SDR FAQ
This FAQ covers the most commonly asked questions by people new to the world of SDR.
Can I use my TV tuner to do SDR?
Q: Hey, I see you guys are using a Realtek TV tuner to do SDR! I have a TV tuner! How do I do SDR with it?
A: This very common question stems from misunderstanding how the Realtek device works. The RTL2832 is a digital TV tuner, which also supports tuning FM radio. Because the two types of signals are very different, Realtek added a special SDR mode to the RTL2832. Their official drivers use this mode to tune and decode FM radio. The Osmocom driver simply makes this existing SDR mode available to more software. The only reason the Realtek TV tuner works with SDR, is because it *is* an SDR device, which also happens to tune TV signals.
Just because the Realtek SDR device can be used to watch TV, it doesn't mean any TV tuner can do SDR. The RTL2832 has a special SDR mode, so your TV tuner or other device will also need a special SDR mode too - otherwise it can't be used for SDR work.
Q: But my TV tuner might have a secret SDR mode too! How do I find out?
Short answer: It doesn't, don't bother. The RTL2832 can be had for $20, just buy one and save yourself a few months of probably fruitless effort.
Long answer: You will have to find datasheets for the tuner and demodulator ICs used on your card. Examine these, and look for anything that sounds like it does SDR. You will have to learn how to write drivers for your operating system, so you can write commands to the tuner and demodulator ICs. This is all done using the C compiler you already have installed on your system and are an expert in using. If your card is no longer available through normal retail channels, you will be unlikely to find anyone who can help you (unless you have a number of identical cards you can donate to other programmers.)
One big hint with the RTL2832 was that it did both digital TV and analogue radio. Since these are so different, it is no surprise they are handled by different circuitry. Most TV cards capable of tuning analogue TV can also do analogue radio, because the two schemes are practically the same (analogue TV channels use FM radio signals for their audio.) If you have a device that can work with very different signals, like the Realtek, you might have something worth investigating.