2G Gone? Bring It Back Yourself!

Some parts of the world still have ample 2G coverage; for those of in North America, 2G is long gone and 3G has either faded into dusk or beginning its sunset. The legendary [dosdude1] shows us it need not be so, however: Building a Custom 2G GSM Cellular Base Station is not out of reach, if you are willing to pay for it. His latest videos show us how.

Before you start worrying about the FCC or its equivalents, the power here is low enough not to penetrate [dosdude]’s walls, but technically this does rely in flying under the radar. The key component is a Nuand BladeRF x40 full-duplex Software Defined Radio, which is a lovely bit of open-source hardware, but not exactly cheap. Aside from that, all you need is a half-decent PC (it at least needs USB-3.0 to communicate with the SDR, the “YateBTS”  software (which [dosdude1] promises to provide a setup guide for in a subsequent video) and a sim card reader. Plus some old phones, of course, which is rather the whole point of this exercise.

The 2G sunset, especially when followed by 3G, wiped out whole generations of handhelds — devices with unique industrial design and forgotten internet protocols that are worth remembering and keeping alive. By the end of the video, he has his own little network, with the phones able to call and text one another on the numbers he set up, and even (slowly) access the internet through the miniPC’s network connection.

Unlike most of the hacks we’ve featured from [dosdude1], you won’t even need a soldering iron, never mind a reflow oven for BGA. 

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Wireshark screenshot with QCSuper-produced packets streaming into it; QCSuper script running in an adjacent terminal

Turn Your Qualcomm Phone Or Modem Into Cellular Sniffer

If your thought repurposing DVB-T dongles for generic software defined radio (SDR) use was cool, wait until you see QCSuper, a project that re-purposes phones and modems to capture raw 2G/3G/4G/5G. You have to have a Qualcomm-based device, it has to either run rooted Android or be a USB modem, but once you find one in your drawers, you can get a steady stream of packets straight into your Wireshark window. No more expensive SDR requirement for getting into cellular sniffing – at least, not unless you are debugging some seriously low-level issues.

It appears there’s a Qualcomm specific diagnostic port you can access over USB, that this software can make use of. The 5G capture support is currently situational, but 2G/3G/4G capabilities seem to be pretty stable. And there’s a good few devices in the “successfully tested” list – given the way this software functions, chances are, your device will work! Remember to report whether it does or doesn’t, of course. Also, the project is seriously rich on instructions – whether you’re using Linux or Windows, it appears you won’t be left alone debugging any problems you might encounter.

This is a receive-only project, so, legally, you are most likely allowed to have fun — at least, it would be pretty complicated to detect that you are, unlike with transmit-capable setups. Qualcomm devices have pretty much permeated our lives, with Qualcomm chips nowadays used even in the ever-present SimCom modules, like the modems used in the PinePhone. Wondering what a sniffer could be useful for? Well, for one, if you ever need to debug a 4G base station you’ve just set up, completely legally, of course.

Building Beautiful Cell Phones Out Of FR4

Over on Hackaday.io, [bobricius] took this technology and designed something great. It’s a GSM cell phone with a case made out of FR4. It’s beautiful, and if you’re ever in need of a beautifully crafted burner phone, this is the one to build.

The components, libraries, and toolchains to build a cellphone from scratch have been around for a very long time. Several years ago, the MIT Media Lab prototyped a very simple cellphone on a single piece of FR4. It made calls, but not much else. It was ugly, but it worked. [Bobricius] took the idea and ran with it.

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