The FCC to Explore Receiver Standards

The FCC issued on April 21, 2022 a Notice of Inquiry to explore alternative approaches to solving issues regarding good receiver design, or the lack thereof.

This stems in part from the recent protests by the FAA about rolling out 3.5 GHz 5G telecommunication services. The FAA said these new services were causing issues with navigation devices on an adjacent band. When engineers investigated, it turned out the real issue was the poor quality of the aircraft navigation receivers. This led to the FAA and FCC agreeing that telecom companies could roll out services cautiously, but that the navigation device manufacturers were going to have to address receiver shortcomings.

Having experienced similar receiver issues firsthand and conferring with design engineers like Mats Lindstrom of RF2B, the problem is likely to be a lack of front-end filters. Software-defined radios (SDRs) are remarkable devices, able to tune in, digitize, and decode directly from the incoming RF signal by simply giving them instructions. However, they can be readily overloaded and made to create intermodulation distortion. You really need to add filters ahead of the tuners to prevent IMD, and it could be that inexperienced engineers are skipping this step or not implementing filters properly.

The FCC is asking what the industry thinks about its taking a role in solving the receiver issues in the interest of spectrum efficiency. What they are saying is that industries shouldn’t require large gaps between radio service bands or channels within those bands.

The FCC almost exclusively regulates transmitters, though regulating receivers isn’t without precedent. The FCC did require receivers to exclude certain ranges within the 800 MHz analog cell phone band that Congress learned scanner enthusiasts were using to monitor private conversations, including those of members of Congress.

What role should the FCC take? Should it require performance standards by rules? Require receiver performance certification? Should it only address complaints and work to mediate them? Should it simply promote and educate about receiver design? The FCC proceeding will address the issue and, in theory, come up with a plan.

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