Hello All,
Just found old datas on a similar line made for the French Army , results
are the following:
The impedance was determined by measurements to be around 150 Ohms
old message:
I measured the losses of the 150 Ohms old military telephone line:
I made two transformers 50 to 150 ohms tested them in serie , had about 0.4
dB losses from 1 to 30 MHz, then I introduced the line, input match
was better than 25 dB, taking into account the losses of the test fixture,
for a length of 30 meters ( 100ft) I had the following losses ( measured
with a calibrated HP network analyser):
1.2 dB at 1.8 MHz, 2.25 dB at 3.8 Mhz, 3.64 dB at 7 MHz, 4.5 dB at 10 MHz.
So for a beverage of one lambda at 1.8 MHz it would be about 6 dB !!
I would not be suprised that line was manufactured in the US
73
Jacques F6BKI
-----Message d'origine-----
From: Guy Olinger K2AV
Sent: Tuesday, July 24, 2012 1:39 AM
To: ZR
Cc: topband@contesting.com ; Bruce
Subject: Re: Topband: Beverage antennas
What may be more destructive is a slow velocity factor in the insulated
wire. There is no way to estimate that, you just have to measure it. If
the VF is low, then you get into the same kind of problems as one has in
designing BOG's (beverage on ground), where the signal already on the wire
is moving much slower than the signal in the air, just about to induce the
wire.
Telco C wire was not designed with anything RF in mind. The dielectric
might be something exotic specifically designed for long life, and a VF
slow as molasses.
73, Guy.
On Mon, Jul 23, 2012 at 9:32 PM, ZR <zr@jeremy.mv.com> wrote:
>
> ----- Original Message -----
> From: "Bruce" <k1fz@myfairpoint.net>
> To: <topband@contesting.com>
> Sent: Monday, July 23, 2012 3:56 PM
> Subject: Topband: Beverage antennas
>
>
> >
> >
> >
> > Re Tom:
> > An impedance error of 20 ohms on a 100 ohm line is as meaningful as an
> > 80
> > ohm error on 400 ohm line
> >
> > Thanks Tom for clearing that up. I tried early Saturday morning, while
> > very sleepy, to get this info out. A 680 ohm line Beverage with fence
> > wire, the error ratio is even higher.
> > (Wide spacing is more RF forgiving, in terms of inches, than close
> > spaced
> > lines). But we do need to be accurate.
>
>
> ** Wide spacing is also more prone to unbalance wheras close spacing and
> twisting promotes good balance.
>
>
> > A few years ago I had customer reports, stating they had run their two
> > wire, fence wire Beverages, fastened vertical with good results. At
> > that
> > time I switched a 300 foot horizontal run to vertical, and could not
> > see
> > any difference. Granted this was not an instant change A to B test, but
> > it sure is an easier installation. I haven't seen anyone frequently
> > transpose their two fence wire Beverages in my area, but may be a good
> > idea.
> >
> > 73
> > Bruce
>
>
> ** That barely qualifies as a subjective test and 300' for Topband isnt
> that
> directive/effective to start with.Try it at 1 wavelength or more in a
> controlled test.
> Carl
> KM1H
>
>
>
>
>
> > No virus found in this message.
> > Checked by AVG - www.avg.com
> > Version: 10.0.1424 / Virus Database: 2437/5149 - Release Date: 07/23/12
> >
>
> _______________________________________________
> UR RST IS ... ... ..9 QSB QSB - hw? BK
>
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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