Amateur Radio and Rockets

Why Radio?

There are at least two strong motivations for putting radios in rockets. The first is to help locate the rocket after flight, either by using radio direction finding techniques, or by having the rocket report its position as determined by on-board GPS over a radio link. The second is to record data about the flight for later analysis in case the rocket itself isn't recovered.

One of the main features of TeleMetrum is the fully integrated radio link. The chip at the heart of our designs includes a highly optimized digital radio transceiver at very low power.

Legal Context

To legally operate a radio transmitter, we need to understand and adhere to the rules that regulate use of the radio frequency spectrum. In the United States, the rules that matter to us are published by the Federal Communications Commission, or FCC. Under various sections of the FCC rules, particularly Part 15, it is possible to design and build radios that can be used without each user needing to hold an FCC license. Complying with those regulations isn't trivial and can get expensive. Fortunately, there is an alternative.

FCC Part 97 and its equivalent in other countries define an "amateur radio" (sometimes called "ham radio") service. Holders of amateur radio licenses can transmit on many different frequency bands in many different operating modes, using equipment that does not have to be specifically certified. This includes permission to operate telemetry links and remote controls such as what we want for our rockets!

Getting an Amateur Radio License

To legally operate a TeleMetrum system as designed in the USA, you need at least a "Technician Class" amateur radio license. This is the entry level license, and getting one is actually pretty easy. The exam fee is low ($15?), and the license is good for 10 years and renewable for life. Anyone who has been through the written test for a Level 2 high power rocketry certification will find taking a ham radio license exam a similar sort of experience. The test is multiple choice with questions taken from a pool that is completely published ahead of time, and there are some great online resources for learning the material and taking practice exams until you're ready to take the real test. This ARRL page is a good place to start. We also have it on good authority that the book and iOS app available from Ham Radio School.com are pretty good.

Operation in Other Countries

In Australia, we have learned that operation of our products is legal without a license in the range 433.05-434.79 Mhz under the LIPD provisions. However, please be mindful of ham radio and other possible licensed users in that band as licensed users have priority.

Related Equipment

It's entirely possible to use just a TeleMetrum in a rocket and a TeleDongle on the ground with simple wire whip antennas and nothing else. But there are other pieces of amateur radio gear that we think are worth mentioning because we find them useful too.

Transceivers

A popular class of commercially available ham radio transceiver is commonly known as an "HT". These are hand-held, cover one or more frequency bands, and usually are meant to operate primarily using narrow-bandwidth FM voice. Various companies make and sell them, and they have multiple uses at a rocket launch. Like walkie talkies or FRS radios (but better!), they can be used to talk to others on the flight line, coordinate search activities, and so forth. Choosing a "dual band" or "multi band" model that covers both the "2 meter" and "70 centimeter" bands is a good idea, since 2m is a good band for local voice conversations and the audio tones put out by TeleMetrum for direction finding are in the 70cm band.

Keith and Bdale both currently own and use the Yaesu VX-7R at launches.

Antennas

Almost any antenna that covers 435 Mhz can be used for receiving signals from TeleMetrum.

The best hand-held commercial directional antennas we've found for radio direction finding rockets are from Arrow Antennas. The 440-3 and 440-5 are both good choices for finding a TeleMetrum-equipped rocket when used with a suitable 70cm HT.

The best home-made directional antennas for this purpose that we're aware of are based on the "cheap yagi" designs by Kent Britain WA5VJB. Bdale makes his using lengths of pine 1x2, 1/8 inch brazing rod for the parasitic elements, and work-hardened 12 gauge copper wire for the driven element. The longer versions are great for roving in radio contests, and the 6-element 432 Mhz design works fine for chasing TeleMetrum-equipped rockets.

Other Uses for an Amateur Radio License

The ARRL web site is full of information about other things that people do with amateur radio.

How about a Doppler radar system for tracking rockets at a launch site? Yes, someone has actually done it! See this page translated from Russian for the details!