Raspi As WSPR Transmitter

Recently the Raspberry Pi (Raspi) has gained much interest in the Ham Radio community. One interesting things is: the I/O pins provide access to a clock signal (GPCLK0) and it is possible to modulate this clock signal via software. This has motivated Guido Ten Dolle (PE1NZZ) to implement a WSPR transmitter and to publish the sources under GPL. Within the last days I have made some minor modifications to the WsprryPi sources, built a 30m QRP filter using the ugly method and connected everything to my doublet antenna.

Raspi as WSPR Transmitter

Immediately my 10mW have been received in 743km distance by G6HUI (WSPR Spots):

Timestamp Call MHz SNR Drift Grid Pwr Reporter RGrid km az
 2013-04-13 15:30  DG6FL  10.140199  -16  -1  JO40cb  0.01  G6HUI  IO81wl  743  286
7869km with 10mW
Timestamp Call MHz SNR Drift Grid Pwr Reporter RGrid km az
 2013-04-22 05:02  DG6FL  10.140238  -21  1  JO40cb  0.01  W4AC  EL86  7869  289

Information on how to do this yourself can be found in the WsprryPi repository.


Control the Yaesu FT 817 Using Arduino

Recently the Arduino microcontroller has become famous for controlling rigs. When it comes to the Yaesu FT817 there exist controllers for satellite operation (VE9RQP), for loop antenna tuners (WW3WW) and for transverters (IZ0MJE). During the development of the xmlbandplan.org project I was in need of a hardware to play with some features. The idea of an Arduino controller library for the FT817 was born. Based upon the sources mentioned above and the Hamlib implementation for this rig I have created a library for controlling the FT817 from an Arduino (the sources are available on github). More details on the usage and installation of this library can be found in the source tree.

Arduino Controller for FT817 with GPS

As the main focus was to play with the bandplan information I have also soldered a little bit (see hardware setup below) and wrote a piece of software (sources are in examples/ft_817_remote/) which uses the library. Once the CAT interface is connected to the serial pins it is easy to read out the frequency and from there it is straight forward now to display band and channel information. The corresponding data structures for band and channel information can be created automatically from the xmlbandplan files. Ready-to-use header files are contained in the repositiory.

In addition to the rig I have also connected a GPS receiver to one of the serial ports on the Arduino. Remark: Initially I have used an Arduino Uno for this experiment. It is not possible to use two SoftwareSerial ports at once: only one port can be active at a time. The Arduino Mega on the other hand provides enough hardware ports for my purpose. Now the GPS information can be merged: it is possible to display the current distance to the selected repeater (i.e. DB0VA in the image above) or even to create adaptive channel lists based on the position.

Feature List

In the current state of the experiment the following features have been realized:

  • Display
    • Frequency & mode
    • Channel & band name
    • Signal level
    • Maidenhead Locator & distance to repeater
  • Operating Modes
    • Watchdog (multiple channels)
    • Switch channels (using buttons & rotary encoders)
    • Gestures (frequency browsing, watchdog mode, …)
    • Scanning
    • Automatic mode selection based on channel

Hardware setup

The wiring information can be found here and in this picture.


During the further development of the xmlbandplan.org project it became clear, that the complete band plan information (repeater lists etc) will use more storage, than the Arduino provides. Even though I have experimented with a SD card reader and thought about soldering some RAM my conclusion is, that for the upcoming development I need more power. Therefore I have switched to a Raspberry Pi 🙂 Nevertheless I guess the FT817 controller library and probably even my example controller could be a good starting point for further experiments.

Outdoor QRP Equipment

Hiking is fun and QRP is fun. Both can be combined using homebrew equipment 🙂

This is my current light-weight QRP equipment for hiking:

  • ATS-4 (KD1JV)
  • T1 ATU (Elecraft)
  • Antenna (Buddipole)
    • VersaTee
    • Shock-cord Whip 7 elements
    • 2x Antenna Arm 22″
    • Ground wire (~10m)
    • Coax Cable (RG174)
  • PPK Straight Key (Palm Radio)
  • 10 AA Cells (Eneloop) with PowerPoles
  • Sennheiser Earphones
  • Everything tied together using hook-and-loop-tape
Buddipole Antenna in Yosemite Park
QRP Equipment

Thoughts on Accu Cells

Recently, new technologies in Accu Cells have emerged, such as the widely known A123 LiPo cells. In particular, for outdoor qrp activities it is suggested to use these cells due to their superior capacity/weight ratio. However, these cells are more difficult to handle: charger, load balancing during loading cycle, low voltage damages, form factor and voltage of the single cells prevent usage in other common devices. Furthermore, the Ready-to-Use NiMh cells, i.e. Eneloop, have overcome the issues with excessive self-discharge.

In order to find out whether it is reasonable for me to upgrade my outdoor equipment to LiPo I made a rough order of magnitude estimation for some characteristic properties of different accu cells.

(a) Weight Efficiency := Weight / Capacity
(b) Cost Efficiency := Price / Capacity
(c) Lifetime Capacity := Lifetime * Capacity
(d) Optime = Estimated operation time of my ATS 4 based on the properties given in the user manual

The results are summarized in the table below and some more details on the calculations can be found in the PDF.

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Efficiency of Compared Batteries
Battery Voltage (V) Capacity (Ah) Cost Efficiency (€/Ah) Weight Efficiency (g/Ah) Lifetime Capacity (kAh) Optime (h)
A123 9,9 2,3 25 111 16,1 6,3
Eneloop 9,6 (8C) 2,8 9 84 3 7,7
Eneloop 12 (10C) 2,8 11 105 3 7,7
Lead Gel 12 2,2 5 491 1,1 6,0


From the table above I conclude, that the technical properties of the new A123 LiPo batteries are impressive, when it comes to lifetime capacity. This is probably the reason, why these cells are contained in mobile phones and laptops. The operation time and the weight efficiency are outperformed by “conventional” Ready-To-Use NiMh cells for half the price.

For my outdoor qrp activities it does not really matter, whether I can be on the air for 6 or 7 hours. As a matter of fact, weight and overall handling is of great importance for me. Eneloop NiMh cells are currently the best choice. In addition, with conventional AA cells I can also power other common devices.

Additional Data

QRP Propagation Simulation: One Day on All Ham Bands

Below a series of images for the band conditions today using the parameters of my QRP station.
The script used for the simulation can be found here:

HF Propagation Simulation: Influence of TX Power

Here I show some contour plots (circuit reliability) of my simulation results on the 20m band at different times (day & night) using 1 Watt and 99 Watt. The simulation parameters are mentioned elsewhere.
1 Watt – 12h
1 Watt – 23h
99 Watt – 12h
99 Watt – 23h

HF Propagation Simulation: Variation of Time on all QRP Frequencies

In this post I show some video results of my Voacap simulations for HF propagation: the time has been varied (0-23h).

Simulation Parameters

  • Antenna: isotrope
  • Mode: cw (required SNR for circuit reliability calculation: 24 dB)
  • Power: 50W
  • Transmitter location: JO40DA
  • Month: July
  • SSN: 72.8
  • Frequencies: QRP frequencies on all ham bands…

3.6 MHz

SNR (dB)
Circuit Reliability (%)

7.0 MHz

SNR (dB)
Circuit Reliability (%)

10.1 MHz

SNR (dB)
Circuit Reliability (%)

14.1 MHz

SNR (dB)
Circuit Reliability (%)

18.1 MHz

SNR (dB)
Circuit Reliability (%)

21.1 MHz

SNR (dB)
Circuit Reliability (%)

24.1 MHz

SNR (dB)
Circuit Reliability (%)

28.1 MHz

SNR (dB)
Circuit Reliability (%)