Tuesday, October 16, 2012

Meet Nordic Real-Time Propagation with Skimmers

Today, I want to introduce you an excellent addition to your VOACAP predictions, Nordic Real-Time Skimmers.

As we all know, VOACAP predictions work on a monthly level. The program is not intended to predict today's or tomorrow's HF propagation. All that VOACAP says, for instance in case of VOACAP Online predictions, is that there is such and such a probability of getting a QSO on that frequency at that time of the day during that month. It is also supposed that ionospheric conditions are calm and quiet.

Now, there is always some activity going on in the sun. It can be solar flares, coronal mass ejections, proton events, or simply coronal holes which can be in a suitable geoeffective position so that it affects the Earth's magnetic field. Those typically mess up our ionosphere in some way.

One way to understand what the current HF propagation conditions are, there is a network of HF receivers that continuously monitor the CW section of the global amateur radio bands from 1.8 MHz to 28 MHz and even beyond. These receivers try to programmatically decode (ie. make into cleartext, find out the callsigns of) all the CW signals they can hear and report those findings into a global monitoring network - the Reverse Beacon Network. Those receivers which monitor several bands simultaneously and decode the CW signals are called skimmers.

The Reverse Beacon Network (or RBN) is a global monitoring system which collects spots (decoded callsigns) from over 80 monitoring receivers (or skimmers) around the world. The majority of receivers is located in the USA and Europe but there is an increasing number of receivers also in Asia Pacific, and one in Africa. Curiously, there is none in South America!

While the RBN is an excellent service, I still felt the need of creating a regional network of skimmers to get a more comprehensive picture of HF propagation conditions in the Nordic countries. This is why I created the Nordic Real-Time Monitoring page. At the moment, there are two skimmers that feed their spots to the system: OH6BG (Finland, that's me) and SK3W (Sweden). And there is a plenty of room for expanding this service for other Nordic skimmers.

This Nordic Real-Time Monitoring page differs from the RBN in the quality of spots it accepts. While the RBN only accepts CQ-quality spots (the highest quality decoding)  from the global skimmers, the Nordic network accepts everything that the skimmers can output. In addition to the highest-quality CQ spots, the skimmers also produce two other types of spots the quality of which may not be as high, namely DE spots and spots without classification.

Let's take a closer look at the Nordic real-time HF monitoring network page at www.voacap.com/skimmer:

There are three distinct sections on this page:

1. The statistics

The number of spots received on each band monitored during the last 15 minutes, 30 minutes, 60 minutes and 24 hours. This gives an easy-to-understand overview where the conditions are the best at the moment in terms of stations. If the 15-, 30- and 60-minute figures are zero, it probably means that either the band is closed or the skimmers are not monitoring that band at the moment.

In this section you will also see this:
» All » 160M » 80M » 40M » 30M » 20M » 17M » 15M » 12M » 10M
By clicking the column names (ie. bands), you will see the spots of that particular band, sorted by time so that the newest spot is shown first. By clicking "» All" you will again see spots from all bands.

2. The spots

Now when you are viewing the spots from all bands or from a specific band which you have selected, you will notice that all spots include the following details:

These seven column heads are clickable. When you click one of those columns, all spots are sorted by the column clicked. Let's briefly review the columns:

  1. DE. This column shows you the station which has sent the spot to the system.
  2. FREQ. This column shows the frequency of the station spotted (in KiloHertz). If you click on this column you can easily see how the stations are distributed across the band. I use this much on 10 Meters just to quickly see all the 10 M beacon signals at the end of the list.
  3. DX. This column shows the callsign (the station) spotted. Please note that the callsign can be clicked and further details can be found. By clicking this column it is easy to see stations by country because all callsigns are sorted from A to Z. In other words, it helps to visualize the geographical direction of the conditions.
  4. SNR. This column shows the signal-to-noise ratio (in dB) as reported by the skimmer. Please note that this is not Signal Strength. Low figures (0-5) indicate that the signal is just about readable above the noise level. Figures over 30 dB indicate a strong signal. I have found that signals from local stations in the same city can produce SNRs as high as 80 dB! Also, once on 160 Meters I saw an SNR of -1!
  5. SPEED. This columns shows the speed of the CW signal in words per minute (wpm). Values close to 40 wpm tell you that the DX is in a hurry :)
  6. MODE. This column shows you the quality of the spots, and there can be three values: CQ, DE or nothing. CQ is the highest-quality spot, it means the decoding program has been able to detect a CQ call and thus the callsign is almost certainly the one that has been decoded. DE is the second-best quality. It means that the decoding program has not been able to find a CQ from the station but maybe there was a DE + callsign detected. The no-mode spot can be almost anything: it can be a callsign given by any station on the band, or it can also be the callsign of the station detected. In other words, it is a callsign which cannot be validated in any degree but it was "heard" on the band.
  7. TIME UTC. This column shows the time in UTC (Universal Coordinated Time) as reported by the spotting skimmer. This is the default sorting column for all spots, ie. they are all sorted by time.

3. The search

All spots that this system receives go to a database, and the third section located on the top right corner of the page address just that - how to find spots saved in the database. The Nordic skimmer started in May of 2011 so there is already a good number of data to search for.

The search box accepts callsigns, and no wildcards are needed. Just type in a couple of letters from the callsign, and the system finds all callsigns that match that query.

You can also restrict the search to a specific band by selecting a band from the "Band" popup menu.

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