From cf459cf5cbbea6c845dc2794751f9e23d192dabf Mon Sep 17 00:00:00 2001 From: Bdale Garbee Date: Sat, 6 Feb 2010 11:48:39 -0700 Subject: [PATCH] add some ham radio info --- Radio/index.mdwn | 97 ++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 97 insertions(+) create mode 100644 Radio/index.mdwn diff --git a/Radio/index.mdwn b/Radio/index.mdwn new file mode 100644 index 0000000..9fc281e --- /dev/null +++ b/Radio/index.mdwn @@ -0,0 +1,97 @@ +# 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 ## + +It is not clear to us that all of the approaches people have taken over +the years to put off the shelf radios in rockets are actually legal. +To legally operate a radio transmitter, we need to understand and adhere +to the rules that regulate use of the radio frequency spectrum. But when +commercial radio components are used in ways the original designer did not +envision, the rules against which they were designed and certified may not +still apply. But because rocket flights are short and often happen in +remote places, and the chance of harmful interference to other radio users is +therefore pretty small, we're never heard of anyone being fined or +prosecuted over this. + +In the United States, the rules that matter to us are published by the +Federal Communications Commission, or [FCC](http://fcc.gov/). Under Part 15 +of the FCC rules, it is possible to design and build radios that can be used +without each user needing to hold an FCC license. However, complying with +those regulations isn't trivial and isn't cheap. + +But all hope is not lost! There's an alternative, unambiguously legal +approach to operating our radio links. 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. If you've been through +the written teste for a Level 2 high power rocketry certification, taking a ham +radio license exam is a similar kind 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. + +## 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-6R](http://yaesu.com/indexVS.cfm?cmd=DisplayProducts&ProdCatID=111&encProdID=4C6F204F6FEBB5BAFA58BCC1C131EAC0&DivisionID=65&isArchived=0) +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](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-equipped rockets. + -- 2.30.2