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Re: [IRCA] 9 Foot Longwave Box Loop (and other projects)
Hi Craig,
Thanks for your comments on the PVC loop experimentation, and the link to
the loop design from VE7SL.
I have received quite a few comments off-list from Ultralight radio DXers
and others, who appreciate the chance to really boost the gain of their
simple receivers by using one of these PVC loops. Many of these DXers were
absent from the radio hobby since teenage DXing long ago, and missed out on the
extensive box loop experimentation in the 60's and 70's. So the concept of
getting lots of DXing gain with a simple, large loop is something new to
them. Even for myself, being in the Navy from 1971-1982 (and deeply into ham
radio after that) made me miss out on a lot of the MW box loop
experimentation-- so it's quite a fascinating subject for many of us.
73, Gary
In a message dated 5/4/2009 10:01:19 P.M. Pacific Daylight Time,
bevdxer@xxxxxxxxx writes:
Hi Gary,
Thanks for rekindling the interest in loop antennas. Below is a link to
one I was contemplating building this summer. I am a bit more motivated to
try this since our last heavy wet spring snow of ~3ft. did a lot of tree
damage on my lot and took out all four of my EWE antennas. I managed to repair
one of them. Unfortunately, crummy weather on recent weekends coupled with
working weekends lately has not been conducive to fixing the rest of the
EWEs. One of these loops equipped with a rotor is beginning to look good.
Here's the link:http://members.shaw.ca/ve7sl/loop.html
73.
Craig Barnes
Wondervu, CO
--- On Mon, 5/4/09, D1028Gary@xxxxxxx <D1028Gary@xxxxxxx> wrote:
> From: D1028Gary@xxxxxxx <D1028Gary@xxxxxxx>
> Subject: Re: [IRCA] 9 Foot Longwave Box Loop (and other projects)
> To: irca@xxxxxxxxxxxxxxxx
> Date: Monday, May 4, 2009, 9:50 PM
> 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
>
>
>
>
> In a message dated 5/4/2009 12:08:52 P.M. Pacific Daylight
> Time,
> k9ao@xxxxxxxxxxx writes:
>
> D1028Gary@xxxxxxx wrote:
> > 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.
>
> Is that a split-stator of a single-section cap?
>
> > 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.
>
> I'd love to see anything you might have, but can wait
> for your article
> too.I know you must be busy.
>
> The split-stator cap and center-tapped loop primary
> winding improves
> loop symmetry and balance.
>
> As to the spreading of the windings, the spreaders that
> splay every
> other turn up and down in two (maybe more) sections help a
> lot in
> increasing the range of tuning. Let me know if photos of
> that might help
> exp[lain what it looks like. I used wide tongue depressors,
> but small
> round PVC pipe sections would probably work better in that
> big loop.
>
> Rick Kunath
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