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Author Topic: APRS and rockets ;)  (Read 7280 times)
VK2ICJ
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Posts: 53




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« on: April 02, 2014, 05:37:37 AM »

Gday all

I am looking for some ideas from people on exactly how to go about setting up an APRS network (if that is the best idea)

Here is the setup.  I fly model and high power rockets and wish to use APRS from BRB
http://www.bigredbee.com/BeeLineGPS.htm
The BRB is essentially just a locator.

Next year I will be going to a national launch site that is fairly remote here in Australia
The models are flown and then parachuted back to earth.  This could be at altitudes of 20,000 feet or more.  Not sure what the wavier will be.  So the models coming back to earth on parachutes will have the ability to cover some serious ground before touch down.  These GPS locator devices are the Bee Knees lol
There will be a number of other flyers probably using the same gear.  I don't know how many could a be a few could be a hundred who knows.
My initial thought is to have a base station at my caravan with an antenna up 10 meters or so to increase range and have everyone use the same freq so that if my base hears the signal it will get repeated to everyone with HT's or other APRS rx.  The laptop in the van will plot the location of the various rockets and or the people with APRS enabled radios on a map.  This way if anyone hears a signal out walking about looking for rockets that signal will get relayed back to the base and then to everyone else.  The other line of thinking is to have everyone on different frequencies that is co ordinated at a board much like the old days of RC airplanes and everyone take care of thier own stuff.  I was thinking the whole idea of APRS was to use networking to improve location identification and wanted to go down that route but I can see the thought that packet collisions could impede on getting good data from the rockets.  Does anyone have any experience with this sort of thing?

Your thoughts will be appreciated

73

Chris de vk2icj
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VK2ICJ
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Posts: 53




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« Reply #1 on: April 03, 2014, 05:58:39 AM »

Ok 345 people have looked at this and no ideas  Huh  let me rephrase what I am asking.

Is it a good idea or not to setup a network where you have multiple trackers using APRS on the same freq for a limited time.  We are not talking hours here but most of these devices will be airborne for only minutes. Once on the ground I would wager that there will be no discernable signal back at the launch site.  Given the rigors of rocket flight there will not be a lot of packets received so every collision is possibly very bad.  Is it better to have everyone on different freqs and running completely independant rx stations?

73

Chris
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KE7AXC
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Posts: 10




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« Reply #2 on: April 03, 2014, 08:58:26 AM »

Seems like you have several problems to solve.  I have never done this sort of thing, but here is my two cents worth just pondering the problem.

As far as the rockets go..  Having all rockets on the same frequency would make it easier for those out retrieving the payloads if you're doing it cooperatively.  With several frequencies, even with a scanning RX, it seems like searchers could miss payloads.  Manually going through several frequencies and "listening" seems like a lot of effort.  (Someone might be able to write some software to do that if the radios can be commanded from a PC but you'd still have to move slow enough so you didn't get out of range before each frequency was scanned long enough.)  I see the BRB devices can time slot their APRS packets.  Depending on how many rockets are up/landed and not retrieved at one time, that might help with packet collisions if you use the same frequency but that depends on many factors I can't address.  Even if you still had to use several frequencies to reduce collisions, it would reduce the number.

Getting position data back to the base and then out to everyone raises a couple of major questions.  Hot do you relay info from the base and then send it out to everyone?  Not sure how to narrow down the many ways that could be done.  Some would require quite a bit of hardware for all the people out searching.

I know there are model rocket launches from the Black Rock Desert in the state of Nevada in the US.  Maybe do a bit of searching and get in touch with some of those people.  I know the tracker2 Yahoo group for the Argent Data devices has some members who launch rockets, so maybe a quick post there would put you in touch with some people for some follow-on private discussions.
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VK2FAK
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Posts: 87




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« Reply #3 on: April 03, 2014, 02:49:49 PM »

Hi all..

Chris.. I suggest you have a chat to the Balloon guys in Australia. The last one a few weeks ago was running APRS and it was tracked from Victoria up into NSW and picked up again when it flew over New Zealand......

John
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W0JRT
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Posts: 7




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« Reply #4 on: April 03, 2014, 02:56:29 PM »

Chris,

I have flown rockets with APRS at various Tripoli launches in the USA including at Black Rock Desert and at K.L.O.U.D.Busters in Kansas.  Generally a digipeater isn't needed because you have line-of-sight to the rocket until just before it touches down.  Even if that is a few kilometers away, the last received position report will get you close enough.  By the time you walk / drive over to that location (and probably before you even get there), you'll most likely be able to start receiving packets from the rocket and therefore will have the final location, or you'll be close enough to see the rocket.

That said, having a digipeater at base camp could make it more fun, and may help in a few cases like you pointed out (you're in the field recovering a rocket while another rocket is on its way down).

One piece of advice: Be prepared to do some manual radio direction finding using a directional antenna, body shield, or other methods, in the event that something happens that causes the transmitter to not send a valid position.
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VK2ICJ
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Posts: 53




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« Reply #5 on: April 03, 2014, 07:26:14 PM »

RDF is what I know best so I am ready there.  The question arose when discussion around a national launch here in Australia started about managing frequencies for unlic 900mhz fsk beepers that put out NMEA strings that spread to fm beepers and UHF APRS type transmitters.  A frequency board like the old RC days before spectrum hopping was suggested and I do like the idea but in my mind it sort of defeats the idea of APRS being a network when everybody is doing their own thing on their own frequency.

73
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W1VT
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Posts: 898




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« Reply #6 on: April 04, 2014, 07:23:13 AM »

I think that having them all on the same frequency makes sense.  If I was out retrieving a rocket, I would like to know the positions of any rockets drifting my way.  Some of those rockets are big and heavy.

Proper flight management could insure that when GPS is a necessity, only one rocket will be airborne at any given time. 

I am assuming the chances of a rocket being stuck up in a tree or powerline is negligible.

Zack W1VT



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RJ22GG
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Posts: 3




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« Reply #7 on: June 26, 2014, 01:16:53 AM »

Already have one and thinking about to have a review
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