Recently, I've been playing with an RLT-SDR dongle and enjoying it. While I've designed plenty of PCBs and other electronics, I haven't had a chance to work with RF at all, so I wanted to design my simple SDR. While I've found a few open hardware SDRs online, such as LimeSDRs, they are complicated designs with BGA components like massive FPGA and transceivers that cost a pretty penny, meaning I'm not too keen on trying to either assemble the boards at home or trying to design a spinoff version of those SDRs. I did spot a framework laptop based RTL-based chip design that looks more hacking friendly, but it's not quite done yet. Does anyone know any more budget friendly and less complicated open hardware SDR designs that I could try to use to learn and assemble RF hardware? I'm okay with not having transmit capabilities, but I want to keep my budget as low as possible so I can mess around with "remixing" the existing designs for my own projects. I also want something that that can receive up to the UHF bands; I know I could probably receive plain HF up to 30ish Mhz with a microcontroller ADC through a direct sampling architecture, but I want to build something a bit more practical. I'm looking for a dongle design; e.g. I want to handle as much of the processing digitally using software like GNU Radio.
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2$\begingroup$ This is a bit of a wall of text, but from what I gather this is more or less an ask for product recommendations, which is not on topic here. To answer your question: decided what you need and do the research. Start with: recv only, or do you want a transceiver? Go from there. $\endgroup$– user26657Commented Jun 5 at 13:21
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$\begingroup$ There are some interesting YouTube videos using Tayloe mixers, if you're looking to roll your own. For example: youtu.be/HCDi5qV1cmU and youtu.be/JuuKF1RFvBM $\endgroup$– spuckCommented Jun 12 at 21:51
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A lot of the current expensive SDR options use expensive chips like DSP, FPGA, an high speed ADC chips so that they can sample a very wide bandwidth (3MHz - 30MHz) and then extract a few scattered frequencies and downsample to fit in the host bus bandwidth (typically USB2 or USB3).
If you are OK with a much narrower bandwidth, you can find some of the original older SDR projects like the softrock that do direct quadrature sampling down to soundcard bandwidth (190KHz). Some of these can nearly be built with discrete components.
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1$\begingroup$ Small correction: None of the SDRs I know of actually use DSP chips. They do need to use some relatively high-bandwidth FPGAs, typically, to bridge the high-speed, timed ADC/DAC buses to relatively loosely timed PC-compatible interfaces. $\endgroup$ Commented Jun 6 at 13:09