Pre-Belgaum Net Radio Propagation Evaluation

Soon after I started coming back on HF in my second innings in Ham Radio, it was VU2TUM who told me that several radio amateurs from different parts of the country join together on 7050 kHz daily morning to check radio propagation on 40m. Hambel Belgaum net starts only at 7.00 am IST or 0130z. Prior to that, sometimes even as early as 5.30 am, though usually around 6.30 am radio amateurs start joining 7050 kHz. Typical nature of ionospheric propagation can be clearly observed if you monitor the frequency for about an hour. To begin with most distant stations like VU2TUM from Gurugram and VU2JF from Rajkot are heard while local stations like VU2RTF will not be heard in my region, even though more distant stations are able to copy.

As the time progresses, distant stations gradually disappear from the waterfall display of my radio while nearby stations become very strong, even as much as 5,9+20 dB. At that time there is a dense display on 7050 kHz on the waterfall display. The time at which this change occurs is not constant on all days. Usually by the time Hambel Belgaum net starts at 7.00 am, stations at most distant parts of the country are no longer audible here. But net control VU2KOC from Belgaum is still able to pick them up, being nearer to the net control located more than 500 km North of my location. Further down the time line, net control also will not be able to pick them up. While my radio signals are heard by the net control very well before 7 am, copy will be less later on as solar radiation increases the angle of reflection from the ionosphere as day progresses.

Most interesting observation was noted during the G5 Extreme Geomagnetic Storm. There were a lot of us on 7050 kHz prior to the occurrence of the storm at about 6.55 am local time. Usual pattern is that anyone coming on frequency is given an opportunity to call as many stations as can be heard locally. That way all of us get to know the propagation of our signals to different regions. Sometimes A41LD also turns up on the frequency and gives out a few calls. On the day of the geomagnetic storm, there was a sudden radio black out with all signals from the more distant stations vanishing from the waterfall display. The change was so dramatic the we did not know what was happening. It was only later that we found out that it was due to the geomagnetic storm. We could hear only the stations within about 200 km, that too only with a very feeble copy and waterfall display!