Topband: Why do rodents eat coax?
Dave Olean
k1whs at metrocast.net
Mon Nov 9 14:38:32 EST 2015
I was transmitting on 160 last week, and after calling a CQ I noted that the background noise from one of my beverages dropped to almost nothing. Something obviously broke right then. All checks pointed to something external to the shack. I finally got out in the woods and checked the antenna system. All looked great. I used my new SARK-110 vector network analyzer and saw very believable results when connected to my 1100 ft long Europe beverage: about 75 ohms impedance and a VSWR that fluctuated between 1.5 and maybe 1.8:1 across the freq range. I double checked the entire beverage run for shorts or anomalies, and even took apart the termination box to make sure all was OK. The last thing left was the 1000 ft run of flooded RG-6 coax. I had run the cable on the ground back to the house about 2 years ago. It was mostly invisible now, being covered with leaves and moss etc etc. A TDR check showed gross "bad" things and a VOM test across the center pin to ground showed a resistance of 35 ohms while the far end was terminated in a 75 ohm load. Obviously the cable was compromised. I made a quick inspection and found a few spots where small animals had chewed on the coax enough to break through the outer plastic covering and into the braid and aluminum foil shield. Water and gunk have caused a low resistance between center pin and the shield.
What are my options now? I don't want to spend another $150 for another roll of coax just so a squirrel can feast on the PVC. Should I route the coax in the air and away from small mouths? That is one option. It seems that digging a 1000 ft trench thru the woods and burying it would work, but it would be an awful big chore for a 70 year old doofus. I doubt that I could manage that. If I run the coax above ground, I run the risk of picking up noise etc. I also worry about falling limbs and old dead trees falling on it. With a few beverages in the woods, I can't afford to spend $150 each time an animal feasts on it. I need to do something different!
Incidentally, the beverage still has great directivity, but signals are very weak with the bad cable. It is barely useable now as a result.
73
Dave K1WHS
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