Because we work with high power and expensive devices, we like to implement some safety measures in the Arduino controller.

What I was planning to do is the following.

For the PA itself:

- Measure the input power, and if it is higher that acceptable, do something with it

  The input power is measured on the PA printed circuit board. With an input of 100W the power after the -10dB attenuator

  the power is 10 Watt. And on the PCB after the 3 dB attenuator there is 5 W left. Because we have an impedance transformer of        1:4, the impedance is appr 12.5 Ohm. 5Watt over 12.5 Ohm gives peak ! 8V. And,....don't forget the bias of 2.7V,.....Oeps,...over        

  10Volt!! By, by (after a while) with your FETs,.... 

  Later I changed the 3dB attenuator into a 6dB attenuator (see here), to further decrease the input power.

 

  So we measure the input voltage directly after the attenuator and here we still have 50 Ohms. 5W over 50 Ohms gives about 15V.

  It is given to the outside world on pin 12 via a 10x divider and rectifier. So there you measure around 1.5V with 5W. I read it on a

  analog port on the Arduino (A5). And if it goes higher, I shut of the PA (later explained).

  So at 100W input the voltage on pin 12 should be about 1.5V Volt.

- Measure the DC input Voltage, just to know that it is ok and within limits, pin 2 of the control port, A0 on the Arduino.

- Measure the 5V within the Amplifier PCB, just to know that it is ok, we measure the temperature with it ! Pin 5 and 7. Connect

  only 7 to  A1 of the Arduino.

- Measure the Drain current and check whether it is withing limits, pin 4 on the control port and A3 of the Arduino.

- Measure output power. Pin 10 on the PA module. Goes to A6.

- Measure reflected power, pin 8, A7

- Measure the temperature of the cooling block, pin 6, A4

- Mechanism to pull down the bias voltage on the gates of the FETs, pin 9, Arduino D52

 

For the Transceiver that excites the PA, in my case the FT-950, I use the standard PA interface, I made a cable for it by myself.

- Read the 13,8V on pin 1, D37 on Arduino.

- Read the band data and use it to present it on the screen and set the correct filter, pin 4,5,6,7 and Arduino D38,40,42,44

- Read pin 2 TX GND to Linear and use it in the Linear, set lamps, disable INH etc.

- Read pin 8 and use TX INH to the Transceiver in case of emergency, D46

- Use EXT ALC for protection, decided not to use it, because the level is controlled by the Transceiver and the PA amplification,

  which is practically constant within 10%.

- Use TX REQ to get a test signal from the Transceiver. For the moment it is not used.

 

For the Filter:

- Use the 12V of the back panel module to feed the Arduino and the filter. And all of the fans. Make sure you don't draw more than

  the specified 3 amps.

- Connect pin 8 and 10 (GND) to the Arduino.

- Connect the 7 filter drive inputs to the filter drive outputs of the Arduino, D22,24,26,28,30,32,34             

 

All cabling between the boards has ferrite to keep the hf from the lines. And before even think of using an Arduino, turn the Arduino upside down and solder 10nf over ALL in and outputs to the ground. Takes some time but it helped me to keep the Arduino running until now,......

 

The rest is explained in the software chapter.     

 

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*   USING ALC as an additional safety measure     *              

*                 see sepatate chapter                               *

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