January 2012 ARRL VHF Sweepstakes Sporadic-E Openings Magic Band enthusiast and CQ VHF Features Editor WB2AMU describes the interesting surprises that occurred during this past January ARRL VHF Sweepstakes Contest. For many veteran VHF operators who participate in the January ARRL VHF Sweepstakes each year expectation for sky wave-based propagation typically is low. Sometimes a short-duration and narrow sporadic-E opening may appear that adds some contacts and new multipliers to onescore. As in the case of the January 2012 event, there were some interesting surprises that makes it one of the more interesting winter VHF contests in recent years. January 2012 Sporadic-E Activity on 6 Meters Prior to the contest, on January 21st, 6 meters (the Band”) was seeing a fair amount of sporadic-E activity in various parts of the U.S. On the day before the sweepstakes I worked a number of Florida stations from my location on Long Island on the band, beginning around 7 PM local time. At 8:45 PM, I actually worked DX, C6AMN on sideband, so I had some hopes that there might be some possible sporadic-E activity for the contest. For VHF contests I typically do a portable QRP effort, where I go to one of the taller hills on Long Island. Without fail, there has always been some sort of inclement weather during this time (the third week of January), typically snow. January 2012 would prove no different from previous years, as the first major snowfall took place (and the only barely significant snowfall for this winter) on the Saturday morning of the contest! Fortunately, in comparison to a year ago, the snowfall was only four inches and it did lighten up to just sleet conditions by 2 PM, the time the contest started here on the East Coast. (This past winter was one of the mildest ones experienced in my area, with a prior very mild winter being in January 2002, and the only snow storm that winter was also on the January VHF contest weekend!) Six-meter band conditions at the start of the contest seemed decent, and then I spotted a narrow sporadic-E opening into grid EM36 on 6 meters on Saturday, January 21st. The opening was to just to the one grid square, where I worked two of the three stations that I heard as shown in figure 1. Again, this was a very narrow opening, as I did not hear any other eastern Canadian stations, although I was told later that a few VE1 stations also were around on the band at the time. It is truly amazing how effective a popular VHF contest is when these narrow sporadic-E openings can be spotted! On a normal day on 6 meters, even with the aid of 6-meter chat pages, a narrow opening such as the one that I experienced to EM36 might have been missed. Contest activity can really help in detecting those narrow sporadic-E events! The next morning, Sunday January 22nd, saw very poor conditions on ail of the bands with line-of-sight contacts limited to just adjacent grid squares on the lower four VHF bands.
Figures 2 and 3 show the details of the forward and backscatter paths. Many 6-meter operators experience the effect of signals coming off backscatter during strong sporadic-E openings on 6 meters in the summer months when there are high periods of activity. Also, during peak E2 openings on 6 meters during solar peak years, this mode can occur during strong E2 openings with loud signals. However, it is very, very rare to see sporadic-E backscatter during the winter season, because most openings tend to be modest in strength. Experiencing this opening was one of the highlights of the VHF contest for me! Sporadic-E activity continued for the next few days after the contest as I experienced evening openings to the Midwest on January 23rd and a short opening to Florida on the 25th. Basically, I saw sporadic-E openings occur on five of the six days between January 20th and January 25th. This is not particularly unusual during the winter months, but it can be hard to catch these events, and thankfully, with the contest in the midst of this time period, a lot of stations were paying very close attention to the activity on the band. The absolute beauty about observing propagation modes such as this on 6 meters, particularly during the quieter times during the winter sporadic-E season, is that the mode can be better characterized and the mechanisms involved better understood. Six-meter openings during the winter months are occasional at best, and when a strong, although narrow, opening like this one occurs, the characteristics become easier to define. In this particular case, there were very strong backscatter characteristics occurring at the same time of the forward-path sporadic-E opening. Sporadic-E backscatter has been observed during strong sporadic-E events during the summer season. However, because of the higher volume of signals, it can often be missed or misunderstood by operators. With this very specific case occurring during the January VHF contest, a number of things were able to be observed with regard to the direction and the strength of the opening. In theory, any sporadic-E formation is capable of some amount of backscatter, but the mystery is why some events seem to be stronger than others. This is where it can be tricky. It is well-known that when sporadic-E formations become denser, they are capable of reflecting radio waves at higher frequencies. What is important to keep in mind is that there are clues that are present when this happens. For example, when distances via a sporadic-E path shorten up on 6 meters from 1000 miles to 500 miles, the formation is denser, such that there can be a possibility of 2-meter sporadic-E paths opening. However, in the case of what was observed on January 22nd, when K1TOL and I were hearing a few stations at very high signal strength from the EM70 grid in Florida, the distance of the sporadic-E path was not shortening up to the point where something might be occurring on 2 meters. So what made the signal so strong if the density was not increasing? The one plausible explanation I have is that the sporadic-E formation was not getting significantly denser but rather more uniform throughout the formation and more well-defined as far as the edges of the formation. When there is more uniformity in the formation, the strength of signals reflecting the formation (either forward or backscatter) will have less fading (QSB) on the signal. Thus, for the strong backscatter off the sporadic-E formation there was very little fading, leading to the ability of K1TOL to work several stations in the Northeast via the backscatter mode. Therefore, in this case uniformity of the formation rather than density seems to be the reason for the very consistent and strong signals that were observed. In theory, then, any sporadic-E formation that is consistently uniform would have a greater likelihood of incidence of backscatter events. Amateur radio observations tend to be continuous (as well as perceptive), since there is a human element involved that can quickly make adjustments when stations from certain locations are heard —such as the right direction to point an antenna, particularly when there is backscatter involved. There were additional occurrences on the Magic Band during January 2012 as well. On Monday, January 23rd at around 2330, KH7Y in Hawaii was heard by K1TOL in Maine, and was then worked by K2ZD and K2MUB in upstate New York in grid FN21. It would be an interesting study of what propagation modes were involved in these contacts. There is no doubt that there was at least one, or two, sporadic-E links in the path, with the possibility of a longer E2 path linking Hawaii into the U.S. Based on many years of observations during January, multiple sporadic-E links or hops are very rare. If only sporadic-E is considered, this would be three or four sporadic-E events, which is highly unlikely. My guess is that there was a weak E-layer path involved with sporadic-E links on the U.S. side. This is why many of us love 6 meters, because of the magic that is created on the band! searscard com