Yes, I read a good deal of that. They have argued it, but no one has
demonstrated it, and AFAIK, no one has modeled one. In the meantime, a
good number of folks, including some who are quite expert, say they are
getting gratifying results. I know Tom is regarded as knowing what he is
talking about. There is no way a loop is a superlative antenna, and you
wouldn't chose that if you had space, no restrictions, adequate budget
etc. I certainly do not expect this loop to perform like my 4-4-5 quad on
60' tower years ago, but I didn't have HOA restrictions then, and was young
and healthy enough to manage the building and maintenance of such a
project.
It's ironic that now that I have the money to do just about anything I
want, I don't want to, because it isn't a smart investment given my age and
health situation, and I am under HOA restrictions anyway. If I went out
and bought a big place, like Tom, and started an antenna farm, I wouldn't
live to finish it. Some of us are very content, indeed happy, to be on the
air with respectable signals, not multi-multi crushers.
The helically loaded loop gets you the same performance of a magnetic loop
but at reduced size, supposedly. IOW, the 80M loop that is 6' in diameter
can be 3 or 4' when helically loaded, so it is said. I'm looking at a one
meter loop for 20-10M, then we'll see.
Maybe it will be a bust. It won't be the first time building antennas that
fell short somehow. It beats sitting around watching Oprah Winfrey re-runs
or whatever it is that old people are supposed to do!
73 de W6OGC Jim Allen
On Sun, Apr 27, 2014 at 2:20 PM, Barry N1EU <barry.n1eu@gmail.com> wrote:
> Good luck with the helically loaded loop Jim. Perhaps you're already
> aware, but several folks (including W8JI) have argued that helically
> loading the mag loop buys you nothing compared to a simple loop of the same
> diameter. But I know those youtube videos sure make it look good ;-)
>
> 73, Barry N1EU
>
>
> On Sun, Apr 27, 2014 at 12:55 PM, Jim Allen <jim.allen@longhornband.net
> >wrote:
>
> > Let me add to what Ric has said, that there are very high voltages and
> > currents developed in these small loops, 5000 v or more even at 100
> watts.
> > According to one calculator, a 5' diameter loop at 40M and 500 watts
> would
> > develop nearly 10,000 volts. It is essential to keep living things away
> > from these loops while transmitting is possible, and not a good idea at
> all
> > to be close to them while transmitting.
> >
> > I'm in the process of gathering the materials to build a helically loaded
> > magnetic loop for 20-10M, with a vacuum variable tuning capacitor, using
> > copper 3" wide wound on a flex PVC loop about 40" dia.
> >
> > 73 de W6OGC Jim Allen
> >
> > 73 de W6OGC Jim Allen
> >
> >
> > On Sun, Apr 27, 2014 at 1:43 AM, Jim Brown <k9yc@audiosystemsgroup.com
> > >wrote:
> >
> > > My neighbor, W6GJB, has built a large TX loop Here's how described it
> to
> > > another ham. The "army mast" he's talking about is a bunch of 4 ft
> > sections
> > > of 2-in o.d. Al tubing that fit together, and fit into a triangulsr
> base.
> > > They've been sold at Dayton and other flea markets for several decades,
> > and
> > > are quite useful. With a tripod section made from two sections per leg,
> > > it's easy for one guy to push them up, then slip another section under
> it
> > > at the bottom, and so on They will, for example, support a small
> > tribander
> > > like a C3 at 30 ft if guyed properly. We've also used them to build a
> > > 2-element vertical array for 40M.
> > >
> > > = = = = = = =
> > >
> > > The mag loop is homebrew, made of 8 segments of Army mast bent (very
> > > carefully) in a pipe bender. The whole thing can break down and go
> into
> > > the big green bags that go with that tubing. The air-variable
> capacitor
> > > should be able to handle 500W, but I have not tried that yet. Running
> > 100W
> > > at this point with a KX3+KXPA100.
> > >
> > > With 8 segments it is close to 1/4 wave on 40, which should be over 90%
> > > efficient with some of it going into low angle radiation. Should be
> > better
> > > than a low dipole. I can add fixed capacitance to tune it on 80, or
> add
> > > another 4 tubes and it should be better than 80% efficient on 80.
> > >
> > > = = = = =
> > >
> > > So to clarify, his loop consists of four sections of mast that are each
> > > bent twice at 45 degrees. They go in the four corners, then a straight
> > > section goes between each of the four sides. That's the 40M loop. So
> what
> > > he's saying is that to build it for 80M, you simply add another
> straight
> > > section on each side.
> > >
> > > This is a current project for him, and he's in the process of on-air
> > > testing using RBN to get comparative signal reports with his other
> > antennas.
> > >
> > > This is fairly inexpensive to build (I'd guess around $500), but you
> need
> > > a good pipe bender, some practice, the sections, and suitable HV caps.
> > I've
> > > given him several big air variables from my junk box to play with.
> > >
> > > An objective is for something he can throw in the back of his truck and
> > > set up quickly for FD or CQP.
> > >
> > > 73, Jim K9YC
> > > _______________________________________________
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> > >
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