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Life & fun · October 8, 2020

IR

I reverse engineered my cable modem and turned it into an SDR

I reverse engineered my cable modem and turned it into an SDR launched on October 8, 2020 with 357 votes, #43 of 4,018 launches that month and more than 99% of that year's launches. The site was still online in September 2026, 6 years on.

Visit stdw.github.io ↗Alternativestop 1% of October 2020

In plain words

A developer reverse engineered their cable modem to convert it into a software-defined radio (SDR). This project, categorized as life and fun, demonstrates the technical process of repurposing consumer hardware for different applications. The work documents how the modem's components and firmware were analyzed and modified to enable radio frequency reception and transmission capabilities beyond the device's original purpose.

written from the facts on this page · September 2026

From the sources

A few weeks ago I got curious about an old cable modem sitting in my closet, a Motorola MB7220. Initially I was interested in what kind of hardware it had and if it was running Linux. Some quick searching brought me to a thread on a web forum where people were discussing the built in spectrum analyzer feature used for diagnostics. Someone mentioned that they could see spikes corresponding to FM radio stations. This sparked a thought: if a cable modem and a digital TV tuner dongle are fundamentally doing the same thing (receiving and demodulating QAM signals), could a modem be turned into an SDR (software-defined radio) a la RTL-SDR ? Going into this project, I knew next to nothing about RF…from stdw.github.io

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