My long standing impression of Part 15 in Re 49.82 + 80 Khz is that as long as you meet the part 15 regs regarding field strength etc, FCC doesn't care what you do, e.g. spread spectrum? This concerns commercial devices. Comments???
Scott Caples
Part 15.235 of the rules covers operation in this band. There is no mention of the modulation method in this section so spread spectrum may be used but the out of band limits may be a limiting factor since spread spectrum can require a wide bandwidth depending on how fast frequency hopping is deployed.
As a practical matter, the field strength limit is to be measured as described in Part 15.35 which could be a problem for someone who builds their own transmitter and lacks the proper test equipment. Perhaps a commercial certified unit would be the easiest approach for operation in this band.
Neil
Where did I go?
I went on a confusing search to clear up my own confusion when, at first I thought this thread was talking about FCC Rule No. 15.49.
But there is no Rule No. 15.49.
The Last Rule in Subpart A is No. 15.37, and the First Rule in Subpart B is No. 15.101.
That's when I began thinking that we were talking about operation on a frequency of 15.49mHz, and that would probably be listed under Rule No. 15.226, but there is no Rule No. 15.226.
Finally I figured out that we are talking about Part 15 operation in the band 49.82 - 49.90mHz, under Rule No. 15.235.
Like Radio8Z just said, the bandwidth limitations are a critical part of operating on those frequencies.
Hope I didn't keep anyone waiting.
§ 15.235 Operation within the band 49.82-49.90 MHz.
(a) The field strength of any emission within this band shall not
exceed 10,000 microvolts/meter at 3 meters. The emission limit in this
paragraph is based on measurement instrumentation employing an average
detector. The provisions in § 15.35 for limiting peak emissions apply.
(b) The field strength of any emissions appearing between the band
edges and up to 10 kHz above and below the band edges shall be
attenuated at least 26 dB below the level of the unmodulated carrier or
to the general limits in § 15.209, whichever permits the higher
emission levels. The field strength of any emissions removed by more
than 10 kHz from the band edges shall not exceed the general radiated
emission limits in § 15.209. All signals exceeding 20 microvolts/meter
at 3 meters shall be reported in the application for certification.
(c) For a home-built intentional radiator, as defined in § 15.23(a),
operating within the band 49.82-49.90 MHz, the following standards may
be employed:
(1) The RF carrier and modulation products shall be maintained within
the band 49.82-49.90 MHz.
(2) The total input power to the device measured at the battery or the
power line terminals shall not exceed 100 milliwatts under any
condition of modulation.
(3) The antenna shall be a single element, one meter or less in length,
permanently mounted on the enclosure containing the device.
(4) Emissions outside of this band shall be attenuated at least 20 dB
below the level of the unmodulated carrier.
(5) The regulations contained in § 15.23 of this part apply to
intentional radiators constructed under the provisions of this
paragraph.
(d) Cordless telephones are not permitted to operate under the
provisions of this section.
NOTE THE PARAGRAPH PERTAINING TO HOME BUILT DEVICES
(2) The total input power to the device measured at the battery or the
power line terminals shall not exceed 100 milliwatts under any
condition of modulation.
This one is particularly nasty since it references the power input to the device and not just to the final amp. This would include things such as the control circuit, modulator, and pilot lamp.
Neil