History of the FCC and FM RC Long but informative

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History of the FCC and FM RC Long but informative

Post  Admin on Thu Feb 03, 2011 9:52 pm

The following timeline is based on information from the AMA, MA Archives, FCC and Futaba documents.:

In 1958 there are six 27 Mhz channels allocated for RC use. CB Channel 23 of the 27Mhz band (27.255 Mhz) was to be shared with CB users for radio control device uses.

"Class C Citizens Band service for radio-controlled devices; no voice transmissions are permitted. It has six channels in the 27 MHz band. Five are unused 10 kHz assignments between channels 3/4, 7/8, 11/12, 15/16 and 19/20, and the sixth is shared with Channel 23. Radio control transmitters may use up to 4 watts on the first five channels and 25 watts on the last, 27.255 MHz. Some in-house paging systems, and car alarms with a paging feature, also use these frequencies, especially 27.255 where more power is permitted."

1959 - The AMA begins working with the FCC to gain the allocation of more frequencies for radio controlled model aviation.

In 1967 six 72 Mhz frequencies with an 80Khz (approx. +3.6 Khz tolerance) seperation were allocated for RC services due to increasing intereference in the 27 Mhz bands.

1979, The AMA begins working with the FCC to work on the the issues for narrowbanding the 72Mhz spektrum to increase the number of bands to create between 25 and 50 new channels.

In 1982 "narrower" banding of the high end of the 72Mhz spectrum to 40Khz seperation was approved and provided 11 new even numbered channels ch.s 12, 38, 40, 42, 44, 46, 48, 50, 52, 54 & 56 from the high end of the 72 Mhz spectrum. 80Khz radios could be upgraded to 40Khz specs through the "Silver Sticker Program".


In 1988 the narrowbanding of radios increased to 20 Khz (approx. +1.4 Khz tolerance). All the 72 Mhz channels were allowed providing for the 50 channels we have today. 80Khz and 40Khz radios could be upgraded to 20Khz specs through the "Gold Sticker Program".

The FCC ended the manufacture of wideband (80 and 40 Khz seperation) radios in 1992 and their sale in 1993. Their use in the USA became illegal on March 1, 1998 :

"The FCC requirements for the width of the signal output by RC radio equipment on 72 and 75 MHz was narrowed effective 3/1/91. MOST radios made before 1991 did not meet these new standards." (from Futaba FAQ, italics mine)


"47CFR95.623 R/C transmitter channel frequencies (c) All R/C transmitters capable of operation in the 72-76 MHz band that are manufactured in or imported into the United States, on or after March 1, 1992, or are marketed on or after March 1, 1993, must be maintained within a frequency tolerance of 0.002%. R/C transmitters operating in the 72-76 MHz band and marketed before March 1, 1993, may continue to be operated with a frequency tolerance of 0.005% until March 1, 1998. {53 FR 36789, Sept. 22, 1988; 53 FR 52713, Dec. 29, 1988; 56 FR 15837, Apr. 18, 1991} "

Note that the frequency spectrum (72.010 through 72.990), where the frequencies allowed for RC resides, never changed from 1982 until today and the lower half of that spectrum has been allocated since 1967. It is the width of bands (80Khz, 40Khz and 20Khz)within that spectrum that changed.

If anyone has links to the original documents or any of the documents themselves I would be very grateful if they could be shared. This is a part of our hobby's history that is often overlooked and hard to document as it was all pre-Internet.

The 72Mhz frequencies allocated to RC in 1967 were:
72.08 MHz
72.16 MHz
72.24 MHz
72.32 Mhz
72.40 Mhz
72.96 Mhz

Note the gap between 72.40 and 72.96. The missing frequencies had known harmonic interference problems.
The use of all these frequencies for RC originally required a Class C FCC operators license.

Diagram of Allocation of the 72Mhz Spectrum


A transmitter never transmits on a single frequency. The transmission is a group of frequencies of diminishing strength around the center frequency. The width of this group of frequencies is called bandwith and is usually based on the power level at which the frequencies become negligible for a particular application. In spectrum allocation each center frequency takes up a certain amount of bandwidth that can not over lap the next frequency's bandwidth.


Note that licensed frequencies within the 72Mhz band are allocated for pagers and industrial use. Their transmitters are in the range of 25 watts and up as opposed to our feeble little under 1 watt radios. They are more likely to drop your plane than you are of messing up a crane or an emergency service pager. They have the right to trample your signal, you do not have the right to trample theirs. Even though the probablity of a legal RC TX interfereing with a licensed transmitter are very slim, RC flying fields should always check with the FCC for licensed users frequencies in the area and avoid the use of any nearby licensed frequencies.
Unlicensed users have no rights from interference. Licensed users have the right to full access of their assigned frequency without interference.
That is given that the lincensed users equipment is functioning properly and legally and/or not being used for malicious or criminal uses.
RC and licensed 72Mhz bandwidths overlap the bandwidth of licensed frequencies on adjacent center frequencies. The licensed high watt TX can easily mask an under 1 watt RC signal, rarely the other way around.
You have no rights over licensed operators.

"FCC Part 95.208
(d) Your R/C station must stop transmitting if it interferes with:
(1) Authorized radio operations in the 72–76 MHz band; or
(2) Television reception on TV Channels 4 or 5."

"FCC Part 95.220
(R/C Rules 20) What must I do if the FCC tells me that my R/C station is causing interference?
(a) If the FCC tells you that your R/C station is causing interference for technical reasons, you must follow all instructions in the official FCC notice.
(This notice may require you to have technical adjustments made to your equipment.)
(b) You must comply with any restricted hours of R/C station operation which may be included in the official FCC notice."

Perhaps a clearer answer from the Federal Register:
"A Proposed Rule by the Federal Communications Commission on 08/04/2010
...
(f) Stations in the 72-76 MHz range are subject to the condition that interference will not be caused to the remote control of industrial equipment operating on the same or adjacent frequencies. These frequencies are not afforded any protection from interference due to the operation of fixed and mobile stations in other services assigned to the same or adjacent frequencies. ...."

In simple terms certain industrial users (railroad crossing controls, industrial cranes, etc.) are the "primary" users of some 72mhz frequencies. We are "secondary" users and as such must accept interference from the "primary" users while not interfering with them.






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