Topband: Shunt feeding the Skyneedle - new developments

[Charlie Cunningham]

Wel, I agree with all of that, Roger.  I plotted Carl's 45-j11 load on a 50
ohm Smith Chart, and it's right near the origin of the chart on a 1.3:1 VSWR
circle. I'd need some more data points at some other frequencies to plot to
get a better picture of what's going on, But his VSWR is so low that the
losses in 70' of LMR-400 on 160 are completely negligible!  As long as he
can match it at the transmitter end - no problem! And at one point, he was
measuring "dead-flat" 1:1at the tranmitterend of the cable. His Henry amp
should handle that just fine without a tuner!

73,
Charlie, K4OTV

-----Original Message-----
From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of Roger D
Johnson
Sent: Saturday, February 22, 2014 11:16 AM
To: '160'
Subject: Re: Topband: Shunt feeding the Skyneedle - new developments

It may not be obvious but often you can get better bandwidth by NOT tuning
for 1:1 at the desired frequency! Those familiar with the Smith chart
probably already know this.

A narrow band antenna will produce a curve between a "U" and a "V" on the
Smith chart. If you tune for a 1:1 SWR, you bring the nose of the curve to
the center of the chart. This often leaves the "tails" outside the desired
SWR circle. If you continue until the nose goes to the opposite side of the
SWR circle, it brings more of the tails into the circle. The resulting SWR
curve is a "W" shape. It won't be 1:1 at any frequency but more of the curve
will lie within the chosen SWR circle.

73, Roger


On 2/22/2014 11:03 AM, Charlie Cunningham wrote:
> 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
>
>
>
>
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