Read the article: Raspberry Whispers by M0XPD.
I just visited the WSPR data base to collect a list of WSPR spots. And made an Analysis of the WSPR spots that M0XPD made on 30 meter with a power of 200 mW.
The stations that are mentioned in the article Raspberry Whispers have Excellent Ears. (Sensitive receivers) The lower the Calculated Field strenght in the better the propagating or the more sensitive the receiving station.
The distance is given in steps of 100 kilometers.
A distance of 250 to 349 km will show up as 300 km.
PI4THT at a distance of 635 km, is placed in the category 600 km.
To compare spots, that are made with a different power (dBm), I calculate the lowest possible power of each spot, using the SNR and the power (dBm) of the transmitting station.
To compare the spots of stations at a different distance, I calculate the Field strength of each spot. This calculation includes the distance in km. In the table, I chose for microVolt/meter, to get nice values.
For one receiving station, the changes in Field strength follow the changes in the propagation to that station.
- The lower the Field strength, the better the propagation.
While comparing two receiving stations:
- The lower the Field strength, the more sensitive the station.
The RPi is working well.