I have always hooked the meter at the radio end of the coax. So the proper way is to hook the meter at antenna end of coax. So if you tune the antenna the proper way, then check the swr at the radio, should the readings be the same as at the antenna?

 

Yes, regardless of the length of the coax.

 

And keep in mind that you should tune antennas in an open area, with the vehicle configured as you're going to use it. So, for a car, the doors, trunk, and hood should all be closed. For a Semi, you should tune it with the trailer attached.

 

Old dogs can learn new tricks!

 

And therein lies the problem, "matched properly"..... sometimes difficult to do on today's trucks and some cars/pick-ups as well. If a "proper match" is difficult to obtain, the length of coax can make a difference in your SWR reading. In this scenario, a good SWR does not mean a proper match and maximum performance, it just means you won't damage your radio when you transmit. You folks that say coax length doesn't matter aren't dealing with real world conditions. It shouldn't matter, but it sometimes does because you can't, or it is very difficult, to get a good rf ground/proper match on today's metal-less vehicles.

You folks that just say "coax length doesn't matter" are not really helping the newbie who wants to hook up his radio and talk on it. You are right in theory, but your comments are not really helpful in real world scenarios.... IMHO.

True, but sometimes you have to do what you have to do! (i.e. use the coax as a matching network)