DIY Text Message System From Old Tech

Gabe Emerson from the SaveItForParts YouTube channel has been demonstrating fun and unique ways to build projects with old, cheap, and abandoned technology for some time now. Lots of the projects he completes in his videos include some sort of wireless communications technology. Some examples include repurposing old satellite dishes for SDR radios, making his own satellite dishes from very unconventional materials (such as an umbrella), creating cyberdecks, and using old devices to receive signals from weather satellites. In one of his more recent endeavors, he creates a DIY text messaging systems using old pocket PC’s along with a few other pieces of technology that have long been abandoned.

The pocket PC devices were acquired from the University of Minnesota’s surplus program for about $10. These are older devices that have typically been used in the past for jobs such as inventory management and control. Some of their typical features would include barcode scanners, laser scanners, and some would even support a Wi-Fi connection. The gadget resemble old Blackberry phones since they have a small on board physical keyboard, however they lack the necessary technology to communicate wirelessly such as a modem and wireless circuits. Around the same time the pocket PCs were acquired he also happened to come upon some modem modules through a different surplus store. This all led to the idea of creating a DIY text messaging system using a combination of the pocket PCs, modems, and a couple business band radios which were already on-hand.

The business band radios operate in an unlicensed spectrum that allow users to do almost anything they want over the wireless spectrum. Typically, the wireless spectrum is highly regulated. For example, amateur radio bands have protocols that need to be followed and users generally need a HAM radio license to operate radios in those bands. On the other hand, it is illegal for users to operate in licensed frequencies such as cellular bands and TV bands. Therefore, the business band offers the perfect spectrum for experimentation with little to no restrictions.

To begin the project the pocket PCs were powered up. Fortunately, two of the four PCs powered up and booted to an old Windows mobile operating system. After much trouble and tinkering, the devices were able to make a Wi-Fi connection and download an old terminal program to send and receive data over a serial port connection. The next step involved testing the serial port connection by connecting the two devices using a serial cable and sending text from one to the other utilizing the terminal. To make the DIY text system wireless, this serial cable essentially needs to be replaced by a modem to convert the text the wireless data and then a radio to convert the wireless data to wireless signals. This is where the modem and business band radios come into play. The modem takes the text data input over the serial cable, and an additional connection over aux cables connects from the modem to the business band radios to transmit the data wirelessly.

The entire effort proved to be more troublesome than originally anticipated. First, the modems did not want to work with one another cooperatively. In fact, the modems eventually got replaced with an alternative option. Second, the radio’s had troublesome squelch control which would interfere with the text transmission. However, after multiple attempts a proof of concept solution was put together. Simple text transmission was demonstrated being transmitted from one device and received by the other. Additionally, an entire text file was transferred between devices. To complete the project the pocket PC, modem, radio, and a battery were all strapped together to make a portable pack. And while the contraption may look like a prop from an 80’s sci-fi movie, it proved there can still be fun use cases for older abandoned technology.