Imax 2000 outperforming Gizmotchy 3 element beam.

[SMILEX2692002]

I have a gizmotchy g31 3 element beam mounted on a tripod on the roof of my home.
I'm only using the vertical elements of the antenna.
The boom of the antenna is 24 foot in the air.

My IMAX 2000 is on a 40-foot Tower.

From my on the air RX comparisons I notice stations that are local are about 1/2 down on my S meter switching from the Imax 2000 to the Gizmotchy G31.
This is with the Gizmotchy pointed directly at the receiving stations omni directional antenna.

For stations 20+ miles out the Gizmotchy is about 1DB down on my S meter vs the Imax 2000.
This is with the Gizmotchy pointed directly at the receiving stations omni directional antenna.

I would assume what I'm seeing is normal due to my Gizmotchy G31 being lower than one wavelength above the ground?

I do enjoy the fact that the gizmotchy is directional and I can null out certain locals by turning the antenna away from them.

I really have no desire to put my Gizmotchy G31 up higher.

If I did put my Gizmotchy G31 up on top of my tower I would assume I would see a increase versus the IMAX 2000 at the same height?

To me it's not worth the time or effort because I have a Sirio Sy27-4 under my IMAX 2000 on my tower.
I like that combination a whole lot.

 

[kopcicle]

https://www.worldwidedx.com/threads/a99-question.220046/page-2#post-601655

 

[w9cll]

I am not familiar with that antenna but looking at it I can only say its either installed incorrectly or there is a polarization difference.

 

[Jay Mojave]

Hello SmileX: Sounds like the antenna height is certainly a factor in the comparison of the two antennas. I would suspect the Giz's coax may have more loss then normal adding to the different S-Meter readings. Or maybe even antenna tuning.

Hard to say not being there to measure it all.

Jay in the Great Mojave Desert...… just down the road ah ways from the fillin station

 

[Tallman]

If the Gizomotcy(Intentional misspelling) is not properly assembled the antenna is not even a dipole. If I understand what you said, "I used only the vertical elements."
Try running the fully assembled antenna and see what a difference that make.

 

[BJ radionut]

Yes, not sure how installed...But "Giz" beam almost 30+ft. lower than Imax tip to tip. So would explain much.
However the 20+miles range only 1dB difference???
How did you arrive at that measurement?
All the Best
Gary

 

[Tallman]

That measurement is called: HPOHA.

 

[SMILEX2692002]

I have an antenna switch. Going from Imax to Gizmotchy or vise versa.
Then i look at the receiving signal on my radios S meter

 

[Marconi]

I have a gizmotchy g31 3 element beam mounted on a tripod on the roof of my home. I'm only using the vertical elements of the antenna. The boom of the antenna is 24 foot in the air.

My IMAX 2000 is on a 40-foot Tower.

Smilex for modeling purposes, I'm assuming your boom is about 5' feet above the roof and this is how I modeled your setup. So, consider my assumptions.

Based on my modeling, the Gizmotchy beam with slanted down radials in the Vertical polarization you might expect to see excessive of Common Mode Currents (CMC) on the feed line and/or mast...unless you have already remedied the problem.

IMO, this is likely due to the radials being to close to a structure...even a wood house. You might need to check this with your setup. Being this close, I also find on rotating my Giz model relative to the frame house I added, I see serious pattern variations that are possibly not so obvious to note while just operating your radio.

Note: the frame house I added is made with reflective wires and that is why I use very few wires to represent the house. That said, it might be hard to determine how much effect your house has on the Giz being close like I modeled here.

My real world experience on my 12'w x 20'l x 19'h sun deck on my home installing a 4 element yagi...showed diminished performance until I raised the boom up to at least 10' feet above my roof line in my case. This is why I modeled the idea for your situation.

Note: my Gizmotchy models also show much more CMC, and IMO that is likely due to the slanted down radials relative to the mast/feed line in the design.

If the Gizomotcy(Intentional misspelling) is not properly assembled the antenna is not even a dipole. If I understand what you said, "I used only the vertical elements."
Try running the fully assembled antenna and see what a difference that make.

I would really be interested in reading your response to Tallman.

 

[SMILEX2692002]

To Tallmams quote.
The antenna is fully assembled.
It has a gamma match for vertical and a gamma match for horizontal.
What I ment is I'm only running it for vertical polarization.
I don't have a feedline hooked up to the horizontal gamma match.

I also have a coaxial choke of around 10 turns of my feedline just passed the feedpoint taped onto the boom.

The antenna is on a 5ft tripod with 6ft of mast coming out. Then the rotor is attached.
Then a 5ft stick of mast out of the rotor.
The Gizmotchy mounted on top of that mast.

I used my comet antenna analyzer when setting up the antenna.
A low SWR dialed right in perfectly.
After a few minor adjustments to each gamma match.

 

[sp5it]

....but where is resonance?
Mike

 

[SMILEX2692002]

27.205

 

[Tallman]

27.205

A picture of the GIZMO antennas would be nice.

 

[Marconi]

I also have a coaxial choke of around 10 turns of my feedline just passed the feedpoint taped onto the boom.

My models are set at 27.205 too.

Ten turns of coax might work, but it could also be a problem if it's not working as intended. I've always been a bit dubious about the use of chokes, but if we're working 11 meters I hear it best told by G3TXQ...that 5 turns of RG 213 or RG 58 is recommended at 27 mHz.

Click here: http://karinya.net/g3txq/chokes/

Just like Jay Mojave told us in this thread, "Hard to say not being there to measure it all."

I say, "...I too have seen some strange things happen that I could not explain."

Maybe you could post some pictures of your Giz?

 

[SMILEX2692002]