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Stock Maco gamma vs off-the-shelf beta match CHALLENGE!

Discussion in 'CB Antennas' started by Master Chief, May 13, 2007.

  1. Master Chief

    Master Chief Guest

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    I submit the following:

    It's MY opinion that the same 3-element Maco, one fed with a gamma match and one fed with a beta match, will perform better with the beta match.

    I'm also willing to put my money where my mouth is.

    I'll supply the stock Maco M103C antenna. You (who ever you are) supply the DX Engineering "hairpin match". I already own the DXE-BEB-2.

    I'll model the antenna using "Yagi for Windows" which is supplied in the 20 edition of the ARRL Handbook. This software allows modeling for both a gamma and a hairpin match.

    I'll build and tune the antenna using both matching networks, taking readings with my Bird 4030 relative field strength meter.

    Once we agree on what "better" means, the winner takes all.

    My investment will be $100.00+. Your investment will be $30.00 plus shipping.



    Who's willing?!
     
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  2. Master Chief

    Master Chief Guest

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    OK, a little thread cleaning was in order. There is a challenge on the table, who will accept?

    My argument is that the beta match is better. I don't set a limit on the amount of efficiency, only that it performs better.

    I won't argue a db or a tenth of one; only the feedpoint that performs better.

    And there seemed to be a bit of confusion so let me add that the arrangement of the elements on the boom will be IDENTICAL. Front to back, rejection and forward gain is not the issue here. ONLY THE FEEDPOINT! Please keep to the subject at hand.
     
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  3. Master Chief

    Master Chief Guest

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    P.S. No thread hyjacking on this one. If you want to call me names, start your own thread and be able to back up your statements.
     
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  4. Master Chief

    Master Chief Guest

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    I like 1/4 wave matching networks. They are narrow banded but work well for feeding a quad.

    However, I'm talking about the gamma vs the hairpin so I need to ask, what's your point?

    Tell me, what do YOU think works better, the gamma or the hairpin? Go ahead and say it, I know you want to , its OK, we all know the answer already, just say it.
     
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  5. Master Chief

    Master Chief Guest

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    They are only similar in the fact that they provide a match at the feedpoint. How they do it is very different. .04db less loss tells me it is "better" than a gamma. Good enough for me. Your point is taken about the little difference between the two.

    I don't think anyone, other than Jay and Steve, have done any real comparisons and tests between various feedpoints for 5/8 wave antennas. But this is a totally different subject from the beam challenge above.

    Most 5/8 antennas used some sort of a coil or shunt feed. Some were etched on very small circuit boards. Other than the Sigma IV (not a 5/8, but a vertical nonetheless), Wolf's .64 wave, and the Son-of-a-Gunn, I haven't seen a gamma on a 5/8 wave vertical. The real world tests of the I-10K is excellent proof that it is a great performing antenna.

    But the "hairpin" on the Penetrator or the I-10K (trombone) is NOT a BETA MATCH! Don't confuse the two because some people call these "hairpins". As far as the Penetrator goes, it only LOOKS like a hairpin, hence the name.

    It was used, and is still used by Hy-Gain. I'm sure their earlier patent prevented other manufacturers from using it. Again, this "hairpin" is NOT the same hairpin you find on the verticals above.

    I disagree. There is case after case where people have seen a big improvement when using an I-10K over any other antenna (again, not the same "hairpin" as a beam). Are they all wrong? The performance of beams have been good enough for people to look into and study different type of matching networks. There must be a reason nobody uses gamma matches anymore.

    Gain is a function of antenna design. We agree. My argument is that you will get MORE energy into your antenna design with a beta match than with a gamma match. In other words, same antenna with same layout, but with different feed systems will work differently. I say the beta will win and am willing to prove it.

    No tap dancing here. I already defined what I thought was better, I only stated that we need to AGREE what the definition of "better" is. .04db is better as far as I'm concerned.

    I like direct feed antennas. What I mean by this is that the center conductor of the coax makes a physical and electrical connection to the main radiating element. This happens with T-match, Beta-match, 1/4 wave transformers, and a few others.

    This does NOT happen with a gamma match. It is a capacitive coupling like the thru-glass antennas that everyone runs out and buys because they are "just as good" as a roof mount. Do they work? Yep! Can you do "better"? Yep Yep!

    That's all I'm trying to say.
     
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  6. Marconi

    Marconi Supporting Member

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    MC, I ran some examples on a three element yagi using YW and when changing from HP to Gamma all I see is a bit broader bandwidth with a little better SWR at center frequency using the gamma. There is no difference noted with the gain or F\B between the two using this software.

    Is this what you might expect if you did it?

    You must have something other than just a thought/idea that leads you to claim the HP is superior over the gamma. Comparing the gamma to a little short thru glass mobile antenna is pretty also. You have to do better than that.

    I also notice that it seems the Gamma design ends up inductively load while the HP is typically capactively loaded when good results are obtained at resonance. This is probably what 'Doc was talking about saying they worked differently. I did not compare the element spacing and length measurements but I notice the HP boom was longer. Is there some way to print out the product of the Elements spreadsheet figures?

    I read what Blanket provided us in a link to Cebik's work in comparing several matching devices and he doesn't seem to support your claim either to any substantial degree.

    I am not good at understanding this software maybe, so I could have done something in error. I will try to post my results soon. Would you take a look and advise. I wish I had saved the two files, but I didn't think to do that before I exited the program. I might go back and see if I can didle those results again.
     
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  7. Marconi

    Marconi Supporting Member

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    See if this works MC.

    [​IMG]

    [​IMG]
     
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  8. Marconi

    Marconi Supporting Member

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    Well, you noticed that the Peak Elevation Angles were different. The HP was 5 degrees and the Gamma was 9 degrees. True, there was a difference in height also. I mess up there and that will have to be checked out to be fair. I suspect that I had made some adjustments to the spacing also and that made the boom on the HP model longer.

    I am also going to try and get a better match with the HP too.
     
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  9. W5LZ

    W5LZ Crotchety Old Bastard

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    I think 'Blanket' has it categorized correctly. Element length and spacing (if any) determine gain, the impedance matching device has (and should have) nothing to do with that part. The impedance matching device only has one job, and you can guess what that is.
    There are differences in the amount of loss in those matching devices, naturally. But, if the device is made correctly, mounted correctly, and tuned correctly, that 'loss' just isn't going to be much at all. I figure you're talking about fractions of a dB. If you're worried about that little amount, especially at HF, you need to take a look at your priorities.
    Nothing wrong with getting things danged near 'perfect'. But that 'danged near' covers a whole lot of ground before you even noticed that it moved.
    - 'Doc
     
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  10. Master Chief

    Master Chief Guest

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    No no no. The physical design of the antenna and the layout will give you your gain numbers as you see when you modeled it.

    What I am saying is that the beta match will get more signal (energy) into your antenna than a gamma.

    My thru-glass antenna analogy was good and made the point. Here is another. What still works but has more loss......100' of RG-58 or 100' of RG-8? If I can get more signal into the antenna, won't you get more signal out......WITH THE SAME GAIN RATING? Need one more? 1 watt vs 100 watt. It makes very little difference on the "db meter", but does it get out better? ;)
     
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  11. Master Chief

    Master Chief Guest

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    I agree, but this is not what I'm saying. I'm not talking about the gain of the antenna, I'm talking about the loss of the matching network.

    You are stuck on the number game. The 2 S-Units you are hearing about is what people are witnessing on their S-Meters. You have an I-10K, did you see a difference?

    I'm in the antenna world and this is not what we all agree. As a matter of fact, I don't know anyone who says just this.
     
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  12. Master Chief

    Master Chief Guest

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    What CB myth? I've never heard it. And for the last time, I'm talking about efficiency, not gain. You keep bringing up the "G" word. Show me where I said that. Are we clear on this part yet?
     
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  13. Marconi

    Marconi Supporting Member

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    OK, so your idea to use YW was not addressing the subject. How do we measure efficiency of a yagi feeder. Can you physically measure the amperage in the driven element of a yagi with a HP and one with a gamma?

    Would that tell us something?
     
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  14. Marconi

    Marconi Supporting Member

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    Well, I did the 3 element yagi over. I did the Gamma first since I knew it was going to require a longer driver element. Then I ran everything the same and just made it match with the hairpin. The gamma driven element ended up at 215.2" and the HP was 212" with similar SWR values. I did not attempt to change the default measurements for the HP device even if it is possible.

    As I said earlier, the HP matched antenna did not tune up as well as the Gamma fed antenna, because the HairPin matcher is looking for a load that is capacitive thus the element needs to be shorter than resonance requires.

    I then re-tuned the HP setup to improve the modest mismatch by adjusting the space and element lengths a bit. This made no improvement to the gain, but did improve the F/B a bit.

    During the process I noticed that it seemed to make a difference as to the order in which you made adjustments to the length of segments, and therefore I would question these results to some degree. Sometimes you get a little difference in results when using exactally the same data input.

    I was also surprised to note that the software does not seem to change the modifier to the element for the mounting hardware when switching from the gamma to the HP. I would think that it should modify some as the HP mount is typically a bit larger. The doc's suggest that the program does modify the elements for the mounting hardware, but I did not see this happen.
     
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  15. Master Chief

    Master Chief Guest

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    The purpose of using YW was to establish an optimized design to test both feedpoints. You couldn't figure that out?
     
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