Re: 43' Vertical and the K2 tuner

Posted by Joe Subich, W4TV-4 on Mar 15, 2009; 8:07pm
URL: http://elecraft.85.s1.nabble.com/43-Vertical-and-the-K2-tuner-tp2481408p2482682.html


Paul,

> According to the author, the so-called "magic" of the 43-foot
> length is that radiation resistance remains quite high across
> the HF spectrum and thus, system losses are minimized.

Unfortunately, that information is demonstrably wrong.  The
radiation resistance varies from very low on 160 to modest values
on 10 meters.  The feedpoint IMPEDANCE (complex) remains high
across all of the amateur bands because except for 10 meters
where the antenna is approximately 5 quarter wave long the
antenna is not resonant (+/- j0) on any band.  

The mistake of equating feed impedance with radiation resistance
is one of the issues that erroneously result in claims of
greater efficiency for folded monopoles on 80 and 160 meters.  

The 43' vertical is simply a convenient length to feed in
that it does not present a high feed impedance on any amateur
band (although it is highly reactive with a low real part
on 80 and 160).  One would be far better with a 58' (80 - 30
meters) or 88' (160 - 40 meters) vertical with matching in
the form of switched networks or an auto tuner at the base
than with the "magic" 43' vertical fed with 50 Ohm coax
and tuner in the shack.

73,

   ... Joe, W4TV
 

> -----Original Message-----
> From: [hidden email]
> [mailto:[hidden email]] On Behalf Of Paul
> Christensen
> Sent: Sunday, March 15, 2009 10:08 AM
> To: Steve Ellington; [hidden email]
> Subject: Re: [Elecraft] 43' Vertical and the K2 tuner
>
>
> > The 43' vertical is recent fad and it makes no sense at
> all. Virtually
> > any trapped multiband vertical should easily outperform it.
>
> Steve,
>
> I thought the same until I read this:
>
> http://vk1od.net/antenna/multibandunloadedvertical/
>
> According to the author, the so-called "magic" of the 43-foot
> length is that
> radiation resistance remains quite high across the HF
> spectrum and thus,
> system losses are minimized.  Compared to a 33-foot vertical,
> system losses
> are much lower across the spectrum.
>
> But to your point, a trapped multi-band vertical can offer similar
> performance.  Personally, I think the negativity associated
> with trap loss
> in multi-band antennas is grossly overblown.  Other
> systematic losses mask
> what little loss exists in most trapped antenna designs.
>
> Anyway, not sure how valid all this data really is, but the
> data presented
> is interesting
>
> Paul, W9AC
>
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