[UK-CONTEST] Cables

Sun Jan 11 17:38:15 EST 2009

And if you're concerned about the effects of weather, all the rhombic 
antennas at VPC Port Stanley (over several km) were fed with Hi-Z open line, 
as also was my own rhombic at Signy Island (VP8/o), which used home-made 
spacers from nylon rod and lasted over 15 years without maintenance (until 
taken down for "environmental reasons").  See
http://picasaweb.google.co.uk/tilgate/Signy#5111704340623019954

73, Peter G3LET

----- Original Message ----- 
From: <g3ory at lineone.net>
To: <rees.a at btconnect.com>; "Ken Eastty" <ken.g3lvp at btinternet.com>; 
<uk-contest at contesting.com>
Sent: Sunday, January 11, 2009 9:49 PM
Subject: Re: [UK-CONTEST] Cables

> Adrian,
>
> If it is any consolation, the now defunct HF station at Rugby used
> open wire feeder and at that location  many of the antennas were huge
> distances from the transmitter buildings.  The characteristic impedance
> they used was quite low as I recall, circa 240 ohms.
>
> 73 Bob G3ORY
>
>>----Original Message----
>>From: rees.a at btconnect.com
>>Date: 11/01/2009 19:58
>>To: "Ken Eastty"<ken.g3lvp at btinternet.com>, <uk-contest at contesting.
> com>
>>Subj: Re: [UK-CONTEST] Cables
>>
>>Hi Ken, all
>>
>>I note your comments regarding losses incurred with open wire feeder
>>under certain circumstances. I do agree with your observation, and
> some
>>of my experiments have confirmed these losses and environmental
> issues
>>(see later).
>>
>>In building my station, I originally planned to use the best coax I
>>could afford / lay my hands on, but due to the distances involved
> from
>>shack to aerial, coax is not an option. For example the distance from
>>the shack to the 14MHz tower is 110 metres plus 20 metres in height.
> 130
>>metres. The 14MHz tower is the closest, and the furthest tower is 250
>>metres plus 20 metres in height.There are others in between.(For
> those
>>who have visited Chez 'LCR you know the problems !)
>>
>>As you can see the cable runs and losses involved are quite
>>considerable. The cost using RG213 is expensive (even buying in bulk
> on
>>1Km drums,and assuming the lorry carrying the drum can get up the
>>hill.... its expensive). Using LDF 4-50, well, I'll get a small
>>mortgage!
>>
>>I have carried out some experiments, using 450 Ohm Ladder line (the
>>black stuff you get from W&S etc) and home brew ladder line. Firstly
> the
>>450 Ohm Ladder line isn't 450 Ohm. Two batches I had, the first
> measured
>>out at 370 Ohms and and the second 400 Ohms.
>>
>>On a 100m run the purchased ladder line showed some loss, as you
> would
>>expect when compared to Coax. It was relatively easy to manage and
>>install. However, it suffered greatly (as you observed) when the
> weather
>>changed. Certainly keeping it above 10 feet off the ground helped,
> (as
>>opposed to heights of 3, and 6 feet I tried as well) but wind and
> rain
>>and snow etc etc caused some real changes in the chracteristics of
> the
>>line.
>>
>>I then removed as much as possible of the plastic and kept it 10 feet
>>above ground. This helped stabilise it, but still some strange
> changes,
>>when the weather changed.
>>
>>I then repeated the experiment with home brew open wire feeder, using
>>the classic calculation in the ARRL Handbook to provide the
> dimensions
>>of the feeder. Whilst a lot more time consuming to install, it was a
> lot
>>more stable than the purchased stuff. In the end I built a 100m run
> of
>>home brew open wire line, tensioning the two cables, between two
> points
>>made of two 10 foot gate posts, sunk 3 foot in the ground with a
>>strainer, (just like a strainer post used in fencing) and ran the
> open
>>wire line across the top of the posts and insulated with ceramic
>>insulators.
>>
>>This worked well, with much more stability in the line. The recent
> ice
>>and snow up here did have an effect on the line, but a walk along the
>>line with a soft brush on a pole gets the snow off.
>>
>>Foretunately I do live in a remote area of North Wales, and
> background
>>electrical noise is very low, and interference is not really a
> problem.
>>So I am going the open wire feeder route, hence the references to the
>>Laport book.
>>
>>I wouldn't use Open wire feeder, of any type, on runs less than say
> 50
>>metres, (or of course as a matching stub, but that's a different
> story).
>>
>>So Coax for some instalaations, Open wire for others.
>>
>>Regards
>>
>>Adrian MW1LCR
>>
>>
>>
>>-----Original Message-----
>>From: uk-contest-bounces at contesting.com
>>[mailto:uk-contest-bounces at contesting.com] On Behalf Of Ken Eastty
>>Sent: 10 January 2009 21:11
>>To: uk-contest at contesting.com
>>Subject: Re: [UK-CONTEST] Cables
>>
>>
>>
>>>
>>> Ken,
>>>
>>> I wish RFS cables were half the price of Andrews.  Sadly they are
>>> competing in the same market and have more or less equivalent
> cables
>>> so the new price is very similar.
>>
>>>John G3UUT
>>
>>John,
>>
>>I bought (not for my own use!) several km's of RSF cable a few years
> ago
>>after a colleague pointed out that it was much cheaper then than the
>>equivalent Andrew product (there wasn't any discount for quantity),
>>perhaps they've changed their prices. When I've peered through the
>>fences (anorak
>>on) of Cellular installations most of the ones that I've seen seem to
>>use RFS as opposed to Andrew cable. Hopefully with the amount of drum
>>ends of hard line that seem to be around no one should have to buy
> short
>>lengths of these cables at new prices, I wouldn't expect to pay more
>>than the cost of RG213, however connectors might be another matter.
>>
>>
>>>I am going open wire feeder on all my HF aerials. Adrian MW1LCR
>>
>>Adrian,
>>
>>I don't recommend using open-wire feeder other than on very short
> runs.
>>Unless the line is really well balanced there's a problem with
>>interference pick up on receive and the characteristics of the line
> can
>>change dramatically with environmental conditions. In some cases
>>especially at the high end of the HF range when insulators are
>>contaminated the loss can equal that of co-ax like LDF 4-50. At least
>>with co-ax the loss is constant regardless of the environment and can
> be
>>overcome (on receive) with suitable pre-amplifiers. There are also
>>maintenance aspects to be considered when using open-wire feeders
> which
>>perhaps aren't so important in the amateur environment and of course
>>with a high power broadcast station the cost of co-ax for high power
> use
>>has got be a consideration. Many years ago when copper was perhaps
>>cheaper than it is today GPO HF radio stations built pre-1940 used co-
> ax
>>feeders made of copper tube at both transmitting & receiving
> stations.
>>
>>>You forgot Westflex 103.
>>
>>>Nigel G0VDZ
>>
>>Maybe best forgotten, I don't like the few thin stands of copper
> braid
>>over copper foil, this in my experience doesn't make for easy
>>termination onto an N Type connector (no one doing a proper job would
>>use a 259's would they?)
>>
>>73...
>>
>>Ken
>>
>>G3LVP
>>
>>
>>
>>
>>
>>
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>
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