[UK-CONTEST] Long Distance Feedlines

[Clive Whelan]

Hi Adrian

Only you will know the benefit of the remote location. I'd
simply ask, is it theoretical or have you actually
experienced it; what you are proposing seems a tough job.

The 450ohm approach will work without doubt. I'd even
suggest that unless you have 9:1 baluns to hand, that off
the shelf 4:1 jobs will probably suffice. If it were open
wire line the loss of a ca. 2:1 SWR would be negligible. On
the ladder line it will be finite, but I suspect not
significant. Of course in inclement wx the characteristic
impedance will vary somewhat, which will mess things up a
bit. I think I'd go for the KISS approach, but you will
never be able to look down the road not taken, so if you've
a will go for it.

Hwyl fawr!


73



Clive
GW3NJW

-----Original Message-----
From: uk-contest-bounces at contesting.com
[mailto:uk-contest-bounces at contesting.com]On Behalf Of
Adrian Rees
Sent: 25 September 2006 09:44
To: uk-contest at contesting.com
Subject: [UK-CONTEST] Long Distance Feedlines


Slightly O/T but this is the Forum that an accurate answer
will come from....

I am planning on having a go in CQWW SSB, but will have to
enter "Field Day" Style, as I have nothing in the air at the
moment....so:

I will use an A3S for 10-15-20 and a Battle Creek Special
for 160-80-40. Feeding the lower band aerial is not a
problem, as it will be about 60-70 Feet From the shack,
(which in reality will be an old cow shed. Told you it was
Field Day Style !).

However, the A3S will be on a short mast, about 10 metres in
the air, and about 300 metres from the shack.
(I could move the A3S closer to the shack, but would loose
the benefit of its location..... Its located effectively on
a 300m Cliff, giving significant benefit to the US / Pacific
and Europe. Moving it would reduce this benefit.)

But ... feeding the A3S with RG213 would cause something
like 7 - 8 dB of Loss. Feeding with Heliax would be better,
but, the Heliax I have is in 55-60m Runs, and I don't really
want to use this for a temporary installation.

What I do have is some 300 m of 450 Ohm Open wire feeder.
So, I was thinking, how about a pair of 9:1 Baluns at each
end, thereby using the 450 Ohm Feeder as "transmission line"
across the field to the A3S.

The question is, has any one done this, and if so what
losses do you incur. (I am trying to figure out is it really
worth doing this, or should I just think about moving the
shack and or the A3S ?)

Thanks

Adrian MW1LCR
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