Guy, You are so right. The gradual deterioration of coax at this location is a most important issue for me. Even a Beverage falling to the ground with a broken tree support laying on top of it is not as devastating as coax deterioration. I do have a few BC station 200 mile benchmarks and A/B tests to give me some indication. But I normally just replace the runs every two years and throw it away or use pieces for spider radials at the end of Beverages.
Herb, KV4FZ On 6/21/2012 11:47 AM, Guy Olinger K2AV wrote: > On Thu, Jun 21, 2012 at 10:40 AM, Jim Brown<[email protected]>wrote: > >> The other element of transfer impedance is the uniformity and >> density of the shield, often described as shielding effectiveness. >> Foil/drain shields designed for use at VHF/UHF (i.e., CATV coax) have >> fairly high resistance at 2 MHz as compared to something with a decent >> copper braid, so they're not great shields at MF and low HF. >> > I have recently replaced some "RG-6" in use for maybe seven or eight years. > I opened it up to see what was happening. The degree of oxidation on the > inside and outside of the foil was perplexing. One could easily draw a > thumbnail along either side and build up a little pile of oxide. The foil > itself had become very brittle. It had been "sealed" and treated outside. > > If Jim says the shielding needs help when it's new, there's not much hope > for some varieties when it gets old. Another reason not to use anything > other than the flooded variety. Particularly so for someone who can look > at the ocean. I'm hundreds of miles from salt air. Would need to go with > flooded for sure close to the ocean. > > The deterioration would be sneaky slow, and unless one had worked out some > kind of benchmarking for it, one would never know. > > I've got flooded "RG6" to my phased loops-on-ground, and the over-the-air > outdoor TV antenna, and they're hanging in there so far. > > 73, Guy. > _______________________________________________ > UR RST IS ... ... ..9 QSB QSB - hw? BK _______________________________________________ UR RST IS ... ... ..9 QSB QSB - hw? BK
