Exactly! All true and Tom is right on point! You have removed a lot of series reactance with that "gamma cage", Carl -as indicated by the required tuning C changing.from 160 pF ot over 400 pF. OF COURSE the Q was reduced as the series reactance was reduced and the real part stayed fairly constant. That does not imply increased or excessive loss!
Regards Charlie -----Original Message----- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Tom W8JI Sent: Saturday, February 22, 2014 9:07 PM To: Carl Braun; '160' Subject: Re: Topband: Shunt feeding the Skyneedle - new developments I was pretty satisfied with this scenario so I mounted my variable cap on a 3/4" thick piece of Plexiglas to the backplane via Teflon bolts inside the steel enclosure. When I did this I saw my analyzer jump to 45 -j11 ohms. No matter how much tweaking was done the lowest "X" on the analyzer was 11. Figuring I could live with that after making 24 contacts this morning I decided to move ahead with my gamma cage. When I completed the cage per the info above I left my analyzer set on the previous frequency setting of 1825 and saw the resistance jump and the X go out of site. Adjusting my variable cap (from approx 140 pf to 420 pf) rewarded me with a 42 + j0 reading. Inside the shack on the 1000D and the BIRD I see 1.1:1 Vswr at 1.800 MHz, FLAT 1.0:1 from 1.810 to 1.860 and 1.5:1 at 1.895 MHz.>>> I would expect you to have that bandwidth. It does NOT indicate loss. Your shunt system now has an operating Q of around 4, because you now have 200 ohms of series C. With a thick radiator and a large yagi on top, and so much capacitance, you are exactly on target. While I don't fully trust the FT1000 meter, no matter what, never automatically assume modest bandwidth like you have indicates loss. It doesn't. There are a whole lot of things that go into bandwidth beside loss! 73 Tom _________________ Topband Reflector Archives - http://www.contesting.com/_topband _________________ Topband Reflector Archives - http://www.contesting.com/_topband