M-104C to M-106C

[freecell]

the opposite to what "regular theory"?

bandwidth alone is no indicator of efficiency. i can think of three methods by which to quantify bandwidth.

#1. bandwidth over a flattened gain figure.
#2. bandwidth for a given front to back ratio.
#3. bandwidth between given values of swr.

the last may be the most insightful of the three as it indicates coupling efficiency between the load and the line.

you are absolutely correct bob, not all gamma matches are equal and the problems arise when power handling is increased without the proper attention to what i will refer to for the time being as "other details".

i'll ask again, where are these 10KW gamma matches coming from?
what is the adjusted value of capacitance in series with the gamma arm?
what is the distance from the boom to the gamma shorting strap?
what is the distance from the active element to the gamma arm?

 

[Master Chief]

and where are these 10KW gamma matches coming from?

We are talking about Maco antennas and replacement gammas so one would think Maco would be a good place to find the parts!

Maco 2600 (5KW)

Maco 4600 (10KW)

Maco 6600 (30KW)

what is the adjusted value of capacitance in series with the gamma arm?

I don't know.....

what is the distance from the boom to the gamma shorting strap?

I don't know.....

what is the distance from the active element to the gamma arm?

I don't know.....

Why is freecell asking more questions instead of doing a real world test?

I don't know nor do I care! I'm going to adjust it to what works and call it a day!

My guess is that he wants to discredit the earlier tests by stating that the loss of efficiency (is he agreeing that there is a loss of efficiency?! ) is caused by improper gamma set up.

Having done my share of gamma adjustments on antennas from 40 meters up, what the BOOK says should be a good setting and what real world tests PROVE are correct are two different monsters. Why? I don't know! But, PROOF trumps THEORY!

 

[freecell]

"Having done my share of gamma adjustments on antennas........"

then you'll have no problem answering this question. after selecting the test frequency what two things must be done first before any gamma match adjustments are made?

"I don't know nor do I care! I'm going to adjust it to what works and call it a day!"

you're here now because it doesn't work, remember?

 

[Master Chief]

you're here now because it doesn't work, remember?

What doesn't work? Where did I say something doesn't work?

Why do you keep asking me to answer your irrelevant questions? If you remember correctly, The gammas WERE set up correctly. The loss of efficiency was not due to the proper set-up of the gamma. Why are you still trying to steer the conversation?

Go do a real world test and let us know what you learned. Then try to explain why you got the results you have. I already know the outcome of the tests because I've actually done them. I want to learn more about the, "WHY". Can you help or are you still stuck on book theory?

 

[bob85]

Having done my share of gamma adjustments on antennas from 40 meters up, what the BOOK says should be a good setting and what real world tests PROVE are correct are two different monsters. Why? I don't know! But, PROOF trumps THEORY!

why does moving the gamma tapping point and retuning by altering gamma and radiator length for a low vswr while monitoring distant reliable stations ( houres of work ) allow an increase in signal strength on tx and rx by as much as almost 1.5 s units ( measured on yaesu ft990's ) over the factory tapping point and tuning instructions, the gains are permanent and more than the difference between our 5/8 and the 7/8 locally by almost 1s unit

You sure like to talk about all your hard work. The antenna manufactures need to build the antenna so any idiot can put it up and run it straight out of the box. Even Jay's antenna has measurements that work right out of the box. But, if you fine tune it, you can optimise it for where you are operating. Good job on your part! Most people won't take the time!

now we have at least some common ground here :!: ,

the antenna manufacturer got it wrong, probably did it by the book,
its nothing to do with selling a product so that any idiot can assemble it,
you will never see that type of antennas true potential unless you take the time to get it right with the gamma you are using just like a gamma matched beam,
i am not just retuning for the small difference in our respective band centres as the same applys if i tune on 27.200 or 27.400 even up on 10mtrs:roll:

no point in testing shit unless its done to the best of its ability steam and all, it gives you a distorted view of the truth :twisted:

"PROOF trumps THEORY!"

maybe i am wrong i just could not resist the opportunity, lmao

 

[W5LZ]

This whole 'fact' vs 'theory' thing is sort of short sighted in my opinion. One always leads to the other. 'Theory' is the explanation or interpretation of fact. It explains what happened when you did whatever it was you did. The first one who does something seldom has any 'theory' to help him, he has to do all the work associated with finding what works best in a particular circumstance. If he's smart, he keeps track of all that he did so that next time he can by-pass all the nonproductive work and get to the finished do-hicky with a lot less sweat. Then if he's really smart, he tells other people about how to go about it and why. That applies to everything, not just radio/antenna stuff.
Learning anything 'new' is a PITA! Learning all that 'theory'. But it sure beats experimenting to find out how much air to put in a tire when you buy a new tire, right? Not that there's really anything wrong with finding out just how much air to put into a tire for particular circumstances, but if you don't have that 'starting point' that theory gives you, you'll go through a few tires before you $top ruining them.
There are no absolute, hard-n-fast, never wrong ways of doing things (theory) for doing things that are affected by their environment. Antennas, tires, starched shirts, how much ice to put in the cooler, all are affected by their environment. Sometimes things have to change a little to get them right. If you don't have that 'starting point' (theory) to start with, all that ice is gonna melt before the @#$ antenna is right, not to mention ruining a tire going after more ice. Fixating on one or the other is a sure way to cause more of that PITA thingy. Then again, some people like that sort of thingy. Personally, I rather spend that time reading. That's cuz I'm lazy, and certain parts of my anatomy are very sensitive...
- 'Doc

 

[freecell]

"I want to learn more about the, "WHY". Can you help or are you still stuck on book theory?" the why in your particular case requires you to determine the cause of the underlying circumstances. it would appear that your capacity to do so is hampered by either your inability or unwillingness to do that for yourself for whatever reason so now you have enlisted the assistance of others. speaking for myself i don't own any gamma matches manufactured by Maco (except for the oem v-quads) so for me to speak to the details of your situation i require some information from which i can determine the suitability of the particular device for the job at hand. your refusal to provide the information requested does tend to indicate that you really don't care as much about the "why" as you claim to. i'm not going to go out and spend money on Maco gamma matches in an attempt to answer your questions, especially when the information gleaned from some simple answers to a few questions that i have asked here would tell me all i need to know.

furthermore it is pretty much common knowledge that in forums such as these that users with questions about a particular problem need to provide as much information as possible to allow those of us who contribute freely to these forums (on our own time and dime) to assist in providing answers and solutions to the questions asked. up until now you have provided insufficient information with which to formulate any positive and/or corrective responses. a simple review of the questions that i have asked here in this thread will show that they have been anything but irrelevant to the subject of the ongoing discussion.

if you can't answer the questions then no one can help you, regardless as to whether the problem is viewed from the babylonian (conceptual) or euclidean (greek mathematical) perspective. you're on your own.

i don't see either of the two anomalies you mentioned using gamma matches rated for 2KW, 5KW and 10KW with 100W of applied power. operating the antenna with the gamma matches in question at their rated power handling limits (as you suggested) doesn't solve the problem either as is evidenced by the receiver attenuation you experienced. if the efficiency suffers at 100W then run all the power into it that you like, nothing will change. the loss is still there and i know where it's coming from.

"........I don't know! But, PROOF trumps THEORY!"

yeah, well here's the PROOF i'm looking at....the receiver sensitivity and the radiated power measurements don't deviate and remain unaffected here when all three gamma matches are interchanged on the driven element of a custom built 6 element wide spaced long yagi. either YOU or Maco have a problem, i don't. the 2KW gamma match in my case is commercially built and the 5KW and 10KW gamma matches are home brew and they all work just fine.

your failure to answer the questions (particularly the last one) tells me all i need to know. i know what's causing the lack of efficiency in the larger matching sections and asking questions is my business. since you remain uncooperative by refusing to answer my questions as they relate to your particular situation then you can figure it out for yourself. as long as your "uncooperative" attitude remains unchanged my involvement in this thread where you're concerned is at an end. for you and i there is nothing else to talk about and that was and is your decision, not mine.

and what BOOK is everyone talking about?

 

[cbshack]

Master Chief,

Is the antenna you are having problems with resonant at the frequency you are trying to use it on? I can't tell you how many amateur operators that come in to my store or I have heard on the air tell me they are using A 99s for 80 and 160 meters with a tuner and think they work great. They are missing contacts they could not even dream of. Sure it will work but how efficeint is it. A99s are only meant for 12-10 meters with a tuner according to Solarcon. A long wire set up in a tree for 160 meters should broadcast further and hear further than the A99. Their are several from Comet, Gap, Cushcraft, and others that would do better as well.

Changing out the gammas for a larger size larger output will change the inductance also. Have you tested the antenna in question for either of these?

Ben in Florida

 

[freecell]

Ben has the right idea. i believe that bob85 alluded to it briefly also in a previous post for anyone who was sharp enough to notice.

it's been brought to my attention recently that some operators have been having problems with signal transfer efficiency when purchasing and using Maco High Power 5KW, 10KW and 30 KW gamma matches with popular yagi arrays.

let's look at some facts:

Gamma Match: a series-resonant matching network....

....and as such the *first thing that needs to be addressed once the gamma match is installed is to determine just exactly what frequency the driven element is resonant at. this is all important as it applies to the efficiency with which the gamma match is able transfer energy back and forth between the transmitter and antenna. if the driven element is NOT RESONANT at the intended test frequency then the *second thing that needs to happen is that it needs to be adjusted so that resonance occurs at the intended test requency. failure to do so will have you spending hours messing with the gamma match without producing acceptable results. your swr meter provides NO indication of the resonant operating frequency of the driven element. either a grid dip meter, noise bridge or one of the popular antenna analyzers will be required to determine at what frequency X = 0.

if this is the first time you have heard anything like this and YOU HAVE spent HOURS messing with gamma matches and found that regardless of power handling capability that you have been unable to achieve satisfactory results or have experienced loss of receive sensitivity and reduced levels of radiation even though the swr meter indicates a good match then now you know why. back and forth a few times between values C and L at the gamma match while double checking the driven element resonant frequency, re-adjusting as necessary and you're dialed in.

the alternative would be to somehow believe that Maco doesn't understand that as gamma matching networks are "grown" to accomodate higher power levels that the maximum amount of available capacitance in series with the gamma arm must be increased as well to offset the added inductance created when the diameter of the gamma arm is increased to handle higher levels of power. i believe that they are aware of this.

the only REAL remaining variable is the operator/installer who is either aware of these parameters or not.

http://www.firecommunications.com/gamma.txt

 

[W5LZ]

...Odd. I don't think I've ever seen an inductance/inductor in a gamma match. A capacitor, sure. An inductance, nope. To think I've been missing it all these years...
- 'Doc

Psst - freecell... I think you missed the point in that other post. But what do I know, right?

 

[freecell]

the gamma arm is the inductor and the value of inductance is determined by the length of the gamma bar from its connection to C and the connection to and through the shorting strap at the other end while also taking the diameter to length ratio into consideration when determining total inductance of the leg. just exactly what variable did you think you were changing when making the shorting strap adjustment? any increase in the length or diameter increases the amount of inductance present. your misconception is that an inductor can only be an inductor if it appears as a wire in a coiled shape or form. that is incorrect. the simplest example to demonstrate this would be a quarter wave vertical known to be resonant at let's say 27.185. if at this point we lengthen the vertical element by pulling out another six inches of the top section then what have we just accomplished? we have added inductance (inductive reactance) to the vertical which now drives the resonant operating frequency down below 27.185. does that extra six inches of length look like a coil of wire? certainly it doesn't but it possesses all of the properties of an inductor nevertheless. the same principle here is at work in that series section of the gamma match (arm) that provides the inductance required to perform the necessary function. the gamma arm is an inductor.

furthermore every time the inductance of the gamma arm increases without a corresponding increase in the series C value then the resonant frequency of the driven element is altered. therefore if you begin with a 2KW gamma and all is well, you can see now that every time the gamma match becomes larger and larger to handle the increased power levels why the resonant frequency of the driven element is shifting further away from where ever the hell it was when you started.

with the OEM gamma match and the manufacturers recommended driven element lengths there is usually no problem because they have more than likely modelled it to some extent and the lengths are fairly reliable as a resonance reference point, usually at some given frequency of interest. this also explains why the anomaly only seems to appear as the larger gamma matches are used.

the gamma match is properly adjusted when the point at which C completely cancels L at the desired resonant frequency of operation is also the point at which zero reflected power is indicated by the swr bridge. this condition is called electrical balance.

for the sake of this discussion the diminished results mentioned at the beginning of this particular section of the thread are the result of a driven element and matching network that has not achieved this electrical balance at resonance. this becomes even more complex if we add the effects seen here in a broadband vs. a narrowband application where in the former the values of C, L and resonance change more slowly than they do in the latter of the two applications. this is one reason why i prefer wide spaced arrays.

 

[W5LZ]

Oh, I know an inductor doesn't have to be a coil, no problem there. The few gamma matches I've seen using a 'C', capacitor, have been mostly of a fixed lenth. Varying the capacitor did the matching. There was some very small adjustment to inductance becasue of the length of the 'tube' and shorting strap, but not much, and that small change was so that the range of the variable cap could be affective.
Then there were the ones that used a sliding section of insulated wire inside the long gamma 'tube'. That sliding do-hickey is actually a capacitor, so the capacitance was being varied. Oh, there was some inductance variation, but it's usually negligible.
I was always under the impression that the 'extra' inductance was provided by the length of the driven element it's self (they usually are a little longer than what you'd expect would be the resonant length). So, in most cases, the capacitance is usually what's being adjusted by the common ol'gamma match, not the inductance. True in all cases? Mmmmm, mostly. Whole lot easier to change capacitance than inductance. Especially if there ain't no coils... right?
- 'Doc

 

[Master Chief]

my involvement in this thread where you're concerned is at an end. for you and i there is nothing else to talk about

Thank you! Feel free to start up a new thread about this topic; this one has drifted far enough!

I can appreciate where you are coming from on most of this and in general do not disagree with what you have to say. Your tact and deliver however, leaves much to be desired.

I don't want you to fix anything and the antenna in question was tested a couple of years ago. The measurements you requested are not available.

Was the driven element length changed? A little. The capacitor was tuned and the shorting bar was adjusted until we had the best match possible. The spacing between the element and the gamma was not changed.

Did it work, YEP! Is the larger gamma less efficient, I believe so. My tests back up this statement. What were the dimensions of your 10kw gamma?

As far as the "book" goes, it could be ANY book on antenna theory.

Now don't tell me I've been unwilling, unable, or anything else on this subject. I've been right there with you the whole time. I know how you like to manipulate conversations to go in the direction you want to take them and enjoy throwing a few quips in just to get a reaction. I guess you will never change. Too bad really, you certainly do have a good grasp on radio theory.