Troubleshooting mylack of distance, receivng and transmitting.

You're kidding.......right?????

 

...Obviously

I forgot my /sarcasm tag

 

Hang around awhile, it's what they do here.

Thank you Dr No for the attempt to explain. Don't forget, some people still think the world is flat, i.e. they have believed something so long no amount of facts will change their mind! I don't think several here really read what I said about coax length. At least it didn't appear so by their comments. I also don't think some on here have the EXPERIENCE I do in installing radios in trucks!!! In fact, I know they don't.....you know who you are so I'm not going to be tacky and name you. As Dr No said, I have found something that works reasonably well in the Freightliner Cascadia. Now those of you who have never tried to successfully install a radio in this truck try to tell me I don't see what I see. Pretty funny really. I'll say it again. Cutting the coax is not how you tune an antenna........but it can work, in certain situations to improve a bad SWR. Now that is all I'm saying!!! If you say "not true", then I have to conclude you really only think you know what you are talking about, because I know better!!! I've have done it....numerous times.

Somebody mentioned the antenna tuner. I may revisit that at some point. The one I had was large, bulky and expensive so I didn't like the idea of it bouncing around in the truck and maybe getting torn up. Plus it was just something else I had to carry and keep up with. Remember, I slip seat and have to take everything with me every time I come to work and go home. With me, this whole antenna problem has to be something I can solve quickly each time I get in a different truck.

I also tried the rear of the cab thing. I couldn't get a good SWR with a 4.5ft Francis, or a Shooting Star.(the one with the nail in the end of it) A 5.5 Francis worked pretty good, but it stuck up higher than the trailer. Several of our drivers tried this and ended up breaking their antenna. Plus it was a pain to run the coax and would also get expensive having to use half dozen or so zip ties every time to tie the coax up. Much simpler to just run it thru the door from the mirror.

It's late. I'm done for now.

 

lol.....o.k. I was being a smart #$% and attempting to be a comedian at the same time.......... By the way, I know I'm masking the problem. But if the meter says the SWR is low, the radio is happy, if not as efficient as it should be. If the meter says the SWR is over 3:1, the radio ain't happy and either am I.

(now I'm really done.................good night!)

 

The coax is only the messenger to the antenna if it is cut to a phase angle of 180 degrees or any multiple thereof. any other length will result in coax terminated in a reactive situation of non characteristic impedance as an impedance transformer. SWR remains constant regardless of coax length-- impedance does not.

Another way of putting it "in laymens terms" is if the feedline is cut at the precise location where current and voltage are equal, the feedpoint impedance will be seen by the radio. Any other random length, and current and voltage will not be equal, hence creating a situation which transforms the impedance seen by the radio. Current and voltage are only equal every 180 degrees through the feedline.
Reactance primarily becomes an issue in mobile installations, and less of an issue on base installations with an actual earth ground, which is why cable length is irrelevant for most base applications and totally relevant for mobile applications.