In response to a post I made about my gamma cap, Ed, N5NUG, sent me
a sample of his gamma match assembly. I installed it on my tower
yesterday morning and have been testing it during the contest.
It consists of a length of coax with a nice WX proofed PL-259 on one
end, terminals for the tower ground and gamma wire about a foot
down from the connector, then whatever length of RG-213 you need
beyond that as your gamma cap. At the end, you install an end cap
which WX proofs the end and also prevents the high voltage from
breaking down the insulation.
On my previous stub, I have had to terminate it with a ceramic
insulator to avoid arcing.
I am pleased to report that the end cap does the job and there hasn't
been any breakdown with full power and lots of CQing. This looks
like a very clean solution for those who want to do a gamma match
on a tower close to a quarter wavelenth. I am not sure it will
stand up to towers closer to a halfwave length as even my ceramic
insulator has problems in this case.
>From Ed:
> The stubs may be ordered by capitance value starting at a price of
> $24.95 for 120pf (3.9' length) with an additional $.75 per 30pf of
> capitance (1') above that. The 120pf length is the minimum capitance
> value I will build. The coaxial cable material used in the stub assembly
> high grade RG213 @30.9pf per ft.
>
> This does not include the "sealed" silver plated teflon PL259 connector,
> but does include the end cap without the silicone grease. Add $9.00 if I
> supply the PL259 and $2.00 if I supply the silicone grease.
>
> The end caps sold separately are priced at $10.95 retail without the
> silicone sealant. Add $2.00 to the price if I supply the silicone.
I would suggest the extra $2 is worth it. The cap comes in a plastic
bag and ready to install. You cut away 1.5 inches of the shield and
then insert it into the cap (goes in about 2 inches). I used some
tape to hold it in place.
You can contact Ed at n5nug@ix.netcom.com if you are interested. I
have no connection to his business.
Had a few hours to play in the contest last night - made about 300
QSOs. Good opening to JA in the morning with some very big signals
just after my sunrise, but not very much activity. This peak occurs
very late in the evening JA time, and all but the die-hards are in
bed.
Stew Perry on Dec 27th/28th. Rules at http://www.contesting.com/n6tr/topband
73 Tree N6TR / K7RAT
tree@contesting.com
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