Using matching transformers and my spectrum analyzer with tracking
generator, I measured a 100 ft length dry and I measured it wet. My
measurements indicated the velocity factor changed when wet, i.e. the
electrical length of the line changed. Thus explains to me the reason
to "retune" when the line is wet or covered with frost, ice or snow.
With my tuner, that means I must push a button. Oh geezzzzz.
I agree the loss does increase a wee bit when wet in a horizontal
position. Considering we have less than 100 days with recorded or
measured precipitation in my area, it is no big deal. My window line is
mostly vertical and that which is horizontal has about 5 twists per 10
ft. Still worst case, I find it has less loss than coax and less
expensive than coax which has equal or less loss.
73
Bob, K4TAX
On 1/18/2019 8:08 PM, Al Lorona wrote:
G3TXQ's work here is awesome, as is N7WS's before him. I'm thinking two
things:
Thing 1 is that, clearly, water really messes up window line's loss. However,
I'm guessing that a/ in a place like southern California, where perpetual
drought is the new normal; and b/ in an installation where the window line,
rather than running perfectly horizontally so water can pool, has a slant,
allowing it to shed water; a ham would probably be fine using it. All one would
have to do to discourage pooling on a horizontal run is twist the line once
every few meters.
Thing 2 is that G3TXQ shows matched loss at 6.72 MHz in heavy rainfall
increasing from 0.2 to 1.1 dB per 100 feet, which seems totally acceptable for
worst-case rainfall. In moderate rainfall the loss increased to only 0.34
dB/100 ft. That's lower than any coax out there.
I myself would never use it (for reasons other than water loss), but window
line seems like an okay choice for those hams who can't or won't use coax.
Al W6LX
Glossary:
"Window line" = Wireman 551 or 552 or equivalent
http://www.karinya.net/g3txq/wet_ll/
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