Prepping 101: Pecking & Scanning Radio Signals Worldwide With RTL-SDR

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Resources:

RTL-SDR Package from Video $47.22
RTL-SDR/w Upconverter (no 9:1 balun) $37.01
9:1 Balun $7.83
SMA Male to BNC Male Cable
Link to RTL-SDR.com Supported Software
SDR# Plugins
Decimation Plugin
Frequency Manager/Scanner Suite
All RTL-SDR on Ebay
RTL-SDR Printed Book (Amazon)
RTL-SDR Dongle (Amazon)

Communications is one of the few topics here that has no real end. After the collapse, or the big reveal as I like to call it, all of us are going to want for resources. You just can’t store enough food to last forever, and as great as “living off the land” might sound, it ain’t easy, even when you know what you are doing. At some point, whoever survives is going to want to connect with others who have survived. You are going to want to have an ear to the ground.

Also, as I explain in this very long video, your first and best sign that some sort of organized force will be coming into your area is via their radio communications. You probably won’t be able to tell what they are saying due to encryption, but you’ll see the signals, and you’ll know to either lay low, or bug out. Watch at least some of the video so you can see what pecking and scanning for signals at least looks like. This is not a huge investment or learning curve, just to get going functionally.

Off grid, off network long distance communications, even from the other side of the globe, not only are possible, they are commonplace. As I have explained several times in this column, you need the right radio, and the right antenna or antennas. The Boefeng UV-5R (the darling of ignorant fools selling prepping advice) isn’t going to be of much use.

For this week I wanted to return to the cheapest option for radios, the RTL-SDR. This is just a receiver. It does not transmit, so if you have the budget, please see my other communications articles here. But even if you have a comprehensive long distance Ham set up, I think the RTL-SDR is still a great investment. With free and easy to use software, you can have access to the entire long distance frequency block, which is called the HF or High Frequency block, as well as VHF and UHF, which includes all police, fire, weather broadcasts, aviation, etc. My simple instructions and a $50 investment, will get you online and listening to frequencies from all over the US, and at times, all over the world.

An RTL-SDR radio plugs into your computer through a USB port. I have only tried it on Windows, but there is software out there for the Mac, as well as Linux and Android devices. The simplest RTL-SDR device itself in its original form goes for as little as $7. They were orignally sold as laptop TV dongles, and the first generation wasn’t capable of frequencies below 50mhz, which does not include the worldwide HF signals. As I show you in the video, you can still buy the original device and connect it to what they call an UpConverter if you want the full frequency spectrum, or you can buy one of the combo devices I suggest.

The antenna in this package is a simple single wire, and it works pretty darn good. That is one of the dirty little secrets of the Ham Radio industry. You can spend thousands on a giant antenna mounted on a tower anchored in cement, but it is only marginally better than a single wire, right off a regular spool you can get from Home Depot, cut to a specific length. The length is the important thing, because it corresponds to a fraction of the bandwidth size.

The kit I have linked above includes what is called a 9:1 impedance balun that goes between your radio and the antenna. You don’t need to know how the radio wave science works unless you intend to go get your Ham license so that you can broadcast (before the collapse). After the collapse you won’t need a license, but these cheap RTL-SDR do not transmit regardless. Anyone is allowed to listen, and the RTL-SDR covers a frequency range much wider than most Ham radios. You just have to cut your antenna for the proper length for the frequency range for which you are listening, so buy a lot of wire.

Out of the box, you will not hear as many and as clear signals with the RTL-SDR as you will with a real Ham radio. At the end of the day, it’s a cheap hack, but as you can see from my video, if the bands are in good shape (which involves sunspot activity and other propagation factors), you will hear signals from hundreds and thousands of miles away. If you take the time to research the plugins, there are also signal filters that will bring down the background noise, so that you may focus on distant signals. I can’t say I have gotten into it as deeply as I can, because I have real radios, and A/B testing antennas and radios takes a lot of time. I am going to test some of the more expensive RTL-SDR devices if we have time, including a couple SDR options that transmit, but this $50 kit is still a no brainer.

Pecking & Scanning: What’s in the Video?

This is the longwire chart from the video that is tough to read.  The far left column is meters, then how many feet of wire. Then it shows you the Standing Wave Ratio, or SWR, for each of the amateur bands. As you can see, 52.5 works pretty well.

This is the longwire chart from the video that is tough to read. The far left column is meters, then how many feet of wire. Then it shows you the Standing Wave Ratio, or SWR, for each of the amateur bands. As you can see, 52.5 works pretty well.


The video this week is over an hour and that was after extensive editing (so if I say “as I mentioned” and I didn’t mention it, that’s why). I could have split each topic into its own video, but I find it easier when all of the information is in one place. I demonstrate in this video:

  • An overview of inexpensive dongles.
  • How a basic wire antenna works with a balun.
  • Installing SDR#, the easy and most flexible SDR software for RTL sticks.
  • Settings for both the black box dongle and the rtl-sdr.com dongle with UpConverter.
  • Pecking signals to check them out.
  • Installing a decimation plugin, which allows you to focus on signals.
  • An explanation of the different signal types and the bandwidth visualization.
  • A basic look at the most popular scanning plugin.

The one thing I didn’t explain fully in the video was that there are literally hundreds of “normal” “Software Defined Radios,” or SDRs, on the market, some up into the thousands of dollars, so when you start your own Googling around, it can get really confusing. My first quest when I found these bugs was to find software that both receives and transmits, but alas, the RTL chip is not capable of transmitting. It took me about a week to figure that out.

SDR is a newer technology approach to regular old Ham radios, which I have covered extensively. And Ham radios aren’t cheap, outside of radios that only broadcast on a few frequencies. One of my prior articles goes through the give and take of Ham radios as it relates to cost. Digital modes in Ham are popular right now (as you’ll see on my 40 meter sweep on the video), so the radios that go for cheap are the ones that can’t do digital. Dedicated SDR radios, and SDR software that is compatible with newer Ham units, are mostly apart from RTL-SDR. They do not work with the chip limitations of RTL-SDR.

Fortunately, the folks at RTL-SDR.com have organized the software that works specifically with these TV dongle technology devices. I can’t say I even fully understood that for my first article, and I even mentioned the Softrock SDR radio in that article, which is not an RTL-SDR. Stick to that supported software list and the extensive instructions and you’ll save yourself a lot of time. I also suggest that you buy the print book from that company. It is printed on demand, so the latest stuff is always in the newest copies, and they do update it.

Phone Apps for Radio Communications

This is a phone app that will tell you the ideal length for a dipole antenna.  For a 9:1 balun with an end fed dipole, you use the total length. The leg lengths are for a center fed dipole, as seen in my other articles.

This is a phone app that will tell you the ideal length for a dipole antenna. For a 9:1 balun with an end fed dipole, you use the total length. The leg lengths are for a center fed dipole, as seen in my other articles.

If you search the Play Store on Android devices, you’ll find a lot of Ham related software. There is an antenna length app that will tell you the ideal dipole length to connect to that little white box for a given frequency. You’ll see in the video that I cut the wire to 52.5 feet, because that is a general length that works across all the HF bands pretty well. The technical name for this wire antenna is an “end fed dipole,” and you use the total length, not the leg length. If it were a center fed dipole you would use two pieces of the leg length with a 1:1 balun line isolator. If I were transmitting I would cut a specific length of wire to the frequency, because there are frequency resonance issues that are not as pronounced on receive as they are on transmit. You can also use a standard Ham antenna with an antenna tuner, as I have shown in prior articles.

There are also specific RTL-SDR aps these days, but I have not tried them. The RF Analyzer by Dennis Mantz looks like it has all positive reviews, but you’d also need the cable to plug it into your power slot. There is also a suite of driver and apps by Martin Marinov. The $9.99 SDR Touch Key seems to have been created specifically for the TV stick dongles, even though it is just called SDR, so maybe I’ll do a separate article on that at some point. The reviews look positive.

You can also check for sun spot activity for HF propagation, and there are now apps that look up call signs at QRZ.com. You can actually get the home address of all of the people you hear on my example calls in the video. And if you want to get licensed as a Ham, I found that there are great apps for the test questions, free.

Licenses, Radio Silence, and Irrelevant Nonsense

The nice thing about RTL-SDR is that it is a cheap technology that has no conflict. You do not need a license to listen to any frequency, so you aren’t breaking any laws, even though it may feel like eavesdropping. I would say that the government is not happy about the general public having this information, because if you look at some of the archives on RTL-SDR.com, you’ll see that you can download NOAA satellite images and Russian satellite images, as raw files. I haven’t personally sat down and done this yet, mostly because I know it won’t do any good to show online yet more images of Solar Radiation Management trails behind the planes (in dufus speak chemtrails), or evidence of radio wave tampering with the clouds that the trails create. All you have to do is look up and you’ll see the trails, and you’ll see the clouds with the wave patterns in them.

Radio silence is also not a concern, because there is no signature caused by a receiver. We don’t think about it much, but all of these waves you see on the screen pass through us all the time. Any radio is a simple device that catches these waves on an antenna and amplifies them.

If you look around the RTL-SDR plugins, you’ll find a triangulation plugin that actually shows a heat map of signals. It is painfully easy to find a radio signal when you have a network of receivers, which of course the government maintains. That is why when it comes to transmit, you have to be really careful. I have demonstrated a number of options for mobile long distance radio, even on a tight budget.

The RTL-SDR is not the most sensitive or powerful method you can buy to monitor radio signals, but it is pretty darn good, and for the money, I don’t think you can beat it, or even come close. Without all of the chatter, after the grid goes down, I suspect that these bugs will be all you need to see what is left out there. You can spend $300-$5,000 on a real Ham radio, get the cables and software, and duplicate the functions here, but I’d rather see you buy an RTL-SDR and $250-$4950 of flour, rice, beans, pasta and canned food.

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