Beginner's guide to WSPR

Weak Signal Propagation Reporter (or WSPR, for short) is - as the name suggests - used for establishing communications between radio amateurs over weak signals. It's designed to be run with very low powers, and alternates between transmitting and receiving, reporting back to the wsprnet.org website. It was originally developed solely by Joe Taylor K1JT, but is now open source and maintained by a small team. It uses a transmission mode called MEPT-JT. MEPT is short for Manned Experimental Propagation Transmitter, and JT are Joe Taylor's initials.

It's got a number of uses - the main one being to highlight propagation links between different parts of the globe on different frequencies at different times of the day. It's also a useful tool for testing antennas - for instance, comparing before and after tweaks and such.

Setting up

Getting up and running on WSPR is pretty straightforward, although the most important thing to do before you start is to make sure that the clock on the computer you will be running WSPR is accurate. I use the NTP client from Meinberg, although there are many others out there for Windows. If you're running WSPR on Linux, most Linux distributions have an NTP client built in.

Assuming you have an accurate clock, grab the latest copy of the WSPR client from the WSPR webpage. Installing it should be a straightforward 'next-next-next' affair. Once the installer's finished, load up WSPR itself.



When the program starts, it should automatically open up the Station Parameters box. If not, you can open it by going to the Setup menu, and then selecting Station parameters, or by pressing F2. The callsign and grid locator should be self-explanatory, but for the rest:-

• Audio In and Audio Out - these options may already be set to the defaults that Windows is using. You can probably leave these as they are, unless you're using multiple sound cards, such as the SignaLink USB.
• Power - this is the power you'll be using in your transmissions. It's in dBm, or decibel milliwatts, and the default is 37dBm, which is 5 watts. Again, 5 watts is a good starting point, so leave this at 5 watts for now.
• PTT method and PTT port - this is how WSPR keys the transmitter, and the rest of the options in this window are the details it needs to do it, such as the serial port and the baud rate of said serial port. I use a Yaesu FT-897D, so I can tell WSPR to use the CAT interface, which makes things a bit easier.

Once you've filled in the details in the Station parameters box, close it and save the settings by going to the File menu and selecting Save user parameters. At this point, it's a very good idea to just let WSPR receieve, so if it's not already, make sure the Idle checkbox on the main screen is ticked.

The next step is to choose which band you're going to work on. The Band menu has a list of all the bands that WSPR is preconfigured to use, from LF (600m) to VHF (2m). If you're using CAT to control your transceiver, picking one of the bands should change the frequency on the transceiver. If nothing happens, make sure that the settings in the Station parameters box are correct.

Receiving

Now you're ready for receiving. All being well (although it may take a minute or two from start-up), the bottom right hand box should be green, and be displaying Receiving. The first task is to adjust your incoming audio so that the noise level is low enough, but not so low that no signals can be decoded! The bottom left hand box should say Rx Noise, and have a value in dB. If this box is red, the noise level is way too high, whereas yellow indicates a not-as-high noise level, but nonetheless higher than ideal.

Adjusting the inbound audio should be as straightforward as altering the level of the recording device in Windows. I normally adjust the level until the Rx noise figure is showing 10dB, which is the highest value before the surrounding box turns yellow.

The crux of the whole operation is the wsprnet.org website. All the spots from WSPR users are uploaded to here, and made available in realtime so that operators can see if (or where) they are being receieved. To make sure that any transmissions you receieve are uploaded, make sure that the Upload spots checkbox is ticked.

Now's a good time to go get a cup of coffee, beer, or whatever your favourite drink is. Might even be a good idea to go for a walk, because ideally you want to leave this receiving for a while. Go on...

In my example here, I actually received K1JT himself on 40m:-



Transmitting

Okay, so you've received others' transmissions, and now you're wanting to give it a go yourself. By default, the Tx fraction is set to 50%, which means WSPR will alternate between transmitting and receiving in equal amounts. You can set this as high or as low as you wish, however bear in mind that obviously the more you transmit, the less you will receieve. The other thing to do is to pick a frequency to transmit on. By default, this is set to the centre frequency, however it's best to choose something else. To adjust this, double-click on the waterfall display, and a dialog box should pop up asking you to confirm you want to change the frequency. Note that this only changes the frequency of the signal itself, relative to the dial frequency - the dial frequency (that shown on the transceiver) won't change.

The activity page on wsprnet.org shows where people are currently transmittng and receiving. You can use this page to choose a frequency that nobody is using, which will ensure you're not doubling up on somebody else's transmission.

If you're happy with these settings, untick the idle checkbox, and wait. After a few minutes, the bottom right hand box should turn pink, and display Waiting to start. After a few more seconds, all being well your transceiver should be keyed and it will start transmitting. At this point, keep an eye on your transceiever's ALC meter. As with any digital mode, you do not want the ALC to be kicking in - doing so indicates that your outbound audio to the transceiver is too high and the signal is being clipped. Worse, this could cause splattering of the signal, and potentially interfere with other WSPR users! Adjusting the outbound audio should again be straightforward, and similar to the procedure used to adjust the inbound audio earlier.

Checking out the results

After running for a few cycles, it's time to see if (or - hopefully - where) your transmissions were received. To check, go to the Spot Database Query page on wsprnet.org. There's a number of options, but all you need to fill in is your callsign in the Call field.

All being well, you should end up seeing something a bit like this:-



Success!

What now?

The eagle-eyed will notice that in the above table, the power reported is 0.05. This is actually 50mW, and is the power I normally run WSPR at. The FT-897D will only go as low as 5 watts, but by adjusting the input audio to an absolute minimum (while watching the meter) I can lower the output power.

Further reading

• WSPR - Distant Whispers by Julian G4ILO
• WSPR at Wikipedia