All good points, Ken.
Before I comment, I want to underline that Jim Brown's paper on verticals is
the single most useful document about verticals on the planet. There are
other great sources of information, but Jim sums it up pretty well in a
single (long) document.
Now to Ken,
Indeed the first point is important: "Works"
As we all know, "everything works." Dummy loads, light bulbs, bedsprings,
etc.
In most cases, the fundamental reason an OM considers the vertical for the
high bands is because he does not have the ability/space/funds to put up a
tower and beam.
For the low bands the reason most people resort to these is "space". The
second reason is to keep a low profile in order to keep the neighbors (and
XYL) happy.
I personally define "works" on a case by case basis compared to what else
one could do with similar space and funding.
In small back yards, typically the size of half of a basketball court, our
options are not so good. This is what most hams seem to have available
these days.
HOAs present further challenges.
The antenna I describe on the web page that Al pointed out is used by many
OM operating under these condx. It can be raised and lowered by one man in
one minute and does not require radials. Put it up when needed, take it
down when finished.
"Operating under the assumption of modern city yard", the vertical dipole
works very good when over average soil. Especially on 80 or 40m, when
compared to many alternatives I see people using, for instance a Buddipole
up 8 to 10 ft. in the air, or an Outbacker mobile whip sitting on the ground
with a bunch of radials, this vertical dipole works OUTSTANDING. I also
prefer it to the common 43' non-resonant vertical for multiple reasons.
If there are houses all around it and nearby, don't expect much from this or
any antenna unless you can raise it high up above the obstacles.
As Steven pointed out, he was considering "working DX".
It is always important to state what the goal is; DX, NVIS, both.
On the higher bands it may be long haul DX but it might also be short skip
across the US.
On 40m it might be DX but might also be NVIS.
If DX, then I would stick with this vertical dipole.
If NVIS on 40, I would add two side spreaders, making a 40m vertical dipole
that has been folded into a quad loop, open at the far end. (Like a Cobweb
antenna, but mounted vertically). A 4:1 transformer (i.e. a balun used
backwards) will give a good match to 50 Ohms and you have a great performing
low space 40m NVIS antenna.
Ken's point no. 3 is also very important. Ground losses are always
important, but two things I want to stress. First, the VD is favored by
people who for one reason or another cannot put down a lot of radials. If
you are renting, your landlord most likely won't be pleased with the idea of
radials. Second, as I have already stated, the ground loss of the VD due to
not having radials is nowhere near that of the quarter-wave vertical. Even
without the radials, the VD works very well as I will show below.
In my description of the vertical dipole on my web, I stress making sure
the bottom of the antenna is at least 18 to 24 inches off the ground. That
is bare minimum! It is what I use for portable use. When I ran this
antenna at home for about 6 years, I raised the entire VD 10 ft. into the
air, so that the bottom end of the vertical was 10 ft. off the ground. A
quarter wavelength off the ground would be better but impractical on 40m.
I have run some very short tests on the effect of the height above ground.
I compared to my horizontal 40m dipole (as base antenna) to VD almost on the
ground, then 2 ft. up, then 6 ft. up, and finally 10 ft. up. As you
approach the ground with the base, the signal strength drops noticeably. I
made no attempt to measure it exactly, I just watched received S-Meter
readings. Lesson learned. Make it as high as you can.
Finally to "works". I will give two examples of my experience using this
antenna on 80 and 40m where I compared it to two other antennas, mostly on
receive.
About 10 or 12 years ago I spent a large part of the CQWW DX CW contest
comparing 3 antennas on 80m and the CQWW DX SSB contest comparing on 40m.
The base was my 80/40m dipole, 40 ft. in the air and strung such that it
favored Stateside. The other two were my 2x 6m long "VD" with its base 10
ft. in the air and also an 80m EH antenna mounted 30 ft. in the air, just 12
ft. away from the house. Of course I swapped the 80m EH for a 40m EH when I
ran the 40m test.
The test was simple. Record the received RST signal strength on all 3
antennas for as many QSOs as possible.
The 80m results are posted here:
http://www.dj0ip.de/antenna-tests/80m-eh-antenna/
Keep in mind that the received signal strength is recorded in the "Sent"
columns.
The columns marked "Received" are the RST report he sent me.
The 40m test is reported here:
http://www.dj0ip.de/antenna-tests/40m-eh-antenna/
I refuse to even discuss the EH antenna here on this reflector. It has been
discussed to death 10 years ago. You can see a picture of its installation
close to the house, and read the short except from the log. I logged the
contest on computer. The paper log shown here was in addition to the
computer log.
AND A FINAL COMMENT ON "WORKED"
The year 2000 was a sunspot maximum.
Although I already held the All-Time High Score record for CQWW CW for
Liechtenstein (Single Op, High Power, Assisted), I was determined to break
it again.
I returned to Liechtenstein and spent 2 days outside in the freezing snow,
wind and ice, installing antennas.
My 3 antennas were:
>> Vertical Dipole (base about 2 ft. off the ground)
>> Horizontal 80m Dipole fed with openwire and matched with an Annecke
Symmetrical tuner.
>> 160m OCFD
Results: I set a new all time highest score (ever) record for HB0 in the
CQWW CW contest. THAT RECORD STILL STANDS TODAY.
You may ask how it is possible to set all time records using just wires.
The answer is "weather". Liechtenstein is located high up in the Swiss Alps
and the WX at the end of November is harsh. Nobody else has been foolish
enough to go up there, build better antennas, and break my record.
This Vertical Dipole is not the greatest thing since sliced bread but it is
perhaps the best kept secret for people who are very short on space, but
wish to work all bands.
The MJF-974B shown in the picture is what I generally use. The Johnson
Viking Matchbox has better efficiency, but does not have nearly as wide of
matching range as the 974B. This means you don't need to adjust feedline
lengths as often using the 974B as you do with the JV Matchbox.
In "Bangs per Buck", it's hard to beat this antenna.
73 - Rick, DJ0IP
(Nr. Frankfurt, Germany)
-----Original Message-----
From: TenTec [mailto:tentec-bounces@contesting.com] On Behalf Of
rick@dj0ip.de
Sent: Sunday, January 10, 2016 8:52 AM
To: 'Discussion of Ten-Tec Equipment'
Subject: Re: [TenTec] INFORMATION ABOUT VERTICAL ANTENNAS
Ken can read emails but not post.
He brings up some good points which I concur with.
I will copy his text below.
73 - Rick, DJ0IP
(Nr. Frankfurt, Germany)
====================================================
Hi Rick,
Again I cannot participate in the reflector because I am using webmail and
the reflector does not recognize me as a registered participant.
Regarding your comment about verticals working without radials. You are
correct, but there are some important details that should be pointed out:
1) Depends what you mean by "works." We all know people can make QSOs using
a light bulb or a poorly shielded dummy load, and have a really good SWR. It
works, but the efficiency is poor.
2) Yes there are vertical designs, such as center fed vertical dipoles which
are much less lossy than an end fed monopole without radials.
3) Any antenna that is close to the ground induces currents in the ground.
If the ground is resistive, these currents heat the ground, instead of
contributing to a stronger signal. Even an antenna which is fairly efficient
(such as a center fed vertical dipole) without radials can benefit from
radials, because the radials will reduce resistive losses in the ground. If
the antenna was tuned for a good SWR without the radials, and then the
radials are added, the impedance will change and without retuning one could
(incorrectly) conclude that the radials made the antenna worse. If properly
tuned the vertical with radials will be more efficient.
4) Antennas with very little resistive losses tend to have sharper
resonances. (Unless they are special wideband antennas such as discones,
conical dipoles, log periodics). The wider low SWR curve of a lossy antenna
is often misinterpreted to be "better" than a more efficient antenna with a
narrower low SWR curve.
A large proportion of the hams using verticals cannot get the vertical very
high off the ground, or their rooftop, so there will be significant ground
losses without radials, even if it can be tuned to give a low SWR.
Wish I could post that. You may if you care to.
Cheers, Ken N6KB
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