How to reverse engineer an analog chip: the TDA7000 FM radio receiver
17 nynyny7 5 8/2/2025, 3:59:51 PM righto.com ↗
Comments (5)
CamperBob2 · 2m ago
The correlator is interesting. I don't see how it works. In the perfectly-tuned case, how does delaying the signal by half an (IF?) period and inverting it yield a match for the original signal? Inversion isn't the same as a delay.
kens · 2h ago
Author here for if you have questions on this chip...
magnat · 1h ago
The separate noise source is a bit of surprise here. Why is it necessary? Wouldn't RF noise produce same results?
kens · 32m ago
I'm not sure what the FM demodulator produces when it's mistuned, but I'm guessing that you'd get pretty much no output, rather than white noise (since there's no frequency for the demodulator to lock onto). The problem for the user is that you wouldn't know if your batteries are dead or if you just haven't found the station. By adding a "hiss" between stations, the radio has better usability
wkat4242 · 44m ago
It depends, if the RF frequency you use has a signal on it then it won't be random so it's not really noise. I wonder why they need a noise generator in a receiver chip though.. They're usually used for crypto stuff.