Picked up an E size cylinder of Helium today - many thanks to Gary from the Elizabeth branch of Air Liquide Australia for making it all happen. I've also made up a balloon filler with a regulator for the cylinder & some hosepipe + PVC tubing, which looks like it will do the job well.
I have been hoping to launch this Sunday, as the weather has been looking very favorable. However, I heard back from CASA today, who are not yet done with processing my application. Hopefully this will be done sometime next week, and we can then start to look at launching.
My Spherachute arrived today! Definitely recommend these guys, great 'chute, great pricing, and shipping was quick too.
I had a chance to test the range of my 25mW Radiometrix NTX2 last night. Whilst we couldn't simulate the true line of sight conditions that we'll see during balloon flight, a few friends and I tested the range of the payload in various conditions. The payload spend the majority of the time on the backseat of my friends car, which would have no doubt limited its range. I used a 1/4 wave piece of exposed coax core as a receiving antenna, sticking it out of the window of my car.
Incidentally, it turns out my car locking/alarm remote is in the same band as the NTX2: ~433mhz, meaning that I wasn't able to unlock/start my car - even after trying my spare keys & scratching my head for a good while.
On flat, straight road with minimal obstruction (a few trees & streetlights), we achieved about 3km of useful (decodeable) range. Given that the antennas were only about 1m above ground level (and probably the street width - it was lined with buildings), we would have had insufficient Fresnel clearance, which would have been a limiting factor.
We decided to position the payload somewhere which might give it better coverage, so headed to Belair, one of the more elevated suburbs in Adelaide. We hoped to test from Windy Point (an elevated lookout with a good unobstructed view of Adelaide), but after arriving and finding a gentleman who was a little too interested in making conversation, we found the prospect of being stabbed a little grisly, so left to find another spot. We settled on a street which was partially shielded by trees & houses, but gave us the best possible line of sight.
One car set off back down the hill to see what sort of range we could achieve - we ended up at the airport (10km away as the crow flies), before I broke the antenna sticking out of my window & we called it a night. Given the pitiful antenna I was using on the receiver & the fact that the NTX2 has the same sort of transmit power as a garage door opener, I was pretty impressed with the range.
I also received another radio I picked up cheaply on eBay today - an ICOM 490A. It's nowhere near as fully featured as my 706, but it'll do SSB on the 70cm band, so it'll decode data just fine.
Yesterday saw a few packages arrive. My Radiometrix NTX2 came, as did the primary camera and a bunch of heatshrink I'd ordered off ebay.
I had a mess around with the NTX2 & potential dividers, & after much tweaking came up with a solution that worked. Testing code on the other hand was problematic - eventually with some help from fergusnoble over at #highaltitude on freenode, I realised that the delayMicroSeconds() call wasn't working with a value as large as 20,000 (20ms = 1/50th sec) - a few adjustments later, and transmission was working perfectly, so I built up the module on a board. So far I haven't tested with any antennas, but it seems to cover the distance across the room just fine.
The camera seems great - and the seller was good enough to give me a discount due to the delay in shipping! External triggering will likely by more tricky than the Kodak, given that it has a half-press button for focusing, which the Kodak does not.
I've also written most of the code to handle the GPS side of things, which I'll post shortly.
Got a visit from the postman and Fedex this morning.
My order from Sparkfun for a Lassen IQ GPS module, antenna & mating header arrived, as well as the Kodak camera I bought on eBay (that was pretty quick).
The Lassen IQ header is seriously tiny - but once soldered onto the GPS shield, everything was working.
The camera doesn't have a memory card & I don't have the proprietary cable needed to download photos from the internal memory, so I'm still unsure of what the quality is like. I've never seen such a simplistic camera, this thing feels like a toy - it weighs less than the batteries which go inside it. It does seem to have a continuous video recording mode though, so using it for video may be a possibility.
I've placed an order with RFMA for a Radiometrix NTX2H - the high power (25mW) version of the NTX2. This is the radio module which will be used for RTTY on Horus, at 50 baud. Previous launches with the 10mW NTX2 have achieved ranges of 100-300km, so the 25mW module should provide excellent range, coupled with a sensitive receiver & antenna.
After much looking around and research (thanks #highaltitude!), I've ordered the transceiver which will be used to track Horus. The transceiver is an ICOM 706 MKIIG which I picked up on eBay.
I also picked up 2 cameras on eBay cheaply - a Panasonic Lumix DMC-LZ2 & a Kodak Easyshare C310. The Lumix is a 5MP image stabilized point and shoot - this will be used as the primary camera. The Kodak is a 3MP ultra-simple point and shoot, with no optical zoom. It might get mounted externally, or oriented downwards, not sure at this stage.