As of 2006 I’m running a VHF propagation warning system. This system analyses all DX clusters, CW skimmers and fmlist.org FM-DX reports. And when there is a chance for Es, multi-hop Es or Aurora propagation a warning message is sent. The chance for propagation is calculated from grid square JO21. Sending the propagation alerts is done via email, SMS and APRS. As of 2010 Twitter messages were added. Now since 2015 the alerts can also be received via POCSAG pager messages.
Information VHF Propagation alert system: http://alert.pe1itr.com
This transceiver is a Yaesu FT7800 with a Kantronics 9612 modem. The modem is linked up to a Raspberry Pi.
Warning messages are sent via all sites of the Dutch Amateur Pager Network to individual RIC numbers. They’re also sent to group RIC so everybody can determine whether or not these messages are to be received. The group RIC numbers in use are shown at this website.
The message shows the band, propagation type, time of the warning and a list of grid squares involved in QSO. The end of the message shows the antenna direction pointing to the reflection point as seen from JO21qk and the distance between the reflection point and JO21qk. A reflection spot at for instance 750 kilometers has best results.