1 # Amateur Radio and Rockets
5 There are at least two strong motivations for putting radios in rockets. The
6 first is to help locate the rocket after flight, either by using radio
7 direction finding techniques, or by having the rocket report its position as
8 determined by on-board GPS over a radio link. The second is to record data
9 about the flight for later analysis in case the rocket itself isn't recovered.
11 One of the main features of [TeleMetrum](../TeleMetrum/) is the fully
12 integrated radio link. The chip at the heart of our designs includes a highly
13 optimized digital radio transceiver at very low power.
17 It is not clear to us that all of the approaches people have taken over
18 the years to put off the shelf radios in rockets are actually legal. To
19 legally operate a radio transmitter, we need to understand and adhere
20 to the rules that regulate use of the radio frequency spectrum. When
21 commercial radio components are used in ways the original designer did not
22 envision, the rules against which they were designed and certified may not
23 still apply. But because rocket flights are short and often happen in
24 remote places, and the chance of harmful interference to other radio users is
25 therefore pretty small, we're never heard of anyone being fined or
28 In the United States, the rules that matter to us are published by the
29 Federal Communications Commission, or [FCC](http://fcc.gov/). Under Part 15
30 of the FCC rules, it is possible to design and build radios that can be used
31 without each user needing to hold an FCC license. However, complying with
32 those regulations isn't trivial and isn't cheap. But all hope is not
33 lost! There's an alternative, unambiguously legal
34 approach to operating our radio links.
36 FCC Part 97 and its equivalent in
37 other countries define an "amateur radio" (sometimes called "ham radio")
38 service. Holders of amateur radio licenses can transmit on many different
39 frequency bands in many different operating modes, using equipment that does
40 not have to be specifically certified. This includes permission to operate
41 telemetry links and remote controls such as what we want for our rockets!
43 ## Getting an Amateur Radio License ##
45 To legally operate a [TeleMetrum](../TeleMetrum) system as designed
46 in the USA, you need at
47 least a "Technician Class" amateur radio license. This is the entry level
48 license, and getting one is actually pretty easy. If you've been through
49 the written teste for a Level 2 high power rocketry certification, taking a ham
50 radio license exam is a similar kind of experience. The test is multiple
51 choice with questions taken from a pool that is completely published ahead
52 of time, and there are some great online resources for learning the material
53 and taking practice exams until you're ready to take the real test. This
54 [ARRL page](http://www.arrl.org/FandES/ead/classes.html) is a good place
57 ## Related Equipment ##
59 It's entirely possible to use just a [TeleMetrum](../TeleMetrum/)
60 in a rocket and a [TeleDongle](../TeleDongle/)
61 on the ground with simple wire whip antennas and nothing else. But there are
62 other pieces of amateur radio gear that we think are worth mentioning because
63 we find them useful too.
67 A popular class of commercially available ham radio transceiver is commonly
68 known as an "HT". These are hand-held, cover one or more frequency bands,
69 and usually are meant to operate primarily using narrow-bandwidth FM
70 voice. Various companies make and sell them, and they have multiple
72 launch. Like walkie talkies or FRS radios (but better!), they can be used to
73 talk to others on the flight line, coordinate search activities, and so
74 forth. Choosing a "dual band" or "multi band" model that covers both
76 and "70 centimeter" bands is a good idea, since 2m is a good band for local
77 voice conversations and the audio tones put out by [TeleMetrum](../TeleMetrum)
78 for direction finding are in the 70cm band.
80 Keith and Bdale both currently own and use the
81 [Yaesu VX-6R](http://yaesu.com/indexVS.cfm?cmd=DisplayProducts&ProdCatID=111&encProdID=4C6F204F6FEBB5BAFA58BCC1C131EAC0&DivisionID=65&isArchived=0)
86 Almost any antenna that covers 435 Mhz can be used for receiving signals
87 from [TeleMetrum](../TeleMetrum).
89 The best hand-held commercial directional antennas we've found for radio
90 direction finding rockets are from
91 [Arrow Antennas](http://www.arrowantennas.com/). The 440-3 and 440-5 are
92 both good choices for finding a TeleMetrum-equipped rocket when used with
95 The best home-made directional antennas for this purpose that we're aware of
96 are based on the ["cheap yagi"](http://www.wa5vjb.com/yagi-pdf/cheapyagi.pdf)
97 designs by Kent Britain WA5VJB. Bdale makes his using lengths of pine
98 1x2, 1/8 inch brazing rod for the parasitic elements, and work-hardened 12
99 gauge copper wire for the driven element. The longer versions are great
100 for roving in radio contests, and the 6-element 432 Mhz design works fine
101 for chasing [TeleMetrum](../TeleMetrum)-equipped rockets.