WSPR and antenna pattern

The frequency bandplan for 20m reserves 14070 to 14099 kHz for the digital modes such as WSPR, it is a fairly busy part of the spectrum as the waterfall plot on the TU Twente receiver shows.


WSPR runs on 14095.6 kHz and you can select a transmit frequency offset within the range 1400 to 1600 Hz relative to that frequency in USB mode. Your call-sign, a dBm value and locator information are put in a two minute sequence, you can monitor stations that transmit their information and report it to the WSPR server. The other way around also happens, stations that heard you report the transmitted signal back to the server. WSPR is intended to show propagation conditions, it gave me the following map on the 7th of May in the afternoon where one hour of data was shown. No more than 5W or 37 dBm was used be me, and some stations use even less power, down to 20dBm.


According to dxheat the Solar flux index was 90, the magnetic K index was 3 and the daily average magnetic index A was 19. These are not conditions where you expect a lot of propagation, maybe there is evidence for 1 or 4 hops, and this is what you see in the above image. The skip distance is approximately 300 km, and the largest distance within the first hour was 1386 km (EA6ALL to PD1EJO), later that afternoon I heard a station in Japan. Within the skip distance it is very hard to receive any stations, occasionally you see some, but this requires several hours of listening to WSPR signals.

The other effect that you see in the plot is the orientation of my antenna, which is a end-fed wire antenna oriented 20 degrees to the North East. This means that the antenna is mostly sensitive to the West East direction which is also where most of the short paths in the above WSPR map are found . For the longer paths the antenna is sensitive to all directions, maybe because the signal has reflected several times. The WSPR map as discussed here looks like an antenna pattern analyzer.

The antenna has undergone some construction work, it runs now between the house and the top of a 7 meter mast so that it is more horizontal. (Did you find the mast?)


Last update: 7-May-2016




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