Gizmotchy 2 Meter 4 Element Beam Review

[Moleculo]

Any new information on the Gizmotchy 2M 4Element? Were you ever able to give the horizontal side a run on 2M SSB?

I have been seriously considering one since I temporarily live in a rental home and liked the "lower profile" aspect of the design. At this point, I don't really need high gain figures, but would like to be able to put a little more signal in one direction as well as gaining the horizontal aspects for 2M SSB.

Excellent review by the way! Thanks!

Yes, I have used it on 2m SSB, although there isn't as much activity here as I had hoped. I have also used it a few times talking to mobile stations with horizontally polarized antennas at distance. You can definitely tell the difference between the two polarities on this antenna. If you are looking for a directional antenna that allows you to switch polarities, you really only have a few choices. One is this Gizmotchy and another is the Cushcraft A14820T, which is a much bigger antenna. The Gizmotchy does do what it advertises, however in it's stock form it doesn't perform as well as it should as evidenced by the model's forward gain and front/back ratio. However, they said they were going to change the design to match my modifications, which gave the antenna significant performance improvements. If you're going to buy one, it might be worth a call asking if they have made those changes yet. If not, at least I've shown you what to do .

 

[Ronin]

Thank You Moleculo,

I actually have the Cushcraft 148/20T, and it works very well. I have had it for about 12+ years, but living in a rental property for the time being, I was looking for something with a shorter boom length until I buy another property. I did see your modifications and I will make the changes if Gizmotchy has not. Every little bit helps!

There is one other antenna manufacturer that I know of that makes dual polarity antennas for VHF/UHF and that is Gulf Alpha antennas. They are of a long boom design with the 8 element being 12ft. long, but the construction looks very good. They are pricy, but if I had to replace the Cushcraft, I would seriously consider one of them.

Thanks again! If I do end up getting a Gizmotchy, I'll keep you posted on how it works out and if there was any design changes.

 

[chris366]

I also bought the gizmotchy 2m 4 element beam, works great with the new updated spacings, I have noticed that I can not use the antenna for MURS as it will not tune there (about 20 local guys use MURS for rag chewing), I just bought another one to try and cut the elements to try and tune it, before I go cutting a $125 antenna i was wondering if anybody can tell me the element length that i need to tune on 151.880,
thanks
chris

 

[Moleculo]

I just bought another one to try and cut the elements to try and tune it, before I go cutting a $125 antenna i was wondering if anybody can tell me the element length that i need to tune on 151.880

Sorry, I can't tell you as I haven't tried to modify it for that high in the band. I would say just keep trimming each element down a bit until you find it...and then report the results, of course!

 

[GnG8d]

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

I know this is an old thread, but 400 series stainless is heat treatable, not very low grade. Being heat treatable it has a higher iron content and therefore magnetic.

 

[chris366]

Sorry, I can't tell you as I haven't tried to modify it for that high in the band. I would say just keep trimming each element down a bit until you find it...and then report the results, of course!

I am down to 1 inch off all the elements and getting closer, I went to the hobby store and bought aluminum rod the same diameter as the elements that came with antenna, I cut them down and when i find the correct length i will cut the original the same and post my results.

 

[Captain Kilowatt]

You could simply just scale the new dimensions to the old dimensions versus frequency. 146.000 ÷ 151.880 X present dimension or in other words multiply all lengths by 0.96 and it should be very close. You will have to adjust the gamma match slightly as well.

 

[michaelt501]

Can you tell me what your messurements were on the vertical gamma match?I just picked one of these antennas up at a Ham Fest for $10.It's not in the best of shape.I plan on rebuilding it with your specs.

 

[Moleculo]

Can you tell me what your messurements were on the vertical gamma match?I just picked one of these antennas up at a Ham Fest for $10.It's not in the best of shape.I plan on rebuilding it with your specs.

Give me a couple of days to measure it - I have to get up on the roof.

 

[Happy_Hamer]

So how did that antenna work out for MURS?

I "know a guy" who uses MURS all the time on SSB, All five channels are pretty busy in this part of the country,,, 154.600 has a following on SSB around here.

 

[Moleculo]

So how did that antenna work out for MURS?

I "know a guy" who uses MURS all the time on SSB, All five channels are pretty busy in this part of the country,,, 154.600 has a following on SSB around here.

The SWR is pretty high on the MURS frequencies with it set the way I have it for the ham band. If you want to use this antenna on those frequencies, you're going to have to adjust the antenna. However, the frequency range mine is set at will work fine well below the 2m amateur band. Based on the bandwidth range I see from this antenna, it shouldn't be too difficult to find a way to adjust the gamma match to get it to work on both MURS and the ham bands. Alternatively, you could cut the elements down a bit more.

 

[w4jle]

A couple of tweeks

The distance between elements is a follows
reflector to driven 21"
Driven to director 1 19"
director 1 to director 2 12"

Modeling this antenna if you change the spacings to:
Ref to Driven 15 1/2"
driven to dir 1 12 11/16"
Dir 1 ti dir 2 20"

The forward gain will be improved by 1/2 dB, however the F/B will improve by 4 dB

Depending on the amount of activity around you the front to back improvement may or may not be worth the effort. The total spacing is reduced to about 48"

 

[Moleculo]

Excellent info! Did you run the model with the element lengths 1/2" shorter where I ended up at?

Also, can you post a picture of the new model you ran?

 

[w4jle]

I have also been playing with the antenna and I would make a recommendation that the mast be replaced with a PVC or other non conducting mast.
There is significant distortion and loss of gain to the vertical pattern. If there is any interest drop me an e-mail to w4jle at w4jle dot com and I will send you the patterns.
Horizontal is no problem. I tried the mast in various positions to see if the effect could be minimized. The only position with out distortion is behind the reflector. Not a very practical solution.

 

[KM3F]

Old thread but here is some more experience with the 6 element Gizzy on 11m many years ago.
The change in polairity when facing another conventional beam config at a distance resulted is no change in signal levels such as at a PDL-II on the other end of the test..
On DX it seemed to do very well where angle and polarity can be anything at anytime.
In light of your re-engineering, a lower frequency model may also respond to improvements..
..
In reference to a previous post on RFI to w2ihy equipment, I found that above 10m the ihy box is not RFI filtered well enough at 6, 2 and 70cm.
The main source was no bypassing on the 12 volt feed from the wallwart.
I went through the unit's inputs, outputs and 12 volt feed with .001 disc caps accross and to ground.
This cleaned up everything.
The cap values are so small at audio frequency they have no shunting effect except at high RF.
Additional filtering can be applied with Faerrite clamp on cores of the right 'mix' to the audio cables.
.
My position is that for serious weak signal work on 2 and 70cm, a high gain planar beam would still be the better selection.
On these bands there is either long distance out to 300 miles or very few locals to make the Gizzy the main antenna especially at the longer distances.
However that could change with enough work on an extended boom Gizzy design.
My feeling is the radiation angles from the Gizzy may be enough different from a planar beam to loose a little signal on topo long distance contacts but that has yet to be proven except what I observed on 11m.
Thanks again for your efforts.