[Elecraft] OCF antennas

[Guy Olinger K2AV]

I have a 425 foot run of "window line", specifically Wireman #554 down to
my 160 antenna base.  The "detuning" that is referred to is really a change
in the dielectric:  from PE to PE+water.  That changes the loss (change =
.5 dB at 1.830), but more particularly the velocity factor, which changes
the electrical length and MOVES nodes and nulls.  Here are the particulars
from the line loss calculator in VK1OD's excellent collection of
calculators at http://vk1od.net/calc/tl/tllc.php .

Transmission Line Wireman 554
Code W554
Data source Wireman / N7WS
Frequency 1.830 MHz
Length 425.000 ft
Results
Zo 360.01-j1.74 Ω
Velocity Factor, VF -2 0.928, 1.161
Length 306.76 °, 0.852 λ, 129.540 m
Line Loss (matched) 0.251 dB


Transmission Line Wireman 554 wet
Code W554w
Data source N7WS
Frequency 1.830 MHz
Length 425.000 ft
Results
Zo 344.94+j3.02 Ω
Velocity Factor, VF -2 0.887, 1.271
Length 320.94 °, 0.892 λ, 129.540 m
Line Loss (matched) 0.780 dB

73, Guy.


On Sun, Mar 11, 2012 at 12:16 AM, Jim Brown <jim at audiosystemsgroup.com>wrote:

> On 3/10/2012 9:05 PM, Gary Ferdinand wrote:
> > The OWL does not suffer from the dreaded detuning in the rain nearly to
> the extent of ladder line.
>
> Right.  And while there is some change in the impedance, the primary
> effect is dielectric loss due to moisture on the "solid" portions of the
> window "frame."
>
> 73, Jim K9YC
>
>