FCC ID Testing For Short Range Remote Control Transmitters

This blog post will focus on FCC ID testing for short range remote control transmitters, or known as SRD – short range devices, these devices mainly work on ISM frequency band, and these remotes will need to be tested in regulatory labs before legally sell on market, for USA market, the test labs would be FCC approved labs, and for Europe, the labs would be ETSI approved labs.

The requirements for ISM frequency band short range remote control transmitters is covered in FCC document CFR47 Part 15 Paragraph 231 and the specific document to look into is for intentional radiators.

First we need to know why our remote control transmitter belongs to intentional radiators, because it radiates at a controlled frequency, while a non-intentional radiator radiates unwanted RF frequencies such as spurs and harmonics of the later, measures must be taken to control the radiation levels.

Basically FCC requirement for intentional radiators, at non-continuous operation mode, includes two parts, one part is mode of operation, the other is power levels of radiators.

From operation mode requirement, we can conclude the following, first, a manually operated transmitter must be automatically deactivated within 5 seconds of being released from operation, second, automatic activation of a transmitter must cease operation within 5 seconds of operation, third, polling is restricted to 1 second of transmission duration per 1 hour for each transmitter.

So when we design hand held remote control transmitter, when activated manually, the transmission must be stopped within 5 seconds of activation, if transmission has automatic mode, then it also must stop within 5 seconds after activation, if the transmitter is being used as a beacon, then it can only transmit no more than 1 second per hour, or it is not allowed to be used as beacon.

The basic idea for above restrictions is not to transmit in continuous mode and under certain power level, so all transmitters and receiver within certain area can share frequency resources with each other, without intervention, it’s better to consult your labs before start to choose tech. specs before starting project.

For power levels requirement, there are following restrictions for non-continuous operation transmitter at 260 – 470Mhz frequency range.

First, transmission power is measured in terms of field strength, measured at a distance of 3 meters from radiating antenna, also keep in mind the maximum allowed transmission power depends on actual frequency, and ranges from 3750uV/meter at 260Mhz to 1250uV/meter at 470Mhz.

Second, there is 20dB difference between maximum haronmic / spurious levels and actual transmit carrier, so we can always transmit at higher power and use lower duty cycle to ease the average transmit power.

Third, the occupied bandwidth of an emission, shall not be wider than 0.25% of the center frequency of the transmit base carrier frequency, bandwidth is measured at -20dB from the peak transmission power with a RSBW at 100kHz at 1.5Mhz to 2Mhz frequency span.

Fourth, emissions shall be measured up to 10th harmonic of base carrier frequency of intentional transmitter / radiator.

Also, please note there is restricted bands in FCC description, and be sure to choose frequency wisely to avoid any restricted bands.

We will list following the maximum radiation power and harmonic level limits for typical frequency between 260 – 470Mhz range, please note these values are for random or periodic intentional radiators, not for either continous transmitters or non-intentional radiators.

Also we have included the mentioned value for non-periodic or continuous transmitters, so we can see the huge difference between periodic and non-periodic transmitters, and we should choose former for much longer operation distance.

We can find online convertes to convert uV/meter to dBuV/m, and we have converted it for you, for the most common frequency as in following table.

And we can use above value in following FCC ID testing, to do a pre-testing in house to find the optimum parameter for development transmitter.