FCC Part 95 R/C Data Link Legal "Beacons" 26-27 MHz Frequencies

[R4002]

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

[ChrisSmolinski]

It is indeed... confusing. The intended purpose of course is for remote control or sensing of devices. For example, switching on a light, water pump, etc. Or detecting some event, like it is too warm, the area is flooding and the pump needs to be turned on, etc.

Are automated control signals allowed, or must they be initiated by a person? The regs use the term operator many times. They don't say they can be automated. They don't say they can't. If they have to be done manually, that would make a beacon impractical. If they can be automated... read on. (But I think it is important to make sure they can be automated) Now a sensor is of course automated. It's reporting an event. But it won't be periodic. Unless the event happens to be. I am sure some are.

You can't use tones or encoding to send data, but can to specify the device to control. So for example, maybe you have an assortment of Christmas lights outside. You send various tones, to turn a specific light on or off. That seems allowed. Those tones happen to sound like Silent Night. Hmm. OK, way too obvious, but they could have a repeating pattern, since you want the lights to animate a pattern.  Likewise you could send a series of bits as tones to address a light to turn on or off.

What's interesting is the regs are very clear about turning a device ON or OFF. Binary. But not setting a device value, that's data. But... millions of radio controlled cars and planes send non binary information to adjust a rudder or the speed. It is not just on and off. It seems to be contrary to the rules. Does the FCC just allow it? Or are we reading the rules too tightly? It is very confusing reconciling the regs and what is actually being done now.

The regs do, in a convoluted way at times, stress that it is not meant for transmitting messages. My interpretation of that would include as a beacon. Sure, it's impossible to tell from the signals heard over the air that it is a beacon (although a repeating pattern might give it away if you listen long enough, but with all the muck on the CB channels anyway, who would?). In practice, no one would know what the transmissions are actually doing, especially if they "sound" like most R/C transmissions on this frequency.  Now, if you advertise that it's a beacon, they might decide to look into it. And you've already given away that it's not kosher.

(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.

It's unfortunate that they do not seem to allow transmitting variable data from a sensor. That would be a natural, set up a temperature sensor that sends a reading every 30 seconds or whatever. But it has to be ON or OFF, no data allowed. They really stress this. Now, I guess your sensor could send a different signal based on what the temperature is, to turn on the correct light. So your receiving station has a grid of lights, one for each degree F. The transmitter sends a message each N seconds, to turn on the correct light. That seems valid to me?

EDIT:

OK, I have pondered this:

(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.

I am not sure you could use a single temperature sensor and send a different msg based on the value. But if you had a bunch of temperature switches, each of which tripped at a specific temperature, I think that would be OK.  Again I am trying to go by as strict of an interpretation of the regs as possible.


I suspect you could write to the FCC, proposing a sensor or control scheme, and ask if it would be permissible under 95.731. Worst case they say no, and you modify your question and ask again. If they say yes, then you save that letter in case a field agent ever visits 

[R4002]

Well said, Chris.  I have re-read these regulations several times and still think that operation of R/C cars, boats, aircraft, etc, seem to be in violation of the "strict reading" of these rules.  Yes, I understand that the ON or OFF function for things like throttle, turn left, turn right, but aircraft seem to be more complex than just on and off.  Perhaps I don't know enough about R/C to make an educated statement on this...but the rules seem to be written in the most cumbersome way possible. 

I do agree that with all the junk on the CB band it wouldn't be noticed.  I was just thinking that building a data link on 27 MHz, within FCC regulations, would also be building a beacon - I guess the intention is the question...not sure the FCC would even care.  They're not going after the operators of these (legal) FSK data networks that myself and other people have heard on 27.255 MHz, even though those systems are operating as de facto beacons. 

I think your example of:  water level has reached X, open gate Y is acceptable, but a varying amount (water level is value X) would be not acceptable...makes sense.  Of course, the FSK network monitored out of New York with near-constant activity doesn't seem to fall within this.  It's certainly automated and has several sites...that I doubt are all staffed with an operator at all times.  The rules even allude to multiple sites/multiple sensors with their discussion of the use of tones/selective calling systems. 

I think as long as the system is transmitting data (by the odd "definition" given) to a remote receiver [and then the remote receiver indicates something, i.e. turns a light on or off], and its binary, then its okay.  The remote receiver being the key part here. 

Another thing that I've noticed is, unlike the CB rules which specifically state 4 watts AM carrier power/12 watts PEP SSB power, the power limit for 26.995-27.195 MHz is given as "mean transmitter output power" (25 watts mean transmitter output power on 27.255 MHz).  Mean as in average transmitter output power.  Rules don't say anything about changing power output levels, as long as it averages out to 4/25 watts or less. 

It's obvious that they didn't want unattended constantly transmitting systems in operation, but monitoring the data link systems seems to indicate that that's what these (FCC approved) systems are doing anyway.

[ThElectriCat]

(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.

This might be a stretch, but all a beacon does is identify itself. If a provision is made to allow data solely for the purpose of identification, would it not be possible to send;
"ON, this is controller'xxx'"
"OFF, this is controller'xxx' "
maybe its even more of a stretch, but the on and off commands might fill the place of a DAID.

line of reasoning could be that "I need my remote control to identify so that The unit being controlled dosen't accidently take commands from any other remote control"

I guess this would only be legal if you had more than one device, but what the heck, build 2 beacons

[ChrisSmolinski]

(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.

This might be a stretch, but all a beacon does is identify itself. If a provision is made to allow data solely for the purpose of identification, would it not be possible to send;
"ON, this is controller'xxx'"
"OFF, this is controller'xxx' "
maybe its even more of a stretch, but the on and off commands might fill the place of a DAID.

line of reasoning could be that "I need my remote control to identify so that The unit being controlled dosen't accidently take commands from any other remote control"

I guess this would only be legal if you had more than one device, but what the heck, build 2 beacons

Sure, this seems reasonable, especially if you have both devices on the same frequency, you need to specify which is being controlled.

The question I have (and I have not seen a definitive answer) is whether or not automated control of devices is allowed. The regs always mention an operator controlling a device.  Of course the regs don't say this is not allowed. And they seem to go out of the way to specify other things you cannot do, like send voice or data, so it seems reasonable to assume you can control a device in an automated way. It even seems like a reasonable thing to do. Say you want to turn a pump or other device on every minute, and then off again after another minute. Or at some other rate. You also might want to poll a sensor for a reading, maybe you have multiple sensors, so you need to address the right one.

[R4002]

Exactly, Chris.

From what FSK systems I've monitored using KiwiSDRs tuned to 27.255 MHz, there are almost certainly more than two sites communicating with each other (going by signal strength relative to the other similar or identical signals) and often its every second or so, a weak signal is then followed by a stronger one, then a weaker signal followed by an even stronger one.  This would indicate various sites/sensors "polling" through - either transmitting "site 1, do X" then site 1 transmits back that it has done X, then so on and so forth.   

This would indicate automated operation.  The lightning detector alert systems specifically advertise automated operation as part of their capability.  The Linear eXtended Range system that operates on 27255 using a 10 watt FSK transmitter also advertises this capability as part of the major selling points of their system.  Remotely turn something on or off based on a normally closed circuit being opened or a normally opened circuit being closed.  That product includes the capability of 'status checks' - to poll remote sites and verify that they're still on/receiving the signal.  All of these things lend themselves to automated operation...and since these products are legal and FCC certified under Part 95, either the FCC doesn't care about their own rules being violated or (more likely) the rules are written in such an odd and cumbersome way that the manufacturers have found ways around them.

ThElectrCat, the data networks I have monitored have several different transmitters going, and the rules allow for signalling to be sent to discern one receiver from another, which, by your reasoning, is identification itself. 

[ThElectriCat]

I wonder how much the "type accepted" rules play into this, like how it is illegal to use a modified 10 meter transceiver for CB, even if all power, modulation, antenna size, and mode rules are followed.
Not that anyone can tell on the air, but if you pissed someone off. the fcc could still use it to stop you.

I imagine there are some similar regulations with this as well, but, given the sheer number of devices active on these frequencies, I really doubt the enforcement option would arise except for the most blatant cases.

[R4002]

I'm thinking that as well.  I was just pondering the way the rules were written after stumbling upon how these systems operate local to the various KiwiSDRs I've discovered them on.  After doing more research into these systems, it seems like there's all sorts of different ones on the market and they all operate within Part 95 and transmit anywhere from 1 to 10 watts using some sort of FSK modulation on 27255 (the Linear Systems system even specifies that it operates on 26995 in Canada, with 4 watts power instead of 10 watts power).   There's a whole bunch that transmit in the 100mw range too, and apparently have more frequency agility vs. only using 26995 at 4 watts or 27255 at 10 watts.  Since FSK is used and CB voice transmissions are AM, I imagine these systems are pretty robust against co-channel and adjacent-channel interference from high power CB transmitters.

Given the nearly limitless applications a two or multiple-site system operating on 27.255 MHz with decent antennas and 10 watts TX power even in urban areas I think you could get some impressive range out of them, especially if base station or mobile CB antennas with good counterpoises were used. 

This would make a good project.  Even using one of the off the shelf systems as intended would mean you're setting up an "accidental beacon" on 27255. 

[Josh]

In the 50s the US mil would plex am voice over fsk on hf with no probs. I just can't see any good coming from using the cb range for anything but cb due to all the traffic on the band. If you want to run a digital mode on cb, ros mode is likely going to get you the furthest along to that end and there's a dedicated ros channel already. Ros mode works lovely on hf.

[R4002]

An ROS beacon would be pretty cool. 27.235 MHz/27.245 MHz and 27.635 MHz are the frequencies right?  I know 27635 is big in Europe for ROS.  In North America 27.635 is often active with AM traffic since its CB channel 19 "up one band" and often has truckers talking to each other when the band is open.

I actually like the idea of setting up a beacon (or, in this case, a legal data link system that operates as an "accidental beacon") on 27.255 or one of the 5 "R/C only" frequencies 26.995, 27.045, 27.095, 27.145 or 27.195 MHz.  26.995, 27.095 and 27.145 are probably the best candidates.  27.195 is right next to CB channel 19 (27.185 MHz) and 27.095 is right next to CB channel 11 (27.085 MHz) - both of which often have high power signals on them, especially during band openings.

Having said that, 27.255 allows higher power and I have personally heard FSK data bursts and POCSAG on frequency (on top of AM voice) during band openings so it may be the best option for data link systems.  25 watts vs. 4 watts with a decent antenna system.

[Josh]

If I can wire up a means to get audio in and out of the cb other than the mic, will let you know when to listen for Josh on 11m ros mode.

[ThaDood]

One good example is what Radio Shack had in the 1980's with the 7W Paging System,   http://www.radioshackcatalogs.com/html/1987/hr058.html
If I remember right, the main FREQ was 27.195MHz. Our college had one that I was sent to work on over at administrations office. Got the system, with included back of set center load antenna, to work from on top of a filing cabinet, where it used that as a GND-Plane.

[R4002]

ThaDood,

A friend of mine actually hooked one of those RadioShack pager transmitters up to a CB amplifier (it did 7 watts on 27.255 MHz before being connected to the amplifier) 

Check this out:

http://linearproaccess.com/radio-controls/xt-1/

The Model XT-1 1-Channel Stationary Mid-range Transmitter is designed for use in various wireless remote control applications. When triggered with an external switch, the Model XT-1 transmitter will send a 10 watt, 27.255 MHz, digital encoded, FSK modulated, signal to its companion receiver. The receiver will verify the digital code, activate its output, and trigger the remote device.

The XT-1 transmitter has full supervision capabilities. If the status option is selected, the XT-1 sends hourly status signals to its receiver. If these signals cease, the receiver will indicate trouble by activating its status output after four hours. Contact supervision allows the receiver’s output to follow the transmitter’s input, staying activated as long as the transmitter input is activated. Alternately, an auto-restore option can be selected, causing a momentary receiver output each time the transmitter is activated. Either a N/O or N/C input (jumper selectable) can trigger the transmitter.

The XT-1's manual even recommends using 102" or 108" ("9-foot") CB whip antennas for "maximum performance" and the 4 foot antennas supplied for base station use are the same as the standard fiberglass trucker CB antenna.

[Exo]

The constant activity on 27385 LSB and 27.185 AM used to be great "distributed beacons".
It sometimes took a while of listening to figure out the general area where they were located, though.

But, CB activity is so low these days, it's like a ghost band.
The spirits of long-inactive operators still haunt it.

[ChrisSmolinski]

One good example is what Radio Shack had in the 1980's with the 7W Paging System,   http://www.radioshackcatalogs.com/html/1987/hr058.html
If I remember right, the main FREQ was 27.195MHz. Our college had one that I was sent to work on over at administrations office. Got the system, with included back of set center load antenna, to work from on top of a filing cabinet, where it used that as a GND-Plane.

I wonder if these things ever turn up at yard sales or thrift stores?