Radioberry preamp
This board is a nice addition to turn the radioberry into a small QRP radio.
The design is based on all the amazing work of Hermes Lite 2 Group!
Power in : 12V
HF Power in : Tx from radioberry. HF Power out: 5W
The board (2-layers) must be plugged on top of the radioberry.
External connections:
| function | Pin | Pin | function |
|---|---|---|---|
| GND | 1 | 2 | DOT in CW pihpsdr |
| GND | 3 | 4 | DASH in CW pihpsdr |
| GND | 5 | 6 | Key in |
| GND | 7 | 8 | PTT in |
| GND | 9 | 10 | TR out |
DOT/DASH
When running pihpsdr with local CW enabled you are able to connect your keyer inputs to pin 2 and pin 4.
PTT in and Key in
The pin 8 is the push-to-talk input. Ground it to put the radio into transmit mode.
Ground pin 6 will put the radio into transmit mode and generate a CW signal.
TR out
This is an "open collector" style output to turn on an external power amplifier for transmit. The pin 10 is pulled low during transmit. An external PA should pullup pin 10 with a resistor. The pin may be pulled up to 28V. Power should not exceed 1W, and should most often be much less than this. For example, don't exceed 80mA at 12V, so minimum pullup resistor of 150 Ohms. Typical pullup resistors will be in the 1K to 10K range.
RX/TX Switching is done using a relais.
I do use this board with my power amplifier (100 W) using built in LPF filters.
The board contains 2 fets for getting the HF power.
This device is used to set both bias settings for the Radioberry preAmp.
The setting can be made permanent (non volatile) by saving the bias values in the EEPROM of the device.
The bias is a specific setting stored and determined specific per preAmp board. (Setup only once).
This device is measuring:
- the temperature of the PA finals
- the PA current during transmit.
The temperature and current are visible in the SDR program.
-
the bias voltage and power supply (swith the PA on/off)
-
switch off the attached power amplifier if the current and temp could not be measured.
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supports the setting of the pa bias setting
-
if temperature of PA is higher than 50C; PA will be switched off!
-
PA recovery after high temperature; switch PA on again if PA temp is in range for 10 seconds.
The control of the i2c devices is not done by the gateware as done in the HL-2 but in the firmware by use of the i2c module running on the RPI, so the i2c module must be selected.
Connecting the board (12V is required to connect) and by opening a command window it is possible to detect the attached devices: sudo i2cdetect -y 1
Use the radioberry development release to make use of this board: https://github.com/pa3gsb/Radioberry-2.x/releases
Please be aware you need to setup the BIAS only once when starting using the amplifier.
Also important to note is that the preamp board can also be used as a standalone PA board.