IoT Based Telemetry for Paging Transmitters – Functional Within One Day

[UPDATE (11/24/18)]

Several additions and modifications have been made to the development/beta version of this transmitter telemetry system over the

The latest look and feel of the online telemetry dashboard, developed as of the beta version 1.4 Arduino Sketch code.

past couple of days. Keyline status monitoring has been added to the circuitry and code (indicating whether the transmitter is in “STANDBY” or “TRANSMIT” mode) which can be seen in real time on the updated dashboard, which has a few added features, including up to 24 hour graphing of the P.A. heatsink temperature, and P.A. duty cycle percentage display. As I mentioned before, this is a “work in progress” and the imagination is about the only limit to what I can build into this telemetry system.


[Original post] Having gotten the Power & SWR Monitor Panel with LCD display to a state that it’s ready to operate permanently on one of the paging transmitters

Arduino Mega 2560, topped with an Ethernet shield, along with a Prototyping board with breadboard for convenient modifications, additions, etc.

owned by a client, I’ve already begun developing the next generation of the project: an IoT based monitoring system which provides real-time monitoring of system performance.

This generation of the project utilizes an Ethernet shield running on an Arduino Mega development board. It also has the added feature of temperature monitoring. The thermal probe is strapped to the back of the P.A. heatsink assembly for now. I plan to test locating the thermal probe inside the P.A. final stage cavity, but it remains to be seen whether the high level of RF inside the cavity may interfere with the circuitry which is actually located inside the working end of the probe.

Screenshot of the online telemetry as it appeared during an intentionally created high SWR event (transmission line disconnected.) VSWR calculated as 3.12:1. (Note: the dashboard no longer looks exactly like this — see photo posted in 11/24/18 update above for the latest version.)

The system monitors and will remotely display forward RF power, reflected RF power, SWR/VSWR, and the heatsink temperature. I am considering adding monitoring of the “key” line. The purpose of doing that would be to be able to remotely determine whether a system malfunction (pages not being transmitted) was related to problems with the linking receiver system (which would result in no transmit “keying” of the other components in the system), keying with no or low P.A. output (most likely P.A. or exciter failure or malfunction), or high SWR (antenna or transmission line issues.) The latter two are already covered, but being able to narrow down a link receiver radio issue before even packing up for a service call could be very useful (one of those radios weighs about five pounds… if you’re familiar with Glenayre/Quintron equipment, then we don’t even need to talk about how much one of the Glenayre or Quintron power amplifiers weighs!)

Now, it’s time for coffee while I sit and ponder what cool things to do to this creation next. It is truly a work in progress.


Demo of Custom Built Arduino-Based RF Power & SWR Monitoring/Alarm System

This video demonstration shows the custom-built, Arduino-based RF Power & VSWR Monitoring/Alarm system which I recently built as part of my engineering work for a client who owns a multi-site paging company and uses Glenayre and Quintron paging systems. They are great systems — built like tanks and extremely reliable. We had a few of their Power Monitor panels sitting around, but despite much searching, nobody seems to have the documentation, schematics, wiring diagrams, etc. on these power monitors, which haven’t been manufactured in many years. To wit, I decided to just “gut” the thing and use the chassis and the old meter bezel/lens and build one that does everything I wanted it to. While this project was originally intended with the client’s Quintron and Glenayre paging transmitters in mind, the monitor/alarm system is just as usable in other transmitter systems or repeaters — it’s really just a matter of having an RF power sensor of the right type (proper operating frequency range and output voltage range.)

Starting with an Arduino Uno R3 development board, a dbProducts power sensor, a 16×2 LCD display, I went to work building this RF Power & SWR

Monitor/Alarm system, which constantly measures the transmitter’s forward and reflected power in Watts, and uses an algorithm to precisely calculate the VSWR, all of which is in turn displayed on the front panel.

In the event of a high SWR event, the LCD display shows the actual VSWR and an audible alarm is activated. In addition, an SWR alarm LED turns on, which remains lit until a momentary contact button is pressed, resetting the alarm condition. I wrote the Arduino IDE sketch code to “latch” the LED so that in the event of a temporary high SWR event (ice on the antenna, for example) the system can continue to update and display real-time power and SWR readings but there will be a visible indication on the front panel that a temporary high SWR issue occurred.

The above video shows the system running my v2.4 Arduino sketch code. There will be future updates to the code and the hardware, as I intend to add features such as temperature monitoring, remote access/monitoring, automatic alerting of alarm conditions via RF signaling and/or internet linking, etc. I most likely will end up designing and building a custom Arduino “shield” for a much neater, quicker, easier installation and deployment. The main thing is that the first working version of this monitoring/alarm system is now built, installed, operational, and doing everything I originally intended to do.

This initial build has a few cosmetic imperfections, but hey… in the future I’ll use a better grade of paint when “masking off” all but the desired portion of the original lens/bezel assembly to accommodate the actual LCD display size and repainting the front panel to do away with the original labeling, etc. Until then, it does the job, so who cares if it doesn’t look all spit-polished like it was made in a factory (with a price tag to prove it) ?!?!?!