BLT-67 was launched on the morning of Tuesday (02 Feb 2021) from NW Houston. It is the maiden flight of my new picoballoon tracker, the SS_PicoTrackerFW (FW = Feather Weight), coming in around 1.4g board weight, and total payload weight of 7.28g. The solar cells comprise most of that weight, but I'm working on that for the next launch.
This new board has been in work for months with many factors driving the final design. My objectives for this board were: 1) use up the uBlox EVA-7M GPS chips I had collecting dust, 2) be as light as possible, 3) transmit both WSPR (HF) and APRS (2m), and 4) be completely solar powered with no battery or super capacitor required. I achieved 3 out of 4 (no APRS), but I hope to work that into my next board. It wasn't that I couldn't get APRS to work, but it requires using the Si5351B chip, and the Arduino library I was using wasn't working properly to set the registers for this chip so...it will happen eventually...more work required.
The board weighted in ~1.4g without the programming header. In addition to the uBlox EVA-7M, it uses an Atmel ATMEGA328P-MU microcontroller, Si5351A clock generator, NCP551 LDO regulator, and 3-pole elliptical low-pass filter. I had planned on using the ST SPV1040 MPPT solar charger chip, but learned I still have things to learn about designing low-power solar-only voltage regulator circuits... While I think I can get it to work, but I ran out of time and patience, and reverted to the old faithful LDO regulator.
Ironically, the software that drives this board greatly influenced its design, at least from what pins on the uController were used. As I couldn't carry forward the code I'd been using for the Pecan Pico boards, I was faced with rolling my own or finding something already in use. I stumbled upon Michael Babineau's (VE3WMB) OrionWSPR software and while not exactly what I needed, I could certainly modify it to do what I wanted. OrionWSPR is an EXCELLENT piece of software! It is well designed, coded, documented... Mega Kudos to Michael for his work on this code. I had already decided/committed to use Bill Brown's (WB8ELK) telemetry format so I proceeded to modify the OrionWSPR code to implement the required telemetry format (flight ID and time slot transmission format).
This telemetry format relies on use of a "Flight ID" and "Time Slot" for proper decoding. I didn't have a Flight ID assigned to me, but fortunately some had come available, so I requested and received Flight ID (channel) 12 to use for my launches. This would allow me to have 5 trackers active at any one time, and I had already planned to share these within the South Texas Balloon Launch Team. If we really need more ID's...well, that would be a good thing to have happen.
So fast forward to today. BLT-67 has been aloft for one week and appears to be doing OK. Honestly, this was a test flight and I didn't expect it to be aloft for this long. I used the "Clear Chinese" party balloons and I wasn't sure we had really sealed them (but apparently Walter, K5WH, did a good job with the iron). The solar panel frame was a new design as was how I connected, secured, and strain-relieved the antennas. I really didn't expect it to survive more than a couple days. And then it drug along the ground after I released it at launch....argggghhhh.
But here we are. One week later and it just woke up over Vietnam. Altitude is a little lower than I would like but still OK. And the transmitter/antenna are working VERY well with very respectable SNR numbers at the receiver sites, and a record (for me) DX reception by VK2COW of 16685 km (JM21RC to QF44OX) on just 10mW of power. Wow!!!
I am really quite pleased with this tracker's performance and hope the balloon will carry it back to Texas. Further is good too, but hopefully one circumnavigation is in its future.
73 de John
Oh, you can track it with these links.
UPDATE: (09 Feb 2021) The flight of BLT-67 has come to an end after just a week. The pictures below shows its entire ground track and last reported location (~150 miles NE of Hong Kong). I would consider this a very successful test flight of the new tracker. Looking forward to seeing how its next flight goes.