[SECC] Coax replacement

Thu Nov 12 15:36:17 EST 2020

Speaking of critters chewing coax...

My “wires in the woods” feedlines mosty lay on top of the ground, but under the years of dropped leaves. I began having an issue with a new antenna/feedline install and discovered squirrels had chewed up about a foot of the cable. The two adjacent feedlines were untouched. I cut out the section, installing connectors and a double female. All was good for a month or so. I found a different area chewed this time and repaired it. 

Not wanting to repeat this on a regular basis, I went to Googling for a suitable solution for my situation. 

Turns out, many of the “newer” cables don’t have PVC outer jackets, but have a Soy based jacket. Well, the critters think that you provided them with a food source. 

Be sure to use an appropriate cable for your installation. 

tnx
Mike / W5JR
Alpharetta GA

> On Nov 12, 2020, at 09:38, Jeff (W4DD) <w4dd09 at gmail.com> wrote:
> 
> OH no, Kevan hit on one of my hot topics, so I can’t resist adding to his info.
>  
> I too had read that coax should be replaced every 20 years.  I’ve had a 100ft piece of RG-213 in a black 4 inch drainage pipe to the tower for 20 years.  I test the loss every few years, but it actually has not gone up much, many half a dB at 28MHz.
>  
> What I have found is coax goes bad primarily because various varmints like to chew on it.  The biggest offenders, at least here north of Atlanta, are squirrels.  It seems they like chewing on it right down to the braid.  Once that happens, water infiltrates the braid and wicks along 10 to 30 ft.  The copper braid corrodes and the coax gets real stiff.  Losses seem to go up then.  The squirrels not only like coax, but also like rotor cables and control cables.
>  
> I’ve found two solutions:
> My wife has kinda adopted a feral cat (now spayed and living a good life).  That cat is one good squirrel hunter and this summer I did not see a single squirrel in the yard and so far no additional coax damage.  Unfortunately, my wife feeds the cat some quality food and the cat has decided it’s better than squirrel.  I did find some squirrel bones in the yard last week so she still is working some.  My wife says I owe her for the good job she did.
> Second solution, where critters are likely to chew on the cables (like near the base of the tower) I cover the coax with .5 inch split loom tubing.  You can get 100ft very inexpensively on ebay.  It is more of a hard plastic and critters don’t seem to like it as much as soft coax.  In addition, once they get through the tubing, they don’t seem to want to chew into the coax.
>  
> I went to the Orlando hamfest this year and did run across a hundred ft of almost new 50 ohm ½ inch Superflex (like corrugated hardline but more flexible).  The commercial vendor didn’t seem to want to haul it to another hamfest, so offered me both a 75ft piece and a 100ft piece for the price of a 75.  One of those deals that you are not looking for but can’t pass up.  I installed the 75ft piece to the tower base with a short flexible jumper at the house end and saw about a 1dB decrease in loss at 28MHz over the old coax.  In addition, it is a solid outside conductor so even it the critters chew through the jacket, no water will wick along the shield.  The other piece of Superflex may be used to feed a 6M beam one of these days, with an appropriate flexible jumper near the rotor.
>  
> My other project is to get a Tic Ring Rotor working and mount it on the tower at 50ft to turn the A-4 tribander.  That will allow me to rotate something for 15 and 20M.  but as Kevin said, we don’t move as fast as we used to.
>  
> And am working on several power line noise issues to the NE and SE.  I’ve identified the defective hardware on 5 of the 7 poles, and am awaiting the engineer and line crew.  Those noise sources killed me during the CQWW a few weeks ago.  Hard to hear weak EU through S-4 noise.
>  
> Jeff
>  
>  
> From: SECC <secc-bounces at contesting.com> On Behalf Of Kevan Nason
> Sent: Thursday, November 12, 2020 7:36 AM
> To: secc <secc at contesting.com>
> Subject: [SECC] Coax replacement
>  
> I like Jeff's, W4DD comment about posting at least once a month.
>  
> Here's something I put in another clubs newsletter about current activity at N4XL:
>  
> ·         Truth or fiction?  It came to my attention while preparing a presentation on different types of feedlines for our local club that most coax cables, including the non-contaminating type, have a finite lifetime of between 15 and 25 years. After that, the loss begins to creep up. I didn’t care enough when I first set up this station to record station data so have no idea what SWR or reflected loss changes have occurred over the years. It seems likely any changes due to aging coax would be waaayyy to slow for me to notice over the 20 years that have passed since I installed my coax runs; and to that point I can’t say I actually do have excessive loss. So, I started looking on the internet. Most posts say it should be replaced.  I ran across a discussion about this on the TowerTalk reflector (at least I think it was that one) where K3LR (I think) said he doesn’t replace his unless he sees a problem. He has quite a station so maybe it doesn’t need to be replaced.
>  
> Looking at my exposed coax it is rough feeling and no longer shiny and black. For the most part, it is Davis Buryflex. I bought some new Buryflex for a doublet I installed a couple years ago. The 20-year-old cable seems to be more flexible than the new. Also, when I put the Rigexpert antenna analyzer on the 175 ft run out to the elevated vertical it says the 7 MHz return loss is a bit over 1 dB (one way) higher than the specifications say it should be. Since most coax runs were installed at the same time I assume they all would read similar loss.
>  
> It is getting harder to work as these bones get older. About 200 ft of my coax is buried in clay. Beginning with the tower, I decided to replace all the coax rather than waiting a few more years. I’ll rent a trencher next spring when the grass starts growing again to replace the buried runs. Is it worth the cost and effort to replace? At the very least I’ll feel better about my system when I’m in the heat of the contesting battle. At best, I’ll remove or prevent a couple dB loss in my antenna system. Loss that I might not be up to fixing 10 years from now. Those crimp on PL-259’s we talked of last newsletter are working out well. 
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