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gamma match insulating materials

B

BOOTY MONSTER

Guest
trying to get a idea on the options i can use for insulating between the rod and tube on a gamma match . i know it has to be non-conductive to RF . the only way i can check that is doing the microwave trick . not the best way , but from what i understand is a good enough indicator for home-brewing .

ATM im thinking heat shrink tubing would be a easier way to keep the layering consistent on the rod compared to wrapping it in teflon plumbers tape . plus the friction from it shrinking should hold it in place compared to having to tape or glue the teflon tape to keep it on . im gonna use 3/8 inch diameter solid aluminum rod and 1/2 inch inside diameter aluminum tube . 200 watts is the most i PEP (if i hit a small lottery i would bump up to an AL-80B...LOL) . i also want to use heat shrink over the shoulder where the rod exits out the top of the tube to keep moisture from running in , as well as on a few other sections .

is the heat shrink tubing a decent material for this use ? or will it cause issues ?
what would you suggest instead ?
 

I did use heat shrink on a gamma match but it ran no more than 75-100 watts pep. I would suggest some nylon ( preferably) or pvc tubing like that used in aquariums. The voltage won't be high at the feedpoint but the RF current will be at it's maximum however at the power you state it shouldn't be a big deal.
 
The only addition I'd make to 'Mack's is to not use the 'foam' type dielectric insulation, use the 'solid' stuff. Lasts longer and water/sun won't affect it like with the foam.
- 'Doc
 
The only addition I'd make to 'Mack's is to not use the 'foam' type dielectric insulation, use the 'solid' stuff. Lasts longer and water/sun won't affect it like with the foam.
- 'Doc

I got the idea from my wolf .64 gp, Eddie Chicone used the foam dielectric his his gamma matches and he had a 5000 watt upgrade on that which I suspect was either teflon or the the clear poly stuff:D
 
I tend to agree with 'Doc and Mack that Wolf uses 3/8" foam inside the 1/2" tubing for his gamma. This may account for why I saw the match go bad for a period of time as some point. I think Mack is also right when he suggested that the top end of Eddie C's gamma was left open to allow rain in and that likely saturated the dialectric and shorted until it dried. I placed a cap on mine, and that should help prevent this from happening again.

However BM, I don't think the 1/4" insulator inside of RG8 will be large enough for a 1/2" gamma, unless you make all of the gamma elements smaller.

I figure a gamma should have insulating material that is at least as effective at handling current/voltage as the coax used.
 
Making a gamma with a 36 inch 3/8 rod and 10 inch 1/2 tube should have more then enough capacitance and length to match this antenna. The tap point from rod to radiator is typically around 27 inches up from the connector bracket.


coax wont work for the gamma that i need . ^^^^^
it needs to be stiff enough for over 2 feet to stay vertical/straight on its own .

i already have 3/8 solid aluminum rod
 
That's some monster rod there booty, are you gonna be putting like 10kw through it? if not you could get by with 1/8 or 1/4'' rod and a 3/8ths tubing and still have a 1 kw capacity.

Just bang the rod end flat a bit and drill a hole through for connections.
 
1/2 inch inside diameter . im gonna use one of the ground elements off of this for the rod .
thanks 359 :)
IMG_0053.jpg
 

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