BLT-62 Balloon Launch & Flight

I've been getting lots of questions about my recent balloon launch so I thought I'd resurrect my Blogspot site and post some information about it.  When I created this post, it was located near 41.5° N / 165° E, about 1600 miles NE of Japan, floating at ~37,000 feet above the Pacific Ocean moving about 150 mph to the ENE.  It woke up Wednesday afternoon (11/11/2020) about 1000 miles off the California coast! Below is a screen capture of its locations and the winds aloft at altitude.

Some details about the balloon and tracker that periodically transits its position. The tracker is a WSPR-TX Pico transmitter from ZachTek (https://www.zachtek.com/product-page/wspr-tx-pico-transmitter). It's solar powered only and transmits a 20mW WSPR encoded message on the 20m & 30m ham bands every 10 minutes. A standard WSPR message consists of a callsign, 4-digit maidenhead grid location, and transmitter power level.  The WSPR-TX Pico uses the power level field to send its rough altitude (see link above for the table to translate power level to altitude).  The antenna is made from 39ga magnet wire attached (lightly glued) to 4 lb. test braided fishing line.  The fishing line connects the transmitter to the balloons and provides strain relief for the delicate hair-thin magnet wire. The tracker (with programming header removed) and antenna weighed in at 11.70g. You may think ~12g is light but my goal is to get a tracker down to ~7 grams (a little more than the weight of a nickel).  The antenna on my previous launch used 36ga magnet wire and I though that was thin.  The 39ga wire is considerably smaller and half the weight of 36ga wire, which allowed reduction of the antenna weight down to 1.17g.  Below are pictures of the tracker (without solar cells obviously) and a comparison of 36ga wire (right) and 39ga wire (left) - marks on the bottom are 0.025"

The balloons used are 36" mylar “party” balloons made by Qualatex (https://us.qualatex.com/en-us/products/12683/?product_type=Qualatex%20Foil%20Balloons). There are two balloons connected in tandem and were filled with Hydrogen but only to the point where they have 5g of free lift with the payload attached.  The fill ports were then sealed with Kapton tape.  You might ask why hydrogen vs helium. Two reasons; cost/availability and performance.  Helium (good near pure helium, not the 80-90% mixed gas you get at the party store) has become very difficult to obtain and very expensive!  Hydrogen is plentiful, relatively inexpensive, and provides more lift per volume of gas.  However, hydrogen is a highly flammable and potentially explosive gas.  If you're reading this and thinking about trying to launch your own balloon, I'd recommend you use helium.  

The transmission protocol used by the tracker is called WSPR (weak signal propagation reporter).  It was developed by Dr. Joe Taylor, K1JT, (former Princeton University professor and Nobel Prize winner). You can read more about WSPR at his website https://physics.princeton.edu/pulsar/k1jt/.  WSPR was created to help monitor HF radio propagation around the world.  WSPR is a forward error corrected 4FSK signal occupying about 6 Hz of bandwidth and transmits 162 symbols in 110.6 seconds. It can be received with a signal-to-noise ratio as low as -34 db, well below what you can audibly hear from a radio speaker. Many amateur radio operators have setup permanent transmitters that are received by a network of receivers (http://wsprnet.org/drupal/). To get my balloon’s position listed on the https://aprs.fi and https://tracker.habhub.org, I asked a fellow balloonatic (WB8ELK) to run a python script that periodically pulls database entries for my callsign (AB5SS) from wsprnet.org and posts them to the APRS-IS server under the callsign AB5SS-14. 

The balloon was launched around 10:00am on October 31st from a friends ranch near Batesville, TX.  After a brief scare, it started to rise (and we started to breath again) and began its journey across Texas, the Gulf of Mexico, Florida, then out across the Atlantic.  It managed to dodge some storms and was predicted to head to the North Atlantic but caught a southerly flow and went over Africa, Saudi Arabia and headed for Nepal.  Then it gave us another scare on Nov 9th as it was going over the Himalayas and we didn't receive any reports that day.  But then it showed up over China on the 10th and now it's over the Pacific expected to travel just south of the Aleutian Islands and hopefully head towards the west coast of the US.  It's been exciting to watch for it every day to see if it's still alive and how far it's gone during the night.  I'm hoping for a circumnavigation (fingers crossed) but am thrilled with its performance so far.  

73 de John
AB5SS