On 4/13/19 8:44 AM, John Pieszcynski wrote:
See "A Novel Approach to Using Window Line" by W6NBC, QST August 2018.
The article is on his website @
http://www.w6nbc.com/articles/2018-08QSTladderline.pdf
73,
John W2FV
Fascinating data..
I would have liked to see one more test run, with the window line loss
without any foam around it.
The lower loss on the metal roof may be a measurement artifact - I'd not
be trusting 0.01 dB kinds of measurements. The metal roof is "mostly"
farther away than the thickness of the foam, except where the roof ribs
stick up.
'NBC didn't give the length of his line, but if we work from the 19.8
MHz half wave, that's about 7 meters (25 feet?), so he's taking the
measurement and multiplying by 4 to get the "per 100 ft" - so 0.01 dB on
the graph is really 0.0025 dB in the measurement. (the picture over the
chairs is consistent with 25 feet)
I'd say that metal and free air are "the same within experiment uncertainty"
One cool thing here is that measurement tools like the VNA are common
enough now that we can actually *measure* the losses, rather than
speculating or using dialectic (aka arguing on forums, letters to the
editor, and email lists).
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