Understanding Ham Radio/RC

Understanding Ham Radio/RC

Robert A. Johnson AA4L

Box 4099 Calabash, NC 28467

Recent changes in the amateur radio regulations can put a ham license within easy reach of almost anyone. Many RC fliers have taken advantage of the new licensing regulations, and many more are thinking about it.

Discussions at club meetings and fly‑ins have convinced me that many new and prospective hams do not have a clear understanding of the rules and practices relating to the "remote control of model craft" (Federal Communications Commission terminology) via amateur radio.

Many six‑meter "old‑timers" who are not active in other phases of ham radio are not aware of the newer types of non‑RC activities in the six‑meter band. Club officers and contest directors who have responsibility for frequency control and compliance with the AMA Safety Code and Radio Control Utilization Plan seem to be singularly uninformed as to what constitutes legal six‑meter operation. This article represents an effort on my part to change all that.

Definitions

Part 97, subpart A of the FCC regulations defines the amateur service as "a radio communication service for the purpose of self‑training, intercommunication, and technical investigations carried out by amateurs, that is, duly authorized persons interested in radio technique solely with a personal aim and without pecuniary interest."

An amateur operator is defined as "a person holding a written authorization to be the control operator of an amateur radio station." That written authorization is an amateur license. The amateur license actually has two parts—an operator's license and a station license. The FCC assigns a call sign to each amateur station. There are five classes of operator licenses. The different classes of licenses convey different operating privileges and require demonstration of different skill levels.

The no‑code Technician license

In February 1991, the FCC eliminated the Morse code test from the examination for a Technician class amateur radio license. The Technician class license may now be obtained by passing a 55‑question multiple‑choice written test on amateur regulations, amateur practices, and basic radio communications theory. The Technician license conveys full amateur privileges on all amateur frequencies above 30 MHz, including the six‑meter band.

Amateur license exams are conducted by FCC‑authorized volunteer examiners. Check with your local ham club to obtain the exam schedule for your area. The American Radio Relay League (ARRL), 225 Main St., Newington, CT 06111, publishes complete study materials for the Technician license and can put you in contact with the nearest ARRL‑affiliated ham club. Many clubs conduct licensing classes, but the ARRL material contains all you need to know. The exam simply isn't that tough if you spend some time preparing for it. Only the simplest math is required.

Regulations (RC privileges and limits)

The only specific reference to RC in the amateur regulations is contained in Part 97, Section 97.215, "Remote control of model craft." An amateur station transmitting signals to a model craft may be operated as follows:

• "(a) The station identification procedure is not required for transmissions directed only to the model craft, provided that a label indicating the station call sign and the station licensee's name and address is affixed to the station transmitter.
• (b) The control signals are not considered codes or ciphers intended to obscure the meaning of the communication.
• (c) The transmitter power must not exceed 1 W."

Section (a) excuses the RC station from the requirement that every amateur station must periodically transmit its call sign via voice, Morse code, or other authorized emission, provided the transmitter is labeled. Section (b) addresses regulations that prohibit ham use of codes and ciphers. The regulations do not specifically define a "model craft," but the FCC would likely not look kindly on using ham radio to control a full‑scale airplane or automobile.

Another regulation of interest is 97.9, which states, in part, that "the license document or a photocopy thereof must be in the personal possession of the licensee at all times when the person is the control operator of a station." The cited regulations should lay to rest some of the myths concerning legal use of amateur frequencies for RC.

Part 97, Subpart D, identifies emission types that may be used on the various amateur frequencies. Those emission rules effectively prohibit the typical RC emissions below about 50.1 MHz, but allow RC operation on amateur bands at 6 meters and higher.

Rule 97.115 does permit unlicensed persons, under certain conditions, to participate in amateur radio communications under the immediate supervision of a licensed control operator. However, the FCC ruled (FCC 80‑634, November 6, 1980) that 97.115 does not apply to RC operations, and that there are no circumstances under which an unlicensed person may operate an RC transmitter on amateur frequencies. Therefore, an unlicensed person cannot legally touch any of the controls of an RC transmitter that is transmitting on amateur frequencies. If you use a buddy‑box system that transmits on ham frequencies, both users must be licensed amateurs.

Part 97 also requires that the transmitter be labeled with the station call sign and the licensee's name and address when used for RC operation.

Enforcement at AMA events

Part 4 of the AMA Radio Control Utilization Plan requires AMA event officials to enforce Amateur Radio Operator licensing requirements at sanctioned events. In my experience, this is seldom done. The usual excuse is lack of access to a Call Book. Regulation 97.9 plainly states no one can legally operate an amateur radio station unless the licensee has the license document in his personal possession while acting as control operator. Event officials should also verify that transmitter labeling requirements of 97.215 are met. Violation of regulations can result in criminal or civil penalties. While FCC enforcement agents are unlikely to visit fly‑ins routinely, the FCC may become involved should an unfortunate incident occur.

Frequencies available for RC

Note that 97.215 contains no mention of specific frequencies. There are no FCC‑designated exclusive RC channels on the ham bands. Today's radio technology makes RC control practical on amateur bands at:

• 6 meters (50–54 MHz)
• 2 meters (144–148 MHz)
• 1.25 meters (222–225 MHz)
• 70 centimeters (420–450 MHz)
• 33 centimeters and 23 centimeters bands

Taken together, that's a large amount of spectrum—ample room for many RC channels (at 20 kHz spacing, many thousands of channels are possible). Of course, many of these channels are used by other amateur activities, but there is still plenty of room if needed.

Six‑meter practices

Legalities aside, most ham RC activity historically and currently occurs in the six‑meter band (50–54 MHz). Common practice includes:

• Ten RC channels between 50.800 and 50.980 MHz, spaced 20 kHz apart and assigned AMA‑RCMA channel numbers 00 to 09. These require narrow‑band receivers and transmitters (the same field identification system as used for 72 MHz, except a black wind streamer is used).
• Additional frequencies at 53.100, 53.200, 53.300 ... 53.800 MHz spaced 100 kHz apart. These do not require narrow‑band equipment and are identified in the field by a two‑color wind streamer system (top streamer black to indicate amateur frequency; the second color indicates the specific frequency). See the AMA Membership Manual for details of the channel‑marking system and the RCUP.

All of these frequencies and channels may be used by licensed amateurs for control of aircraft or surface models.

History of six‑meter RC conventions

In the immediate post‑WWII period, all RC flying was done by hams; there were no FCC‑assigned RC frequencies for non‑hams. Early hams built much of their own equipment and used whatever war‑surplus crystals they had, so frequencies varied and standardization was minimal. Early gas‑tube super‑regenerative receivers had poor selectivity, so simultaneous flights at the same field were impractical.

As technology advanced and receivers became more selective, hams chose frequencies near 53 MHz to avoid interference from point‑to‑point communications in the lower end of the band, and to avoid TV channel 2 at 54–60 MHz (early TV receivers lacked selectivity). With RC superheterodyne receivers, multiple simultaneous flights became practical and the hams, AMA, and manufacturers agreed to standardize on the eight 53 MHz frequencies (100 kHz spacing appropriate to early superhets). The 50 MHz channels later developed because of changes in six‑meter usage and the appearance of new modes like repeaters.

Repeaters and coordination

Amateur repeater stations (which relay signals) are normally located on high sites and can dramatically extend communications range. The FCC has authorized six‑meter repeater operation between 51 and 54 MHz. Repeaters operate on fixed frequencies and are coordinated by FCC‑recognized regional volunteer amateur organizations—the only reliable source of up‑to‑date repeater information in your area. Ask your local radio club or ARRL how to contact your repeater coordinator.

RC users must avoid both the input and output frequencies of repeaters. Operation near repeater input frequencies may result in interference from fixed and mobile stations transmitting to the repeater; transmissions from your RC transmitter may interfere with or jam the repeater—which is impolite, will anger repeater users, and may result in an FCC citation under 97.101.

Six‑meter repeaters pose little or no problem to RC operation on the 53 MHz frequencies in most areas because there are relatively few of them, and they operate on known fixed frequencies. However, be careful when using 53 MHz at fields located near TV channel 2 (54–60 MHz) transmitters—TV stations have very high effective radiated power and interference is a real possibility.

Using the 50.8 MHz channels (00–09)

Ideally, the 50.8 MHz channels will be free of interference from amateur point‑to‑point communications. However, many modern amateur stations are fully frequency‑agile, and operators engaged in communications (especially during band openings or contests) may stray upward in frequency. Six‑meter propagation is normally line‑of‑sight, but ionospheric "skip" can occasionally support long‑distance communications. During band openings and contests, the band can "fill up from the bottom," and operators may move higher to find clear channels—sometimes forgetting band‑plan niceties in the heat of competition.

There is no guarantee you will never experience interference from other amateur activities on six meters. In practice, many RC users report fewer interference problems on six meters than on 72 MHz, but you must understand how the band is used locally. Your local ham club and ARRL's QST magazine are good sources of information on FCC rules, band plans, contests, and local operating practices.

Practical advice — listen and learn

There is no substitute for firsthand experience. Try to arrange use of a communications receiver that covers six meters (many inexpensive scanners do). Typically these are FM receivers and will copy the repeaters and other FM stations. AM, single‑sideband, and digital stations may be audible but not understandable on such receivers.

• Spend time listening at various times of the day.
• If possible, take the receiver to your flying field on flying days and listen.
• The more you listen, the more you'll learn about local usage and potential sources of interference.

Even if you only intend to use ham radio for RC, I urge you to join and participate in your local ham club and ARRL. You're much less likely to experience accidental interference if local hams know of your activities. Offer to conduct a program on RC at a club meeting. ARRL has influence over band plans and operating conventions, and RC modelers need voices within ARRL to represent our interests. If you see proposed regulations that may adversely affect our operating privileges, write to ARRL and the FCC.

Benefits of ham‑band RC and experimental opportunities

Ham radio offers several benefits and opportunities for modelers:

• Free‑flight fliers often equip models with miniature radio beacons and use direction‑finding to facilitate recovery.
• Ham radio has been used to transmit signals from TV cameras carried by model aircraft.
• Experimenters may use ham radio for telemetry—air‑speed, altitude, RPM, and other data from models.
• The AMA technical team used amateur frequencies and equipment when investigating interference potential in experimental work (NPRM 92‑235).
• Communications via two‑meter handhelds and repeaters are valuable for coordinating activities at model airports and large events; autopatch repeaters can even provide telephone access in emergencies.

A few final points

• Use only the channels and segments of the six‑meter band that are recommended in the band plan for RC use, and avoid frequencies used by repeaters or other fixed services.
• Keep your transmitter power as low as necessary to maintain control and good signal quality (97.215 limits transmitter power to 1 W for RC on amateur frequencies).
• Always identify your station as required by the FCC when appropriate, and make your transmitter label available for inspection at sanctioned events.
• If you experience interference, try to work cooperatively with the other station to find a solution. If that fails, contact your local amateur service organizations and the FCC.

A lot of people have been able to use six meters successfully for RC with no trouble. With common courtesy, awareness of the band, and observance of the rules, six meters can be a useful and enjoyable band for RC model control.

Where do we go from here?

RC flying originated on the ham bands. The hobbies of RC flying and ham radio will continue to be closely related. Traditionally, the two hobbies have attracted technically inclined people who like to experiment and make things work. The radio equipment we use today is based on technology developed by amateurs, and the next generation of equipment will likely originate on the ham bands as well.

The radio spectrum is finite; every new user increases the potential for interference. Modern modeling advances—very fast and heavy models, highly valuable scale creations—mean the consequences of interference can be severe. Some promising technical approaches to mitigate interference include spread spectrum and frequency‑diversity techniques; these require reduction to practice, testing, and demonstration. The AMA can and should take a leadership role in coordinating experimenters and liaising with ARRL, RCMA, FCC, and other interested parties to promote technical solutions.

Spectrum pollution will worsen with time. If we want radios that will survive that environment, the time for action is now. Work with the hams and the organizations that represent our hobbies.

Happy landings, and 73.

Thanks to Warren Plohr (W8IAH) for important contributions to this article. Technical review: Bob Underwood.

Robert A. Johnson AA4L Box 4099 Calabash, NC 28467

Transcribed from original scans by AI. Minor OCR errors may remain.