[600MRG] Estimating Rr for non-confirming verticals

[Warren Ziegler]

Hi Ben,

   I have used my 162' dipole fed with ladder line as a top loaded vertical
with very good results on 137 and 472 kHz.
I short the ladder line together and run it to a coil, grounding the other
side of the coil and tapping the coil at the 50 ohm point.
I only used a cold water pipe as a ground. Made lots of good contacts
including ssb on 510kHz under an experimental license.
I was once copied in Germany running 250 watts on 137kHz in the DAYTIME!

I highly recommend using ladder line, I have made DX contacts on all bands
from 137kHz to 50 MHz using proper feeding and matching (I run it as a
dipole with a link coupled tuner on HF and 6m).

BTW, I have run ladder line for almost 30 years with no problems and
excellent results.

73 Warren K2ORS


On Fri, Jul 17, 2020 at 5:37 PM Ben Gelb <ben at gelbnet.com> wrote:

> Hi all -
>
> I decided to try feeding my HF dipole (ladder-line fed) as a vertical
> on 630m. I did so, and it works. But I'm wondering a bit about how
> best to estimate Rr, given that the ladder line feed is not actually
> vertical. The first 20 ft or so are close to vertical, followed by a
> roughly 40ft slanted section (45 degrees-ish, though not a straight
> line since it is not held taught - so it follows a catenary curve).
>
> Top load is 93.8'.
>
> That is what I mean by "non-conforming".
>
> So the question is how to reason about this antenna in service of Rr
> estimation.
>
> Since the whole antenna is pretty small relative to a wavelength,
> perhaps I can get pretty close by decomposing the antenna into its
> vertical and horizontal components? The vertical component (at least
> ignoring that the 45 degress section actually has a nonlinear shape)
> would basically be the height of the dipole feedpoint.
>
> The horizontal component of the ladderline section I imagine would add
> to the effective capacitance of the top loading from the dipole
> (though its more like "mid load" since its not at the top). Perhaps I
> can estimate the increase in effective *top* loading length by
> measuring apparent C of the antenna at the feedpoint - and backsolve
> the equivalent *conforming* T-top antenna (w/ save vertical component)
> that would yield that capacitance. Then use the Rr result for that
> antenna.
>
> Other thoughts?
>
> I could also learn how to use antenna modeling software. But sort of
> fun to try to think about how you might get there intuitively.
>
> 73,
> Ben N1VF
> ______________________________________________________________
> 600MRG mailing list
> Home: http://mailman.qth.net/mailman/listinfo/600mrg
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:600MRG at mailman.qth.net
>
> This list hosted by: https://www.qsl.net
> Please help support this email list: https://www.qsl.net/donate.html
>


-- 
73 Warren K2ORS
                WD2XGJ
                WD2XSH/23
                WE2XEB/2
                WE2XGR/1
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://mailman.qth.net/pipermail/600mrg/attachments/20200717/df33f1e9/attachment.html>