[Elecraft] OCF antennas

[Gary Ferdinand]

To round off this part of the discussion I'll add that what Guy relates in
terms of wet window line is to some extent also true when using insulated
wire (rather than window line) with spacers approximately every 18 inches.
I'm using #14 THNN in my feeders with Ladder Snap spacers and the "wet
settings" on the tuner, while not drastically different, are different
enough to warrant some retuning on some bands.

73, Gary W2CS




>-----Original Message-----
>From: elecraft-bounces at mailman.qth.net [mailto:elecraft-
>bounces at mailman.qth.net] On Behalf Of Guy Olinger K2AV
>Sent: Sunday, March 11, 2012 12:49 AM
>To: jim at audiosystemsgroup.com
>Cc: elecraft at mailman.qth.net
>Subject: Re: [Elecraft] OCF antennas
>
>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
>>
>>
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