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Topband: WD-1A 2-way Beverage

To: <w5un@wt.net>, <topband@contesting.com>
Subject: Topband: WD-1A 2-way Beverage
From: "Lee K7TJR" <k7tjr@msn.com>
Date: Sat, 22 Nov 2008 16:11:44 -0800
List-post: <topband@contesting.com">mailto:topband@contesting.com>
Hi Dave:    One look at the specs for WD-1A scares me. I do not see how one 
could successfully send any RF down one of these wires as a differential 
transmission line. That is exactly what happens, and what you need  in the 
reverse Beverage mode. The loss of WD-1A at 4kHz can be as much as 5 dB per 
mile by spec. Lets see thats about 1dB at 4kHz for the average length Beverage. 
1000/5280 * 5 dB=~1dB. Using a simple 1 dB for each doubling (2^9 * 4khZ) of 
the  frequency as the spec chart shows, one can expect 9 more dB for a total 
loss of at least 10dB. It would likely be much worse than this in real loss 
figures for the cable at 2Mhz. 10dB  loss or more in the reverse direction 
would be very noticeable. I am not certain what it would do to the expected 
operation/pattern but I am sure it would affect the real versus theoretical 
termination resistance of the antenna as well. Some real loose approximations 
here! It is not hard to expect this when it has an approximate 70 ohm trans
 mission line impedance (my guess) and a pure DC loss resistance of 46 ohms in 
1000 feet per side! 

So let me guess, you see 1 to 2 S-units (6 to 12 dB) difference in antenna gain 
forward to reverse?

Here is the specs when it was new. What it might be after 10 or 20 years maybe 
more is anybodys guess. 

Oh, and SWR would likely look pretty good as there is a lot of resistive loss 
here.

"http://www.dscc.dla.mil/Downloads/MilSpec/Docs/MIL-DTL-49104/dtl49104.pdf";

Personally, I would not use this wire. 

Lee  K7TJR Oregon

   

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