4679	2010-05-12 07:38:39	Colin Beeforth	Re: balloon beacon
Message	Date	From	Subject
Hi Corey, Without a lot more info, it is hard to comment much. We don't know if your link is up, down or both, simplex or duplex. >From an wide over view, my first thought was Balloon = Limited Lift, so weight would be the limiting factor. Since Batteries = Big Weight, power consumption will be the major design restriction. I can't imagine how you can afford a power budget that includes DSP and loads of computing. Getting it actually built and working quickly is also a desirable thing. I'd imagine that simple FM would work fine and be very power frugal for VHF or UHF tracking and control. It makes antennas far simpler and gives rough tracking information as well if the on-board GPS fails - just thinking of temperature - the more complex anything is, the less likely it will be reliable. Watch temperature, it will drop rapidly up high. Also, as the air gets thinner, heat sink efficiency vanishes remarkably quickly at altitude. Hence my suggestions for FM and infrequent bursts of transmission - it helps heat and battery life as well if you only transmit one burst per minute - balloons don't move that fast. Balloons crash pretty often, so the simpler and cheaper you can make it will save you a lot of cost and distress. Maybe something far simpler and mostly analogue would answer the design requirements easier. Some scientists launched a serious research balloon in northern Australia recently. The wind blew it away. It's payload crushed a car and smashed a million bucks worth of equipment. The original weather sondes our weather bureau used to use were very simple, so when they blew out over the Antarctic ocean, they just shrugged and let them go. Just some thoughts that might be useful, or not. Good luck with the project! Cheers, Colin VK3KDF Melbourne, Australia
4680	2010-05-12 11:59:16	Tim	Re: balloon beacon
Colin wrote: > Maybe something far simpler and mostly analogue would answer the design > requirements easier. I think there is some validity to the thought of using the most energy efficient mode (e.g. PSK31) possible to reduce battery weight especially for long long flights. That said, scope creep in aeronautical equipment has traditionally been kept in check by the weight budget. Start putting stuff in a DSP though and next thing you know you're not into hardware scope creep, but software scope creep, and this is an issue that even the biggest jet manufacturers have not fully learned to keep under control. When the experimental balloon telemetry radio starts having more communications modes and features than the HF radios used on intercontinental passenger jets, then you know you're suffering from scope creep :-) Tim N3QE
4682	2010-05-12 14:56:07	Corey Minyard	Re: balloon beacon
Tim wrote: > Colin wrote: > >> Maybe something far simpler and mostly analogue would answer the design >> requirements easier. >> > > I think there is some validity to the thought of using the most energy efficient mode (e.g. PSK31) possible to reduce battery weight especially for long long flights. > The PSK-31 thing is sort of experimental, something new to try. This won't be a terribly long flight, just an afternoon, but I'm hoping to be able to supply it with a few lithium batteries. At 2900mAH for the AA batteries, that should be able to keep things going for a while if I'm careful with power consumption. > That said, scope creep in aeronautical equipment has traditionally been kept in check by the weight budget. Start putting stuff in a DSP though and next thing you know you're not into hardware scope creep, but software scope creep, and this is an issue that even the biggest jet manufacturers have not fully learned to keep under control. When the experimental balloon telemetry radio starts having more communications modes and features than the HF radios used on intercontinental passenger jets, then you know you're suffering from scope creep :-) > Yeah, I know about scope creep, being a software engineer :). "Just one more feature." The design of software is much more of a discovery process than hardware, though, and it's often not so much scope creep as realizing things you need to do that you hadn't budgeted. And I'll try to keep it simple for now :-). Better to start with a good fundamental design and add features later. Thanks, -corey - AE5KM