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 To legally operate a radio transmitter, we need to understand and adhere
18 to the rules that regulate use of the radio frequency spectrum. In the
19 United States, the rules that matter to us are published by the
20 Federal Communications Commission, or [FCC](http://fcc.gov/). Under various
21 sections of the FCC rules, particularly Part 15, it is possible to design
22 and build radios that can be used
23 without each user needing to hold an FCC license. Complying with those
24 regulations isn't trivial and isn't cheap. Forunately, there is an
27 FCC Part 97 and its equivalent in
28 other countries define an "amateur radio" (sometimes called "ham radio")
29 service. Holders of amateur radio licenses can transmit on many different
30 frequency bands in many different operating modes, using equipment that does
31 not have to be specifically certified. This includes permission to operate
32 telemetry links and remote controls such as what we want for our rockets!
34 ## Getting an Amateur Radio License ##
36 To legally operate a [TeleMetrum](../TeleMetrum) system as designed
37 in the USA, you need at least a "Technician Class" amateur radio
38 license. This is the entry level license, and getting one is actually
39 pretty easy. The exam fee is low, and the license is good for 10 years and
40 renewable for life. Anyone who has been through
41 the written test for a Level 2 high power rocketry certification will find
42 taking a ham radio license exam a similar sort of experience. The test is
44 choice with questions taken from a pool that is completely published ahead
45 of time, and there are some great online resources for learning the material
46 and taking practice exams until you're ready to take the real test. This
47 [ARRL page](http://www.arrl.org/FandES/ead/classes.html) is a good place
50 ## Related Equipment ##
52 It's entirely possible to use just a [TeleMetrum](../TeleMetrum/)
53 in a rocket and a [TeleDongle](../TeleDongle/)
54 on the ground with simple wire whip antennas and nothing else. But there are
55 other pieces of amateur radio gear that we think are worth mentioning because
56 we find them useful too.
60 A popular class of commercially available ham radio transceiver is commonly
61 known as an "HT". These are hand-held, cover one or more frequency bands,
62 and usually are meant to operate primarily using narrow-bandwidth FM
63 voice. Various companies make and sell them, and they have multiple
65 launch. Like walkie talkies or FRS radios (but better!), they can be used to
66 talk to others on the flight line, coordinate search activities, and so
67 forth. Choosing a "dual band" or "multi band" model that covers both
69 and "70 centimeter" bands is a good idea, since 2m is a good band for local
70 voice conversations and the audio tones put out by [TeleMetrum](../TeleMetrum)
71 for direction finding are in the 70cm band.
73 Keith and Bdale both currently own and use the
74 [Yaesu VX-6R](http://yaesu.com/indexVS.cfm?cmd=DisplayProducts&ProdCatID=111&encProdID=4C6F204F6FEBB5BAFA58BCC1C131EAC0&DivisionID=65&isArchived=0)
79 Almost any antenna that covers 435 Mhz can be used for receiving signals
80 from [TeleMetrum](../TeleMetrum).
82 The best hand-held commercial directional antennas we've found for radio
83 direction finding rockets are from
84 [Arrow Antennas](http://www.arrowantennas.com/). The 440-3 and 440-5 are
85 both good choices for finding a TeleMetrum-equipped rocket when used with
88 The best home-made directional antennas for this purpose that we're aware of
89 are based on the ["cheap yagi"](http://www.wa5vjb.com/yagi-pdf/cheapyagi.pdf)
90 designs by Kent Britain WA5VJB. Bdale makes his using lengths of pine
91 1x2, 1/8 inch brazing rod for the parasitic elements, and work-hardened 12
92 gauge copper wire for the driven element. The longer versions are great
93 for roving in radio contests, and the 6-element 432 Mhz design works fine
94 for chasing [TeleMetrum](../TeleMetrum)-equipped rockets.