Re: [IRCA] 9 Foot Longwave Box Loop (and other projects)

[D1028Gary@xxxxxxx]

Hi Rick,
 
Thanks for your comments, and the correction on the split-stator cap. I'm  
sure that the refinements you suggest will improve the loop symmetry and 
null  depth of the LW box loop, and when the full PVC loop article is finished, 
I'm  hopeful of trying them out. They were a little beyond the initial 
scope of the  project, however, which was simply to create a practical, 
large-size LW box loop  on a PVC frame. Refinements can certainly be done at leisure.
 
Last night I did take the opportunity to remove one of the coil turns  from 
the LW box loop, which optimized the frequency coverage from 149  to 374 
kHz. I'm very pleased with this range, so I'll go ahead and nail it  down. The 
final LW box loop coil now has 21 coil turns of #18 wire, for a  total 
length of 542 feet. The side dimension of the loop is approximately  6.5 feet.
 
Of course, the ultimate value of this project will be in the comparison  
against other types of LW antennas, and hopefully some other DXers will feel  
motivated to build one of these giant LW box loops, and compare it  with 
their existing LW antenna designs.
 
73 and Thanks,  Gary DeBock
 
 
 
 
In a message dated 5/5/2009 8:57:28 A.M. Pacific Daylight Time,  
k9ao@xxxxxxxxxxx writes:

D1028Gary@xxxxxxx wrote:

> 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.

Yes, i sure is. And I think adding  the spreaders, maybe 4 per side in 
each loop side for total of 16 would  likely increase the upper tuning 
limit of the loop without decreasing the  lower limit.

These splay the turns apart, every other turn being spread  in opposite 
directions.

> 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.

If it's a  single section cap it isn't a spit-stator cap, and can't be 
used with a  loop primary winding center-tap. These center-tapped 
connections do  improve loop symmetry and null depth.

Rick  Kunath
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