SWR ON A IMAX 2000

[Marconi]

cominatyalive;

...The IMAX is a .64 wavelength antenna; which is BETTER than a 5/8 wave. That is why it is 24 ft - instead of 22 ft. In fact, I've considered lengthening it by 1 ft 9 inches to see how it would behave as a 3/4 wave antenna - for $#!+s and giggles....

Rob, as you say, I agree that the Imax is sufficiently broad banded enough to work 11 meters and maybe it can do most of 10 meters without needing a tuner or altering the antenna physically. However, I disagree that the Imax is a .64, not that it makes any difference. I'm like 'Doc on this score---what does the little difference matter anyway. Maybe there is a really good technical reason that accounts for such a difference, or we probably wouldn't be hearing this claim repeated all the time, but I doubt you could tell the difference on-air.


I recall at some point reading and article some years ago that described several Japanese engineers studying some other broadcast antenna study that developed the 5/8 wave idea in the science. It seems these experts went a step further than the 5/8 wave idea and discovered the .64 advantage you refer to. I have not been able to find such article, but I have looked for it---hoping to prove the story true and maybe try and understand what was important in their study many years ago. The story in my mind came from somewhere and I don't recall more details. I think I was reading about the scientific history of antenna development after WW1---as broadcast radio was coming on line in America.


Like you, I have also heard it said that the Imax is a .64. I think the idea may have originated from a combination of the story above and an Internet article: The Imax 2000 EXPOSED! written by a Tech on the Copper's Forum using the handle Tech 833. When he published his work on the forum, I argued that his math was wrong and I believe the thread associated to the article is still in their archives. I claimed that 833's radiator length as he measured it was very close to correct, but that his math did not support his own numbers and I asked him to explain his claim that the Imax was as .64 radiator. I do not recall his response, if any.


You can look at his own drawing of the circuit and see exactly where he measured the length he described. If you check out the Imax closely using his images or your own Imax as a reference you will see his number of 270.5" radiator is pretty close to the radiator measurement for an Imax---and he is not counting the matching coil as part of the radiator as noted in his circuit drawing and like 'Doc suggested is typical when measuring the wavelength of an antenna.


Now if the CB wavelength is pretty close to 36' then that is 36' x 12" = 432" x .625 = 270". I asked 833 how he figured that 432" x .64 = 276.5" agreed with his on radiator length of 270.5" noted in the introduction to his article where he made the claim and noted that it was some big secret.


Rob, if this article is also the source of your claim that the Imax is a .64 wavelength radiator and the claim is correct, then tell me where I went wrong in my thinking?


You will also note that I posted a chart for cominatyalive that was not noted in his Imax manual. There is probably a reason that Solarcon no longer adds that information to their manual. I have heard the story of why, but I'm not sure of the truth in the matter.

 

[Robb]

I will admit this antenna is a head scratcher.
There have been a lot of claims and anti-claims about it. Some are true - and some are false. Fiberglass antennas are more prone to noise. That is a ridiculous claim; as any antenna is affected by its enviorment. Some have claimed of the higher db gain figures compared to ground planes; which is as good or better but not as outrageous as claimed!

If it is a .64 or a 5/8 wave - it still works remarkably well for the amount of money spent. Cominatyalive pointed out that it is 24 ft - which it is. Since a .64 is taller than a 5/8 - I just reasoned that it had to be at least that. Most 5/8 wave aluminum ground plane antennas are 21 ft and change. It obviously cannot be a .64 with that length either.

As far as what Doc said, well I won't disagree with that either. Doc knows a lot more about radio than I do. I've only been a Ham for a year, and can learn a lot from him.

One thing that is true about this antenna - is its broadband ability. Not a myth. I talk with my Magnum OmegaForce on 10 meters with a very low SWR for that band. I've been on a net meeting with Arizona with no difficulty -for about an 1/2 hour- couple of weeks ago. They were genuinely surprised that my QRP station did so well with such a humble antenna.

The IMAX Exposed article - I did read. But I've read other articles that pointed out the .64 claim. Surely, the 24 ft length needs to be explained in itself. That is the real 'mystery' that needs to be brought to light - IMO.
24/36 is equal to 3/4! lol! not!

 

[Marconi]

...The IMAX Exposed article - I did read. But I've read other articles that pointed out the .64 claim. Surely, the 24 ft length needs to be explained in itself. That is the real 'mystery' that needs to be brought to light - IMO. 24/36 is equal to 3/4!

No again Rob!!!!!! another mistake in your math.
24' / 36' = .66666666 % not .75 which would be 3/4 of a wavelength. I don't get it, do you just look at the pictures?

It was a joke!
24/36 is two-thirds...

Beside the 1 ft portion of the antenna; the radiator length is still greater the 5/8.
That is the mystery joke!

 

[Marconi]

Hey Ron, got nothing better to do than joke around and use your privilege with the delete button. I think I've seen a similar situation popup on your account before.

Apology accepted, but I won't forget.

 

[Robb]

For those who care; it was an honest accident...

 

[cominatyalive]

Happy New Years!

Just adding my worthless 2 cents here,

With the Imax, that's about all one can do. Is just look at the pictures. lol!
Because nothing really adds up. But hey, Rob is right, you get what you pay for. And for a lousy couple of benjamins, you can at least have a half ass 5/8 antenna.

I'm starting to think even a simple, properly tuned 1/4 wave would walk circles around this Solarcon. I even have a 1/2 wave DP antenna tuned for 11 meters that I've been thinking of putting up lately for sh_ts.

I even went as far as trying to write Big Hair Antennas a couple of times ( in regards to beefing up the Imax with a bigger coil) but never received any reply back from them. I figured they must be too busy on dope or something to bother replying back to me. No phone numbers either. Just as well I suppose. I've spent enough friggen money.

On a lighter new years note, Just thought I'd check in and see what was brewing here.

Nice chart you had in your manual Gramps, no, I didn't have it in my manual just like you said. But I saved the PDF into my archives in case I might want to try resizing to a specific freq in the future. Thank you. And btw, you can just call me James. Spelling out cominatyalive must be a real pain.

Speaking of half ass, the noise is back again slightly. But the neighbors bug zapper is still off. So I'm still looking into her AC drop as the problem too. But it still has not been as bad as it was 4 days ago.

I've even thought about selling & moving out to the county some day just because of this interference BS. If I would have known this before I moved here, I sure as H_ll wouldn't have.

I've been reading about broadbanded interferences, such as bug zappers, light dimmers, appliances, etc. They say there is still no cure except for some kind of spread spectrum technology that the government still has not given the go ahead on because of certain probmatic circumstances.

So it's either deal with it, or get out of Dodge.

But I thought I'd ask if anyone has any knowledge of any EMI device that could possibly block a bug zappers EMI ? Other than that plea of desperation, I know down deep that I'm S.O.L. unless Com Ed can do something about her drop out on the pole out back.

I was told the only antenna that would not catch the broadbanded waves was a beam. Since it's horizontally polarized. Or at least not catch so much of it. Just don't know if I really want to go that route or if it would really do any good. But if I could get any confirmations on that, I might just do it in the spring.

Anyways, the reception has been better though for the last few days now.
Nice to see a few different point of views on here stemming from my post. Carry on you seniors! Oh yeah! I'm taking it all in too. You betcha! op:

Ok, this dummy load is hittin the bed now. Hope everyone has a super
New Years!

PS: Rob, ( I Care ).


James

 

[SharpShooter]

My Imax 2000 with the GPK Ground Radials.

75' LMR-400UF ( ultra Flex )

Feed point is 18' 6"

Top is 42' 6"

I wanted to be able to easily service or remove it....just by standing on my roof.

Over all I think it tuned up " fairly " well and covers the area I use.

26.815....1.7
CB 1....1.6
CB 20....1.4
CB 40....1.2
27.515....1.2
Center Point....27.658....1.1
28.500....1.5



What do you think ?

 

[mackmobile43]

2 MEG is a very broad banded antenna which I'm sure will narrow a bit at higher mounting or will it if it's using the coax as a gp? Maybe if it is mounted at a wave length that would be about the extent of it's efficiency.

Not very efficient but very no brainer.

 

[packrat]

First, salt water dummy load is fine. No problems. Second, why the concern for a non issue of SWR? Anything less than 2-1 you are golden, and wont see any difference in changing it. There is a GREAT article called." SWR meters make us stupid" Look it up for some good info. Remember, swr and swr meters are a recent phenomena .

 

[mackmobile43]

First, salt water dummy load is fine. No problems. Second, why the concern for a non issue of SWR? Anything less than 2-1 you are golden, and wont see any difference in changing it. There is a GREAT article called." SWR meters make us stupid" Look it up for some good info. Remember, swr and swr meters are a recent phenomena .

Better watch what you say, the antenna Mafioso's are monitoring this forum and will hunt you down like a dog if you present a threat to their sales.op:

 

[W5LZ]

Try here;

http://www.eham.net/articles/23317

for "SWR meters make us stupid"... by KL7AJ.

If that Solarcon uses more than about 40 feet of feed line, it will exhibit the same characteristics as a 5/8 wave 'groundplane' type antenna. They amount to the same thing, just a different form of the 'other half' of that antenna. The biggest difference in the two will be in how well each it tuned. That does not mean just adjusting SWR.
So why did they make that Solarcon with the tuning rings? Cuz it's easier for someone unfamiliar with tuning antennas to adjust. Is that method more efficient than other methods? I sort of doubt it, but the difference in efficiency just isn't going to be the 'day light/dark' thing that people make it out to be.
Is the difference in length -alone- going to make a huge difference in how well the thing works? That length difference amounts to something like 6 inches. Sorry Charley, it just isn't going to make the differences claimed. A listener's 'opinion' makes for a very bad way to judge how an antenna is working, and I haven't seen a calibrated 'S' meter in quite a while (referring to 'on the air' testing). Let alone some way of 'normalizing' propagation. Those type of 'tests' are always subjective, never objective. Big difference.
That '5/8' versus '64' wave length thingy is one of the best advertising schemes I've seen in a long time. It's sold a lot of 'ho-hum' antennas. If it makes you feel good to think your '.64' w antenna is better than anything else, good for you! Enjoy the devil out of it.
- 'Doc

 

[BOOTY MONSTER]

 

[packrat]

:w00t::w00t:

 

[mackmobile43]

 

[will85w4]

As some of you know, I have a IMAX 2000. I have a couple posts about this antenna. One on AC crackling hum, (some may call it static), I call it received interference. In dealing with this Stray AC interference over the last couple months, led me to start getting a grip on my SWR.

They all say that the IMAX 2000's SWR is a good 1.4:1 on the meter right out of the box. Well, that might be so. At least mine was at first that is.

I use a PAL KW-1 SWR/Watt meter. But it was telling me that I was putting out 10 Watts on TX. Which led me to believe this meter was out of whack. Especially when I went to put the needle on (SET) right before getting my SWR reading. It was always 1.4:1. But it also always reads 10 Watts on TX.

I just now purchased a Workman SWR/Watt meter. Low & behold my SWR on channel 20 was a solid 1.5:1 and my TX wattage was about 5 Watts like it should be. But 1.5:1 is just way too much for my liking.

So up I went to the tuning rings on my IMAX. As I lowered the rings all the way down, (let's say from the 1/2 mark of the tuning threads and down to the bottom, I got nothing but a 1.6:1.

From the half way level of the tuning threads and all the way up, nothing but a solid 1.4:1 and no better.

What I wanted to know, is there anyone out here who has a better reading than a 1.4:1 on their Imax's? I'm just wondering if a Imax is even capable of a better SWR reading than the 1.4:1 from the factory.

Back in 1976 or 77 when I had the original Avanti Astroplane, I had nothing but a solid 1.1:1 always. Those were the good o'l days. I'm thinking it may be from a not so perfect solder job on my PL-259's. Not that I don't trust my own work, but sometimes I wonder.

Also, I wanted to know if there are other ways of improving one's SWR? Is it possible to raise or lower the antenna height to improve on this? I sometimes also wonder if my antenna is too high. 60' to the tip. Penny for your thoughts.

J.

1.2:1 on Ch. 1, 1.2:1 on Ch. 20, and 1.3:1 on Ch. 40 for me. I have IMAX 2000 w/out GPK.