Gamma Matches

[HomerBB]

. The 10 kw model is supplied with a porcelain stand off insulator with a bolt that connects to "pigtails" on the cable, rather than a PL-259.

I think herein lies 50% of the solution. No SO-239. No PL259.

 

[Shockwave]

I think herein lies 50% of the solution. No SO-239. No PL259.

Yup. But, then you have the problem of deciding on how much pigtail to leave open and unshielded, to prevent arcing at the feed point and too much open length, so that the wire now becomes part of the antenna. Keep about an inch of exposed center conductor insultation, sealed in clear silicon to prevent arcing and water migration into the cable.

Any extra length required to make the ground connection should be done on the braided side of the pigtail. That too should be as short as possible. I use one of the U-bolt mounting nuts on the center of the driven element to make this connection. Note that some cables have a foil bonded to the outside of the center conductor insulation. That must be removed, scraped or sanded off of the exposed portion of the insulation, or it will arc to the foil.

 

[snow bird]

Where’s a good source of information to properly build a high wattage gamma?

More specifically, the in’s & out’s of which material to chose and why, how to build one that will handle higher power input. I’m aware I could buy one but what fun is that?

I’d like to build one that’ll handle at the very least 5kw.

Which brings the question to the table, the ratings offered by Maco, is that PEP figures or CW/AVG?

 

[snow bird]

Pork what did you diced to do Make one or buy One ?

 

[TheRealPorkchop]

You ever see Spaceballs? Remember the part where the guys were “combing” the desert? Remember what that guy said?

Well I ain’t done...it. I haven’t decided yet what to do. I think buying the larger or largest from Maco might be a faster choice. Then go back and “comb” this thread for the helpful tips and apply them generously. My tower will tilt (if I ever get it up) but I don’t to have to fool with it.

I do have a Jo Gunn Pistol I’d like to put up in place of my A99, be nice to beef that gamma up. Maybe I’ll experiment on that junk first.

 

[Ranch55]

I do use the Maco 5KW gamma match. It does have a teflon insulator.
Teflon is generally rated for 500V per mil thickness on the insulating rating.
And I also did replace the connector at the gamma match with a high quality teflon insulator.
All has been well for a couple of years now.

 

[TheRealPorkchop]

I’ll probably just buy a gamma instead of building/modding my own, don’t have much time for it.

 

[freecell]

Some Preliminary Notes on the Gamma Match
L. B. Cebik, W4RNL

https://ea5nd.com/wp-content/uploads/2017/11/Gamma-Match.pdf

 

[TheRealPorkchop]

I think I’m gonna buy one from ICA. I think 20kw average power will be more than enough for my mess.

 

[Rwb]

I think I’m gonna buy one from ICA. I think 20kw average power will be more than enough for my mess.

the CHOP GONNA ARC WELD THE AIRWAVES hahahahaHAHAHAHA

 

[Jay Mojave]

Suggest you look at a hairpin matching system, DX Engineering has the current balun and hairpin kit.

I use the gamma match to stir paint.

Jay in the Great Mojave Desert

 

[Shockwave]

If you give the gamma matched yagi the same benefit of the current balun, you'll never notice the difference in forward gain, pattern or CMC levels.

About the only exception I could find to this, was on a 2 element yagi with no directors. Here I was able to notice a few degrees of pattern skewing, pulling towards the side with the gamma. Adding a director, refocused the pattern, to where I could no longer notice any skewing.