WSPR (pronounced “whisper), which stands for “Weak Signal Propagation Reporter,” is a fantastic digital signal for assessing band conditions and evaluating antenna performance. It’s also great for detecting band openings. WSPR mode implements a protocol designed for probing potential propagation paths with low-power transmissions. The protocol was designed, and a program written initially, by Joe Taylor, K1JT. WSPR is included in the WSJT-X software, along with several other weak signal digital modes (FT8, FT4, etc.) for amateur radio. WSJT-X can be used to transmit and receive WSPR signals.
There may be times when you don’t want to tie up your HF transceiver for WSPR signals, and you really don’t need the power that’s available in most HF transceivers for WSPR. With a decent antenna, you can transmit and decode signals over very long distances with very low power. Because of the encoding of the WSPR signal, a 200 mW signal has the same DX capability as a 1 KW SSB transmitter, or CW at 80W.
You can search the Internet for information on how to build your own transmitter, and there are also some kits for sale. There are also a couple of relatively inexpensive and small WSPR transmitters that are easy to configure and use. I have been using the WSPRlite Classic, made by SOTABEAMS, and two WSPR Desktop Transmitters, made by ZachTek. There are some common features between the two, but there are also quite a few differences. Both transmit a 200 mW signal using 5V (USB) input for power, and both use software for configuring your callsign, location, etc. They can also be powered from a USB power bank.
SOTABEAMS WSPRlite
The first WSPR transmitter I started using is the WSPRlite, which costs around $140. It is very small and light, and therefore great for portable operations. The unit contains internal filters for 20m and 30m, but SOTABEAMS also sells filter kits to expand the capability to include 630m, 160m, 80m, 60m, and 40m. I have not purchased or used any of the filter kits.
A unique feature from SOTABEAMS that comes with the WSPRlite is the DXplorer web site.
The WSPRlite instructions, configuration app, USB drivers, and firmware updates are available on DXplorer. Following the detailed instructions from the website, configuring the WSPRlite is a relatively easy process that involves installing USB drivers and configuration software, connecting to the computer through a USB port, selecting the appropriate COM port, entering data for a few settings, and saving the settings to the device. Once configured, the WSPRlite is ready to transmit. The trickiest part to begin transmitting is pressing a button 2 seconds after the start of an even numbered minute (i.e. 14:58:02, 10:20:02, etc.) to begin transmission. The time must be set accurately for the transmitted signals to be decoded.
The configuration application also provides a link to dxplorer.net, where you can view statistics and maps depicting the WSPR signals transmitted from the WSPRlite. There are several different ways to view the data, including a metric call DX10. According to SOTABEAMS:
We use the WSPR data to generate a special metric, DX10. We recalculate your DX10 range (km) every two minutes. DX10 is a great system performance indicator. The best HF system will give the longest DX10 ranges. … Within seconds of your two-minute WSPR transmit period ending, you can see where you have been heard.
https://www.sotabeams.co.uk/wsprlite-antenna-tester/
The DXplorer website is where the WSPRlite really shines. It’s easy to use and provides lots of useful informaton.
WSPR Desktop Transmitter
The WSPR Desktop Transmitter from ZachTek also costs $140, and is slightly larger and heavier than the WSPRlite, but has several additional features. The unit includes a GPS receiver and antenna, which can automatically set the location (grid) and control the timing of the transmissions. Once initially configured, this makes operation nearly automatic. Additionally, the latest firmware and software supports Type 3 WSPR Messages. A Type 3 message can transmit a more exact location using six figure Maidenhead reports instead of the regular four figure report, which is especially useful if you use the transmitter in a mobile or portable application with it functioning as tracker.
I am using two transmitters, each designed for operation on different bands. The “Mid” model transmits on 40m, 30m, 20m and 17m. The “High” model transmits 15m, 12m, 10m and 6m.
Note: ZachTek now sells three updated models for this transmitter:
– “Low” for 2190m and 630m
– “Mid-Plus” for 160m, 80m, 40m, 30m, and 20m
– “High-Plus” for 17m,15m, 12m, 10m and 6m
You can purchase multiple units at a discount ($254 for a Mid-Plus and High Plus, or $359 for all three models).
The WSPR Desktop Transmitter also uses an app for configuration. The documentation web page has links to the configuration software, a quick start guide, and lots of additional details about the transmitter. A USB driver might be required to connect to the computer, and there is a link on ZachTek’s download page. Similar to the WSPRlite, once the device connected to the computer with the micro USB cable, you can determine COM port using Windows Device Manager. You set the serial port (for my computer, COM13) on the Serial Port tab, and click open. After a moment the software will be connected to the device.
After the connection is open, the next tab to click is WSPR Beacon. This is where you will enter your callsign, and select the bands. With the GPS antenna connected and placed near a window, you should start seeing the GPS signal quality and a position lock. Once the position is locked, the Maidenhead grid information will fill in automatically. When initially powered up, it might take several minutes to start seeing the satellite positions and get a position lock.
Once the WSPR configuration is complete, click on the Save Settings button, then click on the Boot Configuration tab. In this tab, you can configure the transmitter to start up in WSPR beacon mode. When power is applied, once it achieves a GPS position lock, the unit will automatically start transmitting WSPR beacons, cycling through the bands that were set in the WSPR Beacon tab.
There is also a Signal Generator mode so the transmitter can be used as a piece of test equipment in your shack. It can output a 23dBm sine wave from 2kHz to 50MHz, depending on model. I have not tested or used this feature.
The WSPR Desktop Transmitter does not include access the DXplorer website like the WSPRlite, but you could still use DXplorer standard mode to view statistics for signals transmitted from either device. You can also view maps and data for WSPR signal on the WSPRnet.org website. You can get a free account to access all of the features on WSPRnet.
The Weak Signal Propagation Reporter Network is a group of amateur radio operators using K1JT’s MEPT_JT digital mode to probe radio frequency propagation conditions using very low power (QRP/QRPp) transmissions. The software is open source, and the data collected are available to the public through this site.
http://wsprnet.org/drupal/
The Map tab opens a configurable map for a visual representation of where your WSPR signals are being decoded.
Scroll down in the map to configure the view. There are several settings that you can use to tailor the information displayed on the map.
Click on the Database tab at the top of the web page to display a sorted list of spots. This view can also be configured.
Final Thoughts
The WSPRlite and WSPR Desktop Transmitter both performed very well. There are some difference in features and operation. For the price, the WSPR Desktop Transmitter offers a few more features and once configured it operates automatically every time it’s powered up. The WSPRlite is very small and easy to carry, and the DXplorer website offers excellent statistics for those tracking propagation conditions or comparing antennas. You can’t go wrong with either option, and your choice would depend upon your operating preferences.