The AM Forum

http://www.isotronantennas.com/80b.htm

Has anyone ever tried one of these on 80m? How well do they work? How hard is it to build one? How high does it have to be?

73s
geo

It's very sensitive to its surroundings. Even the metal mast can detune it. It's not a DX catcher but they mysteriously do work.
And I think they only handle 200 watts

Fred

Save your money and invest in a good Bird dummy load.
I laughed at the first time I saw it at the TRW swap meet in Ca. back in '81 and it still brings a smile whenever it comes up. A dog log and coil would work better.

The picture below says it all.  Pure junk.  (Caption: "Multiple Isotrons on one mast!" )


This sales statement is laughable:

"THE ISOTRONS HAVE THIS RADIATION "AREA".  The ISOTRONS exceed or equal (depending upon the model) the area of a conventional one-half wavelength dipole (#12 wire)."

Gee... Maybe we should use #0000 welding cable for dipoles to match the Isotron's incredible "radiation area".... ;D


Save your $.

As Frank said, even a small vertical whip with radials would be better.  I've measured a 9' mobile whip on a Blazer for 75M (in the late afternoon for locals) to be down only about 15db from a full size dipole at 60'.  That's not too shabby.



T

Time for an antenna shootout!

Isotron vs. Gotham V-80

looks like one of the antennas off the "cloud city" in Star Wars.. craaaaaazy.  I talked to the salesman at a hamfest many years ago. He explained why they work and how they are resonant. Apparently they generate very high voltages. But I would not prefer one to a long wire or tall vertical + tuner. It says for space restricted areas so there got to be lots of compromises.

A very Close friend an good fist CW man Called sometime ago, "Jack I'm moving can you Help me get this antenna down" member of the local club, good Egg, by all means show respect yes Sir,.. I make the trip climb the tower remove what looked like a I don't know what...But he swears by it an was bragging to me about this thing...his was cut for 80 meter or built rather it some kind of contraption believe me But it werks...His Call is KB3IN his name is Bob I would think he has email I've never had to email him so I don't know his addy ....

But he Liked......that antenna...


73
Jack.

Put up some phased Isotrons and work DX.

It works compared to what?

What Category would you put this thing in Frank..?

It's a Contraption...

73
Jack.


 

maybe we need a new section...stuff that doesn't work.

I would put my money into a gotham vertical before that thing. The first time I saw it I asked the guy a bunch of questions.  I think it was as funny as that guy at Deerfield and his gray box antenna invention.

Frank said:
"It works compared to what? "


Exactly.  "It works" is probably the most common ham antenna anecdotal story out there.

If a ham has nothing to compare an antenna to; no reference dipole for example - and a mobile whip (a so called "poor" antenna) is down only about 15db from a full size dipole, how would he know he has a poor antenna?  The answer is he wouldn't  know.

Back in May, 1965 my father helped me erect a 55' tree (mast) that I chopped down in the nearby woods. We poured concrete and even added a steel pole at the top wid a pulley and rope.  The first night I had no antenna to raise so I took a 110VAC 100' extension light and raised it up. I loaded the 75W rig into it and could see the light flashing CW up there at 60' in the night.  Lo and behold, stations started coming back to me and I worked all over the east coast on 80M that night - on a lightbulb!

If that were the only antenna I had, then I would have said "it worked."  

I've also lived in apartments where I was happy to sneak a wire out and throw it onto the roof. "It worked."

Little did I know that 40+ years later I'd be playing with antennas that often show a 20db difference over a full size dipole into Europe. Now, that works!   ;D   ie, It's all relative.

T

Well then get with Isotron an straighten'em up...other outfits they sell G5RV's everyday an folks buy'em an believe in'em and it's poop antenna too.

There's no use in comparing what this group does on a daily basis and produce quite gud sig's to what the plug an play groups is willing to spend on what they want,,,73
Jack.

Another one is "I work everything I hear."

To find out what's going on with the Isotron (one test that is) put a very high Xl common mode choke on the coax up at the Isotron and see how well it does then.  I bet it's another one of these deals where the coax is the antenna.

Rob

The isotron is an inductor.  Put a "stinger" on the 80 meter or 75 meter model, and you'd have a AM broadcast antenna.

They work.  Akin to a Hustler mobile antenna.  Most of the guys using them are older (no offense to the Seniors), and either can't haul a 6 element 40 meter yagi up themselves, aren't that interested in it anymore, or are restricted by lots or CC & R's.  So, the thing is more than likely being compared to what they where used to as a "working" antenna, something like a Hustler mobile.

I've talked on one of the AM groups with my 100 watt rig, and the ATAS-120 rotary dummy load (screwdriver).  Yeah, people could here me, but nothing like the legal limit full sized 160 dipole at home.  However, Yeasu, as well as the magazines, have all touted the ATAS120 screwdriver as perfect for a pvc flagpole antenna...  They even give measurements for your counterpoise somewhere.  If I lived in a mobile home park, could not have much of an antenna up, I'd sure be happy with this thing on top of a flagpole, and I'd be working 40-70Cm.

So, as others have said, it works, but compared to what?  About as well from what I'd seen as a Hustler or similar mobile antenna.

--Shane


--Shane

So, did any of you use a Gotham antenna back in your novice days?  As much as they were advertised they must have sold a few to have enough cash flow for advertising-unless they were a front company for a money laundering operation :)

I have been licensed since early '75 and I have never seen one, worked anybody with one, or met someone who admits to owning one.  I had put the Boulevard electronics receiver in the same category (advertised heavily but invisible) but I finally found one of those so I know they exist. At least the Gotham antenna looked like it had the potential of radiating a signal.  So one of you loyal Gotham fans, share your experience.

Rodger WQ9E

I had one when I was a Novice in the 60s, Rodger. Not one of their verticals, but a Gotham 4 element 15M band Yagi.

It was an amazing thing. I had been used to working around the midwest with my Knight T-60 on 80 and 40 and a dipole. Ham radio was beginning to be a disappointment. Then I built that Gotham and couldn't believe it, working worldwide DX. I worked *Russia*! And *South Africa*! And *Rhodesia*! And got the QSLs to prove it. Bought IRCs for the first time. I must have worked 40 or 50 countries on that Gotham with that little Knight Kit and S-40 receiver.

The thing about the Gothams was that they were cheap and affordable for someone on a high-school budget. You got a lot of aluminum for other projects, too. That Gotham Yagi was so cheapo that it didn't even have a proper match to the driven element, you were to extend the center conductor of your coax out and tap it directly onto the driven element.

That didn't matter, I didn't even have an SWR bridge and the T-60 loaded it up just fine.

I was even so bold as to mail in a contribution to "How's DX" in QST.

The name says it all.

I had one of those Gotham 15M beams back in the sixties.  As I recall, there wasn't much to it.  The elements were smaller tubing than you would typically use and they had quite a sag to them.  They just used a U-bolt to attach to the boom with no associated bracket...so they turned around on the boom quite easily and were difficult to keep aligned.  The boom itself was very small tubing.  Yeah, I also remember there was no "match" for the driven element.  You just tapped out a ways with the center cond. of the coax.  The bottom line...they were cheap and within the budget....so a lot of guys bought them.  If nothing else, you could utilize the tubing and parts to build something a little more reasonably engineered.  As I recall, I made a six meter beam out of the stuff from that 15M Gotham beam.  The Gotham verticals were a joke.  Seems like they were nothing but tubing and a coil.  If you ground mounted the thing with no radials, it made an excellent dummy load.
Anyway...lots of fun and a way to get some experience finding out what works and what doesn't.  Also lesson learned....You get what you pay for.

I'm not familiar with the Isotron, but I have heard and worked guys on 40 and 75/80 who were using small magnetic loop antennas.  Hard to argue with the fact that they work, although very narrow banded and you have to use some rugged vacuum variables to withstand the high voltages appearing at the tuning point.  I guess they produce some scary field strength levels near the loop as well.  Interesting concept though.  Especially if you have very limited space for antennas.

73,  Jack, W9GT

To a wet noodle

...LOL... ;D

Some comments:

Yes, the screwdriver is a nice antenna. After a year experimenting with HB bugcatcher type whips, a bunch of us concluded the versatile screwdriver antenna was roughly as good. The poor groundplane of the car made the top radiator an insignificant part of the system, so the screwdriver was quite adequate - plus remotely tunable!

Batman's Gotham vertical. As I've written many times, I called CQ for three days as a new Novice with no replies using a Gotham Vert on 80M.  No radials and spaced from the house by 1'. (little coax available)  Of course, it would work FB if installed in the clear with a radial field - just like any short, base loaded vertical.

Funny story on the 15M Gotham beam, Bill and Jack.  I remember 15M in 1965. It was dead and so bad I brought my perfectly good working RX into a shop for alignment... ;D  

There's no way to change the world. Isotron will continue to pull in 100's of $thousands selling them. All I can do is advise fellow guys on this BB to consider something else, if they can.  Even a randon end-fed wire or short mobile whip in a flag pole with radials is better.  Even try a magnetic loop using heavy copper tubing. There's  better ways.

T

Is that a resonant wet noodle?  ;D

73,  Jack, W9GT

  Easily done with a tune-a noodle salad.

Let's be careful not to offend the Macaroni net folks!   ;D

I will gladly give you mine for 80 and 40.  I got better results with a HEATH Cantenna.  You will be MUCH happier with a random wire and a tuner.  Load up your Gutters and Downspouts.
JAS

Bill, Jack, and Tom:  Thanks for your comments on the Gotham antennas and now I know they weren't just vaporware.  In a way they sound like the forerunner of MFJ: low cost products that, for the most part, work but require a bit of user intervention.

I never had a Gotham but I had something kind of like one, the HyGain 18AVT vertical.  That was the one that was a tapering aluminum tube about 18 feet tall (I guess that was the 18 in the model number) with an airdux coil at the base and a manual tap.  I think MFJ may still sell it.  To change bands you were supposed to go out and move the tap.   This was before swr analyzers made such a job trivial.   Not only did I not have any radials I'm not sure I even knew I needed them.  It worked...poorly.   Later I  had a 4BTV vertical, ground mounted and did I use it on 40 m.?  Nah, I recall trying it on the high bands.   Again with no radials.  You can guess how that worked.   You all who got tickets post-internet, have to understand how it was for a kid in the days when ham communication on technical topics trickled out to the country via surface mail and occasional club meetings.   We didn't have a phone for 3 years then we got an 8 party line.  I was in a tunnel wearing sunglasses with the lights out feeling my way along.   Now it is almost the opposite extreme.  I sometimes feel almost overwhelmed with ham information and frustrated that I can't read everything I'd like to read because I don't have the time.

I was thinking recently about how I never seem to make it to local ham club meetings and I suddenly realized the Internet is the ham club now.   I should go support the local club though.

73

Rob
K5UJ

  My wife makes a snack treat from macaroni and cashews. She even named it after that net...or the people in it.


  Yep, you guessed...Macaroni Nuts.

Here's a guy who homebrewed an Isotron type antenna for his low power AM BC transmitters...PVC pipe, chicken wire, etc.

http://www.pcs-electronics.com/phpBB2/viewtopic.php?t=1092 (http://www.pcs-electronics.com/phpBB2/viewtopic.php?t=1092)

The Gotham is touted by K6INI - ex-T12TG. What call is T12TG?

Tp be honest, the Gotham seems to be simple vertical antenna. It is something I could make from telescoping aluminum tubing and a coke bottle insulator for a base. Add a tuner and go to work. Although as said the Gotham uses a match. I'd rather try a tuner.

TI = Costa Rica.

The Gotham used a simple base loading coil that went in series with the whip and the opposite side went to the ground system.  You then connected the coax shield to ground and the inner conductor tapped the coil to find 50 ohms.  No need for a tuner since the matching was done at the feedpoint.  In fact using a tuner in the shack without a good match at the base of the vertical wud produce a high swr on the coax resulting in a poor overall system.

The Gotham in itself was a decent antenna if put out in the clear and used with a good radial system. The only pain was running outside to tap/change bands, but I'd take that any day over a trap vertical.

T

True dat. But a base loaded vertical is the least efficient way to load a vertical. So even with radials, the Gotham would not be as good as a top loaded system, but would probably be competitive.

Yes, ALL base loading is not as efficient.

As we found with the mobile antennas, the best of all whirls would be to have a loading coil in the middle of the whip, some capacity hat loading near the top and a small base coil to have something to tap/ tune.

Remember the 6 foot? 40M vertical in the handbook that had that HUGE capacity hat in the guy's back yard? Maybe 1980 Handbook. W2?)   He claimed that vert was nearly as efficient as a full size 33' vert.

T

Jerry Sevick, W2FMI

Yeah, he wrote a bunch of articles for QST, maybe other mags on physically small loaded verticals.  He owned that story for a time. 

If that guy with the homebrew isotron ant. on the broadcast band is in the U.S. he's   I l l e g a l.   I think someone in that on-line forum said they were running 15 w. down at the low end of the mw bc band.  Definitely not part 15 if in the U.S.   We have pirates occasionally around here on FM broadcast.

Here's one of his articles:
A High Performance 20-, 40- and 80-Meter Vertical System, W2FMI, QST, December 1973.

I wondered about that too. That forum seems to be advertising something called the "AM MAX" transmitter designed to output 15 to 30 (?) watts of carrier level AM on the BC band. Using it that way is definitely not Part 15 compliant. I'm not familiar with international regs, but I notice they are discussing xmtr range in "kilometers", so it's probably outside the US. Did notice some ham mentioned adapting the DIY Isotron for "top band" use, i.e. 160, so I'm curious how it worked out.

Has anyone actually seen a schematic for the isotron antennas? Just looking at the homebrew BCB version pictures, I still can't figure out exactly what he's doing. The text writeup on the forum where he posted the original write-up talks about general parts fabrication, but no real construction details. I'm always interested in different configurations for antennas to use for BCB listening. It seems surprising that these things actually take power and radiate. I worked a guy on 40 meters about a year ago and was stunned to learn that he was using an Isotron that was sitting on a pole on his patio. I have no idea how it would have compared to a half wave dipole, but he was 20 dB over S-9 that day into CT from "9" land.

Here are the 80 and 40 meter Isotron manuals:
http://www.isotronantennas.com/isoman.htm

Thanks Pete. The assembly diagrams show pretty clearly how one could be fabricated. As someone said in a previous post, it does appear to be a simple series LC circuit. Seems like Ted's loop (K1QAR) with its much greater surface area and probably much higher Q would be more efficient. I was amazed the first time I worked Ted on 160 meters while he was on his transmitting loop, but after several QSO's I was convinced that his signal was no fluke!

When I was driving through Marlborough, CT the other day I saw the tower in the picture below and took a picture of it. Wonder how that's working out for this guy?

I have to admit, on the surface of it, the isotron looks pretty good. A series circuit would tend to have alot of current flowing. Is it that different from a DDRR? The isotron has a many-turn coid and a low capacitance, where as a DDRR has a one-turn quite large coil and a larger capacitance at the end. Well it also has a matching section as well. What I am getting at is the DDRR is physically small too. The DDRR was published as being a good antenna in the ARRL handbook. Has anyone ever messed with one?

There was an old boy in AR that had a very ugly DDRR on top of the shed on the side of his barn. It was about 3FT in diameter maybe 4FT. The shed roof was flat, and tilted maybe a couple degrees to run the water off. It had been made from 2" car exhaust pipe bent round and once done he'd painted it to keep it from rusting. It was supported above the "ground plane" by four beer bottles. It was held on the beer bottles by bolts that had been welded to the bottom side of the 'coil', and the bolts fit in the mouths of the bottles and he had silocon-caulked them in. The beer bottles (longnecks) sat in the holes of small car wheel centers that had been torched out and the bottles bases had been caulked in place and the wnel centers tack welded to the tin roof. The ground end of the loop came down to the tin and was held by two L brackets. The match terminal was indeed a muffler clamp. The band was 11M to be sure and the drive was one of those old Maco sweep tube amps. It did seem to work well, although I had a few beers and maybe only thought so. The place was about a mile from the highway and you could clearly hear the trucker chatter. 10-4.

here is a drawing of a little one, I'm sure yall have seen these. Now I wish I had a pic of the contraption.

One summer day in 1966, with the ink still fresh on my general license. We were on vacation and I decided to take a walk to the beach. About 1/2 way down the street I could hear SSB coming out of one of the little rental cottages. Next to the house was a Gotham clamped to an old TV ground pipe. Feeding the Gothm was this giant coax RG17. I walked up to the window and asked the kid inside if he was a ham. Within microseconds we were sitting in front of his TR4 working all kinds of DX. All I had was my GR64 and some wire in a tree next to the house so this was a big deal. We worked a pile of DX that week and that little gotham really worked well on 20 meters.

That's a DX killer - stacked Isotron Yagis!

I can't remember if it was Rauch's website, or one of the Orr books, but I seem to recall that about the best length for verticals (loaded) was 15 electrical degrees on top and below the coil.  Might have also been the ARRL Antenna Book.

I found that made them slightly LONGER than a quarter wave, but yes...  It did give me a little bit more signal strength when I played with them on 2 meters, compared to bottom loading.

--Shane

heheheh... you're too much, Rob. That pic sucked me in for a moment... ;D ;D

This thread got me thinking of building up a homebrew Isotron to run some REAL comparative tests.  I'm thinking of a 75M version wound on a 6" PVC pipe using #10 wire - using aluminum sheet capacitors on each end.  I would suspend it from a rope stretched between two towers at about 140' high, fed with coax.  Using pulleys on each end I could lower it to any height for local tests.  It would be totally in the clear with no metal objects near it - for a 100' clear radius.

That oughta be a cool experiment!  I'm finished with antenna work for the season, so this wud fit right in.

I have no idea of the polarization or pattern. Anyone want to venture a guess?  Maybe omni-directioal, but not sure how the feeding point wud affect the polarization at this point.  Maybe it can be modeled.

T

Such an experiment would certainly answer the question about how it compares to a half-wave dipole. It would be very interesting indeed. Somewhere on the Isotron website, I believe they make the claim that it is a very quiet receive antenna that can be rotated to null out local noise. It may behave similar to a receive loop, with nulls broadside to the faces of the loop. My guess is that it probably favors certain directions on transmit as well. Only one way to know for sure, run a prototype through the completely impartial Vu Labs Testing Facility.

I think the sheet aluminum capacity hats would act like propeller blades. Spin, tangle, stretch, break. That homebrew guy actually had a brilliant solution to use chicken wire to reduce wind loading.

Tom, Maybe you should build one and put it on the front steps Saturday night and see if it will act like a tesla coil

That stack of Isotrons should pose some competition to a well known stack of yagis we read about somewhere else.

fred

Too band there's no way to sneak over to JJ's QTH and swap feedlines while he's inside testing so it looks like the isotron is just as good as the yagis.   You could stick a T in the yagi line with one to the yagis and two to the two test lines.  ;D     But it sure is fun to imagine his reaction   ;D

I think I'd get very depressed and go into the thumb sucking fetal position for a day or two... ;D  

This is different from the usual?

Oh, the humanity.

Considering Isotron hasn't received the Nobel prize in physics since coming out with it in the 80's - nor has there been an exodus of corntesters scraping their Yagis in favor of Isotrons, I think it's safe to say I'll remain fat and happy sitting upright for a while.

T

Hey, you saw that gray box at NEAR Fest in the spring. New technology, baby and a patent to boot.

Yep, we were all jealous, especially Frank.  ::)   I wonder why they didn't show up this fall?   Maybe the demand was so high they had to stay home and work?

Frank has been modeling it ever since.  ;D

Was it you that axed them if it were possible to get in on the ground floor of a private placement before they went $$ public - IPO...?   ;D ;D ;D    


[I hope you were wearing your channel 22 Mucas Member badge at the time to show credibility]

They never replied to my inquires. Very strange.

Funny how these miracle antennas never seem to wind up in commercial service for some reason.  ::)

Hey now that I'm done with the moxon maybe they could send me the file for a laugh. I'm stuck on the gold plated phono plug properties. Then there was the human body model VSWR modulation.
Imagine Tom Vu waking up to see 3 of them in place of the three duces.
Right up there with my friend seeing a mountain lion in his front yard Sunday morning...about 3 miles from here.   

I seem to remember seeing an article on using a tree for an antenna several years ago.  Yeah...really.   I think this concept was utilized by the military, as well.  It involved a coupling device (coil?) that wrapped around the tree trunk.  Results were claimed to be decent, in that it might have been several dB below a conventional dipole or vertical, but it provided a useable antenna.

Hmmm...wonder if it was right up there with the ISOTRON in performance?

73,  Jack, W9GT