On 12/28/2011 5:18 PM, Roger Parsons wrote:
> K8RI wrote:
> "Probably not if it were made of dry wood. If really close to the
> antenna it would behave much like the plastic insulation/dielectric on a
> wire requiring the wire/antenna to be shortened a bit, but I doubt you'd
> be able to measure any attenuation"
> For some reason you totally ignored my next sentence:
>
> 'The amount by which it would attenuate it would depend on factors such
> as size, material, thickness, frequency and so on.'
>
> It is certainly true that the attenuation could be very small. It is also
> true that building such a box would be an exercise in futility.
Yah, but it'd be good for the lumber industry. Unfortunately most of
the wood coming through in the past few years is just about green enough
that it'd sprout roots if you stuck it in the ground. <sigh)
I needed some very straight 2 X 4's to build a fixture to use in
constructing some airplane parts. We (the industry) usually takes this
wood and lays it on supports to keep it off the floor but let air flow
around it. Horizontal supports are usually about 3 to 5 feet apart. We
lay them up like a big sandwich. Then at least once a day we rotate each
stick top to bottom. I had one piece that was already twisting pretty
bad after the first couple of days so I took it out and clamped it to a
heavy steel frame. (The bottom portion of the wing jig). At this point
the darn 2 X 4 was beginning to look like a propeller it had so much
twist. I clamped it down to the steel at each end with supports in the
middle. I figured as it was damp enough I could just add a bit of
pressure each day and it'd eventually be straight.
The next day I found the clamps were really tight, so I just left them
alone. My rig is on the other side of the shop so I took the free time
to do a little DXing. On the second night I was out there...still
chasing DX when there was a very loud bang resulting in a few parts
flying around. When I went over to check on the 2 X 4 the longest piece
was less than 3 feet. That 2 X 4 had shattered into many pieces It
didn't just crack and split, it literally exploded with some pieces over
20 feet from their original location.
Generally the layered drying works very well even if it does take a few
weeks, but don't do it in a dry, heated building. It drys too fast and
the high moisture content causes it to hang together as long as possible
before giving up in spectacular fashion.
73
Roger (K8RI)
>
> 73 Roger
> VE3ZI
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