The Amsat upconverter version-4.2 has a serial interface on a 6-pin header near the LED row. Diagnostic messages and measured values are output here:
Level: 3,3 Volt (for connection to a RS232 interface a 3,3V - RS232 converter is UNCONDITIONALLY required !)
baud rate: 9600 Bd
Data bits: 8
stop bits: 1
The diagnostic messages are not interesting for the normal user.
What is particularly interesting, however, is the output of measurement data:
UPC_AA_BB_text terminated with newline.
UPC … 3 characters header to indicate that display content follows. Lines not starting with UPC can be ignored.
_ … Space
AA … always twice 0, i.e. 00
_ … Space
BB … ID of the following record
_ … Space
text … Data content as ASCII text
Here is a selection of information that will be output:
|00||PA temperature in degC|
|01||internal supply voltage after the 5V step-down converter in mV|
|02||Voltage corresponding to the transmit power (forward power) followed by the dBm value (approx. value)|
|04||status of the LOCK LED|
|05||frequency of the mixer oscillator|
|06||Status of PTT LED, resp. PTT input|
|07||Greeting message after power on|
|08||Message when the synthesizer resynchronizes, e.g. after failure of an external reference frequency|
|09||LOCK status of the ADF4531 synthesizer|
|10||Input frequency of the upconverter, according to jumper M, N|
|11||Overtemperature alarm: ON or OFF (threshold: 75 degrees C) followed by temperature in degC|
|12||Undervoltage alarm (5V Step-Down Converter): voltage in mV|
|13||Overvoltage alarm (5V Step-Down Converter): voltage in mV|
The Amsat-DL downconverter also has corresponding serial messages. To receive both with a single serial port, downconverter and upconverter can be connected in series:
The serial output of the downconverter is connected to the serial input of the upconverter. The serial output of the upconverter is connected to a computer via a 3.3V-RS232 level converter. In the computer you can then read all messages. The messages of the downconverter start with header “OLD”, those of the upconverter with “UPC”.
The power is measured with an AD8312. The AD8312 is a logarithmic power detector. Its output voltage corresponds to the power in dBm.
If one wants to measure the actual power, an adjustment has to be done first. That is, the relationship between measured output voltage and real power must be measured at two powers (one low and one high). Then one can convert each measured voltage into the corresponding power. If this adjustment has to be done for every single board or if it can be done in general is not known yet, because you need a lot of boards. Who needs exact results must carry out the adjustment in any case for the individual board.
The evaluation of several boards showed that the measured values are very similar, so that a dBm exact measurement should be possible. Above message UPC 00 02 gives both the measurement voltage of the AD8312 and the estimated power in dBm. At the moment this “estimation” looks very precise, whether this will remain so will be seen after the production of a larger quantity of boards.