Monday, February 17, 2014

Hearing the Band Open

Often when we sit down in front of the radio, things are already going. We tune to a band looking for something particular or to just search, but usually knowing of feeling that prop is there for something to look for.

It is another thing altogether when one goes to a band waiting for something to happen. Occasionally we can almost hear the door open and the signals come rushing in like the guests to a party or students coming into a room when class starts.

Such was the case this past weekend ( February 15th and 16th GMT 2014) as I tuned the low bands in the ARRL DX contest. I had planned to cruise the lower two bands because of commitments during the day that would preclude a full out effort. The targets would be 80 and 160 meters.

I have learned that these two bands, unlike 40 and 30 meters and the 60 and 49 meter shortwave broadcast bands, do not show much life before sundown. The latter bands often will show long haul activity while the sun is still up, but 80 and particularly 160 meters must “wait” until D-layer absorption begins to drift away. Often short skip will occur early ( first hop stuff out to 1500 miles or so) and even will occur in the standard AM broadcast band. In fact, as I have previously mentioned, I use listening on that band as a  precursor to hunting on the lower shortwave bands and as a sort of barometer for how things will be.

Friday night ( Texas time, Saturday morning GMT) I waited till about 8 pm local before tuning in on 80 meters. The broadcast band had not been particularly hot on the way in from work and I also had read on Space Weather that there was the possibility of some solar activity affecting things, so was almost concerned that the low bands would take a hit as far as conditions anyway.

It was about 0215 GMT when I sat in front of the R-75 as the receiver of choice for the evening. Starting at 3500 and moving up, I heard as expected, mostly Stateside stations coming in. In this particular contest, DX stations work US and Canadians. The “ usual suspects” were down at the bottom of the band calling CQ with very strong signals. Even with one preamp turned off, most were swell above S-9. The band was dominated by stations from the Northeastern US and Eastern Canada. VA2WA was particularly strong on 3503 at 0222 GMT. Though I heard several stations working OE2S from Austria  on 3506 at 0231, he was very weak and I could not firmly pull out his callsign. I heard the first Caribbean station in the form of CO3IT from Cuba on 3510 at 0234. Were the Europeans going to make it this evening at all?
Up the band a bit I heard stations working HG1T from Hungary, usually a powerhouse station during these contests. He was on 3510, but way down in the grass and barely readable here. Another Hungarian, HA5PI was on 3512 at 0244, but again very weak and taking several cycles through his callsign to firmly identify him.

Going on up the band, there was another Cuban CO2JD very strong, and PJ2T pounding in from the Caribbean, but the powerhouse Europeans were just not powering! Over the next half hour, several of the “regulars” began to come in with marginal signals. There was 9A1CY on 3514 at 0253 barely readable, usually powerful contest station YT3A from Serbia at 0255 on 3515.7 by himself on the frequency holding forth with new England stations, but listed as only 539 in the log here. As I went up the band, a few more came in but it was a struggle. ON4IA from Belgium at 0257 on 3516.5 at 549, F5CQ from France on 3519 at 0301 that took a couple minutes and several contacts by him to identify. And signals were up and down, up and down.
By 0330, I had logged about a dozen stations, but all were in the grass. LZ9W from Bulgaria at 0330 on 3531 which usually pounds into Central Texas was easily readable, but just not very strong. But that was when the door began to open. In fact, as I was listening to him work station after station, I could hear him start to come up, almost as if the great cosmic RF gain control was being rotated. Over about a five minute period, his signal was up to S-8 and holding steady. Over the next few minutes several others were logged, including CN2AA from Morocco on 3521 that I had missed completely on the first pass. The log began to fill up with calls like CR3L, LX9DX, OK5D, SK3W, 9A1A( very strong!) OM3RM, OL7M, SP3GEM, IR1Y. Now this was more like it! The band in minutes had gone from stations being barely readable to a crowd appearing. You could almost hear the rush of the door opening!

It was time to try 160. It was almost a repeat of the same story. At first, only Northeastern US stations and Canadians were strong, the lower band showing real life a bit behind the higher frequency 80 meter band. VA2WA was present ( obviously a multi-op contest entry!) on 1825 at 0341 GMT with an astounding signal. It was already starting to happen as I listened. The Caribbeans were already quite strong in the form of P40L from Aruba on 1827, KP2B from the Virgin Islands next door at 1826.3 ( love those dual 250 Hz filters!!) PJ2T on 1829.5, ZF3A on 1830, KP2M on 1832, HK1MW from Colombia on 1821.5, KP4KE from Puerto Rico on 1831, V31TP from Belize on 1812 All were gaining strength before my ears!

But where were the Europeans? It wasn't that long ago that hearing them at all had been a treat for me, and now I was expecting them to prop in easily ( see where our threshold of expectations shifts with time!!) But not to be disappointed, an old friend showed up first with 9A1A, another multi op, multi transmitter contest operation, found beneath a pile of hungry US stations on 1818.4. Then CR3A was found on 1826 and Morocco jumped into the log with CN2AA showing up with a very nice signal on 1832.3 at 0423. The band could be officially declared open!

I have always marveled at how the lower bands open up. Somewhere there is probably published material that tells how the various layers of the ionosphere work, as far as how long it takes for them to disassociate when the sun goes down and how deep each frequency will penetrate before being totally absorbed as it happens. I often wonder if the higher layers remain ionized more with the sun still over the horizon for us on the ground, but perhaps still “visible” to the molecules of the upper atmosphere. Does the angle of the radiation striking them have anything to do with it?

I am reminded of an instance when I was in East Africa in the early 70's ( 1972 or '73) on the occasion of a total eclipse of the sun. I was working in the newsroom of the American Forces Radio and Television Service in Asmara, Ethiopia ( now Eritrea) in early afternoon as the eclipse began. We had several R-390 receivers in a rack used for receiving audio feeds via HF and for tuning in radioteletype signals from news services. There were three receivers in one of the equipment racks and only two were in use at the time. While sorting through news copy for the next broadcast, I tuned one of the receivers to the 60 meter frequency of a broadcast station in Djibouti that was usually just barely listenable in Asmara during the day and left it there as the eclipse progressed. It was amazing to see the signal come up from about a third scale to almost full scale over about a half hour period as we neared totality. I wish I had had the opportunity to tune through the bands and listen for other signals on the amateur bands or other shortwave broadcast frequencies during the eclipse, but duties would not allow it. There was just not the time. But it was amazing to see the band open and close in less than an hour due to the artificial night of the eclipse. I would guess that the lower frequencies might not have been affected as much as the D layer might not have had time to disassociate enough. If anyone has the opportunity to make such an observation during a solar eclipse, drop a note to the “ comments” section of this blog with email contact information and I would love to hear about it, and maybe include it in a future post.

There are many things to marvel at as we tune the bands. Sometimes we don't notice them in the rush to log stations or hunt for the next catch, but sometimes it is very interesting and enlightening to watch the “ mechanism” by which things happen. Gaining this knowledge while making the loggings will also surely help in understanding how prop works and in making it work for us in future DX hunts!

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