Radio Hacks

[Dinah Lianes]

BetweenWorld War II and Y2K, shortwave listening was quite an education. With a simple receiver, you could listen to the world. Some of it, of course, was entertainment, and much of it was propaganda of one sort or another. But you could learn a lot. Kids with shortwave radios always did great in geography. Getting the news from a different perspective is often illuminating, too. Learning about other cultures and people in such a direct way is priceless. Getting a QSL card in the mail from a faraway land seemed very exciting back then.

Unless you hold a First Degree RF Wizard rating, chances are good that coax stubs seem a bit baffling to you. They look for all the world like short circuits or open circuits, and yet work their magic and act to match feedline impedances or even as bandpass filters. Pretty interesting behavior from a little piece of coaxial cable.

[Mikrowave1] had a Unelco shortwave receiver as a kid. This was a typical simple radio for the 1960s using germanium and silicon transistors. It also had plug-in coils you had to insert into sockets depending on the frequency band you wanted to receive.

But how does it work? For an old single-conversion receiver, it works well enough. Of course, when the radio was new, there were many more interesting stations on shortwave. Today, he had to settle for some ham radio stations and CHU, the Canadian time and frequency station.

There were six pairs of coils built on top of tube sockets. The coil was actually more than a coil. There were other components in the case that adjusted other radio parameters based on the frequency.

Like most repeaters, the DME transponders listen on one frequency and transmit on another. Those frequencies are 63 MHz apart. This poses a challenge for some types of SDRs which have limits on bandwidth.

We love minimalist builds like these; they always have us sizing up our junk bin and wishing we were better stocked on crystals and toroids. It might be good to actually buckle down and learn Morse too.

So I'll try to post a couple pictures of this old clock radio I have. I don't want to throw it away, because I'm sure there are tons of cool mods that can be done with it or using it's parts. But I noticed that the display was kind of blinking and making weird characters, instead of numbers, so I can't really use it as a clock anymore, and I already have a stereo. (Even tho I rarely listen to the radio). So if anyone has any suggestions on what I could make with it, please let me know.

U could use something like a single shot shmit trigger (or equiv using op-amps as a comparator) on the output of the alarm. This is so it will stay on when the alarm goes off. Then a relay driver and finally a relay. Off your relay is your switch for what ever.

grab the rss alarm clock from the wiki and set it up. get some quality wireless speakers. rip out the guts of the clock radio out. pick up some cheap little digital clock thats a small size and hotglue it where the original display was. run the power cord to the clock and ac adapters for the wireless speakers through the original hole that the original power cord came out. wrap them somehow so it looks better(perhaps some wide electric tape) and connect the speakers to the alarm clock computer.

Find out which wires go to the buzzer, and hook them up to a relay. Then, get a car horn and hook that up to the relay. Now you have a nice and loud alarm clock to set up under someone else's bed (preferably not in the same house).

I like the car horn idea. Anyway, I finally took some pictures of the radio. First is what it looks like on the outside with the display working right and when it's all weird. Then I'll show you the guts.

You could turn it into a charging station for all your electronic gizmo's. Make it battery operated, with a docking station for your cell/mp3 player, etc. You could gut it and put all the separate chargers inside it, with only the ends of the wires sticking out. :P

That charging station actually sounds useful for me. I have an iPod, 2 digital cameras, and my Xbox 360 controller, and eventually I'll have a new cell phone. I'm definitely going to have to get my hands dirty once I figure out what exactly I'm doing.

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I've been messing around with packet radio and various digital modes on and off for years and have wondered if any vulnerabilities exist that could allow an attacker to obtain remote code execution through the airwaves. I always thought it was a fun idea to be able to hack a computer that isn't even hooked up to the internet. Many ham programs are written by enthusiasts and are quite old, so it seemed likely that there would be exploitable vulnerabilities. In my research I decided to focus mainly on vulnerabilities that could lead to remote code or command execution, though if I found other vulnerabilities, I didn't ignore them. I also decided to start by focusing on Windows software, since the OSED exam focused on Windows user-mode exploitation and it's where I have the most experience. I started this project with a specific goal in mind: get a remote shell over ham radio.

"Packet radio" generally refers to a very specific digital mode of operation that uses the AX.25 protocol. AX.25 is a data-link layer protocol (layer 2 of the OSI model). In this mode, data is split into packets and transmitted over the air. AX.25 has support for different packet types and includes modes that are similar to Transmission Control Protocol (TCP) and User Datagram Protocol (UDP) on Ethernet. In some cases, the protocol can do some error correcting, like TCP. Another mode will just send packets out into the air without waiting for any kind of acknowledgement, like UDP. Windows does not have any built-in way to handle AX.25 traffic, so end-user software would have to do this on its own or it must be abstracted away. The Linux kernel has built-in support for AX.25, so you can potentially set up AX.25 network interfaces that have callsigns for addresses instead of IP addresses.

AX.25 is commonly used today for Automatic Packet Reporting System (APRS), Winlink email over ham radio, Bulletin Board Systems (BBS) operations, and more. It seems it is more generally used for a ham to make a contact with a computer, as opposed to making live contacts with other hams. More information about the AX.25 protocol can be found here: -Jul%2098-2.pdf

How do APRS stations find each other? How does one station find an IGate to bridge to the internet? You can transmit APRS on basically any amateur frequency for which you are licensed, but around the globe each region generally has an allotted frequency where this traffic is used. In the US, that frequency is 144.390 MHz. Just about anywhere in the country you can tune a radio to this frequency and hear data being transmitted at least every minute or so.

APRS is a protocol that runs on top of AX.25, like how HTTP runs on top of TCP. APRS packets make use of the AX.25 unnumbered information (UI) frames. Since I was going to be reverse engineering APRS software, it made sense to examine APRS data frames to understand their structure. AX.25 UI frames look like this:

The APRS specification allows for various data types, formats, and encodings. Most of this information is stored in the information field of the AX.25 packet. A generic APRS information field structure looks like this:

Since APRS is probably the most common packet protocol in use today, and there is no shortage of APRS software to choose from, I decided to start my research here. I focused on Windows-based APRS software that was written in C or C++ so I could continue honing my IDA and WinDbg reversing skills.

Looking over the list, I figured an older client would be the most likely to contain exploitable memory corruption vulnerabilities. Looking at the various options, I found that the WinAPRS download page said it hadn't been updated since January 14, 2013. I figured that was a good sign that the software was likely not maintained and would therefore contain vulnerabilities. I downloaded the latest version (2.9.0) and got to work.

Condenser microphones produce a low level signal that needs phantom power to bring it to line level i.e audible for broadcasting. While many audio interfaces act as pre-amplifiers that have phantom power, using a Cloud Lifter or Fethead is a way you can boost the gain on your microphone without getting too much noise or distortion. They can act like a pre-amp for your pre-amp and give you a louder and clearer mic signal.

The split-seconds of radio silence as one track ends and another starts doesn't make for a seamless listening experience. Applying a cross-fade between them can create a better, more professional sounding broadcast. Either cross-fade your tracks yourself using DJ hardware or software, or set a default cross-fade in your broadcasting software. In the Radio.co dashboard, you can set a default cross-fade of 1-10 seconds by going to Settings > Broadcast.

That's our 10 ways to improve your stream and keep your listeners listening. And remember, sharing is caring. So, let us know how you're making your broadcasts sound better. Be it classic techniques or new, innovative hacks.

Space Hacks was a British radio sitcom produced by the BBC, first aired in February 2007.[1] It is the first direct commission by BBC7,[2] a UK digital radio station. Two series of four episodes each were produced. All episodes were exclusively broadcast on BBC7.[3]

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