Inside Watch Duty’s Echo Radios: Remote Listening, Tone Detection, and Early Warning

November 17, 2023


  • This is a technical overview of the Watch Duty Echo Project, which aims to improve first responder radio coverage in remote areas in the Western US.
  • The challenge: Radio dead zones hinder not only Watch Duty reporting, but first responders, agencies, and volunteer firefighters.
  • Our team built field-hardened Raspberry Pi-based devices and specialized antennas to enhance radio reliability, detect emergency tones, track aircraft, and ensure remote monitoring. 
  • We’re seeking donations (tax-deductible) to expand coverage across the Western US. Please donate to Watch Duty.

In December of 2022, we announced our Echo Project for capturing first responder radio communications deep within the wildlands of California and beyond. Watch Duty reporters, (much like traditional news reporters, government contractors, and even utility companies like PG&E) use handheld radio scanners and internet-based scanners to listen to first responders during an emergency.  This is how we make sense of what is going on in real-time, between the daily official press briefings to keep residents up-to-date.  As it turns out, PG&E and CalFIRE contractors, like dozer operators and water tenders, do precisely the same thing. Contractors and agencies working across multiple regions and states, use the online radio streaming service to listen to local radios in multiple regions.. 

Broadcastify is the primary source for internet-based police and fire radio traffic. It’s free to use, and thousands of people host well-established feeds, which are essentially radio frequencies connected to the internet. Unfortunately, some feeds are unreliable; they go offline or have too much static, and some areas don’t have any feed coverage. As a result, our radio scanning reporters struggle to provide accurate and comprehensive reporting due to missed and/or cutoff transmissions. These feeds serve as lifelines not just for the Watch Duty team but also for first responders and the community as a whole – it’s vital that they operate reliably at all times. Echo aims to fix this.

Instead of scanning channels, Echo-generated streams are fixed to channel sets built for the locality, agency, or region, allowing simultaneous left and right audio streaming from any active channel without the cutoff often generated by scanning-type radios.


Echo Devices are built on relatively inexpensive, single-board computers (Raspberry Pi’s), with several RTL-SDR Blog’s (Software Defined Radios) and a discone antenna. Our volunteer team has sourced, assembled, and programmed Echo to be sent out to local and rural areas throughout the Western States.

Our hope is for Echo to be effective and expandable for the years to come. As radio technologies evolve and frequency bandwidths are modified to adjust to new systems, we want to ensure that Echo is prepared to grow as radio technology advances. 

The shape of the discone antenna provides the opportunity to be utilized in omnidirectional wideband designs and broad-scale data reception. These antennas are commonly used for frequencies above 30MHz and have excellent VHF/UHF (very high frequency and ultra-high frequency) applications over long distances.

Echos are powered by POE (Power over Ethernet) which includes a myriad of benefits including ease of installation, safety, and reliability.  This removes the need for a licensed electrician and also easily allows us to remotely power-cycle the device should it ever stop responding.

Detailed Tech Specs

  • Raspberry Pi 4- Headless Processor: Broadcom BCM2711, Quad core Cortex-A72 (ARM v8) 64-bit SoC @ 1.8GHz
  • 2GB LPDDR4-3200 SDRAM w/ 8GB SanDisk Industrial SD-card
Antenna Diamond D130NJ Super Discone
RX Frequency Range 25 - 1300 MHz
Antenna Cable LMR-400
RX Multi Coupler Stridsberg MCA-208M
Network 2.4 GHz and 5.0 GHz IEEE 802.11ac wireless or Gigabit Ethernet (preferred)
Input voltage POE++ IEEE 802.3bt (48V, 60-watt)
Power consumption 21 Watts during full SDR demodulation
Enclosure Active vented IP65 NEMA 3X enclosure designed to withstand harsh weather conditions.
Operating temperature 0 - 50 degrees C ambient
SDR Specs
Bandwidth Up to 2.4 MHz stable
ADC RTL2832U 8-bits
Frequency Range 500 kHz – 1766 MHz (500 kHz – 24 MHz in direct sampling mode)
Typical Input Impedance 50 OhmsTypical
Current Draw 270 – 280 mA

Deployment Strategy

After many fire seasons, our team has identified broad areas of the Western US that lack proper internet radio coverage.  In order to fill these dead zones, we must find suitable hosts who are willing to host an Echo. Local communities, Firewise groups, emergency managers, and publishing articles like this help to find Echo hosts. 

There are really only a few requirements to hosting an Echo: power, internet, and proximity to radio towers.  The easiest to solve are power and Internet as there are many known solutions off the shelf.  Almost all of our Echos have backup power and most host sites have batteries or generators to ensure uninterrupted power.  Internet connections are becoming much easier with the advent of Starlink, which allows a reliable connection anywhere we need. Many of our sites have backup internet, but that isn't required for Starlink users. 

The more challenging problem to solve is where to locate the Echo so that it can hear the most radio towers.  At first we thought the highest ridges and peaks would be best but it turns out there is a lot of desense at those peaks: meaning the signal strength is too high and is being bombarded by other frequencies from those towers.  As it turns out, putting our Echos in valleys and on peaks that don't have other radio equipment on them yields the best signal quality.  This also makes it easier to find host sites in more populated areas.

We also use radio frequency modeling tools and other geospatial software to allow us to find the best possible locations.  Below you can see a model measuring the coverage radius of an Echo, showing the signal strength based on distance and other environmental factors that affect transmission.

The map below is taken from the same modeling software to allow us to track all our Echos and our estimated signal strength.  The red dots represent all of the repeaters that we are interested in listening to.

Tone Out Detection

In addition to listening to and uploading audio, Echo actively listens live for ‘tone outs’: orders for engines, strike teams, and other heavy equipment.  These tones are similar to telephone keypad tones but are instead broadcast over the airwaves.  Each set of tones equates to a different person or apparatus in the fire service, just like a telephone number would equate to one house or cell phone.

Yellow Pages for tones doesn’t exist, so we had to build our own.  We scoured the internet, partnered with multiple agencies, and recorded all the tones. The result is the most complete list on earth.

Now, when a tone out is detected, our system knows who is getting paged and in what region, and automatically notifies the correct Watch Duty team via our platform.  That team can listen to the audio recording and decide to turn on our scanners or Broadcastify. Our tone out detection tool has proven so invaluable that we are now sharing these tone outs with certain emergency managers.

Aircraft Tracking and Detection

Echos also track nearby aircraft via their ADSB transponders, which are outfitted in all modern aircraft.  We feed this data to public sources to help first responders and use this data internally to alert our team of possible fire starts that other sources may have missed.

When any known firefighting aircraft take off from their respective air bases, Watch Duty is immediately notified.  More importantly, when these aircraft begin circling a potential fire start, alarm bells go off internally if we haven't already acknowledged a fire in the area.

This tool has proven invaluable for our staff of radio operators but also to Watch Duty members who can opt to pay $25/yr to track the firefighting aircraft right in the app.

Remote Monitoring and Maintenance

As many Echos are located deep in forests, we need a way to upgrade and maintain these devices without physically accessing them regularly and to power-cycle them in case the system becomes unresponsive.

With the help of, an Over-the-Air update software, we can manage the entire fleet from anywhere. We conduct health monitoring via Grafana and heartbeat checks to ensure reliability across the network. These feeds are paramount to not only our operation but the operation of many first responders. Downtime can be dangerous.

How You Can Help

Our non-profit relies on donations from the community to make this possible.  We are rolling out Echo’s across the Western United States with the goal of filling all the dead zones to help keep us safe.  If you’d like to get involved, there are two ways you help your community:

1. Donate to fund more Echo Deployments

Donate in the Watch Duty app

2. Host an Echo

If you are interested in hosting an Echo, please email us at