Electronics - 2001/01
Legal and illegal transmitters (letter from Charles Reich)
Charles Reich, St. Augustine, FL, writes:
"I recently attended our local club meeting, where our president announced: 'OK, now I hope all you guys realize that the new FCC (Federal Communications Commission) rules are now in effect regarding transmitters. We'll probably ignore, or turn our heads, out at our field to those of you using old-type transmitters for the time being. Especially considering the remote area of our flying field and little chance of causing interference. Be aware that if you attend AMA-sanctioned contests you will all need to be using legal transmitters.'
"I then asked a stupid question: 'With the plethora of different brands, types, and markings on the backs of transmitters, how will the CDs (Contest Directors) know what's legal and what isn't? Better yet, how do we know which of our own transmitters are legal, how do we tell?'
"Everyone looked at each other in dismay, shrugged their shoulders, and the meeting went silent before quickly changing to a new subject. This may be a good topic for one of your articles. As you are well aware, many of the transmitters carry the gold trapezoid-shaped label reading: 'R/CMA Recheck, AMA Date:'
"Some have dates stamped or handwritten in, others are blank.
"I just counted and I have nine different transmitters, all with different markings on the back. A couple I sent to Futaba a couple of years ago to be updated. The only marking they have is the trapezoid-shaped gold R/CMA Recheck label on the back.
"The CDs are going to need some type of guidelines to know what is legal and how to identify them. I'm fairly sure not all CDs are well-informed on this matter.
"There are literally thousands of used RC rigs that show up at every major swap meet. How will the average modeler know if he's buying a unit that is legal with today's FCC rules? This information will be invaluable to the used-market buyers, especially if they start enforcing this new law.
"I don't think the transmitters are grandfathered in, as are the receivers. Also of interest would be information regarding the procedure and/or possibility of sending our transmitters to a service center marking them as such for CDs and our own relief. What vintage or types of transmitters might fall within this possibility, if any?
"Hopefully you can come up with an article that explains the new rules, and what's legal and what ain't—and how to tell if our own units are FCC legal—before we get to a contest.
"Thanks for listening and your consideration of an article for this subject matter."
Overview and references
Most of the information requested is published annually in the AMA Membership Manual. Additional valuable information about transmitter and receiver quality and testing is included in George Steiner’s A to Z—Radio Control Electronic Journal (available postpaid from GSP Products, 2238 Rogue River Dr., Sacramento, CA 95826). Below is a concise review of the narrowband requirements and how they affect RC fliers.
Narrowband: what it means for RC
- Our allocated frequencies are spaced at 20 kHz intervals.
- "Narrowband" here designates a transmitted signal narrower in width than older "wideband" equipment.
- Think of an RC channel as a fixed-width space. If a transmitter's signal spills beyond that space it can interfere with adjacent channels (and be subject to causing interference from adjacent users).
- Two separate concerns:
- Transmitters must be narrowband so they don't cause adjacent-channel interference.
- Receivers need adequate narrowband selectivity to avoid being desensitized by adjacent-channel spillover.
The FCC federally imposes the transmitter narrowband requirement; it regulates all devices capable of emitting radio waves. Receivers, however, are not subject to the same FCC narrowband mandate—receiver selectivity requirements are an AMA matter that benefits all fliers.
Receivers commonly bear stickers stating compliance with Part 15 of the FCC rules—this relates to their own RF emissions limits, not their narrowband performance.
Receivers and conversion stages
- "Double conversion" describes receivers that convert the incoming RF twice before final processing. Typical conversions:
- Single-conversion: RF is converted directly to the Intermediate Frequency (IF) of 455 kHz.
- Double-conversion: RF is first converted to ~10.7 MHz or 11.155 MHz, then to 455 kHz for signal processing.
- Those IF frequencies are common because the required components (coils, crystals) are widely used and inexpensive.
Most RC aircraft receivers on the market are double-conversion. Two notable exceptions:
- Hitec's HAS-3MB (used with Focus 2 and 3 single-stick systems) — AM, described as "Super Narrow Band."
- JR receivers that use patented single-conversion circuitry marketed as Anti-Blocking, Cross-Modulation and Window (ABC&W).
Double-conversion has long been used in non-RC communications receivers. It is not required or used in transmitters.
Note on crystals: some crystals are cut for the basic frequency while others are half-frequency and then multiplied in circuitry. This can complicate identification in a few cases, especially if an owner is attempting to mislead a contest official.
Regulatory timeline and practical rules
- March 1, 1992: All transmitters "type accepted" (approved) by the FCC must be narrowband. Independent FCC-approved laboratory test results must be filed for each transmitter type.
- March 1, 1993: Manufacturers and dealers were required to market only narrowband transmitters (they were given one year to move older stock).
- January 1, 1995: AMA discontinued the Gold Sticker RF Check program; those stickers are no longer required.
- March 1, 1998: Deadline to use and have upgraded older wideband transmitters expired. As of that date, modifying a wideband transmitter to operate on narrowband was prohibited—upgrading transmitters by anyone (manufacturers or independent service centers) became illegal.
Important practical points:
- Transmitters are regulated by FCC narrowband rules; receivers are not federally required to be narrowband (that's an AMA requirement).
- It is not feasible to "narrowband" an older receiver by adding circuitry; the printed circuit board layout and design do not accept such retrofits. The only cure for an old receiver is replacement with a receiver designed for narrowband operation.
- Any service center advertising transmitter "narrowbanding" after the legal cutoff may be operating outside the law. Flying with equipment modified contrary to the FCC rules is a violation.
Guidance for Contest Directors, buyers, and owners
- Contest Directors (CDs) will need clear guidelines to identify legal transmitters. Many CDs may not be fully informed—consult authoritative sources (AMA manual, manufacturer documentation).
- Buyers at swap meets should be cautious; thousands of used rigs change hands and not all will be legal under current FCC rules.
- To verify legality:
- Check manufacturer documentation and model type-acceptance statements.
- Consult the AMA Membership Manual and contact manufacturers or the AMA for clarification.
- Be skeptical of claims that an old transmitter has been upgraded unless there is verifiable, lawful documentation.
- If in doubt, replace transmitters or receivers with modern, approved equipment rather than relying on uncertain modifications.
References
- AMA Membership Manual (annual publication)
- George Steiner, A to Z—Radio Control Electronic Journal (available from GSP Products, 2238 Rogue River Dr., Sacramento, CA 95826)
Transcribed from original scans by AI. Minor OCR errors may remain.
