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# 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](../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](http://fcc.gov/). 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](../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](http://www.arrl.org/FandES/ead/classes.html) is a good place
to start.
## Operation in Other Countries ##
In Australia, we have learned that operation may be legal without a license
in the range 433.05-434.79 Mhz under the LIPD provisions. However, please be
mindful of ham radio users in that band.
## Related Equipment ##
It's entirely possible to use just a [TeleMetrum](../TeleMetrum/)
in a rocket and a [TeleDongle](../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](../TeleMetrum)
for direction finding are in the 70cm band.
Keith and Bdale both currently own and use the
[Yaesu VX-7R](http://www.yaesu.com/indexVS.cfm?cmd=DisplayProducts&ProdCatID=111&encProdID=8D3254BFC69FB172D78647DC56EFB0E9&DivisionID=65&isArchived=0)
at launches.
### Antennas ###
Almost any antenna that covers 435 Mhz can be used for receiving signals
from [TeleMetrum](../TeleMetrum).
The best hand-held commercial directional antennas we've found for radio
direction finding rockets are from
[Arrow Antennas](http://www.arrowantennas.com/). 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"](http://www.wa5vjb.com/yagi-pdf/cheapyagi.pdf)
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](../TeleMetrum)-equipped rockets.
### Other Uses for an Amateur Radio License ###
The [ARRL](http://www.arrl.org/) 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](http://translate.google.com/translate?js=y&prev=_t&hl=en&ie=UTF-8&layout=1&eotf=1&u=http%3A%2F%2Fserge77.rocketworkshop.net%2Findex.htm&sl=ru&tl=en)
for the details!
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