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Gizmotchy 2 Meter 4 Element Beam Review

Moleculo

Ham Radio Nerd
Apr 14, 2002
9,234
1,757
283
A couple of weeks ago I inquired with Tom Charles, the owner of Gizmotchy and Maco Antennas, about his 2 meter, 4 element Gizmotchy beam. The Gizmotchy is interesting to me because it has the ability to be used either with vertical or horizontal polarization, or both (not at the same time) with the right setup. I told him I was interested in buying one for my own station and would probably end up writing a review on the antenna if I did so. I was was asking what test documentation he might already have for the antenna. He very graciously offered to send me an antenna for free to try out.

I received the antenna very quickly, but had to wait for the weather to clear up to start the assembly. I also had to gather a few other pieces of the antenna system necessary to use the Gizmotchy effectively. Weather in Southern California was nice this weekend, so I was able to make a little progress on getting the antenna up in the air.

Here is a pic of the antenna as it is delivered, once you take it out of the box:

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I don't know what gauge aluminum tubing is used, but I can tell you that it is heavy-duty for an antenna of this size.

This is a picture of the hub used to assemble the elements.

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The mounts for the actual element pieces are solid aluminum and are attached to the center ring by pressing them into a drilled hole. They are then held into place by a roll pin that has been pressed in. The inside of the hub looks like it is then machined for a perfect, smooth fit. The hub shown in the above picture is for the driven element; it is the only one with additional tapped machine screw holes.

The hubs are slid over the boom and held into place by thumb screws. Here is a picture of a the mounted driven element hub:

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This picture shows the boom with all of the hubs assembled:

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This is a good place for my first improvement suggestion for this antenna. The manual gives you the spacing measurements for the elements. You must measure and place them yourself, which is no big deal. However, since there is no need to adjust the spacing, it would be very helpful if the boom was already marked for you. But I'll take it one step better than that: Later on in the installation, you are going to want to make sure that all of the elements are aligned as straight as possible. However, when tightening the thumb screws on the hubs, it causes the whole element to turn slightly. If the boom was pre-drilled and tapped for the thumb screws on the hubs, the user would not have to measure, and they also wouldn't have to align the orientation of the elements manually. A pre-drilled and tapped boom would also make the the element assembly even stronger. I would think that this improvement would be simple to implement and add very little cost to the manufacturing process, but it would be a huge win for the consumer.

As I mentioned before, the Gizmotchy antenna is interesting because it can be used with vertical or horizontal polarization. This dual purpose polarization is achieved by two gamma matches.

These are the main gamma match stubs for each section. The one with the plug is for the vertical elements to keep the water out. The hose clamps make them adjustable for tuning.

1082-1266278810-a723b4905ac9fe9500f14c3c3eda2cf5.jpg


Here are the gamma match tuning sections fully assembled:

1083-1266278810-33430373112d40baf33ec7606b10c3d3.jpg


Notice that there are two SO-239 connectors. If you want to use the antenna for both vertical or horizontal polarization, you must use two feed lines to the antenna. In this picture, you see the boom and driven elements mostly assembled. However, this is where I ran into my first problem: Notice the L bracket in the picture that attaches the boom to the mast. Well, I couldn't mount the U-bolts to this L-bracket as it was delivered from the factory because the holes in the bracket didn't align with the U-Bolts. I couldn't get any of the U-Bolts for the boom or mast through the mounting holes in this bracket because the holes in the bracket were narrower than the U-Bolts. I used a rat tail file on the holes to widen them and make it possible to mount U-Bolts in the boom and mast bracket holes.

Here is a close-up picture of the assembled, not-tuned gamma match:
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It should be noted that the gamma match assemblies do not come pre-measured for best match. I wanted to see where they were out of the box, so I just attached everything together for some measurements down the road. This is also where I encountered my second problem with the antenna assembly: The package was missing one of the small bolts necessary to assemble one of the gamma matches. When you open each of the bags of parts, you'll see a sticker indicating that the bag has been weighed for accuracy. Well, the hardware bag that I received was short one bolt but had one extra nut, which is probably why it weighed out OK. It wasn't a big deal because I had some extra hardware that kept the antenna assembly going.

While I was looking through my bin of nuts and bolts for compatible parts, I decided to give one of the supplied Gizmotchy antenna machine screws a magnet test to verify that it was stainless steel. To my surprise, I found that it was not stainless steel (stainless steel is not magnetic). The supplied machine screws and nuts have a finish that makes them appear to be stainless; they're better than nickel plated, but they're not stainless. I hope they hold up to the weather.

Here is the antenna fully assembled, ready for tuning and testing:

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In this picture, I've already aligned all of the elements. There is probably an easier way, but I accomplished this by having a helping hand hold a straight edge up along all of the vertical elements. I then rotated each of them until they were square against the straight edge. As you can see from this pic, the boom is really very sturdy for an antenna of this size. In fact, the large boom diameter is really unnecessary and just adds extra weight. However, I'm sure that Gizmotchy uses the same boom and element hubs for more than one antenna design, so I'm sure it helps keep the costs down, which is perfectly acceptable to me.

I have one last observation about the assembly before I move on to tuning and testing. Each of the element's radials are attached to the hub by a small hose clamp. After tightening the clamps, the fit is good although there can be a little play on each rod, which isn't a big deal. The package comes with small sheet metal screws, one for each of the radials. The instructions do not indicate what these are to be used for, but if you look carefully at the the assembly diagrams, you can see that they are to be used as an augmentation to the hose clamps to secure the radial to the element hub. however, none of the aluminum parts are drilled and tapped for these screws. There is no possible way that anyone can drive one of these small sheet metal screws into the aluminum rod without it being pre-drilled and tapped for assembly. I tried to attach one screw without success, then tried to hand drill it, and then quickly realized that the only way to accomplish this would be to use a drill press. For this 2 meter antenna, the additional locking screws are completely unnecessary, so I scrapped the idea. I hope their bigger antennas have the element radials drilled and tapped from the factory.


Next, I'll talk about tuning and then finish mounting the antenna for use. I also have some factory test materials to share. Stay tuned...
 

Good stuff. Just a thought about the claims of the hardware not being stainless, some grades of stainless will indeed stick to a magnet but not as strongly as regular steel hardware.You can tell the difference when you compare the pull of a magnet to it. I thought it would be easy one time to separate the stainless from the plated hardware that got mixed together but not so. I don't know what grade it is that will stick to a magnet but I do know that at least one grade will.

Found this on a site called "The truth about stainless steel"

"Stainless Steel Grade: There are many flavors of stainless steel. 304 stainless is the most common (about 50% of the worlds production). It is used in everything from cars and cookware to buildings. What you need to know is that there is magnetic (400) and non-magnetic (300) stainless steel. 400 series stainless steel is not as durable or corrosion (rust) resistant at 300 series. If you want durability in your stainless steel gas grill put a magnet on it. If the magnet sticks, don't buy it. Some manufacturers use a mixture of different metals so put that magnet all over the grill to test it all."
 
That's a good commentary on the Stainless Steel hardware. In that case, the hardware supplied may very well be stainless steel, because it sure looks like it.
 
Correct, all stainless is not created equal. Magnetic stainless is very low grade, mostly used for indoors, non weather related use by people who know such things, and Non magnetic is suitable for exposure. Be aware that there are many grades in both catagories, too. I have seen way too much stainless steel rusting away in the marine enviroment. It is Stain "less". Not impervious to corrosion.

PR
 
Some stainless hardware like the stuff Home Depot sells galls when you try to take it apart. Just as useless as a rusted piece only more dangerous because you have to fight with it up in the air.

Try building an M-Squared 2 meter antenna. Lots of measurement and hand assembley. VERY time consuming. Easy to screw up.
 
I like the fiberglass telescoping mast that antenna is mounted on, VERY COOL

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moleculo....have you ever USED a gizmotchy, wilson/maco V-quad or delta loop antenna before? i have been around a long time, have built more then my share of antennas, and, possibly QUITE FORTUNATELY, was never formally 'schooled' on antennas. everything i know is from reading & DOING.
i've built 3 gizmotchy antennas. the 1st, a 4 element for CB around 1975. i was just a kid back then, but vs. my homemade 2 element quad and a year later a homemade 3 element yagi with quad relector, i was not overly impressed with the gizmotchy performance. it had forward gain, front-to-back and -side separation that was acceptable. horizontal-to-vertical separation was lacking. my snail mail correspondence of 1977 was slow and painful. the response i got from gizmotchy eludes me 32 years later, but i remember mumbo-jumbo that made no sense to my HS electronics teacher(a ham). he wasn't sure how a 4 element beam based on a 1/4 wave vertical radiator, with 2 radials (the horizontal elements) was supposed to outperform a 4 element beam (built traditionally, based on 1/2 wavelength). his thought was the horizontal portion of the antenna was 1/2 wave, and drooping, so he wasn't sure what to think of that. i honestly don't recall what i was told, specifically, but remember my teacher telling me to read the arrl handbook & some other stuff about delta loops.
with that, me & a friend built our own delta loop. still not sure what polarization it really is, but i remember we got the instructions for a V-quad from wilson, and proceeded to build several variations of both. they were not very good local talkers, nor were they all-the-time superb skip talkers. my (by that time) 3 element yagi-with-quad reflector outperformed them all. over the years, i'd end up building more then a few V-quads, singles, stacks, horizontally polarized, vertically, and came to the conclusion that they aren't worth the effort.
around 1980, another local acquired a 6 element gizmotchy. he wanted to be king-of-the-hill and if i remember correctly, it was on par with a locals moonraker 6, size-wise. nobody was impressed with the f/b and f/s of this one either, but it did have more (apparent) forward gain then the moonraker 6, and definitely more then my 3 element beam. horizontal-to-vertical separation was still not what i'd expect. and i STILL doubt forward gain was that of a 6 element yagi.
finally, mid 80's, the giz 6 owner moved to NC. he purchased 5 additional sets of director elements. we spent a week down there building this thing and putting it up on a rohn tilt up tower.....with the pulling aid of a pickup truck. we built it in 2 days, and took the rest of the week to get it tuned. with nothing to compare it to, i think on my ride home, my mobile talked to him for nearly 100 miles. i talked to him during spring & summer e skip seasons for probably 10 years. that antenna survived many wind, rain & snowstorms. his marriage faded off into the sunset & by 1999 all that was standing was the tower and a mass of mangled aluminum. by 2003 or so, the tower was gone.....
so....get it up, get it tuned & tell us what YOU think NOT what mr charles or any justifying-what-he-paid-for-it high priced antenna owner wants to THINK. i haven't touched gizmotchy aluminum in about 25 years. maybe a big reason being i don't understand how it works & find that it is not equal to a yagi of comparable boom length & element quantity. i also tend not to believe what is told to me if it can't be explained in a way i understand.
 
get it tuned & tell us what YOU think NOT what mr charles or any justifying-what-he-paid-for-it high priced antenna owner wants to THINK. i haven't touched gizmotchy aluminum in about 25 years. maybe a big reason being i don't understand how it works & find that it is not equal to a yagi of comparable boom length & element quantity. i also tend not to believe what is told to me if it can't be explained in a way i understand.

Dave, I agree with you. So far Mole has done exactly what you ask, he is showing HIS experience with the antenna. I know that Mole will not "sugar coat" his review just for a free item. If he even thought of doing that you would have never read about his assembly snags.

So far the only part of the review has been assembly, I to await his further review.
 
I had some time to do some tuning with the MFJ-259B analyzer tonight before it got dark. I mentioned during the assembly phase that I just took the gamma matches out of the box and attached them to see where it the match would be without adjusting them. I did this because I wanted to see how badly you could screw things up if you weren't reading or didn't understand that part of the manual. The out-of-the-box settings will still get you a match under 2:1 SWR on almost the entire 2 meter band, with only the extreme top of the band hitting the 2:1 SWR mark. However, the 1:1 SWR point was down around 135Mhz or so on both the horizontal and vertical segments.

I then set the vertical gamma match to the measurements indicated in the manual and tested again. This time, the SWR was well under 2:1 for the entire 2 meter band. The prescribed dimensions make the antenna usable with no further adjustment really necessary. I found the 2:1 bandwidth of the antenna to be 18Mhz, which is pretty broad-banded. Of course, I can't leave well enough alone (especially with an antenna analyzer in my hands) so I decided to try to fine tune the gamma match.

The manual's measurements still had my 1:1 SWR match point fairly low in the band, and I wanted it higher. Of course, this is just a matter of adjusting the gamma match's segments to find what works for you. For my desired frequency range, I found that pushing the second segment all the way down but leaving the top segment at the manual's dimension put me right where I was happy.

It got dark before I had a chance to adjust the horizontal gamma match, but I'm hoping I can have the horizontal side adjusted lower in the band to accommodate the typical 2m SSB frequencies.

More to follow...
 
I had some time to do some tuning with the MFJ-259B analyzer tonight before it got dark. I mentioned during the assembly phase that I just took the gamma matches out of the box and attached them to see where it the match would be without adjusting them. I did this because I wanted to see how badly you could screw things up if you weren't reading or didn't understand that part of the manual. The out-of-the-box settings will still get you a match under 2:1 SWR on almost the entire 2 meter band, with only the extreme top of the band hitting the 2:1 SWR mark. However, the 1:1 SWR point was down around 135Mhz or so on both the horizontal and vertical segments.

I then set the vertical gamma match to the measurements indicated in the manual and tested again. This time, the SWR was well under 2:1 for the entire 2 meter band. The prescribed dimensions make the antenna usable with no further adjustment really necessary. I found the 2:1 bandwidth of the antenna to be 18Mhz, which is pretty broad-banded. Of course, I can't leave well enough alone (especially with an antenna analyzer in my hands) so I decided to try to fine tune the gamma match.

The manual's measurements still had my 1:1 SWR match point fairly low in the band, and I wanted it higher. Of course, this is just a matter of adjusting the gamma match's segments to find what works for you. For my desired frequency range, I found that pushing the second segment all the way down but leaving the top segment at the manual's dimension put me right where I was happy.

It got dark before I had a chance to adjust the horizontal gamma match, but I'm hoping I can have the horizontal side adjusted lower in the band to accommodate the typical 2m SSB frequencies.

More to follow...

____________________________________________________________________________

I really enjoy reading your reviews, very informative and pictures are always the best.

Not being picky or such thing, but one question ? Are you using a MFJ-259B or a 269B..

Can`t wait to see how this thing plays, as i was thinking about trying some 2 meter SSB
and was thinking about another quad..

Regards,
John
 
Of course, I can't leave well enough alone (especially with an antenna analyzer in my hands) so I decided to try to fine tune the gamma match.

The manual's measurements still had my 1:1 SWR match point fairly low in the band, and I wanted it higher. Of course, this is just a matter of adjusting the gamma match's segments to find what works for you. For my desired frequency range, I found that pushing the second segment all the way down but leaving the top segment at the manual's dimension put me right where I was happy.

It got dark before I had a chance to adjust the horizontal gamma match, but I'm hoping I can have the horizontal side adjusted lower in the band to accommodate the typical 2m SSB frequencies.

More to follow...

I know height can effect swr reading, so I was wondering how high the antenna was when you were checking it? Did you happen to check it at a low height compared to a higher height? I only ask this because I was setting up two yagis for 2 meter. One was a vertical and the other was horizontal.

The vertical on the 10 foot mast set up real fast (y)

The horizontal was pissing me off because we couldn't get it low enough to be happy with it, THEN I had a Homer Simpson moment, DOH! and connected the horizontal to the mast you are using and raised it up about 20ish feet and BAM, it set real easy. So it was obviously reflecting a tad off the ground at 10 foot?

Just wondering how that antenna reacts to height?
 
I actually thought about that ahead of time while testing. The temporary mast is about 6 feet off the ground, so it's real close to one wavelength high, which should be good enough for testing. However, I did extend the push-up mast up to about 15 feet to double-check the measurements. I didn't really see much change between the two readings.
 
It's going to be a few more days until I can get the antenna up in the air for testing, so in the meantime, I'll share some EZNEC models of the 2 meter beam in free space. Tom Charles sent these to me to include with the review.

1092-1266527719-98b4401909da824e21ad0b46055c742a.png


1093-1266527719-9595a50c0d8ae506540ab4e97b71f4e2.png


This one pretty much tells the story of the specs on the antenna:

1094-1266527719-f023fe3933cb2135a128f96fbf13b3a6.png


It is interesting to me that the gain of the antenna appears to be about the same as a typical 3 element yagi, although the front/back ratio doesn't appear to be as good as expected.

I certainly would like to hear what everyone has to say about these models.
 

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