This project evolved from assisting construction or completing sold state power amplifiers (SSPAs) including surplus NEC TV modules for 70cm and Larcan TV modules for 2m and 6m. Other pages describe some of these projects. This experience identified the deficiencies in low-cost modules designed primarily for sequencing the relays and power supplies in SSPAs. The lack of protection (over-drive, SWR, excessive current, excessive output, spurious operation released the “magic smoke” from a number of power FETs during setup, testing, and operation.
The controller monitors inputs for a drive detector, SWR reflectometer, temperature sensor, and optional PA current. It controls relays for antenna changeover, power supply, and optional LNA biasT. Example peripherals are described in the CBRS 6m Half Larcan SSPA presentation.
In PTT and release, the controller sequences the antenna, power supply, bias, and LNA.
The state of the controller is shown of front panel LEDs.
The controller:
- Operates PS and Ae C/O relays on PTT
- Sequences C/O and PS on PTT – LNA if fitted
- Monitors Drive, Power Out, SWR, Temp
- Shuts down SSPA on fault – sequenced
- Indicates operation and fault on LEDs
- Indicates temperature rise by flashing LED
- Provide PTT timer – shuts down after 2min
- Provides serial debug to PC for setup
- Traps PTT at switch-on & warns operator
- Test flashes LEDs on startup if normal
For setup and testing, serial text messages are provided via the USB port on the Arduino Nano. Links on the PCB allow faults to shut down the PA during testing.
The Arduino software (a copy is available on email request to <mycallsign> at wia . org. au) operates in a 10ms timed loop. Each input is read and debounced. The states and sequences are then executed through flags.
VK4AMG 