QRSS
To send QRSS you need a simple CW transmitter. For example the Universal VFO and the PA shields I have described for the Arduino UNO. The PA shield may be is a bit overkill and a lower output maybe should be used. An interesting design is a PA using a 74HC240 with out of phase signals fed to it from the VFO and the outputs connected to a balanced 1:4 transformer and LPF.
QRSS can be sent in basically three ways:
1 As simple CW, using dot = 3sec + 1 sec space, dash = 9sec + 1 sec space, word space = 2sec (1 space from each char + 2 extra = 3sec)
2 As frequency shift keying, with the same timing as #1 but on two frequencies, known as FSKCW. The frequencies are typically 2-5Hz apart, with the dot or dash being the higher frequency.
3 As two frequencies representing dot and dash, with a slightly longer gap for character spacing. The dot & dash are the same length. This is known as DFCW.
For example the letter 'C':
Different speeds have been adopted, but the most common is the one above called QRSS3, FSKCW3 or DFCW3. A transmitter must have better than 5Hz stability.
Reception is made by feeding the output of the RX audio (which can be from a simple direct conversion RX or an SDR RX) into your computer, and using an audio spectrum FFT display to show the frequency of the received audio.
Most HF QRSS activity is on 30m at 10140kHz.
Typical messages
Typical messages are very short, and replies are usually on a slightly different frequency to transmissions, for example:
CQ M6KWH K - M6KWH calling CQ
M6KWH ON7YD K - ON7YD replies
YD XDV 000 K - ON7YD call truncated, received, send report
XVD YD TU 73 K - received ON7YD back to you
YD XVD CL 73 SK - ON7YD received clear 73
WSPR
WSPR transmissions are a lot more complicated. As the message is encoded is a series of symbols/tones, each of which is transmitted on one of 4 frequencies (4FSK). For 30m the nominal "Dial freq" of the receiver is set to 10138.7kHZ USB. This transmits a WSPR message at 10140.2kHz, USB.
The symbols are transmitted as one of 4 tones like this
Where tones 0-3 are used for encoding the 4 tone FSK messages. The tone spacing is 1.46Hz (officially 1.465Hz but my DDS cannot resolve the last digit!). This uses a BW of just 6Hz and is transmitted at 1.4648baud, for the whole message the transmission time is 110.6sec. Transmissions are synchronised to start within 0-1 sec at 2 minute intervals based on UTC, that is for example at 00:00-00:01, 00:20-00:21 etc.
Messages
The WSPR message sent is a standard format which must be adhered to
Call Sign - Locator - power (in dBm, must end in 0, 3 or 7)
E.g. _M6KWH_IO92_37, where "_" is a space character - the third character MUST be numeric so there's a space at the front for my callsign
Their is a very good program called WSPR available on the web which runs under all OSs. This program both decodes and generates audio WSPR signals, including generating the symbol data from your information and outputting a modulated audio signal.
Your SDR radio tuned to dial 10138.7kHz USB will look like this
The WSPR program will display a narrow band of audio input from 100 - 300Hz around 1500Hz The display will look like this
It will read the signals being sent in the correct time slots (your PC clock must be accurate!) and decode them like this
the interesting parts which show the time (UTC), the frequency received, the call sign, locator and the power.
By uploading these received signals to a data base at WSPRnet you can plot them on a Google map and see either where you are receiving them from, or how far your signal is reaching.
Setup
There are two ways to set up a WSPR transmitter.
1 Use a program WSPR.exe to encode your symbols. Or use my Arduino based program described above, which tunes your transmitter with a sketch to shift the frequency of the DDS by the correct tone frequency.
2 Use an SDR TX shield and modulate your transmission with the audio output of the PC based WSPR program audio signals.
I will be investigating both or these methods and the transmission of QRSS in the future.
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