There was a delay getting my 20 meter polar modulation prototype back, so I decided to design a 2-channel phase coherent direction finding system for 2 meters.
I decided to see just how inexpensively I could do it. The answer kind of surprised me. $4.51 in parts, plus my trusty Pico2!
I wasn’t about to build it like that. It was a pretty bad design. But there was room to triple my BOM and make it decent. So that’s what I did.
SMA inputs. ESD / RF limiter. Band pass filter to reject FM & TV. RF preamps. Dual conversion superhet design. Nice temperature-stable transistor amplifiers, high linearity mixers, and clean power. Crappy ADC though (using the Pico 2’s onboard ADC), but the right amount of gain for it to optimize dynamic range & sensitivity.
Just ordered them! Hopefully I’ll have time to write the software and build the antenna before the next fox hunt!
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