Topband: Low Dipoles

[Dave Cuthbert]

The radiation pattern plot shows the dipole end on. Rotate azimuth 90
degrees and the two antennas show the same gain at 30 deg elevation.

    Dave KH6AQ

On Fri, Dec 11, 2020 at 10:51 AM VE6WZ_Steve <ve6wz at shaw.ca> wrote:

> I know this thread has gone on-and-on-and on, but I felt I needed to add
> to the discussion.
>
> Regarding Roger G3YRO's 50 years of TB experience using a low dipole, I
> feel I need to support his observation from the DX side.
>
> This winter season since August I have had 56 QSOs with the UK, and worked
> 21 unique G callsigns. (Total this season is 775 EU QSOs)
> The top 3 UK repeat QSOs are:
>
> G3PQA 12 QSOs
> G3YRO 10 QSOs
> G4UFK 7 QSOs
>
> The truth is, I have heard Roger many more times than we have QSO’d since
> he seems to have a challenging RX location.
>
> Now, just working DX is not proof of good performance, BUT the FACT is
> Roger usually has a signal as good or better that the any of the other
> regular UK operators.
> This would seem to agree with his RBN observations.  I am also aware that
> these “QSO totals” could be just a function of Rogers activity, but I have
> listened to Rogers signal **at the same time** as other UK and EU are QRV,
> and he is as good as the rest.
>
> I love to build antennas and I do a lot of modelling.  I know exactly what
> the zenith and AZ plot a dipole at 50 feet looks like compared to a
> vertical antenna.  On paper it looks like the worst antenna possible for
> DX.  I am also aware of the concept that even though the dipole has a lot
> of energy radiated straight up, there is still some at lower angles.
> However, the gain from the low dipole compared to a vertical at these lower
> angles will still contradict what I copy from Roger.  Rogers signal
> “should” be much diminished compared to others in the UK (or anywhere in
> EU)  that are using vertically polarized radiators.
>
> Here is a screen shot from 4NEC2 showing a dipole at 50 feet overlaid with
> a vertical over average ground. (2.1 dBi).
>
> https://drive.google.com/file/d/1Rdu94dVqrZQeYOa8KSJjM8MdSin63Pfj/view?usp=sharing
> <
> https://drive.google.com/file/d/1Rdu94dVqrZQeYOa8KSJjM8MdSin63Pfj/view?usp=sharing
> >
> At best Rogers dipole should be a great vertical iono-sound for testing
> the ionosphere!  At a 30 deg wave angle the vertical has an 8.5 dB
> advantage !  That is a big number.
>
> So, I have fair-good copy on Roger one Wednesday night :-) while he is
> CQing with his dipole, and then he switches to a newly installed vertical.
> If indeed his signal bumped by 8.5 dB I think that would be pretty
> spectacular, and he would then be eclipsing the biggest signals out of EU.
> His RBN skimmer spots would also jump by 8.5 dB !?. He would probably be
> spotted by double the skimmers in NA too.
> In no way do I doubt what the modelling is showing us, but there is
> something else going on here.
>
> This really is an interesting study.
> Perhaps our propagation assumption about low-angle dominating is wrong?
> As Roger said and I can attest, most of my copy and QSOs have NOT been at
> his or my SR or SS.
>
> Roger, do you have a common mode choke on your dipole feed line?  If your
> feed line is radiating could it be emulating a vertical?
>
> 73, de steve ve6wz
>
> _________________
> Searchable Archives: http://www.contesting.com/_topband - Topband
> Reflector
>