System Overview
Primary Radio
Secondary Radio
Micro-Trak AIO HA with Hanging J-pole - Link
Operates on 144.39
Transmits APRS packets with GPS coordinates
Need to use high altitude version of GPS or you'll get tracking errors introduced
Configure with call sign
Default packet encoding is mic-e, turn this off for plain text APRS packets
Hanging antennas are great for balloons while they're in the air.
Cutdown System
Need two methods of “cutdown” (bringing the balloon down from altitude) to fulfill regulatory requirements by FAA
Bursting balloon counts as one, so you only need to design one method of cutdown (unless you launch an under-inflated or balloon using a non-conventional material)
Melting the rope connecting payload to balloon is a common method of cutdown
May have trouble generating enough heat to melt through rope
Conduction of heat through air is lower at altitude, air is colder, so it takes longer to melt
If the rope fuses to the cutdown system then it's not going to work
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Regulatory Stuff
Not as many as you'd think, it's pretty easy for private citizens and groups to launch balloons provided you follow some rules the FAA and FCC have in place
Notify FAA air traffic controller nearest the site of operation 6 to 24 hours before launch
Individual payload must be less than 6 pounds
It is illegal to put a cellphone in a balloon for the purpose of tracking the balloon.
The rope used to connect the payload to the balloon should break when 50 pounds of force is applied.
You may not launch projectiles or gliders from the balloon.
Do not operate the balloon over a restricted area.
Do not launch a balloon between sunset and sunrise unless it is equipped with lights that are visible for at least 5 miles and have a flash frequency of at least 40, and not more than 100, cycles per minute.
If your antenna is longer than 50 feet, it needs to either snap with less than 50 pounds of force or be covered in brightly colored streamers visible for 1 mile.
Weather conditions need to permit the launch.
Cloud cover must at any altitude must be less than half the sky.
Any altitude under 60,000 feet must have 5 miles of visibility.
There are more rules that apply if your balloon doesn't meet the Title 14 Part 101 §101.1 exemptions, so try to follow them.