This may be off topic? I am helping a neighbor who is just getting into high power model rocketry (Tripoli) He is interested in _two way_ telemetry with his rocket and wants the downlink for the usual sensors like altitude, GPS, XYZ-attitude etc. There are _one way_ products that provide the downlink but he also wants to be able to uplink to fire parachutes or thrusters (during descent). I am leaning toward an 900 MHz ISM solution for the RF but am stumped as to what digital platform would be most flexible (and light weight) for the communications needs. Are there any standards or better yett off the shelf products? I am open to suggestions.
Hello,
Being in high power rocketry, I have used the Maxstream 900 MHz radios which are two way. They have the Xtend version that puts out a watt for several miles of range. There is also Aerocomm modules sold at mouser. Maxstream can be bought from Digikey. Both are ISM band radios.
I used the Maxstream XCite 4mW 900 MHz radio with a solid link for a 1 mile range flight.
Now for doing an uplink to deploy parachutes, maybe as a backup. For safety reasons, he should use an altimeter. My favorite is made by Perfectflite, the HA45. It can support flights up to 45,000 feet. I would not rely on a comm link to deploy a parachute. I would do it as a back up in case the altimeter doesn't do its job. There have been at least one past product that allowed you to command the rocket to delpoy a parachute. I don't think it exists anymore. With the money invested in the rocket and electronics plus safety requirements, you need a reliable parachute deployment system and a radio link is not considered reliable.
You will see that as the rockets get bigger and more expensive, the builders include two or more altimeters for improved reliability.
Good luck and use an altimeter for parachute deployment.
Ivan
On Mar 5, 2008, at 7:37 PM, RFI-EMI-GUY wrote:
This may be off topic? I am helping a neighbor who is just getting into high power model rocketry (Tripoli) He is interested in _two way_ telemetry with his rocket and wants the downlink for the usual sensors like altitude, GPS, XYZ-attitude etc. There are _one way_ products that provide the downlink but he also wants to be able to uplink to fire parachutes or thrusters (during descent). I am leaning toward an 900 MHz ISM solution for the RF but am stumped as to what digital platform would be most flexible (and light weight) for the communications needs. Are there any standards or better yett off the shelf products? I am open to suggestions.
-- Joe Leikhim K4SAT "The RFI-EMI-GUY"©
"Treason doth never prosper: what's the reason? For if it prosper, none dare call it treason."
"Follow The Money" ;-P
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On Wed, 5 Mar 2008 20:05:10 -0500, Ivan Galysh wrote: <snip>
Now for doing an uplink to deploy parachutes, maybe as a backup. For safety reasons, he should use an altimeter....I would not rely on a comm link to deploy a parachute. I would do it as a back up in case the altimeter doesn't do its job.
<snip>
Not to mention that it would be darned near impossible to be able to ascertain when apogee occurs with even a medium sized rocket at one mile high - and I know that I wouldn't want to deploy my mains after my rocket has had a thousand or more feet of altitude loss from apogee - instant shred! ---------------------------------------------------------------------- R. Wayne Day N5WD n5wd@charter.net IRLP Node 3997 -> Lake Worth, Texas Fort Worth, Texas USA ----------------------------------------------------------------------
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Ivan Galysh -
RFI-EMI-GUY -
Wayne N5WD