Re: [IRCA] Monster PVC-Frame Passive Loops

[Len <donutbandito@xxxxxxxxx>]

Back in the 1990s, I built an 8' tall doubly balanced PVC loop that had excellent characteristics. It was doubly balanced (two identical loop windings emanating from the center ground point, and was tapped at one turn out on each side, feeding a balanced toroidal balun. The loop did require amplification off the toroid. I logged KNX-1070-CA on it one night from Blacksburg, VA. This loop had amazing nulls. The tiniest movement had a large effect.

That was in an apartment environment, and the loop was only usable late at night after people had gone to bed and turned off their appliances.

Today in an apartment environment, that loop is worthless. There is so much more man made RFI now than then that it is never quiet. Computers, dimmers, smart appliances, CFLs, etc. make the noise level unbearable.

The only way I can DX now in a similar environment is with an 8' tall shielded loop enclosed in thin wall metal conduit. The Q of this loop is much lower, and the nulls quite poor - yet, it conquers most of the noise.

Oh, for a little house on a hilltop somewhere with no neighbors for 5 miles. LOL.

--- On Mon, 4/13/09, D1028Gary@xxxxxxx <D1028Gary@xxxxxxx> wrote:
From: D1028Gary@xxxxxxx <D1028Gary@xxxxxxx>
Subject: [IRCA] Monster PVC-Frame Passive Loops
To: irca@xxxxxxxxxxxxxxxx, am@xxxxxxxxxxx
Date: Monday, April 13, 2009, 9:23 AM

Hello All,
 
The annual "March Madness" antenna project here this year was to
construct  
a series of tuned passive loops, using ultra-cheap PVC tubing and fittings. 
 Loops of 18", 2', 3', 4', 5', 6' and 7.5' (side
dimensions) were  
assembled, using PVC diameters suitable to support each size without any 
sagging.
 
One of the primary design considerations was to isolate the loops from the  
support structures as much as possible, to provide clean electromagnetic  
reception patterns. Perfect symmetry of the coils was also an important  
objective, with equally-spaced wire slots cut in each of four frame tubes, and 

the tuning capacitor located exactly at the loop ends, with the far end of 
the  loop routed through a short PVC tube to the capacitor. These steps seem 
to have  provided maximum sensitivity and nulling ability for each loop size.
 
Lightweight, rugged, waterproof PVC was found to be an ideal frame material 
 for tuned passive loops, and of course, it is also ultra-cheap  (even in 
the larger sizes). The 7.5 foot (side) monster loop frame cost all of  $35 to 
build, and the cost of the "tabletop" 18-inch model frame was about 
$7. 
The 7.5 foot (10 foot diagonal) PVC loop does require some serious real  
estate for construction, however, and is certainly not recommended if you have
a  
shaky relationship with any of your neighbors :>)
 
Photos of the 18", 2' and 7.5' PVC loops have been uploaded to the
 
Ultralightdx Yahoo group site, and are available upon request. An article  
containing full construction details for these new PVC-frame loops should  be 
written shortly, which hopefully will provide a new, inexpensive option for  
boosting the DXing ability of any receiver.
 
73, Gary DeBock
 
 
        
 
 
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