FROB
Well-Known Member
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- Jan 23, 2009
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Hi Folks!
The topic of this week's poll is GPS and radio telemetry;
If you're like me, and you'd like to get such a setup to easily and accurately track your rockets, (or balloons, RC airplanes, or anything else or that matter)
Tell us what you think is the minimum acceptable range either in the air or on the ground (at recovery time)
for your current needs or for what you are planning to build in the near future.
Of course its tempting just to go for the longest range offered but there's a catch you have to keep in mind:
As radio power (range) goes up, so does the cost, the size, and the amount of power it uses.
As an example, lets say for 50,000 feet range in the air (Line of sight) the best designed radio needs ~ 1Watt of transmit RF power- and uses about 3 watts of electricity-
though for our uses it can be run on a pretty low duty cycle, maybe 50:1 or so, so actually ~50mW average power consumption.
Every doubling of range requires at least 4x the transmit power and battery size, and adds significantly to the cost-
at the lower power levels, its maybe 50% added cost, increasing exponentially so at higher power levels, it can go up by 200% or more.
You will notice the range on the ground is listed at about 1/5 of the air "line-of-sight" range- thats a very approximate guess since it depends a lot on things like vegetation, terrain, buildings humidity, and how the thing landed. The point i you should expect the range on the ground to be a small fraction of what you'd get in the air. Normally, if you're getting live telemetry up until it almost touches the ground and loses contact, you just go to the last known coordinates from telemetry and you'll likely re-acquire the signal as you approach.
The question I'd ask you to comment on is, which is the limiting factor in your choice? Is it the range in the air, or the range on the ground?
Again as in my other polls, if this actually bears fruit as a working system, i will draw a winner to receive one "beta" unit from everyone who posts a thoughtful comment on the subject.
Thanks again for participating, and please post a comment if you have any thoughts at all on the subject!
The topic of this week's poll is GPS and radio telemetry;
If you're like me, and you'd like to get such a setup to easily and accurately track your rockets, (or balloons, RC airplanes, or anything else or that matter)
Tell us what you think is the minimum acceptable range either in the air or on the ground (at recovery time)
for your current needs or for what you are planning to build in the near future.
Of course its tempting just to go for the longest range offered but there's a catch you have to keep in mind:
As radio power (range) goes up, so does the cost, the size, and the amount of power it uses.
As an example, lets say for 50,000 feet range in the air (Line of sight) the best designed radio needs ~ 1Watt of transmit RF power- and uses about 3 watts of electricity-
though for our uses it can be run on a pretty low duty cycle, maybe 50:1 or so, so actually ~50mW average power consumption.
Every doubling of range requires at least 4x the transmit power and battery size, and adds significantly to the cost-
at the lower power levels, its maybe 50% added cost, increasing exponentially so at higher power levels, it can go up by 200% or more.
You will notice the range on the ground is listed at about 1/5 of the air "line-of-sight" range- thats a very approximate guess since it depends a lot on things like vegetation, terrain, buildings humidity, and how the thing landed. The point i you should expect the range on the ground to be a small fraction of what you'd get in the air. Normally, if you're getting live telemetry up until it almost touches the ground and loses contact, you just go to the last known coordinates from telemetry and you'll likely re-acquire the signal as you approach.
The question I'd ask you to comment on is, which is the limiting factor in your choice? Is it the range in the air, or the range on the ground?
Again as in my other polls, if this actually bears fruit as a working system, i will draw a winner to receive one "beta" unit from everyone who posts a thoughtful comment on the subject.
Thanks again for participating, and please post a comment if you have any thoughts at all on the subject!
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