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Using a Direct Conversion SDR as a 10.7Mhz IF & Demodulator for VHF or UHF applications

Fri, 08/05/2011 - 16:07 — admin

I've always thought a low-cost single band Software Defined Radio (SDR) might be used to convert a VHF or UHF Radio into an "All Mode" Receiver. Recently I came a across a low cost PLL VHF FM 0.2uV telemetry receiver card on ebay. So I removed a few component to disconnect the 455khz down converter and FM limiter and then wired in the software defined radio which I tuned to 10.7Mhz to match the first IF satge frequency.

I'm pleased to report this actually works quite well for bandwidths less than 100khz.

Direct Conversion Software Defined Receiver

VHF SDR 173Mhz

Using a 48Khz USD PCB Sound card and the WRplus SDR Software and a Signal Generator tuned to 173.308Mhz

SDR 173.308Mhz

Signal Generator tuned to 173.328Mhz giving this reciver a bandwidth or tuning range of 24khz

SDR 173.328Mhz

10.7Mhz Local Oscillator on the SDR PCB

10.7Mhz Crystal Oscillator