If you know me, you know I like to build electronics. It doesn't always have to be radio-based, as I've built many things using Arduinos and Raspberry Pis. Today, I want to put something together that is both practical, fun and creative! And one day, it could even be useful in emergencies when information is crucial.
Solar Powered FM Radio
Stuck in an Altoids tin too, of course. For the curiously strong.
At the heart of this project lies those cheap, inexpensive FM radio kits you can find off of AliExpress, eBay, etc.
This one has an LED on it, and while useful for power indication, it could also function as a flashlight if you use a super bright LED. Maybe even a small lantern-esque light too.
The tactile switches provide the functions of station seeking, volume, and power on/off. The radio relies on the RDA5807 radio-on-a-chip. It is the only SMD device in the kit, the rest being through hole components. Power is supplied by 2 AA batteries, but instead these kits will be powered via two 1.2V garden light batteries. The batteries will be recharged (and the radio should be able to run) from two small solar panels, also scrapped from the garden lights.
RDA5807
The RDA5807 is a REALLY cool chip. It has everything on board for a professional FM receiver, including (but certainly not limited to) an LNA, oscillator synthesizer (with help from an external 32.768KHz crystal), and a built-in audio amplifier too. The drawback? It's SMD.
What's even cooler is that it can decode RDS streams! Those are carrier-encrypted messages that give details such as the song name, artist, album, station ID, etc. How we can access this I have no idea, but maybe soon I'll figure it out. Now if you aren't into SMD, you can buy the module pre-fabricated on a PCB board with the crystal. This module is more for use with microcontrollers such as the Arduino or Pi Pico. This should enable easier RDS decoding, and in fact the Arduino has a library specifically for this chip too!
Power Draw
This is all very impressive but cmon...there's a catch, right? Like how much power does it draw, a solid amp?
Nope.
Okay, 750mA?
Not even close...
20mA. That's it, 20mA of power is all this thing needs! That means with standard alkaline batteries (6 ampere-hours), this little thing will last constantly on for 12.5 days.
Now with a single 3.7 li-ion battery, that's a different story. Most single cell 18650s are rated at 3.5Ah maximum, so that means about a week of playtime if the radio was constantly on. However don't forget we have solar panels to charge! So in theory? This should last for years. Tens of years even.
Or, let's take some standard 2.4V (2x 1.2V AAA Ni-Cd, what I'm using) rechargeable batteries, again with the solar panel charging setup. I found these in the solar lights I bought from Dollar Tree. These put out about 200mAh of current per battery. For this application we're looking at about a day of power, around 20 hours. But remember this is single use, charged once if we just use standard alkaline batteries. The rechargeable batteries will be constantly charging, discharging and recharging when exposed to the sun.
Take a battery-powered radio for your stay
In the event of an emergency, be it weather, civil, or unfortunately nuclear, this small device would most likely be a lifesaver. Sure, you can purchase a ready-made radio off of the shelf that has both AM and FM (sometimes even weather band), but I feel like it's easy and more common-sensed to make your own. You actually know the layout of the board and you know what components you've used so you can replace them if need be. These FM radio kits are about a dime a dozen online and are good practice for soldering. You can even buy them in bulk amounts too.
What'd be even better would be an AM radio based on the TA7642 that's solar rechargeable. This IC only needs 0.2mA of current to run and a single 1.5V voltage source. In doing calculations (using one 1.2V 200mAh battery again), this equates to 1000 hours of constant playtime!
Why an AM radio though? Sure, FM is crystal clear but AM travels leaps and bounds. Most infrastructure that would still be surviving in an emergency situation would most likely be AM radio stations. My city has at least 3 FM stations though, and in the event of a tornado or other natural disaster, I think they too would still be on the air. However, it's never a bad idea to have an AM emergency radio if you are in rural places like Martin, North Dakota - great for listening to AM DX but very poor if you want FM reception from places like Bismarck or Minot.
In summary - populated places like Maryville, Kansas City, etc., you'll be fine with an FM radio. For sparse areas, consider an AM radio. But having both is not a bad idea...
In fact here's one you can make!
Final Words
By no means am I a prepper. I never claimed to be and in fact I probably would be the first to fizzle out :)
But...
Starting with something as simple as this project is leaps and bounds for emergency preparedness. As a CBer and a ham, I feel that radio has become the Swiss army knife for communication, be it anywhere from commercial broadcasting to Morse Code. Radio most certainly has a place in any emergency situation and it's a guarantee that phones will fail in these scenarios. Mains power will also be far from functional which means that renewable power is a must.
As a licensed amateur, I feel that it is important to inform as many as I can about the importance and relevance of radio in all parts of life, even in a non-emergency scenario such as sporting events. I always find myself saying that it's easier to listen to the Bearcat football games on the radio since it's a ridiculous cost for just one season of MIAA Network TV access. Radio stations are free of charge and are made possible through vendors in your community. My college's radio station is made possible by vendors like NPR (receives governmental grants too) and the Corporation of Public Broadcasting, but it is also up and running through the curriculum that media majors go through to earn a degree.
If we give up on radio, it may not be there when we need it the most. Things like Spotify, YouTube Music and Pandora will not be able to relay any emergency information as the internet would most likely cease to exist in an emergency. Without radio stations, crucial information about the who, the what, the when, the where, etc. would not be passed along, leaving many, if not all in the dark and unaware of how to prepare or what to do to protect their lives.
And also, radio has some hidden gem stations too! KMALand, a radio station in Shenandoah, Iowa provides crucial weather information for all parts of southwest Iowa, southeast Nebraska, and northwest Missouri when the weather turns south. I caught my first-ever tornado emergency broadcast on this station and I have tracked storms with this station too. KFEQ in St. Joseph, Missouri on 680 AM has late-night radio shows from bygone days after 10pm most nights, and in the morning provides farming data and relevant news and information to my area, not that I know much about farming.
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