Building a WSPR transmitter
At the beginning of 2017, Jos ON6WJ told me that he wanted to make a wiper transmitter to test a few antennas. I had never heard of WSPR (pronounced wisper).
But Doctor Google offered advice. PA3EDR gives the following description
WSPR is a software program that can be used to gain insight into the propagation of those signals using weak radio signals. The name is an abbreviation of : Weak Signal Propagation Reporter. It is pronounced as “wisper” (=whisper).
More information can be found via this link
http://www.pi4zut.nl/wp/wp-content/uploads/2012/01/wspr-21.pdf
A full transmitter is described on the PA0RWE website.
(link to transmitter )
Rob has written a program in which a dds-60 generator is used.
More info at http://midnightdesignsolutions.com/dds60/
Rob makes the frequency change from band from 160m to 6m.
I still had an ebay module that I had left over from my antenna analyzer project.
As an amplifier I found a schematic with BS170 mosfets.
I have adjusted the software so that the frequency is fixed.
Let's go over the schedule.
The processor is an Arduino Nano.
The dds is a module with an AD9851 Chip.
The LCD screen is a classic 2 line 16 character screen.
I designed a print.
The diode is intended as protection against wrong polarization. Use what you have lying around.
JP2 is a bridge with which you can release the tension from the screen. If you feed your project battery you can save some consumption.
You can freely choose the value of R1 according to the screen used. This allows you to vary the lighting.
The power supply voltage of the output stage can be selected via JP5.(5V or the full input voltage)
This way you can adjust the output power.
If you leave the screen, you can still get an indication via the LED when you are transmitting.
With JP3 and JP4 you can set the frequency.
Both open = 80M
JP4 to ground = 40M
JP3 to ground = 30M
Both to mass = 20 M
I have connected these contacts with 2 switches so that I can set the frequency without having to open the box every time.
With 6V as the supply voltage, approximately 260mW comes out of the output stage at 40m.
Consumption is around 300mA. At 20m, the power is about 100mW.
This is due to the decreasing amplitude of the dds.
The dds must be calibrated. The wspr bandwidth is barely 200 Hz (if I have read it correctly). Connect a frequency meter to the output of the dds module.
Press switch CAL and reset the arduino.
The software will now generate 10MHz. Measure the frequency.
Keep the CAL pressed and then press CAL- or CAL+ to adjust the frequency as best as possible to 10MHz. My module shows 95Hz too much at 10MHz.
When you release the CAL, this offset is written into the arduino and it remembers that so that the correct frequency is made at the next startup.
How do I know where to receive me?
Each receiving station automatically forwards its data to a central database.
There you can request the reports in 2 ways.
In the first way, after filling in some conditions, you get a world map with your results.
(link = http://wsprnet.org/drupal/wsprnet/map )
You can also request a list as sender or receiver. This list also includes the bridged distance.
(link = http://wsprnet.org/drupal/wsprnet/spots )
I put the gps module, dds module and the Arduino on headers.
These headers cost barely 1 euro for 10 pieces of 40 pins.
This way you can easily change something if necessary.
Mounting the GPS and Antenna
My GPS module was delivered without the pins. Since the module is mounted upside down on the PCB, the long side of the pins must be on the component side.
I then secured the antenna on the other side with some double-sided adhesive tape.
Programming the Arduino
The Arduino must be programmed without the GPS module connected.
Otherwise, conflicts will arise on the internal bus.
If you want the software or gerbers pleasen contact me.
