WSPR
The Weak Signal Propagation Reporter (WSPR), commonly called ‘whisper’ is a beacon system that can be used to assess propagation and antenna performance by amateur radio operators on amateur radio bands.
To check that your signal is being effectively radiated from your antenna, you might want to send a WSPR beacon signal and check on www.wsprnet.org to see where your signal is being received. This makes WSPR a useful tool for QRP operators where every bit of radiated signal can make a difference. In addition, by checking on www.wsprnet.org you can see the WSPR signals being received near you. Therefore, it is worthwhile to take a few moments to look at how WSPR works.
Operators typically set their transmitting station to transmit a beacon signal at a selected power level containing their call sign, the first four characters of their Maidenhead locator and transmit power level expressed in dBm. These operators are referred to by their call sign using the title ‘Call’.
Other operators run monitoring stations. Each of these receiving stations are referred to as a ‘Reporter’. An amateur radio licence to transmit is not required to be a reporter and many are short-wave listeners. Reporters send reports of each received Call (i.e. callsign) by received frequency MHz, signal-to-noise ratio SNR, Drift of received signal, Maidenhead locator Grid coded in the signal, PWR coded in the signal, Reporter (callsign of the reporter which may be a shortwave listener title), Maidenhead locator RGrid of the reporter, and km distance – via the internet. Reports appear on www.wsprnet.org within seconds of completion of the transmission. You will need to set up a login on the website – this is free of charge.
The easiest route to set up a WSPR transmitting station is to use a Sotabeams WSPRLITE module, which is pre-built and ready to use. You simply download a small program to run on your Windows computer to add your callsign, and Maidenhead locator, and select your preferred transmit power level to the WSPRLITE module via a USB cable. It is worth noting that there are two different models of the Sotabeams WSPRLITE.
At the time I started to write this article, I had already bought the WSPRLITE Classic which includes internal low pass filtering for the 20-meter and 30-meter bands. I am primarily interested in the 20-meter band as a ‘daytime’ band. I am not a night owl or vampire! So the WSPRLITE Classic is great for me. My curiosity led me to think about how much of my signal leaving my Yaesu FT-817nd transmitter was radiated. I routinely check the SWR at the radio using a NISSEI RX-203, which has 2/20/200 watt ranges and therefore ideal for use with the FT-817, but does not differentiate between radiated power and resistive losses. To check that signal is being radiated, I substitute the FT-817 for the WSPRLITE and check on www.wsprnet.org for reception reports.
One of the first things I did was to compare a resonant centre-fed half-wave dipole trimmed for the 20-meter band with a resonant end-fed half-wave EFHW dipole similarly trimmed for the 20-meter band. Even with a feed point choke on the centre-fed dipole, reception using my FT-817nd was very poor and background noise was horrendous compared with the EFHW. However, when transmitting 200mW WSPR signals, the two antennas performed equally satisfactorily. The next thing I checked was propagation. Using the WSPRLITE Classic, reception reports on www.wsprnet.org clearly demonstrated that daytime propagation of signals on the 20-meter band could be worldwide, especially on the ‘grey line, but reports of Corona Mass Ejections CME and of aurora borealis in the northern hemisphere would coincide with the 20-meter band seeming to close down.
It is easy to see that WSPR is a quick and effective way to check equipment performance and signal propagation.
At this point, I was lent a Sotabeams WSPRLITE Flexi along with a Sotabeams low pass filter kit for the 40-meter, 80-meter and 160-meter bands. The WSPRLITE Flexi does not include any internal low-pass filtering – hence the filter kit. I currently have a resonant end-fed half wave dipole which is tuned for the 40, 20, 15, and 10-meter bands and so built up the low pass filter for the 40-meter band. This would be a good opportunity to compare propagation on the 20-meter band with the 40-meter band.
In comparing the two bands, I made every effort to only run WSPR beacons when I was not receiving notifications on my Android app of aurora borealis.
Typically examples of WSPR DX reports on the 20-meter band are as follows:-
By comparison, examples of WSPR DX reports on the 40-meter band are as follows:-
Just to show a comparison of best signal reports over similar distances and directions, Reporter TF4X picks up the 200mW signal on the 20-meter band whilst Reporter TF4AH picks up the 200mW signal on the 40-meter band, with the best results as follows:-
The Sotabeams WSPRLITE comes with additional software to that available at www.wsprnet.org, through a link in the program used to configure the WSPRLITE module – known as http://dxplorer.net This facility includes the ability to generate an azimuthal map of WSPR reports.
FIGURE 1 – dxplorer 20 meter band 2022-07-11.jpg shows examples of DX reception of WSPR signals on the 20-meter band.
FIGURE 2 – dxplorer 40 meter band 2022-07-11.jpg shows examples of DX reception of WSPR signals on the 40-meter band.
For those interested in the format of WSPR beacon signals, each transmission always begins 1 second after even minutes (UTC). Operators typically set their beacon using either the time from the National Physical Laboratory NPL in Anthorn, Cumbria or similar clocks such as https://time.is. The beacon signal is of 110.6 seconds in duration. It is not necessary to transmit every 120 seconds. Operators would typically transmit every ten minutes or even less often. Modulation is ‘F1D’, frequency-shift keying, with the frequency shifting between 4 tones every 0.683 seconds, each tone separated by 1.46Hz, with a total bandwidth of about 6Hz. 50 bits of information are packed into a 162-bit message including Forward Error Correction FEC.
WSPRLITE beacons are showing as temporarily out of stock on the Sotabeams website. However, other WSPR beacons are available. Hans Summers G0UPL owns and runs QRP Labs www.qrp-labs.com which offers the Ultimate3S kit, a beacon transmitter that I have used successfully for WSPR in the past. A more recent offering by QRP Labs is the QCX+ 5W CW transceiver kit. This kit is relatively easy to construct – I have one. It is a fully operational single-band CW transceiver that offers transmission as a WSPR beacon via menu selection.
I have also successfully used my Yaesu FT-817nd with the Yaesu SCU-17 USB Interface Unit and PC computer as a WSPR beacon and also to operate as a WSPR Reporter. However, I do prefer to use a separate WSPR beacon and not tie up my Yaesu FT-817nd.
In conclusion, if I make any changes to my antenna I will check the SWR. Then, I will run my Sotabeams WSPRLITE to see if my signal is getting out; see if local WSPR Reporters in the UK, such as G6JTB or MW7SIF, are receiving WSPR signals from DX signals; and then tune my radio. Alternatively, if reception is poor, I will switch to doing something else like homebrew construction. Thank you for reading.
