Jim,
If you have trees behind the house, I can suggest a 40m dx antenna to you.
Use a vertically polarized delta loop.
Take a 40 ft. fiberglass pole, paint it dark green and put it up near the
trees.
Use very thin wire, such as CQ-534 from the Wireman.
This is a very good DX antenna for 40 that I have used often in the past.
Here is a description of how I build them:
http://www.dj0ip.de/my-favorite-antennas/my-favorite-40m/
The pole just blends in with the trees when painted dark green.
You can't even see the wires from the street.
73 - Rick, DJ0IP
(Nr. Frankfurt am Main)
-----Original Message-----
From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of Jim Allen
Sent: Sunday, April 27, 2014 11:47 PM
To: Discussion of Ten-Tec Equipment
Subject: Re: [TenTec] Big TX Loops
The problem here is the ground is so rocky that radials are all but
impossible to hold down and the HOA restrictions limit me to no more that
10' above the highest point on the roof, which effectively means about
35-39' depending on which part of the property I put it on. It also
shouldn't be obviously visible from the street, which is not so much of a
problem with trees advantageously situated. If they work decently, the loop
ought to be an ideal solution for me and many others similarly situated,
more and more of us. Is helically loaded better than plain? I have no
idea. Some say yea, some say nay!
Higher is always better, I suppose, but these loops are reported to work
satisfactorily close to the ground. Am I going to crack pileups with my
100 watts or less and these antenna? Hardly, but I'm not fretting about
that. I'm not going to be on the Honor Roll, no matter what. I missed
Mellish Reef last month. So what! I'm on the air with the best signal I
can arrange in the circumstances, right now.
".... it's not practical to model it in most modeling software."
I bet if they wanted to, someone could. They can model all sorts of things
these days, or claim to anyway.
"But it's those restricted conditions we're talking about."
That's where they will want to be used. The ones that have been used are
claimed to work as expected. Are they monobanders at 120'? Nope, and
nobody claims otherwise. Most of the users are happy to get close to dipole
performance if they can, or at least where they can get on the air.
Those folks are faced, in many cases, with no verticals (except flagpoles in
some areas), no horizontal antenna, certainly not at a respectable height,
no towers, no directional antennas as we have thought of them all these
years, not even a hex or moxon for the most part and even then not high
enough to really perform.
I spent quite a few years in San Diego as a Volunteer Counsel going around
trying to help get antennas through HOA boards or city councils/planning
departments, and this is a very daunting problem for someone to have a
really effective antenna. The naysayers ignore the dozens of operators who
have these antenna and are satisfied that they are effective and as best
they could do in the circumstances.
73 de W6OGC Jim Allen
On Sun, Apr 27, 2014 at 3:40 PM, Rick - DJ0IP / NJ0IP <Rick@dj0ip.de> wrote:
> I have to agree with Barry (and Tom), but don't let that hold you back
> from building one, Jim.
> It's always fun to build stuff like that and even more fun when they work.
> The advantage I see of the helical wound loop is, it will be much
> cheaper than using aluminum or copper of the same diameter.
>
> For those online demos, the antenna in use was located outdoors, in
> the clear, with not much around to interfere with it.
> That for starters is a big help!
>
> I saw 3 different worlds with my 6' diameter commercial loop:
> 1) Indoors it was a poor performer - though it did work on some bands
> 2) It came to life when moved to the balcony
> 3) Mounted at 10' height, in the clear out in the front yard, it was
> as good as the 40m dipole about 10' above the roof of my 3 story
> house.
>
> I also had it mounted to a push-up mast on the back of my RV, but I
> only used if for a couple of trips.
> It wouldn't work at all when dropped into position for traveling, and
> it was a pain to have to push it up and down all the time. It was not
> light. But it did work quite well, once into position.
>
> IMO, its single biggest strength is its ability to enable a decent
> signal, even when you are prohibited from running wires. Too bad it's
> just so narrow bandes.
>
> 73 - Rick, DJ0IP
> (Nr. Frankfurt am Main)
>
>
> -----Original Message-----
> From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of Barry
> N1EU
> Sent: Sunday, April 27, 2014 9:21 PM
> To: Discussion of Ten-Tec Equipment
> Subject: Re: [TenTec] Big TX Loops
>
> 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
> > > _______________________________________________
> > > TenTec mailing list
> > > TenTec@contesting.com
> > > http://lists.contesting.com/mailman/listinfo/tentec
> > >
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> >
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