I've developed an Iridium board with built-in processor, u-Blox 7 GPS and is based on the SBD-9602 Iridium modem. I haven't tried the smaller 9603 module yet since it appeared to be more difficult to mount to a daughter board than the 9602 and more difficult to attach an antenna directly to a board. I've flown my Iridium prototype on 30 missions and it works great. No altitude limits as long as you configure the u-Blox for Air mode and works once it hits the ground and you can customize your telemetry output. I use a helical antenna (more expensive than a patch) but it does allow the payload to transmit successfully to the Iridium satellite network even when upside down or in odd positions while on the ground.
The processor on my board is programmable in Arduino format so can be easily configurable. I had a problem finding a replacement antenna as good as the Sarantel ones that were discontinued and that has held up my production release, but I have finally found a helical antenna that works as well and just got them in. I also just received my new PC boards and am putting together the first production board so will be offering these soon online after I test them out. It's a real shame that Sarantel has gone belly up....it really caused a lot of grief and delay trying to find equivalent antennas out there.
I have written a program that takes the emails you receive from Iridium, parses that info and then plots it onto APRS.FI just like it came from an APRS transmitter.
There is a monthly subscription that is more reasonable than a Spot and allows you 12,000 bytes of free data per month which is more than enough for several ARHAB flights. I also use NAL Research for the subscription plan as they are the most reasonable that I could find.
I will let you know when I finish up this new board and when it will be available.
I recently flight tested a Spot TRACE unit. It didn't work at all during the ascent portion of the flight and didn't start working until below 38k feet. However it reported every 5 mins during the final descent and also reported the final landing location. It's small and lightweight and reasonably priced. However it will not report altitude or any telemetry and won't work above 38,000 feet or so. The older Spot units also work but are limited in altitude and do not report altitude either. If you hack a Spot Messenger and pay the expensive message units, you can send reports in any format but I have not tried that one out since the Iridium was more reasonable in cost to operate. I can get about 2 to 3 minute updates on the Iridium board but for best cost effectiveness I usually set it up for 5 minute intervals. Oh, one more advantage to the Iridium system is that you can email a command TO the balloon payload and have it activate things or change the data updates.
- Bill WB8ELK
To: GPSL <GPSL@...
Sent: Fri, Jan 9, 2015 6:09 pm
Subject: [GPSL] Which SPOT (or other satellite tracker)?
I'm considering joining the club and adding a SPOT tracker to the traditional APRS tracking devices I use for balloon launches. Questions:
1. I see a variety of SPOT devices, with the Trace ad Gen3 models looking most appropriate for balloon use. What are you all using, and why did you choose that one?
2. Is there any way to subscribe to the required SPOT tracking service for shorter periods of time than a full year? I only expect to use the service occasionally.
3. Anyone using RockBlock (or another Iridium approach) as a SPOT alternative?