Stan,
Interesting. I did a quick EZNEC plot of the pattern of a 44' doublet (close to a full
wavelength) at 30' on 18.07 MHz and didn't see any deep nulls in the horizontal pattern.
But in the direction of Italy from NY it is down about 5 dB from the maximum gain in the
E-W direction. I recently modeled the 'cobweb' antenna, which is a 'square' dipole similar
to the Omni-angle configuration; it had a maximum gain of about 2 dB less than a dipole
and would be down an additional 1.4 db in the direction of Italy.
So my guess is that about only 1.6 dB of the difference between the dipole and the
Omni-angle antenna came from the patterns. The rest could be attributed to the location of
the doublet in the attic and the dropped ends (I didn't model this, but I suspect it has
an effect).
On 9/26/2013 11:46 AM, stan levandowski wrote:
Hi Vic. My 44' doublet is in my attic, arranged as a flat top for 24' and then
drooping
straight down at both ends. The antenna is almost exactly 30' above the earth.
It is fed
with 14' of 450 ohm ladder line straight down through a slit in my ceiling and
into a
linen closet where it meets up with an SG237 autocoupler. This keeps the
autocoupler out
of the winter cold and summer heat of the attic. From there I have a run of nice
"clean"
50 ohm coax to my second story "shack" This attic doublet arrangement is
nearly 4 years
old and has served me exceedingly well on 40 through 10 meters, inclusive. I
only run 5
watts CW at all times simply because I love QRP and I love CW and it's my
"thing." The
frequency agility of the doublet/autocoupler combination has been wonderful
because those
of us in restrictive environments usually don't have room for more than one,
possibly two
"good" antennas. I have a very RF friendly attic in terms of no foil
insulation, no HVAC,
only PVC plumbing stacks, etc. Of course, there is some attenuation but at HF
I believe
(from what I've been able to research) that this attenuation is frequently
overstated
and often considered to be far worse than what it really is. In my experience,
the
"worst" penalties that follow an attic (or any indoor) installation - RF
exposure
notwithstanding - are skewed radiation pattern and "house noise."
i
By comparison, the Omni Angle when this video was made was at 27' - 3' lower
than the
doublet's flat top section. That was 15' above the lower deck + 12' up on the
Jackite.
The Omni Angle was "facing" E-W in the sense that the "front" wire portion was
pointing in
that direction; the attic doublet was pointing in the same E-W direction. Of
course, we
can all agree, I'm sure, that this information doesn't help all that much in
comparing
these two antennas because the drooped attic doublet had some vertical
component and most
assuredly some skew in its pattern + as another Lister pointed out, on 17M
there are lobes
on the doublet.
But here's what I think is important to know: For those of us (and we're
probably an
increasing number in today's world) who can't enjoy "antenna freedom" this Omni
Angle
represents another option and a darn good one from my experience of the last 3
weeks. In
my case, it fits the footprint of my deck. I can put it up on my 31' jackite
to about the
25' + 15' for the upper deck gives me 40' of height, clear of my roof line, and
away from
the attic "house noise."
My attic doublet is my overall favorite antenna and out of the weather and is
always ready
for me. It's earned me DXCC at the QRP level, QRP WAC, and I've worked all
states too.
It's gotten me to Japan from NY on 5 watts more than once. But this Omni Angle
also got
me to Tokyo on 5 watts just last week. So, based on my experience, the Omni
Angle is a
competitive antenna for a restrictive home QTH, for portable work and, in my
case, for
"stationary mobile" where I drive to a scenic rest stop, drop a fiberglass pole
into my
hombrew mount on my VW Bug, hoist an antenna that's significantly better than a
Hamstick,
and enjoy ham radio.
Hope this helps to answer your questions, Vic, as well as those of other
Listers with
antenna restrictions.
73, Stan WB2LQF
On Thu, Sep 26, 2013 at 12:33 PM, Vic K2VCO wrote:
> How high was the 44' doublet?
How was it oriented compared to the Omni Angle antenna?
Is the doublet in inverted V or horizontal configuration?
I am finding this interesting because I am soon moving to an antenna-restricted
location.
On 9/26/2013 6:57 AM, stan levandowski wrote:
About 3 weeks ago, I learned about a new "miracle antenna" - I usually
dismiss such
nonsense because there *is* no miracle antenna. However, the person who
informed me is a
trusted, capable, educated ham and DXpeditioner who is not easily impressed.
I still don't believe in "miracles" but this 2.5 lb, 7 by 4 foot, easy up/easy
down, no
tools required, easy-to-tune $99 new product by Dale Parfitt [designer of the
PAR End
FedZ series] offers a realistic alternative to those with severe antenna
restrictions,
attic installations, SOTA needs, and so on. It is easily mounted on a Jackite
or similar
fiberglass pole. Just put it on and slide it down until it's a good friction
fit.
The antenna is resonant for a single band ( choose: 20, 17, 15, 12, 10 or 6) and
additional matchboxes can be purchased for around $25 each.
I bought the 17 meter version and in two weeks of non-scientific, casual A/B
testing
against my 44' doublet, the Omni Angle has been equal or better on receive the
majority of
times and about the same on transmit. On receive it seems notaby less noisy
than my
doublet. It is horizontally polarized.
I don't want to create an antenna controversy here on proper antenna testing
techniques --
I seem to have a flair for doing that -- ;)
But I do want to pass along info on this new product which might be very useful
to those
of us who have to live with antenna restrictions or who need options for
effective
portable operations.
Here is a short Youtube video I cobbled together to demonstrate my 17 meter PAR
Omni
Angle.
http://www.youtube.com/watch?v=JGTq4zVAW_w
73, Stan WB2LQF
--
Vic, K2VCO
Fresno CA
http://www.qsl.net/k2vco/
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