Gain Master thought...

[RadioDaze]

If this 3D plot of the GM in free space is accurate

Would it not be the case that the radiation that appears to be at an elevation of 0 degrees (afterall that is what I think Sirio is trying to tell us here.) will largely be absorbed by the ground and everything in it's way to the horizon. So whilst you have a very low "incident angle/cut in" into the F2 layer it may well be that the signal that hits the F2 will be significantly attenuated by things it has to pass through en route to the F2 across the earth surface. (relative to say 10-16 degrees which would slowly rise above attenuation causing earth based structure such as houses and buildings.)

Or does the fact it will operate above an actual earth mean the 0 degree max radiation angle will never actually occur / or be 0 degrees ?

I wonder what the model of a 5/8 wave centre fed dipole looks like in one of those snazzy antenna modelling software's you guys have? Has anyone modeled the Gain Master to see if Sirio's plots are representative of the antenna in theory or practice ?

 

[RadioDaze]

Seems a guy with the forum name Marconi modeled it, the post is about 1/3rd the way down this page on this topic:

http://www.worldwidedx.com/threads/new-antenna-from-sirio-gain-master.76970/page-4

 

[RadioDaze]

In fact it was such interesting responses that I will quote what he says here:

"Shockwave have you received your Gain Master yet. I was hoping that Dxswe would have some reports by now, but no word. I'm anxious to hear some good news about this antenna. Hope you can also get us some good photos. Dxswe's pictures were great, but it would be great with the radiator straightened out a bit so we can see the portions and its relationship to the fiberglass a little better.

At first I thought the connector in the coax was due to handling, to prevent having to bend the coax which has a warning in the manual, but after seeing Dxswe's pictures, I'm not too sure about that idea. Why do you think Sirio found it necessary to add the connector at that point?

I have played with an Exnec model of a 1/2 wave dipole that came with the software. I adjusted it to work on the CB band and generated the free space reports for SWR, Currents and Phase, Pattern and Gain, and Wires. With it resonant at 27.205 it shows R=71.9 X=<.09 with all currents in phase, with max gain on the horizon at 2.13 dbi.

When I increased the radiator element length about 2.6 feet to make it about 5/8 wavelength at 27.205, the reports show R=173.2 X=358.3 with all currents still in phase with max gain on the horizon at 2.43 dbi.

I also noted a small dip in the current indication in the 5/8 wave antenna view that seems to suggest something similar to what Sirio notes in their bandwidth curve---a little dip in the middle. I'm not sure that this is relative to anything, but this dip does show up on the 5/8 wave antenna view and doesn't show on the resonant 1/2 wavelength antenna. I will post the antenna views so you can see this dip in the current indications.

I also note that all currents remain in phase on the 5/8 wavelength like Sirio indicates. The 5/8 wave also shows more current flowing all the way across the entire 5/8 wave radiator, which to me suggests more RF to radiate. I also noticed an increase in current on the first three segments on both sides of the center segment which is noted as "1" amp. This is apposed to decreasing currents in the same first three segments on both sides of the resonant 1/2 wave model---from the center segment all the way to the open end of each element the current decreases as we would imagine.

My model shows no signs of error in segments or geometry. I did not match either antenna, they are free space models with no ground affects, and I have no feed line or mast attached. I also did not have wire loss turned on. I do not know how all of this would affect the antenna results if real world controls and matching are applied, but I suspect things will be different somehow. Maybe some of you guys that know the in's and out's of Exnec can do something in this regard, so we can better see what Exnec can do that we might understand."



Following on with:



"I was also surprised to see other similar results that Sirio showed us for the GM. They looked to be right on mark when compared to the 5/8 wave model of the I-10K I made using thin wires. All the trends they noted in their modeling seemed to be present in my model of the I-10K too, and in particular the comparison parts where Sirio makes a note with the area marked up in yellow. The area they suggest shows a better response on the horizon.

IMO, what Sirio shows us are all free space models. When Mother Earth enters the mix though---things begin to change. That said, my Eznec 5/8 wave dipole model shows a narrow lobe maximum gain pattern over real Earth @ 8 degrees, and a little gain at 4 and even less at 2 degrees, but no gain on the horizon like Sirio would have us believe. IMO, with some nice gain at low angles, the simple profile, and the seeming heavy duty fiberglass---the GM should prove to be a better antenna than the A99 and Imax---if the price is right.

I don't think the Sirio Gain-Master will go-over big however, if it's much over a $100 US.

I'm surprised we haven't hear anything from Shockwave about his new MG, and what happened to to our new member Dxswe? I see he put his antenna up on his house, but no reports as yet. Must be the weather."

 

[M0GVZ]

Would it not be the case that the radiation that appears to be at an elevation of 0 degrees

No because you're not using the antenna in free space. It would need to be many wavelengths above the ground before it was considered to be as good as being.