You are right Tom,
I measured the losses of the 150 Ohms twisted 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 twisted 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 !! for
short beverages it is still an acceptable trade off but not for longer ones.
Can somebody tell me what are the typical losses of the called 450 ohms
ladder line sold for example at the Wireman ??
what about a two wires home made line ?
Thanks
Jacques F6BKI
----- Original Message -----
From: "Tom Rauch" <w8ji@contesting.com>
To: "Joe Subich, K4IK" <k4ik@subich.com>; "'Jacques RAMBAUD'"
<f6bki@wanadoo.fr>; "'Jim Brown'" <jim@audiosystemsgroup.com>;
<topband@contesting.com>
Sent: Wednesday, July 28, 2004 1:51 AM
Subject: Re: Topband: two wires Beverage
> >
> > Other than the possible impedance change with weather that
> W8JI
> > warns about, you should not have any problem using the 150
> Ohm
> > line for a reversible beverage as long as you adjust the
> > transformers for the new impedance ratios.
>
> I might worry a little about loss when dry also. I'm not
> sure how this line behaves as a transmission line at radio
> frequencies.
>
> Maybe someone has measured some? I know rubber telephone
> parallel wire is pretty bad at radio frequencies. One line I
> measured was about 3dB per 100ft at 3.5Mhz. That may have
> been an exceptionally lossy line, or it may have been better
> than normal.
>
>
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>
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