Topband: Shunt feeding the Skyneedle - new developments

Carl km1h at jeremy.mv.com
Sat Feb 22 22:08:00 EST 2014 

That is the type of report I really like to hear Carl. All that work has 
paid off in spades.

As you increase the number of radials the VSWR bandwidth might decrease 
along with the R which is normal as the ground resistance decreases. Since 
it appears to work so well you might just leave it alone for awhile, operate 
and get a feel of how your signal compares with others.

With the top loading Id say the tower is close to being a 1/4 wave and the 
perfect world impedance about 35-36 Ohms with the remainder as ground 
resistance. That will result in very decent efficiency.

That cage you connected this morning sure changed the numbers from the 
single wire I was responding to.

OK on the steel panel. The usual rule of thumb there is to space coils and 
variables at least their width away. There were some amps and tuners on the 
market that would have radically different tuning, and more power out in the 
amplifier examples, with the cover removed.

Take a bow, Im impressed!!

Carl
KM1H


----- Original Message ----- 
From: "Carl Braun" <Carl.Braun at lairdtech.com>
To: "Carl" <km1h at jeremy.mv.com>; "'160'" <topband at contesting.com>
Cc: <ad6dk at arrl.net>; <WX9J at att.net>
Sent: Saturday, February 22, 2014 7:15 PM
Subject: RE: Topband: Shunt feeding the Skyneedle - new developments


Carl and Topbanders

Here are the latest details and I will try and be as thorough as possible.

Good news!  I built my gamma cage and the antenna now performs MUCH better.

Here's where I stand:

90' Tri Ex Skyneedle shunt fed with the gamma arm at 67' and a three wire 
gamma cage with 10" separation between wires.

My tower is grounded at the base via three 1" copper strap 1/8th inch thick 
and tied to a 1 1/2" copper pipe radial ring that measures 4' x 8'. The 
radial ring is also bonded to three 8' ground rods via 1" copper strap.

Currently I have approx 30 ground radials screwed to the radial ring with 
copper clad stainless screws and then painted with copper paste.  Some of 
the radials are formed from heavy control cable (similar to rotor cable) 
that are fanned out at the radial ring...converge into the Cable jacket, 
cross the 10' blacktop driveway and then emerge from the jacket and fan out 
across the property.  The radials vary from 30' long to 100' long with three 
of them tying directly into the radial field of my 40m phased array.

The three-wire gamma cage is made of 14ga stranded wire and converges into a 
cone with a single brass bolt holding all three ring lugs together 1.5' off 
of the ground at the base.  An additional 14ga wire is also connected to the 
brass bolt and bolts to a porcelain feed through insulator that brings the 
feed into the metallic (STEEL) panel.  A 14ga wire then bolts to the other 
end of the feed thru insulator and taps onto the input of the Cardwell air 
variable capacitor.  The output of the capacitor connects to a SO 239 
connector that is mounted to a 2" copper strap that travels down the 
enclosure where two brass bolts bolt the strap to the bottom of the panel. 
Under the panel, where the brass bolts emerge from the panel, two 2" copper 
straps connect to the brass bolts and then travel to the copper radial ring 
where they are terminated.

Before the gamma cage I used a single 14ga wire dropped down from the gamma 
arm where it connected to the variable cap that was mounted outside my steel 
enclosure and sat on a plastic 5 gal pail.  The gamma wire connected to the 
variable cap and then it was wired to the same standoff insulator I 
mentioned above and into an empty steel panel where I had the same SO 239 
connector mounted to the copper strap and then to my grounding system.  This 
config netted me 41 + j0 ohms.

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'm eager to get back on the air tonight and tomorrow morning to see how it 
plays

73

Carl AG6X



-----Original Message-----
From: Carl [mailto:km1h at jeremy.mv.com]
Sent: Saturday, February 22, 2014 1:22 PM
To: Carl Braun
Subject: Re: Topband: Shunt feeding the Skyneedle - new developments


Subject: Re: Topband: Shunt feeding the Skyneedle - new developments


The measurements are being taken, and have been taken, at the same point
since the beginning of the antenna experiment.

**  How about refreshing my merory about those details Carl? Frequency also.
I wasnt involved in the early parts and deleted them already.


The ONLY difference is that the variable cap is now mounted inside the steel
panel as described in my previous posts, instead of outside the panel, as
described in previous posts.  Same length of wire each scenario.

I believe Tom W8JI called it when he stated that a change was likely when
the cap is enclosed in a metallic enclosure vs sitting on a 5 gal plastic
jug.

** No discussion needed there, thats been known for 100 years. It would also
help to be more specific when presenting details, what does metallic really
mean?

The Henry amp seems to be OK with a little reactance so I'm going to
concentrate on my gamma cage and radial system while waiting for RF Parts to
deliver some necessary connectors. Once I get the PL259s installed I can
replace my temp RG 58 jumper with the good stuff and then hit it with the
Henry. I've kept the power below 500w during the contest so as not to stress
the small coaxial cable.

** Good move.

Carl
KM1H


73

Carl

Sent from my iPhone

> On Feb 22, 2014, at 8:42 AM, "Carl" <km1h at jeremy.mv.com> wrote:
>
> I suppose I missed that part while doing things around here but this is
> the only pertinent info I can find from him. Nowhere does it say he has a
> 1:1 anywhere with the cap in the cabinet.  Granted some of the posts are
> very confusing as to where things are being measured.
>
>
> ----------------------------------------------------------
> 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.
>
> The swr at my given freq as tuned with the variable cap is 1.3:1 or
> less...outside the enclosure the system had 1.0:1 swr readings and X=O
> over what appeared to be a broader bandwidth...even with 42 ohms at the
> feed point.
> ---------------------------------------------------------- 
> So maybe you can explain where the 1.0 at the transmitter end with the cap
> in the box came from?
> Additionally the VSWR may/will change with added radials and ground
> moisture conditions.
>
> I'm going out for several hours so no rush on the answers.
>
> Carl
> KM1H
>
>
> ----- Original Message ----- From: "Charlie Cunningham"
> <charlie-cunningham at nc.rr.com>
> To: "'Carl'" <km1h at jeremy.mv.com>; "'Carl Braun'"
> <Carl.Braun at lairdtech.com>; "'160'" <topband at contesting.com>
> Sent: Saturday, February 22, 2014 11:03 AM
> Subject: RE: Topband: Shunt feeding the Skyneedle - new developments
>
>
> Well, I agree with all that, Carl. But Carl Braun, was reading "dead-flat"
> 1:1 at the transmitter end of his cable. I believe he is done!! The
> antenna
> Q is what it is! As for "improving his 2:1 VSWR bandwidth" he could reduce
> his radial field and increase his ground losses to improve his 2:1 "BW" -
> but I believe that to be self-defeating!! I'm not "missing your point" - I
> just don't see what you'd change to improve on a "flat" line! Carl is well
> past the point of "diminishing returns"!
>
> The math doesn't "lie"!
>
> Charlie, K4OTV
>
>
> -----Original Message-----
> From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of Carl
> Sent: Saturday, February 22, 2014 10:41 AM
> To: Charlie Cunningham; 'Carl Braun'; '160'
> Subject: Re: Topband: Shunt feeding the Skyneedle - new developments
>
> Charlie youre continually missing the point; ignore cable loss period.
>
> The only issue is what impedance does the amp see from lets say 1800 to
> 1900
>
> KHz? AND can the amp load into it without a problem at full power? This is
> a
>
> system issue, not just what is measured at the antenna and needs to be
> addressed that way.
>
> Put all that info into your program and post the results. Saying that a
> 1.3
> VSWR at reasonance at the antenna is sufficient is too simplistic. Compute
> the VSWR at the amp with whatever length of coax is actually used over the
> lower 100 KHz with a range of " at resonance" VSWR's.
>
> Carl
> KM1H
>
>
> ----- Original Message ----- From: "Charlie Cunningham"
> <charlie-cunningham at nc.rr.com>
> To: "'Carl'" <km1h at jeremy.mv.com>; "'Carl Braun'"
> <Carl.Braun at lairdtech.com>; "'160'" <topband at contesting.com>
> Sent: Saturday, February 22, 2014 9:57 AM
> Subject: RE: Topband: Shunt feeding the Skyneedle - new developments
>
>
> Well, Carl the looses in 70' or even 200' of LMR-400 are so low at 1.8
> MHz,
> even at 2.0:1 or 3.0 :1, if he can match it at the transmitter  end of the
> line, it really doesn't matter!
>
> Charlie, K4OTV
>
> -----Original Message-----
> From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of Carl
> Sent: Saturday, February 22, 2014 9:46 AM
> To: Charlie Cunningham; 'Carl Braun'; '160'
> Subject: Re: Topband: Shunt feeding the Skyneedle - new developments
>
> That 1.3 is only at ONE frequency Charlie, he is not crystal controlled.
> What is the 2:1 bandwidth at the amp?
>
> Carl
> KM1H
>
>
> ----- Original Message ----- From: "Charlie Cunningham"
> <charlie-cunningham at nc.rr.com>
> To: "'Carl'" <km1h at jeremy.mv.com>; "'Carl Braun'"
> <Carl.Braun at lairdtech.com>; "'160'" <topband at contesting.com>
> Sent: Saturday, February 22, 2014 9:23 AM
> Subject: RE: Topband: Shunt feeding the Skyneedle - new developments
>
>
> I don't expect that ANY of those are valid concerns at 1.3:1 VSWR!!
>
> -----Original Message-----
> From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of Carl
> Sent: Saturday, February 22, 2014 9:14 AM
> To: Charlie Cunningham; 'Carl Braun'; '160'
> Subject: Re: Topband: Shunt feeding the Skyneedle - new developments
>
> Im not concerned by what is measured at the matching unit or a miniscule
> cable loss; just what is transformed back to the amp and its ability to
> load
>
> at full power without arcing, running out of or having too much fixed
> padder
>
> C during QSY's. Contests do not stay just in the narrow CW 50 KHz
> "window"
> and not having to use an external tuner is a big plus.
>
> Ive always modified my amps to work with my antennas on 160 and 80/75.
>
> Carl
> KM1H
>
>
> ----- Original Message ----- From: "Charlie Cunningham"
> <charlie-cunningham at nc.rr.com>
> To: "'ZR'" <zr at jeremy.mv.com>; "'Carl Braun'" <Carl.Braun at lairdtech.com>;
> "'160'" <topband at contesting.com>
> Sent: Friday, February 21, 2014 10:35 PM
> Subject: Re: Topband: Shunt feeding the Skyneedle - new developments
>
>
> Well, if I recall correctly, Carl, Carl said his  feedline was about 70'
> of
> LMR-400, so even at 2 2:1 or 2.5:1 VSWR, the excess losses in 70' of
> LMR-400
> at 1.8 MHz are almost 0, so if he can match it OK at the transmitter end
> of
> the line- no real point in making heroic efforts to achieve a "perfect"
> match!  He'd gain more by working on his radial field, and he really
> should
> do that before doing any more tuning because improving the radials WILL
> affect the antenna impedance.
>
> 73,
> Charlie, K4OTV
>
> -----Original Message-----
> From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of ZR
> Sent: Friday, February 21, 2014 10:11 PM
> To: Charlie Cunningham; 'Carl Braun'; '160'
> Subject: Re: Topband: Shunt feeding the Skyneedle - new developments
>
> 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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