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Author Topic: satellite digipeater over the Atlantic  (Read 3811 times)
KJ6UIM
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Posts: 6




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« on: December 05, 2012, 09:57:38 AM »

I am working on a near-space balloon project for school and this will be our fourth launch. We have collected data, tried going really high (99,011 feet) and now we are going for distance.We are planning on launching from the San Francisco Bay Area and going east, if all goes well it should end up going of the east coast by the second night. Once the balloon gets about 200 miles of the coast we will lose contact with it until it gets to Europe or Africa, if it gets there.

The idea came up of using a satellite repeater but that would possible mean we can't use regular ground based repeaters. The idea we have is to time our launch so there is a satellite over head of at least part of the way over the Atlantic and we can get an update. The two proposed ideas to do this are having two radios (which means more weight ) or switching channels  at a certain time or place (complex).

Are there others ways we could do this?
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K0JEG
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« Reply #1 on: December 05, 2012, 05:54:04 PM »

The ISS orbits the Earth every 90 minutes and NO-44 is in a polar orbit, so unless your balloon is really moving, it should be in a position to be heard by one or the other several times during the trip over the Atlantic.

At that height I would think your chances of being picked up by a satellite would be much higher than a ground station. It would be an interesting experiment to see if using satellite APRS exclusively would work, but I'm sure you'd rather see reliability over experimentation when it comes to telemetry.

How complex is your controller? I could see testing the balloon location against a boundary that could then switch in a different crystal in a radio something like this: http://tinyurl.com/bbzq4k3 (Google conversion of a Ramsey 2meter crystal controlled FM transmitter manual). There's not much available that would be simple enough to be switched unless your controller is fairly advanced. In fact the only small agile synthesized transceiver that can be remotely tuned "off the shelf" I can think of right now is the FT-817.

Maybe reach out to Byonics.com and see if they have any way of changing freq on their beacon radios. Don't forget that your TNC will also need to have a different path (ARISS) for the ISS and NO-44 to digipeat.
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KJ6UIM
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« Reply #2 on: December 06, 2012, 09:29:25 PM »

Thanks, we are using an arduino with a trackuino shield. Total out put 300mW but we have a very good twin lead j-pole antenna built by your truly. Upping the power could be good, but at that altitude the difference is minimal, also more power means more weight which is our enemy (our current set up weights 200g)
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K0JEG
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« Reply #3 on: December 08, 2012, 01:49:15 PM »

I did a little more checking and came across this:

https://www.argentdata.com/catalog/product_info.php?products_id=134

Don't know how easy it might be to interface, but it will change frequencies with a command from a microcontroller.
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