Is 72 MHz dead?
Written by Tony Stillman In the Air Column As seen in the September 2014 issue of Model Aviation.
If you are fairly new to the RC modeling scene, you might not have any idea what a 72 MHz RC system is. More experienced modelers will know exactly what they are and have probably owned several. The 72 MHz digital proportional RC systems have been around since the 1960s. Evolution of this equipment provided us with first Amplitude Modulation (AM) sets, then Frequency Modulation (FM), and then the latest versions, which were Pulse Code Modulation (PCM). This progression gave us a more reliable link between the transmitter and receiver and provided fail-safe operation in the PCM systems. The big drawback with these systems was that they operated on a specific frequency channel within the 72 MHz band, and it was vital that only one system be operating at any given time on each channel. To ensure safe operation, a system of frequency pins was developed. You were issued a pin when you wanted to operate your transmitter. Each club had a similar system at its flying site. Before turning on your transmitter, you had to get the frequency pin from the frequency board at the flying site. You usually shared the pin with others and kept track of those at the field who were flying on the same frequency as your own, to ensure that you did not cause interference and “shoot” the other pilot’s aircraft down by mistake. The FCC gave us 72.000-73.000 MHz as our area for operations of RC model airplane equipment. In the late 1980s, AMA worked with the FCC to obtain permission to expand the number of usable channels we enjoyed from 7 to 60. The FCC did not give us any more frequency bandwidth, but allowed manufacturers to make “narrow-band” equipment so that it could safely operate more frequencies in the same amount of bandwidth. We now have frequencies starting at 72.010 MHz, and then spaced 20 KHz away is our next frequency, 72.030 MHz. This spacing continues throughout the band to give us Channel 11 (72.010 MHz) through Channel 60 (72.990 MHz). Having more channels allowed more pilots to fly at the same time with less worry of interference. These additional channels fueled a growth in RC. Along with the new frequencies, improvements in encoder design led to many enhancements in transmitter design. New features were added including programmable mixing, preprogrammed mixing, and exponential. The latest designs included microprocessor-based transmitters that were capable of memorizing complete model settings, for the first time allowing a transmitter to operate more than one aircraft. Multimodel memory exploded onto the scene and transformed sport radios into sophisticated, affordable transmitters with new features finally made available to the masses. So, what has changed? As far as 72 MHz RC operations today, nothing has changed since the 1991 narrow banding. The 72 MHz equipment that meets these requirements is still legal to operate today and will be legal for the foreseeable future. The FCC regulates radio frequencies in the US and we work closely with them on anything that would change the frequencies we are allowed to use. At this time, nothing is in the works that would change the current rules. With the introduction of 2.4 GHz spread spectrum equipment, the need for frequency pins has nearly disappeared. Now you can go to the flying field and not worry about interference from other RC pilots if you are flying on 2.4 GHz. As soon as this technology was proven, many modelers began trading their 72 MHz gear for spread spectrum gear and demand for 72 MHz systems plummeted. Manufacturers of RC radio equipment have determined that sales of 72 MHz RC equipment have slowed to the point that it is no longer profitable to continue to offer it to retail consumers. They have discontinued manufacturing this equipment, and are pointing to 2.4 GHz RC equipment in its place. Obviously, 2.4 GHz equipment cannot be interfered with by other users of RC model aircraft systems (as designated by FCC rules) so 2.4 GHz RC equipment is deemed inherently safer and more current. Some even refer to 72 MHz RC equipment as obsolete and unsafe. Nothing could be further from the truth! It could be argued that 72 MHz RC equipment is safer today because so many fliers are using 2.4 GHz RC equipment making the 72 MHz band less crowded, so there is less possibility of interference from other RC model fliers. With many good used RC radio systems for sale, many modelers purchase this gear to save money and to obtain a system with more features than what they currently own. This makes good economic sense! Although a company may not be making new equipment on 72 MHz, there is a large amount of it available, and good bargain hunters can save money while obtaining a quality RC system. The AMA has not changed its stance on 72 MHz equipment, and will continue to work with the FCC to keep 72 MHz, as well as the other frequencies, available to modelers. Unless a particular event or club decides to restrict operations to certain frequencies, 72 MHz (as well as 27 MHz, 50 MHz, 53 MHz, and 75 MHz) will continue to be available to modelers in the US. If you are looking for a good deal on RC equipment, consider purchasing used 72 MHz equipment. Plenty of it is available at swap meets, flea markets, and online. Many club members still have good gear that they no longer use. With so many modelers operating on 2.4 GHz spread spectrum, 72 MHz is a good bet today. Most of the time you will find that you are the only one at the field on 72 MHz, so you have your own private frequency. Isn’t that just as good? 72 MHz is alive and well, but you probably won’t find it at your favorite hobby dealer. —Tony Stillman Flying Site Assistance Coordinator
41 comments
72 MHz
This is a great article and
72 mhz
Use of 72 Mhz
72 MHZ
Thank You
Comments by Christopher Ada - - - - -
72 mhz
Completely untrue. I fly a
I'm good...so this article
Another good way to economize
72 MHZ
72 MHz Radios
And it makes a very handy
I am still flying on 72 mk
VHF RC Frequencies and Having a Ham License
72 MHZ
72 is still a viable radio system
72 MHz
72MHz is UHF and 2.4 is
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72 MHz radios
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72 MHZ
Great article. I fly on both
72Mhz systems
72mhz narrow band
72MHz Radios
72 Mhz
Flying on 72Mhz
Flying on 72Mhz
72 Mhz, all I've ever used 44 years
72mhz
72mhz narrow band
SS on 72Mhz
I have zero interest in using
72 MHz alive and kicking
72 MHz FM Dual conversion RX
72 Mhz. 50. Mhz. ham band, and 2.4 Gig.
72mhz dual conversion/chips
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