[UK-CONTEST] Long Distance Feedlines

[Brian Miller]

Hi Chris et al

Sorry about the delayed response - just catching up after reading through some
older messages from this reflector.

The ZL6QH open wire lines use 2.5mm to 3.5mm diameter wire and are spaced around
250mm to make a nominal 600 Ohm impedance. The correct spacing is important at
each end but it is acceptable to vary the spacing along the line. Wider spacing
allows you to get away with fewer spacers and longer spans.

Note that the ZL6QH lines are mounted about 5 metres AGL on telegraph poles to
keep them clear of stock, horses and vehicles.

The ZL6QH baluns are nominally 12:1 ratio. The capacitor helps to improve the
SWR by cancelling unwanted inductive reactance from the transformer. See
http://www.zl6qh.com/000225.html

73

Brian ZL1AZE


----- Original Message ----- 
From: "Adrian Rees (MW1LCR)" <rees.a at btconnect.com>
To: "'Chris Tran'" <zl1ct at gm7v.com>; <uk-contest at contesting.com>
Sent: Tuesday, September 26, 2006 9:52 AM
Subject: Re: [UK-CONTEST] Long Distance Feedlines


Hi Chris, all
Well I have seen the ZL6QH website, and noted the baluns used to match
the feeders. These seem to be quite typical Guanella Baluns, at 8:1 to
match 50 Ohm Coax feeder, although I am somewhat puzzled by the
capacitors...(I'll need to think about that one on the way to work
tomorrow).

I have plenty of 450 Ohm open wire feeder, and can easily get it 6 to 8
Foot above ground and insulated. Browsing the Amidon website, I will use
T-400A or T-200 cores for the Baluns.

Only question is, how high off the ground does the open wire feeder need
to be ? I thought only 3 or 4 feet, but the  boys at ZL6QH are using
telegraph poles..... Or is this just safety ?

TIA

Adrian



-----Original Message-----
From: uk-contest-bounces at contesting.com
[mailto:uk-contest-bounces at contesting.com] On Behalf Of Chris Tran
Sent: 25 September 2006 18:38
To: uk-contest at contesting.com
Subject: Re: [UK-CONTEST] Long Distance Feedlines


Hi Adrian et al

The set-up you describe is used at ZL6QH - see www.zl6qh.com    The
open-wire feeders are approximately 400 ohm - 12-14swg wire space about
12
inches apart - at the TX end there are 1:9 baluns fed with RG213 from
the
shack, but at the antenna end the open-wire feedline is connected
directly
to the antenna.  Even the 2 x 10m, 1 x 15m and 1 x 20m yagis are fed in
this
way, because they are fixed yagis so there are no mechanical rotation
considerations with open-wire feed. I think the 1:9 ferrite baluns are
described somewhere on the ZL6QH website.

This system seems reasonably efficient - there are no coax-fed reference

antennas to do any real comparisons, but results are good. The open-wire

feedlines are anywhere between 10 and 15 feet above ground - the longest
run
is about 300m similar to your proposed set-up.

I would think that your main considerations will be the mechanical
mounting
of the feedlines - you need about 15-20 old telephone poles, complete
with
insulators !

73
Chris
GM3WOJ

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