Re: [IRCA] 9 Foot Longwave Box Loop (webpage for the variable cap used)
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Re: [IRCA] 9 Foot Longwave Box Loop (webpage for the variable cap used)



As an addendum, if you don't want to look on eBay for the seller of the variable capacitor Gary is using, the seller has a webpage http://www.crystalradiosupply.com/, with lots of interesting items besides variable capacitors. Note he also has a dual-gang variable cap with 6:1 vernier that would reduce the number of turns needed for the LW loop by about half. With 770 pF for both gangs, that roughly gives an 11-turn loop compared to the 22 turn, and 144 kHz minimum, for half the wire needed. But I don't know how much the loop sensitivity might suffer compared to the 22 turn version.
73,
Steve

----- Original Message ----- From: <D1028Gary@xxxxxxx>
To: <irca@xxxxxxxxxxxxxxxx>
Sent: Monday, May 04, 2009 8:50 PM
Subject: Re: [IRCA] 9 Foot Longwave Box Loop (and other projects)


Hello Again Rick,

After adding three more turns of #18 wire to the 9' LW box loop, I now have
567 feet of wire in 22 coil turns, and a tuning range from 142 to 350 kHz.
This should be OK for DX testing, so I'll probably wrap it up this way.
It's amazing how much wire you need to add to get the tuning range a little
lower, on LW.

The coil turn spacing on the loop is actually wider than .25 inches,
because although that was the width of the wooden spacers used with the circular
saw to cut the wire slots, I forgot to account for the kerf width of the
circular saw blade. The actual coil turn spacing is about .4 inches.

The variable cap used in this project (and all the PVC loops) was a
compact, 8:1 vernier drive single-section unit from the eBay seller
"crystalradiosupply." This split-stator cap fits neatly inside of a section of 1.5"
diameter PVC pipe, for waterproofing the loop tuning system.

This LW box loop project was essentially an afterthought, after the
construction of ten MW PVC-frame box loops of various sizes. The mail goal of the
project was to design and test lightweight, structurally strong PVC frames
for extremely large loop sizes-- a goal which was entirely successful.
Refinements to some of the larger loops can probably be made for  optimum
performance, and I'm happy that Steve R. has expressed interest in making one of
these LW box loops according to my design, for testing  against his 1600'
long wire. Living on a residential lot of .33 acre, I don't quite have the
experimental freedom that he has, in deploying sizable LW  antennas.

73, Gary

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