|To:||Tom Rauch <email@example.com>|
|Subject:||Re: [TowerTalk] Shields|
|From:||"Tower (K8RI)" <firstname.lastname@example.org>|
|Date:||Wed, 13 Oct 2004 21:30:14 -0400|
Tom Rauch wrote:
At any rate, running a tad over 100 watts into the Heliaxwith the base
It gets even more interesting. The guy lines were insulated from the tower and bonded to the ground posts I was rubbing the screw driver on the lines only 3 feet from the anchors.
It was definitely rectifying the transmitter output on 147.00 as it only happened when the transmitter was up. None of the other bands bothered.
"I think" the noise we never located was probably an abandoned, or unused TV antenna preamp. The area had just gone to cable around that time. It may have still been connected to a TV set. OTOH I guess it could have even been a poor ground on a nearby electric fence.
I don't think we had any problems there. "It appeared" to be external to the system, but appearances can be deceiving. Something external was rectifying the signal and reradiating it covering the input.Noise on repeaters caused by poor connections in antennas and hardware around antennas is common. My two-way business maintained and installed dozens of repeaters and we found all sorts of things causing problems. Despite that, I never once noticed a problem from using single shield cable. Quite frankly, I think it is IMPOSSIBLE for single shield to behave any differently than double shield on VHF or higher, assuming the inner shield is of similar construction in all cables or the cable simply isn't defective.
This would have been about 130 feet from the base of the antenna. The guy line was galvanized wire rope.The repeater out back, for example, has 50 ft of RG-213 in a lightning retarding and RF decoupling choke. It has RG213 jumpers at both ends, and not a lick of noise problems. I just tried grounding and ungrounding the connector at the jumper, and scratching my car keys on the floating cable connector and there isn't the faintest trace of noise on a 10dB quieting test signal injected from an antenna 500 feet away.
Of course this was close to 20 years ago so my memory could be a tad foggy on that. I think you may have still been in the Toledo area at that time.
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions and ask for Sherman, W2FLA.
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