Steve et al:
I'm not saying that loss does or does not change with the vinyl type window
line between wet and dry. I do agree with your results in that loss does
increase with a wet line as opposed to a dry line. I also agree that loss
is greater per unit at 28 MHz vs. the same length of line at 1.8 MHz or 3.8
MHz regardless if the line is wet or dry.
My point, with today's receivers, in most all cases the atmospheric noise
and man made noise will mask any receiver internal noise and will easily
overtake any loss in the transmission line. However, the loss in the
transmission line will affect the NF of the receiver, which on HF is of
little significance. In many cases, we worry about 2 or 3 dB loss in the
transmission line but run the attenuator of 10 dB to 20 dB at the input of
the receiver. Now on transmit, that point makes a different in the power
arriving at the antenna. Again, typically less than 1 S unit on the other
end. To that point, most of the time I run the Argonaut VI at 10 watts and
can work about any station I hear, regardless of line loss.
True open wire line, by definition, is two conductors supported only at the
source end and the termination end, drawn taught, and without any spacers.
This of course is a real challenge to make work reliably in practice unless
one uses large conductors and spaced at 6" to 18" and used at lower
frequencies and typically with very high power in the near megawatt range.
We used this feed line approach in some of the commercial SW stations to
which I attended. Some of these feed lines were each several thousand feet
in length. All of this is far beyond the scope of most ham installations.
I would like to see more data on dry line vs. wet line from natural cause as
opposed to "wetted" line. I use the vinyl covered line with 66% of the web
spacers removed. {Remove 2, leave 1, remove 2, leave 1.} I see little
change from wet to dry on HF.
73
Bob, K4TAX
----- Original Message -----
From: "Steve Hunt" <steve@karinya.net>
To: "Discussion of Ten-Tec Equipment" <tentec@contesting.com>
Cc: "Phil Sussman" <psussman@pactor.com>; "Bob McGraw - K4TAX"
<RMcGraw@Blomand.net>
Sent: Saturday, August 03, 2013 8:01 AM
Subject: Re: [TenTec] OT: Openwire/Window Line and Bad Wx
We're talking here about reported changes in loss that - if true - would
be equivalent to a 5dB change between dry and wet on a 100ft of ladderline
feeding a doublet on 10m.
Are you folks trying to tell me that 5dB makes "little to no difference"?
Steve G3TXQ
On 03/08/2013 13:27, Phil Sussman wrote:
Bob is right! In the end, propagation will dictate. External
conditions have more of an effect than the subtle differences
over which we have control.
Sure we can increase efficiency, yet the results are subtle.
It all depends upon whether the band is open, eh?
Well said, Bob!
73 de Phil - N8PS
------
Quoting Bob McGraw - K4TAX <RMcGraw@Blomand.net>:
As I said in my closing remark in an earlier post:
"I realize that we'd like to eak out every dB we can, but in the end, it
makes little to no difference on HF."
If one can match the load, using what ever means and equipment, then
energy will be transferred. On receiving, atomospheric and man made
noise will overtake any losses in the antenna system and will over ride
most all receiver noise.
73
Bob, K4TAX
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