Several topbanders have had both horizontal dipoles at various heights
-- including both very low and very high -- and high performing vertical
antennas that we could compare on the air in real time.
While there are always isolated cases when horizontal antennas
might be the best transmitting antenna, in my experience they're
isolated cases, usually occurring near sunrise.
I long ago removed my 160 meter horizontal transmitting antennas
and never regretted it...
73
Frank
W3LPL
----- Original Message -----
From: "VE6WZ_Steve" <ve6wz@shaw.ca>
To: "topband" <topband@contesting.com>
Sent: Friday, December 11, 2020 8:51:19 PM
Subject: Topband: Low Dipoles
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
_________________
Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
|