2003 ARRL International DX Contest (Phone)
03/20/2003 |
K3DI
To all who observed strange 10-meter propagation in the ARRL SSB DX contest February 28-March 2.
I would greatly appreciate hearing from you so that more information can be obtained and more can be learned.
Please e-mail your observations to me at Fred595@yahoo.com
Tnx es 73,
Fred, W3ICM
The following message was sent to Dr. William Kissick, who has a PhD specializing in ionospheric propagation research.
Dear Dr. Kissick,
I was operating 10 meters at K3DI near Baltimore over the Feb 28-March 2 weekend in the ARRL DX contest.
On both Saturday and Sunday mornings and early afternoons, the strength of the European signals on 10 meters was peaking with our antenna (7 elements on 10 meters) pointed to around 100-110 degress rather than the usual 20-50 degrees. We were getting stronger signals from Europe when beaming towards central Africa!
The strange propagation was most noticeable when I was attempting to work a station in Latvia, whose signal should have peaked at 27 degrees. He had a big pileup, but I worked him easily with the beam pointed to 105 degrees. His signal strength increased noticeably when I pointed the beam to 105 degrees.
Several times during the contest, European stations asked what my beam
heading was...there is no time for much discussion during contests, so I didn't ask why they were asking. I now wish that I had discussed their inquiry, but there just wasn't time during the contest.
Another station in the area, N8II, Jeff, in the West Virginia panhandle region, also reported that he had had to swing his beam in several directions to get peak signals from Europe.
From your HF propagation experiences, to what do you attribute this
strange propagation phenomena?
73,
Fred Matos
W3ICM
Fred:
This is unusual; but possible. It seems that you have the main beam aimed about 70 degrees or so off the great circle path towards the equator. That is a lot, but there are two phenomena that could conspire to make this happen. They are:
1. If the propagation path through the ionosphere is complicated (and at times it is), for example: xmtr to the upper F-region, then refracted down to the upper edge of the E-region (assuming some strong sporadic E development usually only after a solar flare and during daytime), then back up to the lower F-region..., then down to the E-region, maybe right through it this time. The point is one can get a "secondary" reflection within the ionosphere upward. And, as you can imagine, there will be some lateral structure of electron density thus one can get an "off-the-great-circle" reflection here. This stuff is more likely at the higher frequencies like you were using.
2. If the above is happening, there are some other effects that may occur. Maybe the phase front (electric field vector or magnetic field vector) of the wave is not perpendicular to the direction of propagation. This can only occur if two components of the same wave are reaching you at "almost" the same time. The composite is not a plane wave therefore the gain pattern of the antenna is not the same as for a plane wave (it could develop a notch in the middle of the main beam and max gain would off boresight). This phenomena would probably only occur if there is some rather complicated reflection mechanisms as described above and the ordinary and extraordinary (circularly polarized but opposite) components of the original (linearly polarized) signal arrive at the receiver at "almost" the same time. Note that these are likely coming from near the great circle path, but the antenna is behaving funny due to the non-perpendicular phase
front.
Thanks for describing your experience to me. This is very interesting and I feel like I am stretching things a bit with the above explanation but these things can happen. Assuming your gain pattern is not distorted by other conductors near the antenna, which would always be there, it must be that enigmatic ionosphere. Finally, you report that the Europeans were asking about antenna pointing. That seems to imply that this was really the ionosphere doing something. I think it is quite rare. Please tell me if it happens again.
As a footnote, about two weeks ago I turned on the old HF receiver and was amazed. It has been many decades since I heard such amazing propagation. Signals from all directions were very stable and very strong...from 80 meters all the way up to 20 meters. And, for whatever reason, the 'spherics were very quiet. I think that was Feb. 15.
73's
Bill
Dr. William A. Kissick, Chief
Spectrum and Propagation Measurements Division
Institute for Telecommunication Sciences
National Telecommunications and Information Administration
325 Broadway
Boulder, Colorado 80305-3337 -- W3ICM
I would greatly appreciate hearing from you so that more information can be obtained and more can be learned.
Please e-mail your observations to me at Fred595@yahoo.com
Tnx es 73,
Fred, W3ICM
The following message was sent to Dr. William Kissick, who has a PhD specializing in ionospheric propagation research.
Dear Dr. Kissick,
I was operating 10 meters at K3DI near Baltimore over the Feb 28-March 2 weekend in the ARRL DX contest.
On both Saturday and Sunday mornings and early afternoons, the strength of the European signals on 10 meters was peaking with our antenna (7 elements on 10 meters) pointed to around 100-110 degress rather than the usual 20-50 degrees. We were getting stronger signals from Europe when beaming towards central Africa!
The strange propagation was most noticeable when I was attempting to work a station in Latvia, whose signal should have peaked at 27 degrees. He had a big pileup, but I worked him easily with the beam pointed to 105 degrees. His signal strength increased noticeably when I pointed the beam to 105 degrees.
Several times during the contest, European stations asked what my beam
heading was...there is no time for much discussion during contests, so I didn't ask why they were asking. I now wish that I had discussed their inquiry, but there just wasn't time during the contest.
Another station in the area, N8II, Jeff, in the West Virginia panhandle region, also reported that he had had to swing his beam in several directions to get peak signals from Europe.
From your HF propagation experiences, to what do you attribute this
strange propagation phenomena?
73,
Fred Matos
W3ICM
Fred:
This is unusual; but possible. It seems that you have the main beam aimed about 70 degrees or so off the great circle path towards the equator. That is a lot, but there are two phenomena that could conspire to make this happen. They are:
1. If the propagation path through the ionosphere is complicated (and at times it is), for example: xmtr to the upper F-region, then refracted down to the upper edge of the E-region (assuming some strong sporadic E development usually only after a solar flare and during daytime), then back up to the lower F-region..., then down to the E-region, maybe right through it this time. The point is one can get a "secondary" reflection within the ionosphere upward. And, as you can imagine, there will be some lateral structure of electron density thus one can get an "off-the-great-circle" reflection here. This stuff is more likely at the higher frequencies like you were using.
2. If the above is happening, there are some other effects that may occur. Maybe the phase front (electric field vector or magnetic field vector) of the wave is not perpendicular to the direction of propagation. This can only occur if two components of the same wave are reaching you at "almost" the same time. The composite is not a plane wave therefore the gain pattern of the antenna is not the same as for a plane wave (it could develop a notch in the middle of the main beam and max gain would off boresight). This phenomena would probably only occur if there is some rather complicated reflection mechanisms as described above and the ordinary and extraordinary (circularly polarized but opposite) components of the original (linearly polarized) signal arrive at the receiver at "almost" the same time. Note that these are likely coming from near the great circle path, but the antenna is behaving funny due to the non-perpendicular phase
front.
Thanks for describing your experience to me. This is very interesting and I feel like I am stretching things a bit with the above explanation but these things can happen. Assuming your gain pattern is not distorted by other conductors near the antenna, which would always be there, it must be that enigmatic ionosphere. Finally, you report that the Europeans were asking about antenna pointing. That seems to imply that this was really the ionosphere doing something. I think it is quite rare. Please tell me if it happens again.
As a footnote, about two weeks ago I turned on the old HF receiver and was amazed. It has been many decades since I heard such amazing propagation. Signals from all directions were very stable and very strong...from 80 meters all the way up to 20 meters. And, for whatever reason, the 'spherics were very quiet. I think that was Feb. 15.
73's
Bill
Dr. William A. Kissick, Chief
Spectrum and Propagation Measurements Division
Institute for Telecommunication Sciences
National Telecommunications and Information Administration
325 Broadway
Boulder, Colorado 80305-3337 -- W3ICM
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