Hi Rick, Thanks for your interest in the 9 Foot LW box loop project, and for your helpful information. The design was a basic one-loop coil system in a traditional box loop (non-spiral) design, wound on a PVC support frame, tuned by a 4-400 pf capacitor connected directly at the coil ends. The coil windings are spaced by slots cut in short sections of PVC pipe, which are offset from the main PVC frame by 90 degree PVC "elbow" fittings. The spacing slots are separated by .25", and are all symmetrically cut into the PVC by a circular saw with multiple wooden spacers of identical .25" width. The 19 coil windings (of #18 wire) are then pulled tightly to ensure optimal loop symmetry, in a system which apparently provides excellent nulling capability. The 490 feet loop coil of #18 stranded wire tunes from 167 kHz to 444 kHz in the current setup, but I plan to add a few more turns to drop the coverage down to 150 kHz. Photos of the loop and support structure are available upon request. This LW box loop project was primarily an offshoot from a successful 10 foot medium-wave PVC box loop effort, using almost identical frame 1.25" diameter PVC frame material. Steve Ratzlaff, an experienced LW DXer (and my partner in crime in various ultralight radio modification projects) suggested that the design might have potential as a monster LW box loop application, and although I'm not an experienced LW DXer, I've been extremely pleased with it so far. 73, Gary DeBock (in Puyallup, WA) In a message dated 5/4/2009 4:51:45 A.M. Pacific Daylight Time, [email protected] writes:
[email protected] wrote: > A 9-foot (diagonal) PVC-framed box loop was built for LW reception, using > 1.25" diameter PVC for rigid framing. About 490 feet of #18 wire was wrapped > in 19 turns across the PVC frame, with the frame offset from the coil for > maximum performance. Using the standard tuning capacitor from eBay's > "crystalradiosupply," this monstrous antenna tunes from 167 kHz to 444 kHz, > providing serious gain on any frequency near resonance. Not being a particularly > active LW DXer, I assume this tuning range is suitable for some LW DXing > :>) Otherwise, I'll just add a few more turns to get the coverage down to > 150 kHz. I'm wondering about the turns arrangement Gary. I take it that this is a traditional box-loop design and not a spiral loop? I've never seen decent loop balance out of any spiral design I tried. Assuming you used a solenoidal loop winding scheme, is the primary winding center-tapped and this connected to the split-stator tuning capacitor frame? Also, what is the inter-turn spacing on the primary winding? I generally use about a half-inch, maybe less for longwave, but not less than 3/8 inch. Did you spread the turns of the primary winding using non-metallic spreaders to reduce the inter-turn capacitance and increase the tuning range? Generally the turns need to be separated from each other, i.e. every other turn above and below the spacing spreaders, at least two spreaders per side, but in the case of a big loop like yours you may need more. This also stiffens the loop winding nicely. I can send along a photo showing how I accomplished this on my loops. This has the effect of reducing the loop winding's distributed capacitance. This distributed capacitance is effectively in parallel with the tuning capacitor, so by spreading the windings you get the loop to tune higher in frequency with minimum capacitance on the tuning cap. This actually gives you a wider range of frequencies covered by any cap, so you can add more turns if needed to get the lower end down and still tune up high on the other end. Rick Kunath _______________________________________________ IRCA mailing list [email protected] http://montreal.kotalampi.com/mailman/listinfo/irca Opinions expressed in messages on this mailing list are those of the original contributors and do not necessarily reflect the opinion of the IRCA, its editors, publishing staff, or officers For more information: http://www.ircaonline.org To Post a message: [email protected] **************2009 3 Free CREDIT SCORES: See Your 3 Credit Scores from All 3 Bureaus FREE! (http://pr.atwola.com/promoclk/100126575x1221797372x1201397989/aol?redir=https:%2F%2Fwww.freescore.com%2FOffers%2FStart%2FFreeCreditRepor tAndScore.aspx%3FID%3D91831F371F138345B53A153F49D4D872%26siteid%3De927580bf7 ) _______________________________________________ IRCA mailing list [email protected] http://montreal.kotalampi.com/mailman/listinfo/irca Opinions expressed in messages on this mailing list are those of the original contributors and do not necessarily reflect the opinion of the IRCA, its editors, publishing staff, or officers For more information: http://www.ircaonline.org To Post a message: [email protected]
