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We are developing a product that will hopefully soon be sold internationally and will therefore be put through FCC & CE Certification testing. Part of that design is an audio mixer with an integrated Bluetooth receiver. This receiver sits inside a large metal chassis so to increase the Bluetooth link strength a module was chosen which requires an external antenna (BTM625, based on CSRA64215 IC), which in our current design is attached through the chassis on an SMA connector.

The Bluetooth module in question already has FCC compliance, but reading through the compliance document I am concerned that we are in breach of 'Section 15.203 Antenna requirement' of the FCC rules, which essentially state that we must make efforts to prevent the end user from changing the antenna that is used with the product by implementing non-standard RF connectors or permanently attaching it. The idea is that the antenna (intentional radiator) cannot be changed for something that will invalidate the FCC certification.

I have seen many other products (including Bluetooth radios, for example the Denon DN-200BR) that use standardised connectors for antennas, so I am confused about this clause. Is there an exemption we can use which will allow us to pass compliance with a standard antenna connector? Or do we simply need to state in the manual that antennas other than the one provided is strictly prohibited?

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  • \$\begingroup\$ Afaik, reverse-polarity SMA connectors were "non-standard" when WiFi cards were initially released, and these satisfied those FCC rules at the time. Problem with that is once an entire industry starts using something "non-standard" for a high-volume commercial product family it very quickly becomes just another different standard.... \$\endgroup\$
    – brhans
    Jun 8 at 12:55
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Taking a closer look at it, it says:

Further, this requirement does not apply to intentional radiators that must be professionally installed

So my take is that the requirement is concerning commercial products only, not ISM etc. Not sure if that makes any difference in your case.

That aside, a regulation forcing you to use anything but the common antenna connectors (U.FL, SMA etc) would be senseless, to put it mildly. This is where I'd ask input from a FCC approved test house. Usually, pedantic issues like this can be solved by putting a sticker on the product next to the connector "Note: only use with antenna x" or something along those lines.

Though as another requirement from the Bluetooth SIG, you must use the exact connectors and antennas that were used by the module manufacturer during testing, in order to avoid a complete re-qualification by the Bluetooth product. This is a more serious concern; are you using a reference design with one of the approved antennas?

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