Raspberry pi Zero used as a 30 metre Wspr Transmitter

I have assembled a 30 metre low-pass filter from Language Spy (link here) and soldered header pins to the GPIO on the Raspberry Pi zero.
Note that the Pi-LPF kit uses surface-mount components and provides a 7-pole Chebyshev low-pass filter for harmonic suppression.

WsprryPi was loaded onto the micro sd card. The RF output is 10mW, time will tell how far I will get. 30 metres was very busy at the time of testing with a contest . Tested over the weekend, it ran for 8 hours on a quarter-charged 10,000 mAh battery .
From the WsprrPi application notes:-

“….As the Raspberry Pi does not attenuate ripple and noise components from the 5V USB power supply, it is RECOMMENDED to use a regulated supply that has sufficient ripple suppression. Supply ripple might be seen as mixing products  centered around the transmit carrier typically at 100/120Hz.”

I am using M0CVO’s HW-42HP Off Centre Fed Dipole antenna in the loft, link here  .

Pictures below.


Derek M0XDC
Email: m0xdc@lefars.org.uk

P.S. 20m and 40m filters now also assembled. Map and 40m log below.  Updated 30m map and log. Also comparison with all three filters…





Update 15th October 2016 – 20m filter board
The 20m filter board has been built.  Shown below mounted on the Raspberry Pi Zero. Note that the USB cable connects the Wi-Fi dongle.

20m filter on Rpi Zero, 40m top right, 30m bottom right

20m filter on Rpi Zero, 40m top right, 30m bottom right

With 20m filter

With 20m filter

Without 20m filter

Without 20m filter


Update 6th October 2016 – 30m WSPR map and log


Update 1st October 2016 – 40m filter board
The 40m filter board has been built. 10mW (+10dBm) on 7.040MHz from M0XDC was heard by DF5FH 649km away. Map and 40m log below.

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