[VHFcontesting] RE: [70cm] Pre-amp question follow up

[John Allen]

I recommend RG-214 for a rotor loop.  (Double Shielded RG213, Silver Plated
Shields).  0 failures in multiple rotor loops in 15+ years of service.

Some RG-214 Info:
http://www.universal-radio.com/catalog/cable/0390.html

http://www.tessco.com/products/displaySkus.do?groupId=403&subgroupId=25

It can sometimes be found at flea markets.  It is quite expensive new, but
you are only talking about 6-8 feet per rotor loop.
Also, I recommend N connectors at both ends of the rotor loop.  (UG-21/D is
a good choice.)  NOT UHF Connectors, not even for HF.  N connectors will
keep water out of your coax better than UHF due to the construction with the
gasket.  I still use high quality electrical tape and Krylon on the tape.

I have never tried solid center conductor coax as a rotor loop.  All of my
runs above the rotor and up the tower to the rotor are solid center
conductor such as 9913.  Larger coaxes tend to have solid conductors
(remember RG-17?)

73, es good DX to all, John K1AE

John Allen  - PC Support Solutions www.pcsupportsolutions.com PC House
Calls: Computer HW/SW/Network debugging, installation, maintenance, and
upgrades
mailto:john at pcsupportsolutions.com  978 779-6189 M: 508 361-6229

-----Original Message-----
From: 70cm-bounces at mailman.qth.net
[mailto:70cm-bounces at mailman.qth.net]On Behalf Of Michael A. Urich
Sent: Sunday, July 25, 2004 10:27 PM
To: VHF Contesting; 50mhz at mailman.qth.net; 2m at mailman.qth.net;
222mhz at mailman.qth.net; 70cm at mailman.qth.net
Subject: [70cm] Pre-amp question follow up


Original comment

My vision is to run a single LMR-600 feedline to the top of the tower and
then switch it to masthead pre-amps with LMR-400 runs to the antennas.

* * *

A point of clarification + a follow up question.  I haven't ruled out
running a single feedline per band and the pre-amps do not have to be
installed at the time the tower goes up, and due to budget limitations may
have to come later but I want to plan for them when the tower goes up.

One individual indicated that the LRM400 from the top of tower around the
rotor is a bad idea because of its solid center conductor.  My intention
is to have the rotor down inside the tower actually a few feet lower than
my thoughts about where the weatherproof box for the pre-amps will go.

My question(s) is Why would running a solid center conductor near the
rotor be a bad idea?  And a follow up, If a solid center conductor is the
improper approach then would running an even larger feedline past the
rotor be incorrect as well?

Mike Urich, KA5CVH
www.ka5cvh.com

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