Topband: Shunt feeding the Skyneedle - new developments

[Carl Braun]

Thanks guys

The j11 ohms is the best I can get period. I was able to get j0 when the cap was outside of the steel enclosure with a better bandwidth. Maybe I should throw my $400 enclosure and find a fibergla$$ enclosure. But as others have indicated I should probably just live with it. 

Do you think a smaller (physically) vacuum cap would have less interaction with the steel enclosure.  The one I have is only 3" round and 6" long. The air variable I'm using is 13" long and 7" round at mesh

Carl AG6X

Sent from my iPhone

> On Feb 21, 2014, at 7:11 PM, "ZR" <zr at jeremy.mv.com> wrote:
> 
> The only benefit of getting it better would be a bit more 2:1 VSWR bandwidth to keep the amp happy but even then there is sometimes a gotcha when tuning an antenna.
> 
> Carl
> KM1H
> 
> 
> 
> Subject: Re: Topband: Shunt feeding the Skyneedle - new developments
> 
> 
> Well, you can do all that, Carl
> 
> But if your series variable capacitor is not maxed out (fully meshed) if
> you can increase the capacitance enough  to get to j0, you would be at 45
> +j0 and on a 1.1:1  VSWR circle. No point int trying to do better than
> that!!
> Otherwise, just increase the series capacitance to bring that -j11  as
> close to j0 as possible and take that! You'd be so near perfect that there
> would be no real point in going further!
> 
> Your time and efforts might be better spent working on  your radial field!
> 
> 73,
> Charlie, K4OTV
> 
> 
> -----Original Message-----
> From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of Carl
> Braun
> Sent: Friday, February 21, 2014 8:46 PM
> To: Charlie Cunningham; 'Tom W8JI'; '160'
> Subject: Re: Topband: Shunt feeding the Skyneedle - new developments
> 
> 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 at 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 at 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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