WorldwideDX Amateur Radio Forums

Try this:
1.5 KW PEP Gain-master Modification (page 3)

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Homer/NB, I think of the GM design as somewhat simple looking, but very technical in its function and design. It is not like a coil or gamma match.

The GM basically uses several complicated and technical functions in its design and operations, that will make such success...a bit different than duplicating one of the physical all aluminum CB antennas you guys make from scratch...that amazes me. Maybe the GM would be easy to duplicate, once the components, dimensions, and construction items are all proof tested, measured, and assembled correctly.

I never say never though.

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NICE!!! you got me interested...

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QTH: Vert 160/80, Fan 40/20/10, Fan 17/15/12/6, 2m J pole, 2m halos Mobile: 12/15/17/20/40, 10, 6, 2/440

Great!
This antenna does very well.
I'm still getting good reports on it daily.

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Homer I was referring to the red coax not the brown rg303 coax. I'm not sure if it's 50 ohm or maybe 75 or even 90 ohm to get the swr down.
Seems a center fed 1/2 wave dipole at 180 degrees should be 72 ohms and the 5/8 could be even higher. An end fed 5/8 is close to 150 ohms so I wonder if the phasing network also matches the impedance to 50 ohms or if Sirio are using a 3/4 wave matching transformer section from the connector to the center feed point.
16 turns at 2.75 inch diameter plus 3 inches from the connector to the coil plus the 133 inches above the coil ends up right at 274", a 3/4 wave length around 27.5 if the velocity factor is about .85 like LMR400.. But if the velocity factor is 66% then only taking the coil of 16T x 2.75 inch dia + 3 inches is a half wave unless the velocity factor of the braid inside the casing also comes into play
I might take mine apart to get an exact measurement.
One thing is for certain, the gainmaster design is a serious balancing act to get it right. I am definitely impressed by the Sirio design team.
I wonder if the patent info would reveal these details?

Your questions are the biggest reason I haven't tried this antenna as a homebrew, yet.

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