Hi Carl and top-band lovers
I would like to mention Chapter 7.6 as well, polarization matching, and also
7.7 Fading. I started developing my HWF early 2009 and I think there is no
more to squeeze from it.
Here some update in respect of polarization on 160m. It is a game!, vertical
and horizontal field changes all the time, an elliptic can describe better
the waves on 160m. My last HWF tuning gave me another 6-8 db improvement on
the signal noise ratio. The HWF is really an "all directions noise
cancelling antenna ( Va-Vb=0)", the goal is maximum attenuation on the
vertical field an good directivity on the horizontal field. The takeoff
angle is always the same and does not change with the height above ground
,it always very close to 40 degree. It is alike high horizontal dipole that
takeoff change with the height from ground. The HWF has a deep null from
high angle signals at any height above ground.
The game is maximum attention on the vertical signal because most of the
manmade noise, power line noise, city noise propagate with vertical
polarization due the proximity with the ground for 160m waves. For 160m the
HWF needs to be over 100 ft. to perform well on the horizontal signals, 50
ft. is ok for 80m and up. The HWF works 160m to 30m with excellent
performance depending on the area of the loops. The HWF gain is around -43
db, and the vertical attenuation can be adjusted to deep another -50db, the
total attenuation front and back is > -90 db , It has a front null and a
back null for vertical signals.
This is a weak, weak, weak signal system implementation, very complex by
nature by receiving near the receiver noise floor most of the time.
Depending on the direction of the wave the H/V ratio can be -20 db or more
both ways, most of the time the vertical component is 10 to 20 db stronger
than the horizontal component. When you combine the 4 variables, vertical
gain, horizontal gain, vertical noise QRM and the signal H/V ratio you have
your final signal to noise ratio, however on top of that you need to add the
propagation noise as well.
Another dependence is the solar cycle. We are at the peak of the solar cycle
and the propagation this year has been very different . Long pass is peaking
at the SS or SR and the signals from North are showing a strong horizontal
component. or it could be just coincidence, just time will tell.
Nowadays I can copy better weak signals with my HWV than my VWF in all
directions. I just observed that recently with 8Q7BM, NH0Z,V63DX,4J6RO,
4K6FO and 4L5O, signals from NNW and NNE better on HWF. It is the first time
I can hear better signals coming North with the HWF. It is all about signal
noise ratio.
For long path the new adjust also helped a lot. I detuned the TX tower to
minimum noise on the HWF, making the diagram symmetrical on the polar plot.
It looks like a butterfly for local vertical signals. Peter HS0ZKX is coming
strong from SSW every 28 days. Just after the solstice last month the long
path propagation was just fantastic. WV8. H40,RA0. JA. BA. BG and DU7 copy
with Q5 from SSW from Dec 25th to Jan 1st , but few QSO's. only JA and DU7
on the log. FT5ZM only on the HWF as well.
I agree with Carl. There hasn't been much work in polarization field on
160m, however It is a fascinate subject. Come on in folks!
Regards
JCarlos
N4IS
-----Original Message-----
From: Topband [mailto:topband-bounces@contesting.com] On Behalf Of Carl
Luetzelschwab
Sent: Monday, February 03, 2014 12:17 PM
To: topband@contesting.com
Subject: Topband: circular polarization on 160m
I hope everyone has had a chance to work FT5ZM on topband.
With respect to circular polarization on our HF bands (3.5 - 28 MHz) and on
6m, theory says both the ordinary and extraordinary waves propagate thru the
ionosphere with pretty much equal ionospheric absorption. Thus circularly
polarized antennas can provide an advantage. Some of the real-world examples
I'm aware of have been documented by G2HCG on 10m (in the old Communications
Quarterly), by the original K6CT on 20m (in the RSGB Bulletin) and by WA3WDR
on 75m (a web paper). I'm sure there are others out there, too.
On 160m, theory says the extraordinary wave incurs much more ionospheric
absorption (more heavily attenuated) due to 1.8 MHz being so close to the
electron-gyro frequency. Thus in theory only the ordinary wave is useful on
160m, which says circular polarization wouldn't do any good.
Now things happen on 160m in the real-world that we simply don't understand.
For example, an ordinary wave can excite an extraordinary wave under certain
ionospheric conditions (if you'd like to read more, curl up in a warm place
on a cold night with Chapter 3 in Ionospheric Radio by Kenneth Davies).
Could this be happening? I don't think we can rule it out.
In my opinion based on all the reports on this reflector over the years, it
seems to me that having selectable elevation angles is more important than
polarization. But I also admit that there hasn't been much work in the
polarization field (no pun intended) on 160m (except for N4IS with his
horizontal Waller flag - which makes sense with theory for roughly East-West
propagation close to the geomagnetic equator).
Carl K9LA
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