In practice I don't run anything near the full output of the amp as I prefer to
leave a large safety margin and over-engineer things as much as possible. I
don't buy new stuff but build from fleamarket junk at minimal prices, hence
much of what I use is an unknown quantity (see recent discussions). Better to
build something and operate it at 25percent of its capability for ever than to
suffer any sort of reliability problems. Sure, if I bought new and certified
components that would be a silly engineering margin, but with old El Cheapo
junk it works for me and apart from failures that have been down to my own bad
construction (lessons learned!) I've had few failures.
As KM1H states separately with good quality RG213 and PTFE PL259s/SO239s
there's no problem on shortwave. 2m/70cm EME enthusiasts I know tend to run
Heliax and 7/16 connectors.
There are (allegedly) several G3s (who shall remain nameless) in the south of
England who run 10kw++ on shortwave, but I don't know what they use. One of
the Italian big guns I know uses Andrew LDG550 hardline (about 1 inch diameter,
sourced from a uk cellphone company, second hand following tower re-fits) and
some sort of PTFE coax at the antenna. However he has a fixed 100' tower and
most of us in the UK (apart from the rich guys who can buy off the councillors)
have crank-up towers due to planning restrictions from the little Hitlers at
the town hall. Hence use of hardline would be a bit difficult!
There was a PTFE coax about the size of RG213 that I saw in Germany (at
Friedrichshafen maybe?) some time ago, but I can't remember what it's called
and have never seen it since. Anyone know of this stuff?
Dave G0OIL
-----Original Message-----
From: donroden@hiwaay.net
To: amps@contesting.com
Sent: 05/02/2010 20:45
Subject: [Amps] QRO Questions
I've never run anything stronger than a SB-220 or a 30S-1, and I was wondering
after seeing some of the European QRO+++ stations ....... what do they
use for a rotor loop ? Seems that RG-8 and PL-259s or type "N"s would
be a limiting factor to any QRO project ... not to mention burning up
TA-33 CL traps ( or other trapped beams ) ??
Don WA4NPL
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