Bruce KX4AZ is a operator that makes very interesting WSPR spots with just 10 milliwatt.
Believe it or not. A WSPR station with 10 mW will be spotted, but ONLY when the propagation is very good. Please study the diagrams below, to convince your self.
Lowest Possible Power diagram
To show the propagation, I developed the Lowest Possible Power diagram. You can immediately see how good or how lousy the propagation is, for each individual spot.
The better the propagation, the lower the Lowest Possible Power.
2019-04-19 I visited the WSPR old database and collected some interesting spots.
Time slot 1
In the time slot of 17:46 UTC ND7M spotted 7 stations.
4 stations with 5 W, 1 station with 1 W, W6CLB with 100 mW and Bruce KX4AZ with 10 mW.
Luckily for Bruce, the propagation from the stations with 5 W and 1 W, to ND7M was not that good, so Bruce's signal was not over shouted by the 1 W and 5 W signals. Something that can easily happen, even with a power of 100 mW.
In the first diagram Bruce was spotted by ND7M with a SNR of -29 dB. It's the spot in yellow, on the line of -29 dB and the line of 10 mW. So in this time slot Bruce needed the full 10 mW. Hi.
In this time slot the best propagation is shown by the spot of W6CLB with 100 mW and a SNR of -15 dB. This spot has a Lowest Possible Power of 5 mW. Thus about 3 dB better than the spot of Bruce.
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| KX4AZ with 10 milliwatt spotted by ND7M over 3100 km |
The second diagram shows the next spot of KX4AZ by ND7M.
In this time slot the signals of W6CLB with 100 mW has a SNR of -12 dB.
The signal of KX4AZ has a SNR of -22 dB. please notice that both spots, show the same propagation, which is very good. The Lowest Possible Power of both stations is 2 mW. The signal of Bruce is even about 7 dB stronger, than in the first time slot.
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| KX4AZ with 10 milliwatt spotted by ND7M over 3100 km |
