QCX assembly Rev 1.08
88
locator will be calculated from the received latitude and longitude, and the time decoded nicely
from the GPS serial data stream.
The microcontroller in this kit takes care of the WSPR message encoding algorithm, without any
assistance from a PC host computer. It also calculates the tone spacing and symbol duration.
In between message transmissions, the display will show instead just a clock (see below), while
we wait patiently for the next WSPR transmission to begin, according to the settings of the
configuration parameters Frame and Start. This is useful for checking that the time on your kit is
accurately set. The display also shows the minute at which the next frame will start transmitting. In
the example below, the time is 14:55:31 UT and the next frame will start at 14:56:01.
14,097,140 WSPR
14:55:31 < 56
When a GPS unit is connected, the firmware automatically uses the 1 pulse-per-second signal to
measure the transmit frequency and compensate for any inaccuracy due to calibration error or
frequency drift due to temperature. The serial data stream from the GPS is used to set the real
time clock (for syncing the WSPR transmission timing). The Maidenhead locator is computed from
the latitude and longitude information parsed from the GPS serial data.
A WSPR transmission takes 1 minute and 52 seconds. The GPS time and location data is parsed
from the GPS serial data stream at the END of every WSPR transmission. On the first WSPR
transmission after power up, the time may not be accurate. The 27MHz synthesiser reference
frequency is measured and adjusted, in a 4 second period after the end of the WSPR
transmission. Parsing the time and location, and adjusting the 27MHz reference frequency, all
takes place in under 7 seconds. The process is completed before the start of the next WSPR
transmission slot. Nevertheless, you should not configure your kit for continuous WSPR
transmissions in every 2-minute WSPR slot (Frame parameter is 2), which is considered very
antisocial to fellow WSPR operators.
A GPS receiver isn’t essential for WSPR operation but it is highly recommended because it makes
operation more accurate, easy and fun.
During the actual WSPR message transmission, the display shows something like this:
14,097,140 122 2
G0UPL IO90 37
The elements of this display are explained as follows:
•
14,097,140 Transmission frequency (tone 0)
•
122
Current symbol is 122 (of 162 symbols making up a WSPR transmission)
•
2
Current tone being transmitted (one of 0, 1, 2 or 3)
•
G0UPL
Callsign encoded into the transmission
•
IO90
5-character Maidenhead Locator square, encoded into the transmission
•
37
Power in dBm, encoded into the transmission
Summary of Contents for QCX 5W CW
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