----- Original Message -----
From: "Rick Karlquist" <richard@karlquist.com>
To: "W0UCE" <w0uce@nc.rr.com>
Cc: <topband@contesting.com>; <cwops@yahoogroups.com>
Sent: Thursday, December 08, 2011 9:41 PM
Subject: Re: Topband: K2AV 160m Folded Counterpoise Antenna - New Details
Posted
> W0UCE wrote:
>
>> * The ONLY means of achieving the required degree of Isolation is to
>> use the Isolation Transformer as specified by K2AV
>> * Tests using 1:1 Baluns and Line Isolators have ALL FAILED - you
>> waste RF Power, Time and Money unless the specified xfmr is installed
>> * DO NOT attempt to use Insulated Window Line for the FCP - We already
>> tried it and it does not work - too lossy
>> * Use #12 Bare wire for the FCP elements - Moisture gathers on
>> insulated wire and detunes the FCP
>
> I haven't built this system, but the suggestions above make sense.
> I have been trying to encourage using transformers instead of baluns
> on 160 meters for years, but it's a tough sell to overcome the balun
> habit. The tendency for loss in the open wire line also makes
> sense. It is well known that window line is lossy when wet.
> What is new here is that the Q is so high that you can't even
> use insulated wire for open wire line. It would be interesting
> to see if teflon insulated wire worked OK. The electric field
> is maximum right at the conductor surface, so the insulation has
> a considerable effect on characteristic impedance, thus I could
> imagine it would affect loss too. I am feeding my vertical
> using 850 feet of open wire line with XHHW insulation (whatever
> that is made out of). It would be interesting to measure the
> loss on a rainy day and see how much it increased. It's only
> a few tenths of a dB when dry (the wires are 4 AWG aluminum).
>
> Rick N6RK
Using a 120VAC 60Hz source and a 10A load the loss in 850' of #4 copper is
5.1V or 4.2%
With aluminum it is 7.3V and 6.1%.
It only gets worse at RF and once you reach about 3dB loss the input VSWR
flattens out until it appears to equal the line impedance. Ground losses in
a vertical have the same effect.
Adding a pad between the signal source and DUT in the lab is the standard
procedure to eliminate a matching problem.
Carl
KM1H
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