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<jim@audiosystemsgroup.com>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
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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