You're Almost Entirely Blind: A Guided Tour of the RF Spectrum
You're Almost Entirely Blind: A Guided Tour of the RF Spectrum
Tales From The Dork Web #11
In a moment I want you to close your eyes and imagine you were blind from birth. How might you describe the colour red? Would you describe it as warmth? The colour of love? Is red an abstract concept? Is it radio at a wavelength of between 625-740nm? Do it now, and spend 10 seconds thinking how you might describe red, having never seen it. Now imagine how you’d describe the colour red if you only saw in black and white. Would it be any different?
What if I told you that you’re almost completely blind? That which you perceive as darkness is you missing 99% of available information. In this issue, I look at ways we can reduce that loss.
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This issue’s music is brought to you by the amazing Gabor Szabo, a brilliant guitarist who fled Hungary for America after the 1956 uprising. His music is timeless and great for playing along with The Dork Web. Give it a go.
Because we’re talking about what you can’t see, I wanted to contrast this issue’s blindness with beautiful colours. This issue’s art is brought to you by the colourful posters of Leonetto Cappiello who changed advertising posters forever.
I’m experimenting with affiliate links in this post. I’m not keen on monetizing The Dork Web but for those that want to it’s a no-cost way to support the newsletter. A link with an asterisk, like this* is an affiliate link. Links without asterisks are not.
How Little We See vs How Much There Really Is
I made this infographic to illustrate how little of the universe we actually see with our own eyes. What we perceive as heat is often wavelengths of light we can feel but can’t see. Those dangerous X and Gamma Rays are just deadlier forms of invisible light.
That little band between 1000nm and 10^15 hertz is everything you and I can see with the naked eye. Yet the universe has so much more to offer if only your eyes could see it.
How can we experience more of the universe? Different frequencies have different properties. Some are obscured by clouds, others bounce off the moon. When you can’t see through something it’s because it’s opaque to the sliver of wavelengths we experience. If you could only see X-Rays, you could hold your hand up to an X-Ray light and see your bones. I mean, you might be dead soon after but it’d probably work.
Lets start with wavelengths you can’t see but will have experienced from 1km to 1cm.
The easiest way to experience this is with a Software Defined Radio. This is a radio device that connects to your computer and lets you explore parts of the RF spectrum. Before buying one, check out this WebSDR directory for some really well put together stations that you can access online. The biggest mistake I made was thinking radio was an expensive hobby and buying tons of kit. 90% Of exploring radio can be done for free with a WebSDR and a virtual cable to reroute audio to another program.
A typical WebSDR looks like the above. The blue area is a waterfall diagram. It shows RF activity across a range of frequencies. The pink dots are activity at those frequencies. The yellow arrow shows the currently tuned in frequency. You can route the audio to decoding tools using a virtual cable tool. ModernHam’s excellent video walks you through the process from start to finish.
If you follow the video, you’ll be able to project yourself to almost anywhere in the world and pick up local signals at a quality way in excess of what you’re likely to get at home. There’s some jargon there but don’t be put off. With WebSDRs, you can chip away at this for 15 minutes at a time here and there for as long as it remains fun. All you need is an Internet connection and a few tools. If you can’t route audio via a virtual cable, most WebSDRs will let you record the audio to be played into tools later.
The video mentioned FT8 digital mode. Digital modes are different ways of sending and receiving data over radio. Think of them as languages. Popular modes include:
FT8 - 13 character bi-directional messages used for reporting contacts around the world. JT9 and JT65 are similar modes you can pick up with a WebSDR.
WSPR - 1-way incredibly resiliant signal mode for low-powered transmission, used by people around the world to see how far they can travel.
PSK31 and it’s older sibling RTTY (and to a lesser extent, Hellschreiber) are bidirectional text-based modes.
APRS, or Packet is used for everything from weather reports to general messages.
SSTV* - Slow Scan Television is used to send pictures over huge distances, even from the International Space Station.
*Technically speaking SSTV isn’t a digital mode, although it has a rich history of it’s own worth an issue. There is digital SSTV which is more like sharing a link from what I’ve read.
The Essex Ham Amateur Radio Society has an amazing site with nicely written step by step tutorials for most of the above. I’ve found the best approach for me has been:
Find tools, frequencies and tutorials for interesting modes
Test everything on YouTube capture videos
Point a WebSDR at the frequencies, capture for a day
Come back, see what was picked up
Refine and improve
Do it live with physical kit
Other digital modes have legal constraints depending on where you are and where the WebSDR is. These include POCSAG (used for pagers), ADSB, AIS and others.
There are specific rules as to what should be transmitted, how and where set by regional and international standards bodies. By way of a map, a bandplan explains frequency ranges normally at a very high level. The ARRL bandplan applies in the US, while the RSGB publishes bandplans for the UK.
When you’re ready to move on from a WebSDR to your own physcial kit, expect your range and performance to drop. WebSDRs are generally very well built by experienced radio hams, or societies.
The best beginners’ radio (in my opinion) is an RTL-SDR USB stick*. These are USB digital TV tuners without frequency restrictions starting around £10. They’re not very good at the cheap end, but they are incredibly good value when combined with a WebSDR. Nooelec and RTLSDR sticks more expensive but are noticeably better. So what are the sticks good for?
POCSAG, ADSB and high power digital modes.
FM Radio and DVB-T, natch.
Low powered radio devices around your house on some ISM bands.
If you get a stick with a normal TV aerial connection, you’ll get better results using your TV aerial than the one supplied. At certain frequencies you’ll pick up signals fairly well. I get about 300 square miles of ADSB coverage from mine.
You probably have things at home that use low-powered radio signals. Your remote control, garage door opener or wireless thermostat may use what’s called ISM bands. These are areas of the RF spectrum reserved for Industrial, Scientific and Medical (ISM) unlicenced use. Your Wi-fi uses an ISM band, as does your microwave. You’ll probably find other non-ISM frequencies used by low-powered devices. Common frequencies worth checking your devices with include:
13.56Mhz - ISM band used for Near Field Communications (NFC cards)
27.12Mhz - ISM band used by Remote Control Cars
315Mhz - Short range remote controls and keyless entry systems.
403-433.92Mhz - Garage Doors, Remote controls and other devices. 433.92 is ISM.
862-868Mhz - ZigBee, M-Bus, KNX RF, LoraWAN, Thermostats and all kinds of crazy things just waiting for someone to listen to them.
915Mhz - ISM band for all kinds of devices.
Once you start looking you’ll find lots of signal sources. Andreas Spiess has a great video on hacking 433Mhz IoT devices with a Raspberry Pi and RTL-SDR dongle below.
But what about if we hear something we don’t recognise? If you want to identify a specific signal, the Sigid Wiki usually has audio of the same kind of signal. Don’t expect 100% matches all the time. It's good enough to distinguish between military comms and amateur satellite traffic. If you’re playing with low-powered devices and struggling with a particular product, Matt knight and Marc Newlin’s 2 hour workshop walks you through examples of hacking different types of RF signals.
That’s the digital world, but surely people still talk over Radio? Yes they do, and you can pick them up on your WebSDR but you might want something a little more handy.
Going Handheld With A Baofeng UV-5R
Depending on where you live, different laws may apply both for listening and broadcasting. In the US, Brazil, Mexico and Canada, some people use the Family Radio Service (FRS) and General Mobile Radio Service (GMRS), with some restrictions in some places. In Europe, we use the Professional Mobile Radio (PMR) services. PMR and FRS are accessible without a licence in the US.
During the COVID crisis, my partner and I kept our phones indoors. This meant that if one of us was out and had an emergency they’d have no way to contact home. Thankfully we already had 3 Baofeng UV-5R handheld radios for emergencies.
The Baofeng UV-5R* is a cheap chinese family of radios all built around similar hardware and mildly different firmware revisions. They have been unlawfully marketed in the US before, but are available on Amazon for just over $20. There are many different variants, model names, brand names but they’re mostly the same underneath. The UV-5R is neither a PMR, GMRS or FRS radio and if you want to transmit you should get a radio specifically for those services. It is cheaper than radios for those services and is fine for listening on the go.
To use one you’ll need:
A Baofeng UV-5R* (or similar)
A Chirp Cable* (for programming frequencies)
A replacement antenna (the Retevis RHD771 is fine for beginners)
Once your kit arrives, it’s very important that you program in the frequencies you want to listen to and disable transmitting on the ones supplied with the radio. Do not transmit on the default frequencies, as these are often used by emergency services. For example, here in the UK the defaults overlap with Ambulance service frequencies.
If you don't mind a little pain you can program the devices using the menu. If you ordered a programming cable you can use the free Chirp software. Tin Hat Ranch’s video above is worth watching before buying one. It walks you through configuring and setting one up to use a repeater. Repeaters are radio stations that listen on one frequency and rebroadcast on another. This boosts your range to 10s of miles with a handheld radio. You should only use repeaters where you’re licensed to do so. Local laws permitting, listening should be fine.
You can use nearby WebSDRs or your own RTL SDR to find local audio traffic, and program it into your Baofeng. Your local Amateur Radio Society should hold on-air meetups, or ‘nets’ that you can listen into. It’s worth joining your local group online and going through Ham Foundation certification. I had planned to do it this year but COVID derailed my plans.
As well as your local ARS nets there are other frequencies worth listening to with a Baofeng. These include the PMR/GMRS and FRS ranges and some of the ISM bands. The Baofeng can receive FM at the low end of Air band up to 127Mhz. Air band is AM, meaning you’re unlikely to hear anything. If you do hear anything at all, voices will sound bad. You should be able to pick up the same signals more clearly using AM on an RTL or a nearby Web SDR.
If you’re in the UK, it’s easy to find your nearest airport frequencies to avoid having to scan. In the US, Radio Reference will help you find hot wavelengths in your area.
Analogue audio I’ve heard so far includes:
Local baby monitors
Local supermarket staff complaining about toilet roll
Local hams talking about seriously bizarre things
Town centre security guards and taxi drivers
The International Space Station
For digital modes on the go, play Baofeng noise into phone apps or record it for later.
Don’t get hung up on how you access signals. It doesn't matter if it’s a WebSDR, RTL SDR or a Baofeng. You can swap things out when you have a specific idea in mind.
WebSDRs can target long wave, Radar and even satellites at very high frequencies. One such satellite worth listening to is Es’Hail-2 and it’s QO-100 amateur satellite payload. It’s a geostationary satellite covering Europe, Africa and the middle east. You can even listen to it online with a dedicated WebSDR.
You can explore really low frequencies with this Heppen-based WebSDR. At 129.1 Khz(!) you can listen to the DCF49 signal used for central European energy management. You can even decode the signals with a virtual cable setup.
Beyond Baofeng, RTL SDR and Human Signals
While it’s true that you can do a lot for free and/or cheap, there are areas that aren’t covered for under £30. The Baofeng doesn’t cover AM, has frequency gaps and doesn’t do Digital Mobile Radio (DMR). An RTL SDR can do DMR and a lot more, but there is an upper limit to where your £10 stick can take you.
For mobile scanning I use a Whistler TRX-1. It’s expensive but easy to program and a ton of fun. It has great DMR support, which is what I wanted. My Baofeng can do 60% of the TRX-1’s job badly but at 5% of the cost. Until you push up against the Web/RTL SDR and Baofeng kit combo's limits there’s little point in spending more.
Beyond human transmissions are hydrogen emissions from the Milky Way galaxy. Radio astronomy needs more than a £10 USB stick alone but you can still detect the hydrogen line of the milky way and other galaxies for under £200. Eat your heart out, Jodrell Bank! Pulsars can also be detected relatively cost-effectively, but it requires in-depth knowledge across several fields. Unlike visual astronomy, radio astronomy can be done in the daytime. So what else is out there beyond long waves to ultra violet?
Things get more difficult from here. The atmosphere absorbs shorter wavelengths than UV, which in turn stops us from dying. The downside is that signals at these wavelengths never reach the ground. This is still better than the alternative.
Professor Michael Richmond of the Rochester Institute of Technology puts his lecture materials online. If you’re feeling brave, his AST 613 Astronomical Observational Techniques and Instrumentation: Fall 2019 class notes include a walkthrough on analyzing a Tycho supernova remnant using Chandra X-Ray space observatory data. It looks scarier than it is and the DS9 walkthrough on using DS9 is very very good. I took a screenshot of the Tycho remnant featured in his tutorial above. If I can follow it, you’ll probably be fine.
Gamma Ray Bursts (GRBs) are some of the most violent events in the known universe. Teams of scientists have built satellites and expensive tech to watch out for GRBs. Gamma Rays are hard to detect from the ground, but we can observe their effects on the upper atmosphere. Home scientists can infer the presence of GRBs through detecting disturbances in the ionosphere. Using SID receivers it’s even possible to detect solar flares and other space events.
Closer to home (by which I mean on Earth) you can detect Gamma Rays with a geiger counter. I use a GQ GMC-320+V5 geiger counter at home. I live in both a radiation information black spot and fairly close to the UK’s Atomic Weapons Establishment near RAF Aldermaston. I chose the GMC-320 because of it’s Internet connectivity. I don’t usually like Internet-connected devices but contributing to GMC’s world radiation map seems a worthy cause.
I’d like to think I’ve covered as much of the RF spectrum as we can here. It’s amazing how little we see yet how much we can observe. I’m blown away by the fact that I can wake up one morning and decide to engage in X-Ray astronomy analysing NASA space observatory data in my underwear. What a time to be alive.
Things You Might’ve Missed
Microsoft planned to replace contract journalists with AI, which didn’t go well.
Stuff Made Here built a Robotic Golf Club to improve their scores, proving it don’t mean a thing if you ain’t got that swing.
Kyle Hill has an interesting video on information hazards, Roko’s Basilisk and future blackmail.
Canadian coffee shop chain Tim Hortons is tracking peoples’ locations. If they’re doing it, what else is happening on your phone that you don’t know about?
This whole story about eBay executives cyberstalking a couple who were critical of eBay in a newsletter is wild.
Rome-based artist Agnes Cecile’s drip painting is the perfect accompaniment to Ólafur Arnalds’ Fyrsta, from his album Living Room Songs. I thought I’d end with a quote from Winnie The Pooh:
“People say nothing is impossible, but I do nothing every day.”
With the Smart Watch, missing links and AMA I feel I’ve pushed myself a little too much. I’m going to be back in 2 weeks with issue 12 but am considering a change of schedule after that. I hope you’ve enjoyed this issue enough to share it with someone who might like it too. If you haven’t subscribed, now’s the time to do it, below.