Difference in AstroPlane vs. New Top One per Eznec5

[HomerBB]

No, my strap is not adjustable. Moving it up or down is the only way to spread or narrow the radials.
Your frequency appears to change with your adjustments. Narrower, the freq slipped up. Wider, the freq went down.
As I see it, the original strap has some adjustment, but a limited amount, inward only, and can easily be moved up or down. Given it can move narrower only if not moved upward, I would surmise that any spreading wider would be accomplished only by moving the strap upward. With the radial lengths a static number, and the strap non-conductive, the point at which the strap contacts the radials is of no consequence. The change is in spread/distance of the radials at all points except its ends where the the top bracket and loop keep the distance apart immobile.

 

[Marconi]

No, my strap is not adjustable. Moving it up or down is the only way to spread or narrow the radials.
Your frequency appears to change with your adjustments. Narrower, the freq slipped up. Wider, the freq went down.
As I see it, the original strap has some adjustment, but a limited amount, inward only, and can easily be moved up or down. Given it can move narrower only if not moved upward, I would surmise that any spreading wider would be accomplished only by moving the strap upward. With the radial lengths a static number, and the strap non-conductive, the point at which the strap contacts the radials is of no consequence. The change is in spread/distance of the radials at all points except its ends where the the top bracket and loop keep the distance apart immobile.

Homer, I just described my further findings with my best model for the A/P and when I submitted it, the Internet browser closed down on me. This happens all to often, but what can we do?

So, I'll try again and send the models along with the original working model, one set with the strap -1" lower and the other with the strap set +2" higher for a total of 3" in range. They react just as you describe above, and this time I moved the strap. I put notes on the models.

I don't think the original was designed to move the strap or you would loose the securing mechanism for connecting the two 48" radial elements. I also found the radials on the original model were a few inches longer, 93"-94", than the Top One I have at about at 89.25".

I also think Avanti set this strap point at the best spot, so there is no need to tune. Just install it where it belongs, no measurement. If we want to tune this one I think the top hat radials will do that just fine, but I'll have to check out how that responds for the match.

Your words above cleared up some issues for me and I thank you.

I did a model with the radials straight and that shows the model needs the bow to get the better match. I have included an overlay, but I forgot to include the model with straight radials.

View attachment AstroPlane strap issues.pdf

 

[bob85]

eddie,
the patent claims they made a vhf version for measurements and took readings about 100ft from the antenna,
the way i read it when they say parallel conductors caused downtilt they made the hoop smaller changing the spacing to restore 50ohms at the feedpoint,
they also had the mast extend 1/4wave below the hoop noting that shortening the mast caused takeoff angle to rise,

i don't imagine the measurements were taken with the antenna at ground level with a grounded mast but its not clear,

if the astroplane works like the sigma, closer spacing should lower impedance and raise resonant frequency.

 

[Marconi]

eddie,
the patent claims they made a vhf version for measurements and took readings about 100ft from the antenna,
the way i read it when they say parallel conductors caused downtilt they made the hoop smaller changing the spacing to restore 50ohms at the feedpoint,
they also had the mast extend 1/4wave below the hoop noting that shortening the mast caused takeoff angle to rise,

i don't imagine the measurements were taken with the antenna at ground level with a grounded mast but its not clear,

if the astroplane works like the sigma, closer spacing should lower impedance and raise resonant frequency.

I remember something about that, but I never thought about the vhf part much. Regarding the height, I think I did something the other day, maybe for you, that showed models of the A/P lower to the ground, and I saw the natural effect of the antennas being lower, and like you, I don't think this fact is in dispute. I saw nothing that stood out either, like the antenna going to heck in a hand basket, or the angle going up out of site with a higher dominant lobe. In fact, when comparing my Sigma4 vs. A/P vs. I-10K, the Sigma4 preformed very well down low, just as you have predicted. The A/P shows a little less gain at noticeably higher angles, and the I-10K was no-way-no.

I didn't produce the models, and I'm not sure I saved them in a fashion that I can recapture exactly. I just used some models I had, and I didn't consider to do anything else at the time. At the same time, I also set the model of the A/P at odd and even wavelengths in height to show how the currents responded on the mast...and I'm sure I posted those.

Here is my note of the results comparing the S4, A/P, and the I-10K.

View attachment Check for height of AstroPlane.pdf

 

[Marconi]

eddie,
for a better understanding of transmissionline mode currents read the open sleeve antenna article in the arrl,
CEBIK also gives some clues in his "some j-poles that i have known" article,

the astroplane needs the mast or coax to form the transmissionline, its in the patent and won't work without it,
the relative conductor diameters / spacing and flare control impedance,

avanti claim the flare also controls takeoff angle as does mast length.

Somewhere else I think you posted a link to the Cebik work noted above, but this post will do. I think you'll be interested in the results of a project I'm doing using as many suggestions as Cebik makes in this article on my I-10K model...which nobody seems to be interested in, by-the-way. And we hear all about how it's the top gun. I don't have any quarrel with my I-10K, it works fine, but I don't see the big deal either, as usual I guess.

As always with me whenever some one describes something with a difference and uses the word, I jump at the chance to ask............

HOW MUCH DIFFERENCE ARE YOU TALKING ABOUT? IS IT REALLY ENOUGH TO MATTER WITH GOVERNMENT WORK? IF NOT, WHY BOTHER?

So far I'm not seeing much improvement in my I-10K model, but it is better in almost all cases except for a little lowering of the apparent gain, and if I understand all these antenna guy's point on the issues for errors in modeling, I suppose a little reduction in the gain of my models...might be expected.

BTW, I didn't get upset with Roy Lewallen the other day when I asked him for some modeling advice on one of my models. He did me the same way Cebik did you, politely refuse. So I go on the best I can, with what the good Lord in Heaven has given me.

However this project turns out, I'll post the results anyway.

Thank's for your words,

 

[Henry HPSD]

Marconi,

Your always welcome to send a mail regarding modelling.
I certainly dont know all..but perhaps a second pair of eyes migth help.

Kind regards,

Henry

 

[Marconi]

Marconi,

Your always welcome to send a mail regarding modelling.
I certainly dont know all..but perhaps a second pair of eyes migth help.

Kind regards,

Henry

Thank you Henry. I know you're busy, so I don't like to bother you needlessly, but I have your email, I think, and I'll use it. I'll send you my model of the I-10K with the trombone tuner included when I get through Cebikerizing' it a little.

 

[HomerBB]

I cut 1.5" of length off the ends of the four AP cap hat wires. No change.
I put them back on. Perhaps when I get to building a metal model I can make the cap hat wires adjustable. Right now they require cutting.

I know you are modeling the I-10k by default specs. I wonder what it looks like at overall vertical length 5/8 with the top hat added to that length.

 

[Marconi]

I cut 1.5" of length off the ends of the four AP cap hat wires. No change.
I put them back on. Perhaps when I get to building a metal model I can make the cap hat wires adjustable. Right now they require cutting.

I know you are modeling the I-10k by default specs. I wonder what it looks like at overall vertical length 5/8 with the top hat added to that length.

Do you mean to remove the top hat and extend the tip back to tune? BTW, sorry that I encouraged you to cut your antenna. Like I said earlier, I'll have to recheck the top hat idea for changing frequency, but it works on my I-10K. I'll get back in a few minutes.

 

[HomerBB]

I mean the cap hat made from small tubing and rods, the rods inserted into the tubes and adjustable in and out.
No big deal on the cap hat. it's disposable . . .

 

[bob85]

the i-10k does not interest me eddie,

its a good 5/8wave with secret not to be revealed test procedures enveloped in a cloud of nonesense in contradiction to respected sources, thats the curse of antennas with 10k in the name,

i can't fault mr Cebik for not wanting to get into an argument with the j-pole camp, the j-polers never had anything factual to contribute to the discussion,

i would use mr Cebik's words below as my sig if i could,

"Despite the success of the antenna, disputation about the antenna persists. This disputation has largely put me off the J-pole as an object of study, since much--but certainly not all--of it has lent more smoke than fire to the understanding of J-poles.
As well, almost everyone has his or her own favorite version of the J-pole. There are as many versions of the J-pole antenna as there are versions of the letter J in the collection of type fonts supplied with modern computers. Some variations are subtle, others are bold. How much differences each variation makes in actual performance seems to depend upon who has built the antenna"

 

[Marconi]

OK Homer, here is the model with the Top Hat reduced 2" vs. the original model. The frequency went up from 26.950 to 27.255. I change the frequency a little to get nearer resonance also...just to show the effect of the change.

I noted on the page the effect on match, the resistive part of the match got a little worse, and that is not so good.

View attachment Changed Top Hat length.pdf

 

[Marconi]

the i-10k does not interest me eddie,

its a good 5/8wave with secret not to be revealed test procedures enveloped in a cloud of nonesense in contradiction to respected sources, thats the curse of antennas with 10k in the name,

i can't fault mr Cebik for not wanting to get into an argument with the j-pole camp, the j-polers never had anything factual to contribute to the discussion,

i would use mr Cebik's words below as my sig if i could,

"Despite the success of the antenna, disputation about the antenna persists. This disputation has largely put me off the J-pole as an object of study, since much--but certainly not all--of it has lent more smoke than fire to the understanding of J-poles.
As well, almost everyone has his or her own favorite version of the J-pole. There are as many versions of the J-pole antenna as there are versions of the letter J in the collection of type fonts supplied with modern computers. Some variations are subtle, others are bold. How much differences each variation makes in actual performance seems to depend upon who has built the antenna"

Well Bob, you know I couldn't let this go.

Like I've suggested to you before, these guys like Cebik have spent their whole lives talking about things related to stuff they're interested in, and Cebik's article list and body of work probably proves that.

Roy Lewallen proved to me he is in the same position as Cebik was, and those two among others...probably talked often about how and when they would handle certain inquiries. Their time is important to them, so they made up pat excuses for when they felt confronted and for sure if it was CB related. They love nothing anymore than to talk their interests, it feeds their egos. Only a man like Cebik would use a word like disputation, and still make the statement above in the preface of several long articles on the very subject as being disputatious. That is true circular logic.

Sorry, but you're sounding more like a politician right now, but that's alright, just ignore the thread when I post it. And, don't worry, you're in what seems to me to be the predominate crowd today, regarding the I-10K, they don't care about the I-10K either.

 

[Needle Bender]

Marconi, what would this forum be without your colorfulness! Never stop keeping things rolling!

Regarding the I10k, I agree with Bob85 in that the I10k is an incredibly well built, strong-as-an-ox bottom-fed 5/8 which performs a whole lot like a bottom-fed 5/8, exactly like a SigmaII 5/8 and every other bottom-fed 5/8 out there.

There is no voodoo, magic or ultra-efficient anything which makes even a needle width improvement over any other 22.5' 5/8, but if I lived on top of a very windy hilltop- I'd have to have one.

If you read around you will find people claiming 2-3 s units improvement when compared to a Penetrator. That's just BS soaking in snake oil.

Regarding raising the resonant frequency of the AP, don't you think you should also shorten the base proportionally to the top so you keep the mounting plate at the point of highest current?

 

[Marconi]

Marconi, what would this forum be without your colorfulness! Never stop keeping things rolling!

Regarding the I10k, I agree with Bob85 in that the I10k is an incredibly well built, strong-as-an-ox bottom-fed 5/8 which performs a whole lot like a bottom-fed 5/8, exactly like a SigmaII 5/8 and every other bottom-fed 5/8 out there.

There is no voodoo, magic or ultra-efficient anything which makes even a needle width improvement over any other 22.5' 5/8, but if I lived on top of a very windy hilltop- I'd have to have one.

If you read around you will find people claiming 2-3 s units improvement when compared to a Penetrator. That's just BS soaking in snake oil.

Regarding raising the resonant frequency of the AP, don't you think you should also shorten the base proportionally to the top so you keep the mounting plate at the point of highest current?

As I told Homer earlier, I haven't checked out how the match is effected by making the top hat shorter, I just know it is far more effective with the changes I've made vs. those changes to the bow in the radials. So, I surely haven't checked out the currents either. I'm also not convinced by my models that the bow actually controls the resistive part of the impedance like we often read about, which I consider very important for the radio and for the match. It seems to me the best performing antennas are the one's that do a really good job of controlling the resistance over a modestly wide range, and let the reactance take care as it will, in mitigating any reasonable mismatch, as it is prone to do.

This seems to be the process that allows our antennas to show us bandwidth...and I think that is good.

Mostly what I see with changes to the A/P are changes to the reactance, and that controls mostly the frequency. The bow or the top hat both seem to effectively change the reactance, and that does affect the match, but I have not found any thing that really controls the value of R to any notable measure.

I appreciate your idea however, I hadn't thought about it and I probably would not have done that useless the match went to heck in a hand basket... while changes were being made in either location.

I was also looking for the magical effect that is supposed to happen with the angle, and I sure haven't seen that elusive bugger either. The only thing I know, off hand, that directly affects the angle, and is something I can control a little bit, is the height of the antenna above Earth. I expect most antennas are that way.

The A/P looks to make a funny maximum current pattern anyway, and IMO it is due to the seeming fact that it has a top hat on both voltage ends of the 1/2 wave radiator, and that really affects the current distribution in a positive way...using what appears to be a little compression.

I think those guys at Avanti really knew what they were doing and understood the art of antennas. They probably didn't want to spill the beans even in the patent, so they could have been playing with their results a little...and that tended to keep the competition looking for witches with magic wands.

I don't see a perfect match with my A/P, but I do see a nearly bandwidth wide control of the resistance R=50<>, and a similar control over the complex match Z=50<>, all the while the reactance tends to be a bit inductive all the way.

I'm just trying to understand what I can about this antenna and I will likely get some wrong ideas in the process, but with guys like you and others...maybe I'll get some things right too.

Thanks, I'll be sure and watch the maximum currents around the mounting plate.