REPAM - Remote PA Monitor

REPAM - Remote PA Monitor

For some of my projects (Ham related) I need some way of remote monitoring (and controlling) the remote power amplifiers (PA) I use. I decided to make this board with enough I/O for most of my projects.

It communicates via 10/100 MBit Ethernet (RJ45 connector).

It has the following interfaces:

  1. 4 x digital inputs (opto isolated), has separate ground
  2. 6 x analog inputs, 12 bit resolution, 0 to 5V (can be changed via resistor divider at inputs). Calibrated.
  3. 6 x relay outputs. COM/NO brought out for each relay (50V/2Amp).
  4. CAN bus.
  5. Dallas 1Wire bus, for multiple temperature sensors etc. Initially REPAM supports 8 sensors.
  6. Two separately PWM controlled 12V/2A FAN outputs (0..100%) Can be controlled autonomously.
  7. RJ45 connector for Ethernet.
  8. 2.1mm DC plug for 12V power.
  9. USB port for update/diagnostic.

It contains two autonomous fan controller loops, each one can use one of the 8 temperature sensors to control a fan. You set the lowest temperature for the fan to kick in and the speed for that, the highest temperature and the corresponding fan speed for that temperature. The fans will then be regulated according to the measure temperatures (for cooling of PA modules etc).
You can set alarm triggers on high/low thresholds on the analog inputs, on the temperature sensors and the Dual RF Head sensor (FWD, REF and SWR). The triggers can bring one of the relay output s on/off/pulse. They can also signal an alarm on the JSON data etc.
A few more things will be added along the way.

The board uses a 220 MHz Cortex M4 processor, a NXP LPC54628, ethernet Phy is LAN8270. I have a complete (LwIP) TCP/IP stack running on the board (and RTOS of course). 

Communication to the outside world is via TCP socket connection. JSON formatted data flows both ways. Multiple clients are handled by the box. Has also a simple command interface using netcat over UDP.


Currently the hardware has been tested 100%, a small number of boards has been produced and software is being finalized.


Check also my Dual RF Head product

Below is a link to a Youtube playlist for the REPAM module with several videos.
REPAM Playlist

REPAM and Dual RF Head demo

Voice alarms

Updating firmware in REPAM

Box design

I designed a box for the REPAM board. I made the design so it can both be 3D printed and be milled (I use JLCPCB for that). The size is 99 x 84 x 24 mm.
The milled housing (2 parts, top and bottom) ended up costing a total of €45.78,- (€26.24 for top, €19.54 for bottom). Surface treatment is conductive anodizing. Shipping with 3 days DHL express added another €18.67.
3D printing it will obviously be cheaper.

First prototype box arrived from JLCPCB. Quality, fit and finish are absolutely perfect! I can only recommend JLCPCB's PCB and CNC milling service!

The front plate is designed in CAD as a normal PCB (without any copper), produced in 0.8 mm thick PCB with black soldermask.

Configuration and testprogram

To configure and test the REPAM device I made the "REPAM Monitor" application. This lets you define triggers, fan controllers, calibration of a connected Dual RF Head etc.

PAMonitor application

I developed a small C# application (source available) for "everyday use" of the REPAM module. In this case, it monitors my tower mounted 500W 70 cm EME amp (W6PQL design).

Application lets you log data to a CSV file (1 second intervals) for studying behavior of a new amplifier, below are graphs for forward power versus efficiency, and below that, forward power version Idd (LDMOS current).

If you enter a loss factor (in dB) for the cable between PA and antenna, click on the "Pout" indicator and it will change and show the power delivered at the antenna feedpoint instead (each click switches between "Pout" and "Pant"):

All alarms can be configured and its even possible to assign WAV files to each of them for announcements when a alarm is triggered

Update follows....