By the way, Carl. it sounds like you might have eliminated a bit of series inductance when you moved the variable capacitor into the enclosure and you may have picked up a bit of shunt-C by moving it into the metallic enclosure, but you are so close to "dead-flat" 1:1, that it really doesn't matter. You could just tweak the variable C to minimize the reactance at the load, but -j11 is just fine! As I said earlier your 45-j11 resides near the origin of the chart on a 1.3:1 VSWR circle!
Enjoy and have fun! 73, Charlie, K4OTV -----Original Message----- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Charlie Cunningham Sent: Friday, February 21, 2014 8:30 PM To: 'Tom W8JI'; 'Carl Braun'; '160' Subject: Re: Topband: Shunt feeding the Skyneedle - new developments BTW BTW. Carl I agree completely with Tom that there's no point in having a static-bleed choke on a grounded shunt fed tower! 73, Charlie, K4OTV -----Original Message----- From: Topband [mailto:topband-boun...@contesting.com] On Behalf Of Tom W8JI Sent: Friday, February 21, 2014 8:02 PM To: Carl Braun; '160' Subject: Re: Topband: Shunt feeding the Skyneedle - new developments Since then I've moved the variable capacitor inside the panel and mounted it to a ¾" think Plexiglas sheet mounted to the back plane with nylon bolts and washers. There is a 1" air gap between the Plexiglas and the backplane. I now have seen the 42+j0 ohms change to 45 - j11 ohms...that's the lowest reactance I can tune the capacitor for. Not really sure if its +j11 ohms or - j11 ohms but I assume if the reading was + j11 I could continue to tune it out with the capacitor but I cant. Does the capacitor not play well with a steel enclosure?>>>> Any enclosure will change things, especially a metallic enclosure. Just readjust the cap. <<<<The other strange situation I'm experiencing is when I connect my Array Solutions static bleed choke to the feed thru insulator at the outside of the panel to ground the resonant frequency jumps to 2.014 MHz at 25 +j0 ohms...remove it entirely and I'm back to my 45 - j11 ohms.>>> The choke is completely unnecessary with a shunt feed tower. It won't help a thing, so leave it out. 73 Tom _________________ Topband Reflector Archives - http://www.contesting.com/_topband _________________ Topband Reflector Archives - http://www.contesting.com/_topband _________________ Topband Reflector Archives - http://www.contesting.com/_topband