Weird Coax Problem

[flintstone mop]

Well Folks
It looks like I have to spend some money on about 150 feet of coax. Prolly call RadioWorks or RadioWare, depending what comments are made from this thread.
I'll have to replace a length of RG8U with some RG213.
                                                 The Story
The cable I was using and was only a couple of years old developed humps and bumps over the HF bands. I was wondering why my latest addition to the antenna farm was giving me a 1.7:1 SWR on 160M, when I was at the base of the antenna with my Antenna god (MFJ259), reading 1.2:1 at 1885. The vertical is about 400 feet from the house, going through an MFJ RC8V antenna switch about half 200 feet away, where there is an 80/40M vertical. Looking back (MFJ connected at the disconnected vertical) towards the shack with a known good 50 ohm load on the distant end (shack) I saw this weird 1.7:1 SWR. I swept the line and saw that it was fairly flat from 3.2 mhz to about 4.0 mhz then there would be these humps and bumps of high SWR and then it would settle down around 40M with almost 1.2:1 SWR then it was off in never never land above 20M. I replaced both connectors and same results. It must have been some low life cable I bought cheap from an on-line source. Does JSU cable sound familiar?? Any way it's off to the copper man.
That's my story
G'day

Fred

[flintstone mop]

oops!

I forgot that this length of  coax was plain ole bad junk high SWR 1.8:1 for the entire 160M band and down to the B'cast band.
I never saw anything like this before. Any other stories out here??
Fred

[Jim, W5JO]

I have seen that type of thing with hardline, but never coax.  Usually that means water has invaded it.  I have about 75 ft. of RG 8 in use that is about 26 years old and it still does not exhibit loss in excess of the specs. 

Get the direct burial type of feedline, can't remember the designation, but do watch Alpha brand.  The manufacturing of it leaves a lot to be desired.  Some of the private label stuff is made by them and can give problems in the long run.

You can check the following web site in your quest.

www.coaxman.com

Just get the name brand and mil spec.

[W1RKW]

 Slap an ohmmeter on one end of the co-ass and see if you read anything. Make sure the other end is open. That will tell you if you have moisture in the cable.  Been there.

[W3SLK]

I guess I'll throw my $1 worth of advice in here too, (it used to be a nickel but due to inflation.......) I would see if I could track down some mil-spec surplus stuff. I bought a 200' spool of RG-213 a few years ago. Its seen its share of weather and UV rays and it is pretty much like the day I (and the government) bought it.

[N3DRB The Derb]

or slap a known 50 ohm load on the far end, and hammer down, carefully. if it dont read 1.1, you have bad soldering a connector or water has gotten in it or contaminated the outside part of it.

[W1RKW]

I thought I had a weird coax problem....  A couple of months ago I discovered my direct buried coax was acting flakey or so I thought. Not giving it a second thought I just figured it was time to replace it. Not having the time to mess around with it the last couple of months, today I decided I was going to simply replace the buried section. 

I went through all the trouble of running another section under the ground and connected everything up to discover I still had the same problem.  I got to the point of scratching my head wondering what the deal was, then got pissed. I through my hands up in the air and said the hell with it.  It can wait until spring, what's a couple of more months.  It's too cold out for this.

Well, it kept bugging me so I went back outside and decided to look up instead of down.  The feedline was disconnected at the feed point. The end of the coax was hanging in mid air by the strain relief on the center insulator.  From where I was looking at it, it looked like it was connected.  Looking at it from another angle (directly below) one could easily see that the end wasn't connected. 

The wind must have flexed the cable and strain relief just enough to cause the connector to unscrew itself over time.  So I dropped the sucker down.  Reconnected it, secured it tightly, hoisted it back up and shazam, signals are coming in nice and strong again. Then I was really pissed for wasting all that time and cutting up a good piece of cable.  So I tipped a couple of 807's and then all was better.

[flintstone mop]

Bob,
It sounds like a neighbor trying to put you off the air.
We ran across the same thing in Company vehicles with the 2-way radio. How in the HELL does a PL259 UNscrew itself from under the seat? So, we took a pair of plyers and gave it a little extra knudge to tighten. The next tech would be cussing trying to unscrew the PL259 on that COLD day to get an RF watts reading for another trouble call on the same vehicle. The RED line battery cable had a nail through it. LAZY no good mow fow!!!
Fred

[W1RKW]

Fred,
I wondered about that too.  Not sure if a neighbor was the culprit or not.  I tend to think not.  I don't think they'd come over to my yard, lower the antenna, disconnect it then raise it back up.  Heck, the thing is nearly invisible and they'd need to know how I set the thing up to lower it.  I think the wind got it and over time is just came loose.  But I wrenched it up tight and taped it so if it happens again then I'll know for sure if it was tampered with.

[kb2vxa]

Now if me was ye me think the lack of noises my receiver makes... hmmm?
(ducking)

[flintstone mop]

The very high SWR made no difference in the way the receiver operated. The TX didn't like the big SWR.
Fred