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A Raspberry Pi as a WSPR beacon
21 March 2013 | by Thanks to the Southgate Amateur Radio news, I’ve just seen that Guido, PE1NNZ has turned a Raspberry Pi into a 10mW WSPR transmitter that works up to 250MHz. Just a low pass filter and an antenna are required in addition to the Raspberry Pi and the software.
The code is available here
The Readme file at Github says the following:
Makes a very simple WSPR beacon from your RasberryPi by connecting GPIO
port to Antanna (and LPF), operates on LF, MF, HF and VHF bands from
0 to 250 MHz.
Credits:
Credits goes to Oliver Mattos and Oskar Weigl who implemented PiFM [1]
based on the idea of exploiting RPi DPLL as FM transmitter. Dan MD1CLV
combined this effort with WSPR encoding algorithm from F8CHK, resulting
in WsprryPi a WSPR beacon for LF and MF bands. Guido PE1NNZ extended
this effort with DMA based PWM modulation of fractional divider that was
part of PiFM, allowing to operate the WSPR beacon also on HF and VHF bands.
[1] PiFM code from http://www.icrobotics.co.uk/wiki/index.php/Turning_the_Raspberry_Pi_Into_an_FM_Transmitter
To use:
In order to transmit legally, a HAM Radio License is required for running
this experiment. The output is a square wave so a low pass filter is REQUIRED.
Connect a low-pass filter to GPIO4 (GPCLK0) and Ground pins on your
Raspberry Pi, connect an antenna to the LPF. The GPIO4 and GND pins can be
found on header P1 pin 7 and 9 respectively, the pin closest to P1 label is
pin 1 and its 3rd and 4th neighbour is pin 7 and 9 respectively, see this
link for pin layout: http://elinux.org/RPi_Low-level_peripherals
The expected power output is 10mW (+10dBm) in a 50 Ohm load. This looks
neglible, but when connected to a simple dipole antenna this may result in
reception reports ranging up to several thousands of kilometers.
This software is using system time to determine the start of a WSPR
transmissions, so keep the system time synchronised within 1sec precision,
i.e. use NTP network time synchronisation or set time manually with date
command. Reception reports are logged on Weak Signal Propagation Reporter
Network: http://wsprnet.org/drupal/wsprnet/spots
As the WSPR band is only 200 Hz wide, some frequency calibration may be needed
to ensure that the transmission is done within the WSPR band. You can correct
the frequency error manually in the command line or adjust CAL_PLL_CLK in the
code.
Usage:
sudo ./wspr <callsign> <locator> <power in dBm> <frequency in Hz>
e.g.: sudo ./wspr K1JT FN20 10 7040074
WSPR is used on the following frequencies (local restriction may apply):
LF 137400 – 137600
MF 475600 – 475800
160m 1838000 – 1838200
80m 3594000 – 3594200
60m 5288600 – 5288800
40m 7040000 – 7040200
30m 10140100 – 10140300
20m 14097000 – 14097200
17m 18106000 – 18106200
15m 21096000 – 21096200
12m 24926000 – 24926200
10m 28126000 – 28126200
6m 50294400 – 50294600
4m 70092400 – 70092600
2m 144490400 -144490600
Compile:
gcc -lm -std=c99 wspr.c -owspr
This looks amazing! Congratulations to Guido and also to Dan Ankers, MD1CLV whose work led to Guido’s enhancements.
2 Responses to “A Raspberry Pi as a WSPR beacon”
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Would be nice if there was a WSPR modem iPhone app.
i have a few rpi wspr transmitters. they do not work as documented
i will try this one. i have read and know about the gpio pins.
plz give me more info. who else is running this iteration
Niece