I have been in some discussion with Chris regarding this - after discovering the extensive number of FSK data link networks operating on 27255 / 27.255 MHz. Most of these networks appear to be transmitting using 10 watt FSK transmitters with multiple sites. It's used to turn devices on and off and to "turn on/off an indicating device for the operator". WAVE Systems has a lightning detector alert system that uses 10 watt FSK transmitters to turn on and off sirens/flashing lights at remote sites as well.
During band openings I have heard POCSAG and FSK signals on 27.255 MHz, there are at least two FSK data link networks operating in New York that I have heard on two different KiwiSDRs (and are local to the SDRs). One of them is transmitting basically constantly and the other transmits once every few seconds...going by the signal strength of the different FSK bursts there are at least 3-4 different sites in this network.
These are, effectively, beacons for 27 MHz CB.FCC rules for the R/C services fall under Part 95 - Personal Radio Services, and cover the six 26 MHz / 27 MHz RC frequencies:
26.995 MHz - 4 watt maximum power output
27.045 MHz - 4 watt maximum power output
27.095 MHz - 4 watt maximum power output
27.145 MHz - 4 watt maximum power output
27.195 MHz - 4 watt maximum power output
27.255 MHz - 25 watt maximum power output
see 95.767(b)
(b)26-28 MHz frequency band. For an RCRS transmitter operating on 27.255 MHz, the mean transmitter output power must not exceed 25 Watts. For an RCRS transmitter operating on 26.995, 27.045, 27.095, 27.145, or 27.195 MHz, the mean transmitter output power must not exceed 4 Watts.
§ 95.731 Permissible RCRS use.
RCRS transmitters may only be used to transmit one-way communications and only for the purposes set forth in this section. (One-way communications are transmissions which are not intended to establish communications with another station.)
(a)Control of model crafts and devices. When an RCRS transmitter is used to control a model craft or device, the RCRS channels in specific frequency bands must be used, based on the type of model craft or device being controlled, as follows:
(1) RCRS channels in the 72 MHz frequency band may be used only to control and operate model aircraft.
(2) RCRS channels in the 75 MHz frequency band may be used only to control and operate model surface craft.
(3) RCRS channels in the 26-28 MHz frequency band may be used to control or operate any kind of device.(b)Telecommand. Any RCRS channel may be used by the operator to turn on and/or off a device at a remote location.(c)Telemetry. Any RCRS channel in the 26-28 MHz frequency band may be used to transmit a signal from a sensor at a remote location that turns on and/or off an indicating device for the operator.§ 95.771 RCRS emission types.
Each RCRS transmitter type must be designed to satisfy the emission limitations in this section.
(a)Permitted emission types. RCRS transmitter types may transmit any type of non-voice emission that is technically appropriate for radio control use.
(b)Voice emissions prohibited. RCRS transmitter types must be incapable of transmitting telephony (voice communications).
95.731(c) is what interests me. Could one, in theory, set up a transmitter on one of the six R/C frequencies that transmits on/off keying to turn a green "RX" light on a remote receiver somewhere? Say the temperature is above 32 degrees at a "remote location" and I need to know this? And that could also act as a beacon on 26-27 MHz? As long as its transmitting some sort of data from a remote site (an example would be the beacons around 4096 kHz that transmit wind, temperature and battery charge information) then it would be within the regulations for the 26-27 MHz frequencies. 25 watts is an impressive power limit, but means the potential for QRM since 27.255 is also a legal CB frequency. 4 watts on the other R/C exclusive channels interest me too...of course during a band opening its not unusual to hear voice on these frequencies as well.
Seems like the rules sort of contradict each other though:§ 95.733 Prohibited RCRS use.
The rules in this section restrict certain uses of RCRS transmitters.
(a)Simultaneous use of multiple channels. An RCRS station must not transmit simultaneously on more than one RCRS channel in the 72-76 MHz band when such operation would cause harmful interference to other RCRS operations.
(b)Data transmission. No person shall use a RCRS transmitter to transmit data. Tones or other types of signal encoding are not considered to be data for the purposes of this paragraph, when used only for the purpose of identifying the specific device among multiple devices that the operator intends to turn on/off or the specific sensor among multiple sensors intended to turn on/off an indicating device for the operator.(c)Pay for operation prohibited. RCRS stations must not be used for commercial purposes. An RCRS operator must not accept direct or indirect payment for operating an RCRS transmitter. An RCRS operator may use an RCRS transmitter to help him or her provide a service and be paid for rendering that service, provided that the payment is only for the service and not for operation of the RCRS transmitter.
(d)Limited transmission. No person shall use an RCRS station to transmit any message other than for the operation of devices at remote locations. Accordingly, the transmission of other messages by an RCRS operator, such as voice, telegraphy, etc. is prohibited.
Just thinking out loud. Of course, I could just buy one of these 10 watt FSK data link systems and operate it as intended - for example one of the commercial products on the market can be set to normally open or normally closed - and can be set to send a signal every time the input condition changes...thus making an unintentional 27 MHz propagation beacon in the process....
I wonder what the rest of HFU thinks about this. Did I stumble across a loophole? I'm talking about Part 95 compliance here - a legal 27 MHz data link operating for the purposes of turning an indicator on and off, but also accidentally operating as a beacon, not Part 15 (which I know also covers the 26995-27255 R/C channels within 26957-27283 kHz).
A Part 15 beacon on 27 MHz would be cool too but that's another topic