I bet!
What do you use to 70' masts? Trees?
73 de W6OGC Jim Allen
On Sun, Apr 27, 2014 at 4:52 PM, Rodney <w3krq@dejazzd.com> wrote:
> I have a 320ft dipole up 70ft feed with ladder line works great on 160
> to 10 meters most of the time hams think I running a amp.
>
> -----Original Message----- From: Jim Allen
> Sent: Sunday, April 27, 2014 5:46 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
>> > > _______________________________________________
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>> > >
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