The reason open wire line has less loss is that the dielectrics for true
open wire line is air. And this reduces feedline losses for high SWR's
substantially.
Carl Moreschi N4PY
121 Little Bell Dr.
Hays, NC 28635
www.n4py.com
On 1/25/2012 7:28 PM, Jim Brown wrote:
> On 1/25/2012 3:09 PM, Stuart Rohre wrote:
>> Les Moxon. in his RSGB England book, "HF Antennas for all Locations"
>> shows ladder line fed quarter wave verticals as you describe.
>
> BALANCE is defined by equal impedances from each side of the circuit to
> the reference plane (in this case, the earth). The feedline is only one
> part of that circuit, and using twin lead does NOT provide balance if
> the ANTENNA is not balanced and the antenna tuner is not balanced. A
> vertical antenna is NOT balanced.
>
> The primary virtue of using higher impedance feedlines has NOTHING to do
> with balance, but rather that their higher impedance reduces losses if
> the system is matched. But twinleads are just as likely to carry common
> mode currents and couple them to the antenna if they are not very
> effectively choked.
>
> 73, Jim K9YC
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