WSPR Experiments

WSPR screen with received stations

http://wsprnet.org/drupal/
http://www.knology.net/~gmarcus/
http://midnightdesignsolutions.com/dds60/index.html

For WSPR based on an Arduino Nano please visit my Arduino page.

After reading some interesting stories about WSPR I decided to install the WSPR software on my computer and try to receive the WSPR signals.

What is WSPR?

WSPR (pronounced “whisper”) stands for “Weak Signal Propagation Reporter”. It is a computer program used for weak-signal radio communication between amateur radio operators. The program was initially written by Joe Taylor, K1JT. The program is designed for sending and receiving low-power transmissions to test propagation paths from LF to UHF bands.

WSPR implements a protocol designed for probing potential propagation paths with low-power transmissions. Normal transmissions carry a station’s call sign, Maidenhead grid locator, and transmitter power in dBm. The program can decode signals with S/N as low as -28 dB in a 2500 Hz bandwidth. Stations with internet access can automatically upload their reception reports to a central database called WSPRnet, which includes a mapping facility.

Receiving WSPR signals
I’m using my KTH-SDR in combination with the WSPR software to receive the signals. The WSPR software is very good usable with a SDR receiver, it has special settings for it. Also USB control is working well. There are a couple of prerequisites for successful receiving WSPR signals:
–  Your computer must have an exact system clock time, not more than 2 seconds variance
–  Your receiver must have an accurate frequency display (not more than 10 Hz variance)
–  Al signals are transmitted in USB, whatever band your are listening
–  Aware of the I/Q signals of your SDR otherwise exchange them
–  Be patience! You have to wait until the even minute starts and then wait for 2 minutes for a complete transmission, before you know that all your settings are OK….

And if it’s all OK then you will see the following screen:

WSPR screen with received stations

WSPR screen with received stations

You see stations received in the 30 and 40 meter band. I used a simple loop antenna in my shack for receiving this WSPR stations.

Transmitting WSPR signals
It is also very interesting to transmit WSPR signals and see the distance you have been heard. I searched the internet for WSPR transmitters and found an interesting site where you can find schematics for a stand-alone WSPR transmitter based on a PIC for control and the DDS60 (from the American QRP Club) as low-power transmitter. I build the Multi-band DDS WSPR Signal Source  transmitter and added a DCF77 receiver to it to determine the exact 2-minute starting moment. This unit transmits in steps from 160 until 6 meters. Below you see the transmitter as it is running for some month.

WSPR Transmitter

WSPR Transmitter

On the left you see the DCF77 receiver (Conrad) and at the top of the board you see the DDS60 VFO, used as a 50 mW transmitter. The PIC used is a 16F628. I modified the software for my own purposes.
The transmitter is heard all over Europe but also in America! I’m using a 14 MHz dipole under the roof of my house.

Below you see a part of the Spot Database.

WSPR spot database

WSPR spot database