Acute Angle Skew on Es

During the period I was working on these pages I had an opening to the Gulf Coast on Es. Right in the middle of it I was called by W6OAL from DM79 Colorado, who was a rather weak but fully readable at 5/1 to 5/3. He was running 100 watts. I was running 1kw and had a better report. When I tried to swing the beam directly towards him in the attempt to bring up his signal, he disappeared completely. He reappeared when I returned the beam to the original heading. I could only hear him beaming towards south Alabama and Mississippi. He was beaming towards the same area I was. Dave writes:

I thought the beam heading was a bit south for MD (probably around 105). Now, TN and NC/SC stations were coming in where they should have been about 090. But, I played with the beam a bit during a couple of QSO's of yours before I finally called you. I am using a 6M7JHV (7 elements) at 75'. The AMSL altitude here is 6550' and the grid is DM79ql if you are doing some research on the E-clouds of July. You were the only station that far north that I worked yesterday (on 6M). We are 1500 miles apart so I would think our QSO was via double hop. But, another thing I noticed was that on occasion signals were stronger here (on the S-meter) using my 4 element Cubical Quad also at 75' than they were with the 7 element yagi. This tells me that there was a lot of low angle stuff coming in and this suggests (to me) single hop. Another thing that made me consider low angle was that we were getting a lot of polarization shift for whatever reason, w! as that stations I was working using verticals were equally as strong as those with horizontal beams. That doesn't really compute with the fact that the verticals are high angle radiators. Something strange was going on and I had no indication from NASA Space News that the Sun was acting up. It sure keeps us guessing doesn't it?

Considering Dave's observations, my guess is that ours was a double-hop event, with a reflection somewhere near the intersection of our respective beam paths. The time of the year, lack of solar activity at the time and the tonal qualities of the signals throughout the opening have convinced me there was no F2 involvement at all.

The fact that Dave was also hearing Tennessee, North Carolina and South Carolina stations on this indirect path may also imply the skip zone was a bit further to the North and East than the map indicates. W6OAL was copiable for me on every heading within the shaded angle on the east side of the map. However, all attempts to recieve a signal to the North or South of this zone were futile.

Aside from the skew itself, what our respective observations have in common is the reception of signals from Tennessee. Both of our paths crossed at least a part of that state directly, though for W6OAL even these signals were a bit skewed. North and South Carolina stations, which I could not hear but were on a direct path for me, were also skewed for W6OAL. Thus, the fact our paths directly crossed the Georgia, Alabama and Louisiana regions leads me to believe the scatter point was somewhere in this area.

Does it really matter? Given the contact was on Es, probably not, but then again it could help to predict how one could use known active Es clouds to intentially seek out similar contacts off the direct path. One may consider this type of contact to be a product of FAI, but I disagree. Field Aligned Irregularities are said to be marked by a sometimes extreme doppler shift, and also a TEP-like flutter. I did not notice such an effect here, and indeed have not with many other skew contacts I have had on Es. Instead, if not a simple reflection off an Es hotspot, these contacts can be explained as a form of Es side-scatter, where multipathing at the midpoint sends at least part of the signal off at an angle to be received by a station a suitable distance from the hotspot. In essence, an E layer version of F2 sidescatter.

This was the most acute-angled long distance Es skew QSO I have had thus far, presuming of course that the propagation followed the central or southern portion of the projected path. It is possible however that the the skew occurred along the northern edge of the projection, and it might make more sense to assume it did, as virtually all other multihop Es skew I have worked seemed to involve a more obtuse angle between the intersection of the respective beam headings.

Then again, if I am wrong & it was some form of single hop opening, the possibility of an acute skew angle increases (at least with my admittedly sparse statistics), as I have definitely experienced extreme skew at least once during an exceptionally strong Es opening. The most dramatic example occurred on June 2, 2001 when I worked W4WRL in FM04 while beaming somwhere around 270 degrees, which for me was where his signals peaked. I repeatedly rotated the antenna trying to peak his signal before and after working him, and noticed that the path of his peak signal for me changed fairly rapidly at times. I heard him direct briefly but signals were extremely weak in that direction. When we worked he was a very strong 5/9, whereas my report was a 5/5. I noted some doppler shift on his signal at times, and there was a rapid QSB at others, as well as an occassional hollowness to the signal. Was it FAI? I doubt it, as the band was open on Es in many other directions, including West and South of me, but if one assumes FAI is a phenomenon different than an Es skew or scatter effect it is arguable. I think it was some sort of short Es/multipathing effect, but this purely a guess. What I am sure of is my beam heading, which was almost a full 90 degrees off the true heading.

Es scatter can also provide a means of working those odd-distance grids during particularly strong openings. As with that on F2, the stations work each other via scatter reflected signals while beaming into the hotspot. Though Es scatter is generally weaker and rarer than that of F2 backscatter, it can still an effective and fun way to work new grids. It is sometimes hollow & distant-sounding with a multipath echo, and rarely, marked with a bit of flutter.

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