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Author Topic: Did anyone see the plywood box antenna at Nearfest?  (Read 28593 times)
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KM1H
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« on: May 07, 2009, 12:49:16 PM »

The mystery antenna shown by Phoenix Technology had the academics pulling their hair for 2 days as demos were given on various HF bands.

I watched one MIT PhD type start as a full skeptic, walk away and come back with his remote rig access doodad. Transmitted on 75, and listened to his signal relayed from his home in VT. Then reversed the procedure. Loud S9+ both ways with 100W.

Its apparently different enough that the inventors have filed patent paperwork and are not releasing much detail yet so it was hidden in the box on the ground. Nor were they taking orders or any other questionable activity.

Carl
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Steve - WB3HUZ
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« Reply #1 on: May 07, 2009, 01:17:06 PM »

Discussed here.

http://amfone.net/Amforum/index.php?topic=19587.0
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K1JJ
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« Reply #2 on: May 07, 2009, 01:22:13 PM »

I'm a skeptic. To put it into context....

I once ran 75M tests on a 9' mobile whip with a big loading coil compared to a full-size 75M dipole.  I had the Blazer truck with the whip parked out in a field and the full-size dipole at 60' about 200' away from the truck.  When switching between A/B repeatedly, there was usually a 15db difference on average for stations that were about 100 miles away or more.  This was done for both receive and transmit.


My point is that even a 9' whip on a truck using a poor groundplane is down only about -15db to a full size dipole. (-20db at most)  So, one would expect any small antenna to make a good showing of itself - if within 15db.  That's like about 4 watts into a full size dipole at 60'. (compared to 100w into the mobile whip) Many guys have great signals running even 10w riceboxes into 75M into dipoles.


Bottom line is, until we find out how to use superconductors and make a 2 foot long 75M Yagi with an input impedance of 0.01 ohms work efficiently, there is nothin new under the sun.... Grin

T

 

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« Reply #3 on: May 07, 2009, 02:15:36 PM »

Could this be one of those EH or CFA antennas that was introduced to the AM bcst band industry 10 to 20 years ago?  I believe they rearranged Maxwell's equations and supposedly proved electrically short antennas could perform as effeciently as full size antennas.
Some W5 was a big proponent of this for Ham radio.  He was saying one could build one of these antennas, supposedly not much larger then a shoebox, put it on your closet shelf and work 80mtrs with only 100watts and of course, all around good signals.  Doesn't everybody have one of these? ;-).

I always thought wave acceleration along the "wire" had something to do with antenna effeciency; the longer the better.  I really don't know, but I bet Walt W2DU knows a bit of theory on this subject.

Bill N4WC
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Bill Cook
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« Reply #4 on: May 07, 2009, 02:32:04 PM »

Quote from: Opcom
I would like to know what is in the box.

A Hammarlund Super Pro?
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K1JJ
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« Reply #5 on: May 07, 2009, 02:53:15 PM »

There's one way to get to the bottom of it all...  put up a 75M dipole and compare the two A/B.

We should have axed to carry the "Antenna in a Box" (AIB) over to QIX's or Dale's 75M dipoles and run some tests.

If they really want to impress people, then put up a 75M dipole as a comparison at the next fall Nearfest.


Precautions:

1) Be sure to lower the dipole when testing the AIB to insure the AIB is not coupling into the dipole.

2) Be sure there are no power lines close by that can cause coupling and radiation.

3) Be sure the AIB is not using the power line system as a ground to reduce its vertical component losses, assuming it is of vertical polarization... unless this is part of the intended design.

4) Be sure to test it on 75M where the AIB physical length is far from a full size antenna to prove if there is something really going on in the AIB.

5) Drop a one minute dead carrier for both antennas and have at least three stations in widely varied locations listening. Each will report back their estimate of the average signal and the peak signal during the one minute carrier test.


I'd be curious to see a test like this for the Isotron antenna too.  Has anyone bothered to do so?  The AIB could become a big hit if marketed well. Most new apt dwellers don't have the knowledge or simply don't bother to dig deeper than reading anecdotal ham stories of how they were "59" in Algiers using the new miracle antenna.

If the AIB  is closer than -12db to a full-size 75M dipole, (better than a mobile whip on 75M) I will be impressed.


BTW, the guy said it was NOT a loop inside the box. However, from his verbal polar plot elevation pattern description, I got the impression it was vertically polarized. Also, he said he wasn't sure if moving it above the ground would help much, but was worth testing, which also indicated vertical polarization.   I didn't see any liquid nitrogen tube connections running in, so it's not using super conductors.  ;-)

I wonder if it's using large ferrite rods with wire wound around them - tapped for the various bands, using the open wire and ant tuner for matching? Just a guess though.

A axed him if I bought eight AIB's, could I hang them on a long tram line and phase them like a phased array. He encouraged me to try and let him know how it worked out... Grin


Hey, if anything, they're getting a lot of publicity for the roll-out!


T
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KM1H
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« Reply #6 on: May 07, 2009, 03:35:20 PM »

Hey Tom, it was nice to run into you there, its been a long time.

I know one of the co-inventors quite well and he is a bit eccentric but not a flake. He is the guy in the Merchant Marine Radio Officer uniform, Dave Ring, N1EA.

I leaned on the other guy a bit late Saturday when the traffic was nil.

Its not A loop but rather several in series. No ferrites.

Bandwidth on 75 without retuning is around 100 khz.

The voltages on the "balanced" feedline are very high

Not supposed to be better than a dipole, the concept is for apartment dwellers, restricted condos, and similar where nothing else is permitted or works. Supposed to be completely ground independent. Heck it was sitting on sand at Nearfest.

It will be sold as a kit in the $200 dollar range. It will fit in a plastic garbage can.

Supposedly the initial inventor has found a loophole in Maxwell and all the others which will be divulged as soon as the Patent Applied For stuff is returned. He knows his theory and I couldnt trip him up. They dont want it to be a secret.

Im trying to get it here for evaluation and comparisons.

Im a natural skeptic but the damn thing intrigues me.

Carl
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« Reply #7 on: May 07, 2009, 04:47:24 PM »

I would think it is multiple loops to get the voltage higher. As I moved in front of it HUZ said I was modulating the VSWR. Maybe the switch box switched them between series and parallel depending on frequency. I read an Army study of multiple loop configurations and they concluded a single 1 turn loop generated the best field and the best matching was a cap across the feed and one in series with the loop.
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K1JJ
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« Reply #8 on: May 07, 2009, 04:50:01 PM »

Interesting, Carl -

Yes, it was fun comparing various antenna war stories with you at NearFest.

The AIB - I assume it's vertically polarized then?

If so, it might be harder to compare, needing a full-size vertical with a good ground system. As we know, it could be down up to -40db locally compared to a horiz dipole cuz of the high angle null on verticals.

A loophole in Maxwell's equations?   That would be something -  and in line for a Nobel prize for physics.... :-)

We're probably being a little hard on them with our fun, so we'll cut them some slack since you can vouch for their expertise. Let us all in on the test results as soon as you get some, OK?

Later -

T


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There's nothing like an old dog.
KM1H
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« Reply #9 on: May 07, 2009, 05:31:25 PM »

Quote
would think it is multiple loops to get the voltage higher. As I moved in front of it HUZ said I was modulating the VSWR.


Sounds like a side benefit for Planned Parenthood.

Carl
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WA1GFZ
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« Reply #10 on: May 07, 2009, 08:04:19 PM »

No plans to be a parent any time in the future I'm done.
I didn't feel any heat
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KM1H
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« Reply #11 on: May 07, 2009, 08:38:02 PM »

Ive known Dave for years Tom, I met Mike for the first time on Friday when Dave yanked me out of passerbys as I was sorta checking out a nice body on the other side. Grin I miss lots of radios that way......

IF I get a chance to play with it, or build one once the design is released, the forum will be the first to know.

I dont think it will handle the power that many of us on here run.

Carl
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« Reply #12 on: May 07, 2009, 08:50:48 PM »

I dont think it will handle the power that many of us on here run.

so get a bigger box! Honestly I hope it works well. The magic behind small antenas has always interested me.
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« Reply #13 on: May 07, 2009, 09:40:13 PM »

 "  It will be sold as a kit in the $200 dollar range. It will fit in a plastic garbage can. "

Is this that 'forshadowing' thing they talked about in high screwl?

klc

 
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WA1GFZ
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« Reply #14 on: May 07, 2009, 09:53:26 PM »

take the primary inductor on your link tuner. Why not go directly to 377 ohms and skip the secondary, feeders and antenna.
RX would still be an issue.
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KM1H
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« Reply #15 on: May 07, 2009, 10:22:00 PM »

I also talked to Mike about a 4 square and mutual coupling. Dont know if that was before or after Tom but his head was in full bobbing mode as he was taking notes.

If this thing is even half as good as a 80M vertical over poor ground the possibilities of a decent directive signal from a small lot will change a lot of thinking and operating. Even more so on 160. Just visualize a green garbage can in each corner of a small surburban lot Grin  The wife can even have a flower box on top.

Carl
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K1JJ
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« Reply #16 on: May 07, 2009, 10:29:17 PM »

I wonder about the "high voltage" on the feedline they mentioned. That openwire spacing is set up for something like 100KV +++.   They  were using a small MFJ class tuner.  The feedline was pretty short, so the tuner would see most all the voltage generated at the load.  How could a tuner like that (or any average ham tuner) possibly take a  level of voltage that is suggested by that wide line spacing?

Probably in the next version they will use a smaller and more reasonably spaced openwire line.

T
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There's nothing like an old dog.
Steve - WB3HUZ
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« Reply #17 on: May 07, 2009, 10:35:44 PM »

I think someone said the feedline WAS the antenna. The box was there just to draw your attention away from the feedline.  Cheesy
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KB2WIG
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« Reply #18 on: May 07, 2009, 10:47:57 PM »

  " the feedline WAS the antenna "

Lying on the ground like that... A stealth NVIS antenna ?.......


klc
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Tom WA3KLR
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« Reply #19 on: May 07, 2009, 10:56:30 PM »

Maybe it's not really ladder line at all but to fake you out; RG-6 rf in to the box, one cable out with bridge reflected power or remote tuner serial data?
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« Reply #20 on: May 08, 2009, 06:22:16 AM »

This brings to mind the URI antenna from a few years back.

http://www.uri.edu/news/releases/?id=2659

Can't say that I've heard or seen much after all the initial hype. But then again, I haven't been on the lookout for it.
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« Reply #21 on: May 08, 2009, 10:08:07 AM »

This brings to mind the URI antenna from a few years back.

http://www.uri.edu/news/releases/?id=2659

Can't say that I've heard or seen much after all the initial hype. But then again, I haven't been on the lookout for it.

Check the review on EHAM for it.

Sheesh, had I been the inventor of the antenna, I would have fled in shame off the reveiws on eham, not to mention the other sites.

I especially like Tom Rauch's reply. 

It seems his antenna was nothing more than a cb antenna, a loaded whip with a tap.  Wilson still makes them, and they actually make decent radiators.  I ran across an article someone had online of using the Wilson Silver Load CB antennas with longer stingers on (I think) a semi-truck, and in comparison to the other antennas he tried, it beat them or matched them.

--Shane
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« Reply #22 on: May 08, 2009, 12:20:27 PM »

Steve,
If you remember I was moving near the box away from the feedline. I was doing that to avoid coupling to the feeders.
I bet the feeders were wide to raise the Z a bit so the tuner would work.
My guess he coupled RF into that switch box and welded the contacts requiring the vise grips
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« Reply #23 on: May 10, 2009, 08:15:18 AM »

The AIB reminds me of the monolith in 2001: A Space Odyssey.  Just need some AAMCO transmission apes and some bones  used to beat each other right into the future and maybe no feedline will be necessary.
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« Reply #24 on: May 10, 2009, 09:27:01 AM »

It seems to me... 

Antennas seem to be an area of Black Magic. Mostly because it's difficult to determine real performanec numbers for real antenna installtions. We have to infer a lot from sketchy data. Most amatuers rely soley on VSWR indications as a prediction of antenna performance.  Some measure other parameters, like feed point impedance, but I think few of the population actually know how to apply the numbers (I wouldn't with out reading alot).

Antennas in the HF range are hard to accurately evaluate. Microwave horns and yagis were easy. Put them on the Goni in an Anachoic chamber with a reference dipole. Transmit a with a calibrated signal and bingo, You plot real performance compared to a nearly isotropic radiator, I say nearly because there were tiny but measurable differences in a reference cal. Nothings perfect, but often Close Enough is.   

Since you can't do that with a large HF antenna, we're stuck with labor intensive field strength measurements Someone driving around and checking over a fairly wide area.  Unfortunately that can be subject to environmental effects, and few hams go to the trouble of running those measurements anyway, at most if we have the real estate you can get an A/B measurement, which is fine for relative performance for your particular setup but it begs the question, relative to what? Ideally we'd A/B with an Isotropic radiator, but who's got one of those?

So we go the simple route,  with anecdotal evidence being sufficient to claim either outrageous sucess or dismal failure.  How many of use have either heard or said, "I put up that new XYZ Diaper Pole and I worked 72 stations with DX etc. etc. etc."  The other side of the coin is the dismal failure of a new installation.  Do people check propagation prior to these test transmissions? Check DX spots? Compare the antenna to another local hams station performance.  It seems that few of us actuall take a real scientific approach to antenna work, with the exception perhaps of modeling the ants.  With so many variables effecting a single peice of equipment in the shack, it's no wonder the Antenna and it's performance is subjected to so much argument and discussion.

So evey once in a while, someone builds a radiator that gets out a signal, and makes claims of awsome performance. And then the REAL fun begins.  Grin
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