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(2023) Very nice. It's not a "crystal radio", though. It's a direct sampling receiver. That is, the processing takes place at the RF frequency directly. Most r
by Animats 2y ago
(2023)
Very nice. It's not a "crystal radio", though. It's a direct sampling receiver. That is, the processing takes place at the RF frequency directly. Most receivers use heterodyne conversion to down-convert a desired chunk of spectrum to a convenient working frequency. This doesn't. It just runs the raw RF through an A/D.
As A/D devices and processing have improved, the frequency upper limit for direct conversion receivers has moved up. There are low-cost direct conversion receivers going up to 50MHz, but they have to use an FPGA rather than doing all the work in software.
- ninalanyon 2y agoThe comparison is not with the crystal but with the low parts count and simplicity.
- _paulc 2y agoIt looks like it is a Direct Conversion (Zero IF) rather than a Direct Sampling Receiver [0] - ie. it uses does a quadrature LO to down convert to baseband I/Q (in this case a Taylor QSD as a mixer). The RP2040 ADC bandwidth is only 250KHz. [0] https://www.analog.com/en/resources/technical-articles/a-review-of-wideband-rf-receiver-architecture-options.html https://www.analog.com/en/resources/technical-articles/a-rev...
- Animats 2y agoOh, you're right. Affordable direct sampling receivers for low bands do exist, but this isn't one.