Changed Coax And Now Have Problem

[Doughboy]

Here it is in a nut shell change coax from lmr 400 solid copper center 18 ft run to 213 about 13 ft or so.......Good swr's 1.3 to 1.4 on 1 thru 40. Checked coax with meter everything checked good....and now my dead key jumps all over the place when I turn on the big box....all so made a home made magnet mount...so I put everything back on bracket mount and the same thing again.....same coax the 213.... I am going to try the lmr 400 this weekend if it doesn't rain on me.....

What you guys think could be the problem bad ground or what......

[Doughboy]

No body has any ideas on how to remedy this problem.

All i know is this shorter run of coax isn't working. I would think somebody out there has come across this before. Will have to work on it tomorrow when the rain stops......

['Doc]

I have to say that the quick-n-dirty answer is that you ought to tune your antenna correctly. If it's input impedance is 50 ohms, the feed line's impedance is 50 ohms, and the radio's impedance is 50 ohms, then the SWR is going to be good. If you stick that amplifier in there and it's output is 50 ohms, the same thing will hold true.
It's jsut a simple fact that SWR meters are easily fooled into thinking that something 'not right' appears to be 'right'. It's not a very common or nice thought, but it's a true one.
- 'Doc

[231]

I have several thoughts of what it could/might be. But without more information would be purely speculation.

I'd be curious though of why you switched the coax in the first place, did the LMR-400 have a problem? Granted, it doesn't like tight bends (usually) but really that confuses me to start with when LMR-400 is usually of lower loss and higher quality.

But you didn't mention what antenna we are talking about too, and exactly what your "big amp" is? Did the hard mount ever have grounding issues before? Did you remove it and then re-install it? If so, indeed it could be not enough grounding...but also there is the question of amp. If you have a bad ground with the amp, it'll usually show up without it in line, too. Where are you locating the meter? It should be between the amp and antenna.

There are allot of little details missing that really could help narrow it down. Doc is right (of course) if everything is correct, that leaves little else.

More info' please.

[Doughboy]

Ok if it is easy to fool a swr meter than why use one anyway ......Believe me I use two to three meters you may fool one but not three or four. Have used MFJ Analyzer the meter was showing a grounding problem by fluctuating, that was with the lmr 400 coax. And the antenna is a Black Al Capone.
I spend days or weeks at finding this problem. And yes the bracket had a ground problem so I started with the coax after I put the biggest strap that was given to me, monster braid from a tractor trailer or something. But anyway the problem has been resolved. By clipping the coax and put new connections on. Ground was exposed to the weather.
I hope this can help someone else with a similar problem.


And Doc every time I read your post it's like you are talking down to people I may not be as smart as you or some of other the members here. I do have a little common sense to get it.
That is why I asked the question. Just my .02 cent have a nice day every body.

This will be my last question asked here..........Thanks a lot...

['Doc]

If you have a '259 and know how to use it then you obviously know what reactances are and how they can affect an SWR meter making them a very 'not good' meter to use to tune an antenna all by them selves.
I don't "talk down" to people. If I disagree, I also say why I disagree. Am I 'smarter' than some people? Of course, and so are you. I'm also not as smart as some people, just like you. If I'm wrong about something, show me how I'm wrong! Also expect the same from me. I can't think of anything more normal than that, can you?
If you don't like what I say, fine. I would suggest that you ignore me, don't pay any attention to what I say.
- 'Doc