Thanks to all who replied
Tom W8JI, your comments on the metallic panel and the static bleed choke make
sense. I was so pleased with the FLAT SWR reading with the variable cap
outside the panel but I guess I can live with the slight SWR. (Thanks Charlie
K4OTV). I have a Nye Viking monster tuner but I hate to use it as my Henry amp
seems to load strangely when I have it inline so I think I'll just live without
it.
Can I add some coax (coiled) to bring the X down on the -j11 reading? I did
this with the old Telrex and brought the X right down and out of the pic. I'm
sure Ill need much more than I would on 14MHz but I think I'd like to try
anyway.
I'm still going to drop the tower down and add two more gamma wires to create a
cage and I still have the option of pulling the gamma wire(s) away from the
tower another 8-10 inches to add a few more ohms to the equation.
I'm having fun with the experiment.
Right now I'm hearing the beginnings of the SSB contest with N7GP, WD5COV, W6YI
with the big signals so far. XE is the only DX I've heard.
Lots of stateside calling stateside
Carl AG6X
-----Original Message-----
From: Charlie Cunningham [mailto:charlie-cunningham@nc.rr.com]
Sent: Friday, February 21, 2014 5:21 PM
To: 'Tom W8JI'; Carl Braun; '160'
Subject: RE: Topband: Shunt feeding the Skyneedle - new developments
Well, Carl
I plotted your 45-j11 load on a Smith Chart (normalized to 50 ohms) and it's
very near the origin on a 1.3:1 VSWR circle. Since you have a relatively
short feedline of LMR-400, You should be able to just tune it out at the
transmitter end of the line, and the LMR-400 line will be operating at such
a very low SWR (around 1.3:1 that the excess loss from a 1.3:1 VSWR at 160
is completely trivial and negligible! It may not be completely
"intellectually satisfying to have -j11 of reactance at the load, but it
should match easily and the antenna should work very well! Enjoy!
Sounds like that Array solutions static bleed is not as high in impedance as
we might wish! A large resistance might give you more satisfactory results!
GL! Enjoy!
73,
Charlie, K4OTV
-----Original Message-----
From: Topband [mailto:topband-bounces@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
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