TAPR WSPR Without Tears Manuale utente
WSPR Without Tears
Table of Contents
Introduction................................................................................................................................................1
Approach....................................................................................................................................................2
Raspberry Pi...............................................................................................................................................3
What you'll need to complete the assembly...............................................................................................3
Programming an SD ard..........................................................................................................................4
Setup......................................................................................................................................................4
Program SD ard..................................................................................................................................4
Install SD ard into Pi...........................................................................................................................5
Assemble WWoT and Pi............................................................................................................................6
Setup and Adjustment................................................................................................................................7
What You Need......................................................................................................................................7
Getting SSID and Passkey.....................................................................................................................8
Initial Setup...........................................................................................................................................8
Locate the Pi IP Address........................................................................................................................8
Setting WSPR onfiguration..............................................................................................................10
Restart Pi.............................................................................................................................................11
Measure RF Output.............................................................................................................................11
IP Addresses........................................................................................................................................12
WWoT Schematic....................................................................................................................................12
Troubleshooting - It Doesn't Work ..........................................................................................................14
Appendix 1 – ommunicating With the Pi over SSH..............................................................................16
Appendix 2 – Postprocessing Data..........................................................................................................17
WSPRnet Map.....................................................................................................................................17
Downloading Data...............................................................................................................................19
WSPR Data Filter................................................................................................................................19
Introduction
Thank you for purchasing the WSPR Without Tears transmitter (WWoT). We hope you’ll be pleased
with it. WWoT is our attempt to put together a WSPR transmitter transmitter that avoids (hopefully)
most of the problems associated with building a fairly complicated digital mode transmitter. All of the
information, data and files are accessible through the TAPR website:
tapr.org/kits_WsprWithoutTears
WSPR stands for Weak Signal Propagation Reporter Network. It's a digital mode used by hams. The
process is similar to a beacon. WSPR is a wonderful communication mode created by Joe Taylor
(K1JT). WWoT is our attempt at simplifying the process of getting an actual transmitter up and running
so you can enjoy working with WSPR and avoid dealing with the headaches associated with building a
working system.
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What makes it really interesting is that WSPR is optimized for operating at very low power. For
example, it's normal to transmit with 200 mW from the US and be received in Australia or Europe.
There are hams all over the world with WSPR receivers. They record what they receive in a central
database that can be queried over the Internet. So you put your WSPR transmitter on the air and
monitor its performance from the Internet. Monitoring WSPR is sort of addictive. It's fascinating to see
what effect time of day, seasons, and weather have on propagation.
There is a wide array of choices for setting up a WSPR beacon. The most obvious and possibly the
simplest is to use your regular transceiver. This requires a computer and sound card connection. Most
of us have at least one computer in the shack and many of us are already using digital modes, so the
equipment is already in place to run WSPR. All you have to do is download the software (free) and
you're off to the races. This approach works well and the price is right if you're already are set up for
digital modes. Even if you're not set up for digital modes, the interface between your transceiver and
computer can be had for less than $100.
Using your base station for WSPR is an excellent approach. The downside is that you are tying up your
station while WSPR is on, so leaving WSPR on for an extended length of time gets in the way of radio.
A second point, the output power of many transceivers can't be adjusted below 5 watts. An output
power of 5 watts will certainly work, but it's interesting to see how little power you can get away with
and the useful power range is a lot less than 5 watts.
The alternative to using your regular station for WSPR is to have a completely separate WSPR station.
That's a lot more realistic when you're dealing with output powers in the range of milliwatts. When we
started down this path we looked at different approaches. One approach we looked at was high quality
and well done, but there are some operational complaints we had with it that we wanted to fix. This is
our version for a fix.
Approach
We found an alternate approach using a Raspberry Pi (Pi) computer to generate WSPR transmissions. A
Pi is about the size of a deck of playing cards and costs about $40. It has an amazing amount of
computing power for something so small and so cheap. It runs the Linux operating system.
The Pi can be configured to generate the WSPR signal without any external components! That's just
amazing to me. Somebody figured out how to modulate the clock/oscillator and generate a WSPR
signal. The Pi will also set the time by calling an NTP server and use the time information to adjust the
frequency, eliminating the need for any calibration or timing setup.
There are two problems with using the Pi for WSPR. First, the output signal is a square wave with
harmonics from here out to next Tuesday. A low pass filter is necessary to keep other hams and the
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F happy. Second, the output power is around 10 mW. We talked about the thrill of using low power
to make contacts, but it's nice to start with a little more power than that.
Our WSPR Pi is a circuit board (pcb) that plugs into the Pi 40-pin header. It boosts the signal level to
about 200 mW and contains a seven pole low pass filter to keep out-of-band transmissions down by 43
dB. It also contains an LED that lights when transmitting and a crude output power indicator. (We
found it annoying to not know when and how well our system was working without connecting a 'scope
or power meter and wanted something simple as a sanity check.)
The Pi is a computer, and most computers need to be shutdown properly rather than just have the power
turned off. We added a push button to the circuit board to initiate a shutdown sequence in the Pi. We
wrote a program to run in the background that monitors the push button and shuts the Pi down when it's
pressed.
Raspberry Pi
The Pi is a computer and is subject to all of the headaches associated with computers. We wanted to
make life easier for anybody trying to duplicate our WSPR experience by limiting the amount of
computer exposure you're subjected to. Loading the software into the Pi is not difficult, but there are
quite a few areas that can go wrong and it can be frustrating if you've never done it before. It only takes
one problem to kill the whole process. There are a lot of steps involved in getting to a working WSPR
transmitter.
We created a version of the software that runs automatically when the Pi is turned on. There are several
parameters that you (the user) have to set: callsign, grid square and WiFi (if you're using wifi). We
programmed a web server in the Pi (we told you it's a computer :-) that lets you fill this stuff in from a
web page onyour P . In other words, you bring up Internet Explorer or hrome or Firefox and type in
the Pi's address (we'll get to that) and the web page comes up and you enter the data. This means no
programming of the Pi at all. Bring up the web page, type in your callsign, grid square, and WiFi
parameters and you're up and running.
The operating system (Linux) and all of the software are stored on a micro SD card. The SD card is
plugged into the Pi. Set it and forget it. You need a card reader (<$10) and software (from the TAPR
website) and an SD card to do this. We'll repeat the important part: you have to burn the image onto the
SD card (similar to burning a D/DVD) and then plug it into the Pi. There's *no* programming.
What you'll need to complete the assembly
1. Raspberry Pi 2.0 Model B or Raspberry Pi 3.0
2. 2 amp (minimum) power supply w/micro USB connector.
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3. Ethernet cable.
4. WiFi USB dongle. You only need this if you're using an Pi 2.0 and you want to use WiFi. WiFi
is built into the Pi 3.0.
5. SD card (4 GB min, grade 10)
6. SD card reader (micro SD card to USB)
7. antenna (mate to BN connector on WWoT)
Programming an SD Card
Setup
1. You need an SD ard; at least 4GB, 8GB is better. lass 10.
2. SD ard reader/writer. We've got a Targus Micro SD/T-F. It doesn't really matter what card
reader/writer you use. It connects your SD card to a USB port.
1. Win32DiskImager – It's a freebee. Download it from: tapr.org/kits_WsprWithoutTears or
source orge.net/projects/win32diskimager/.
2. Install Win32DiskImager.
3. Disk Image – Download it from: tapr.org/kits_WsprWithoutTears (file
WSPR_Baseline_********* where the *'s are a date. This is a big file (e.g. 500+ meg).
4. Unzip the file after it's finished downloading (it will take a while).
Program SD Card
1. Plug the SD ard reader/writer into a USB port.
2. Plug the SD ard into the reader/writer.
Figure 1: Win32DiskImager
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3. Start Win32DiskImager.
4. lick on the folder icon in the upper right and find the disk image you downloaded and
unzipped.
5. lick Write and go get a cup of coffee. Note: Win32DiskImager shows a small message box
when it's done writing the SD card. Unfortunately, the message box likes to hide behind
anything else you have up on the screen so you can't see it. Be forewarned that you might have
to go looking for it.
6. lick Exit.
7. Remove the SD card and install it into the Pi. Make sure that power is disconnected from the Pi
before doing this.
If you haven't annoyed the gods of the Internet too much today you should be in luck and everything
will work!
Install SD Card into Pi
First, insert the SD card into the Pi ( Figure 2: Inserting SD ard into Pi and Figure 3: SD ard
Installed in Pi). The SD card sorta slides in up side down. On Pi 2.0 it ratchets in (pops in then out a
little and sorta locks in place). On Pi 3.0 there's a friction fit, so there's no locking.
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Figure
Figure 2: Inserting SD Card into Pi
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Assemble WWoT and Pi
Attach the WWoT board to the Pi. The BN connector is on the opposite side from the Pi USB
connectors( Figure 4: WWoT and Pi Assembly). The micro USB power connector is coming out of the
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Figure 4: WWoT and Pi Assembly
WiFi
Adaptor
RF Out
BN
Micro USB Power
onnector
Figure 3: SD Card Installed in Pi
USB onnectors
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lower left. RF output comes through a BN connector shown in the upper left. A WiFi dongle is
plugged into one of the USB ports (pi 2.0 only - it's built it to Pi 3.0). The Pi LEDs are on the left hand
side of the Pi board below the WWoT board. They are not visible in the picture.
The side view of the completed assembly ( Figure 5: WSPR Beacon (Side View)) shows how the
WWoT is plugged into the Pi. It's definitely possible to connect them incorrectly, so don't do that.
Notice from this view that the Pi USB connectors are on the right hand side and the WWoT BN
connector is on the left. That's how it should be. Also, make sure that the Pi pins and the WWoT plug
are lined up. It is possible to offset one from the other, so you only have one row of pins connected.
Setup and Adjustment
What ou Need
I'm assuming that you have -
1. Assembled Pi/WWoT
2. 2+ amp power supply for the Pi
3. Ethernet cable to connect Pi to your router
4. SSID and passkey for your router (see below if you don't have these)
5. P connected to your network
6. Optional: USB WiFi adapter for Pi 2.0 (Pi 3.0 has WiFi built in)
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Figure 5: WSPR Beacon (Side View)
BN
USB onnectors
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Getting SSID and Passkey
Start by looking on the router for login information. Also, try the Internet for a router manual (we
know, we hate to read directions, too).
Next, you're looking for your router's web page. Open a browser and type the IP address 192.168.0.1
into the address textbox at the top (just as if you were typing www.google.com). If nothing happens try
192.168.1.1 and 192.168.2.1.
Log into the router using the username and password printed on the side of the router or in the manual.
Look through the various wireless setting for SSID and passkey (or something similar). We're sorry, but
we can't offer too much more because each router will be different.
Initial Setup
The power is off at this point.
1. Make sure that the power is turned off.
2. onnect the Pi to your router with the Ethernet cable. This part is a little tricky. The Pi has to be
connected to a DH P server. That's normally your router. It won't work i you plug the Pi into
your laptop, at least not without some advanced setup.
Locate the Pi IP Address
1. Working from your P , download WSPR Executables (zip file) from the web site
(tapr.org/kits_WsprWithoutTears), unzip the zip file, and extract the program WSPR_Locate.exe
to a suitable work area.
2. Execute WSPR_Locate.exe. The program will take about five minutes to execute and will
(hopefully) give you the IP address of the Pi.
Some assumptions have been made: 1) your network is a private lass network (IP addresses
begin with 192.168..), and 2) you have DH P enabled on your router (router hands out IP
addresses). If you have no idea what we're talking about then don't worry about it – these are
typical settings for a home network.
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With any luck, the display will look something like Figure 6: WSPR Locater. Look for the line starting
with eth0. The line below it shows inet addr: 192.168.1.210. Your setup should be similar except for
the last two numbers (it will begin with 192.168, but the last two numbers will probably be different).
Record the full number (192.168.aaa.bbb – aaa and bbb are the numbers for your Pi) for the next step.
That's the IP address of your Pi. If the program fails to find the Pi, try it again. If that fails, go to the
Troubleshooting section.
Note: The first time you run WSPR_Locater inet addr will be displayed for eth0, the Ethernet
connection. After setting the WiFi portion of the WSPR configuration (see Figure 7: WSPR
onfiguration Screen), WSPR_Locater will display inet addr for eth0 if the Ethernet cable is still
connected and inet addr for wlan0, the WiFi connection.
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Figure 6: WSPR Locater
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Setting WSPR Configuration
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Figure 7: WSPR Con iguration Screen
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