Stratoballoon Ground Antennas

We’re down to just under 3 weeks to launch now (T-minus 18 days), and there is still a lot of work to do on the balloon.  As a result, I’ve decided to hold off doing any more podcasts until after launch so we can focus on those tasks.

There’s no reason I can’t give you some teasers, though.

Today’s teaser is about the two ground antennas built for this mission.  The first is called an eggbeater:


The eggbeater is an omni-directional design for communications with satellites, or more generically, things that are really high up.  Mike – the excellent ham who has been consulting with us on antenna design – suggested this as a good way to communicate with our balloon while it is in flight.

The second is a 5-element yagi:


The yagi is a directional antenna, used to pick up weaker signals, but only in one particular direction.

So far, all of our testing with the transmitter and these two antennas have been in my home office, about 6 feet apart, so of course the signal was coming in loud and strong.  In the next week or so, we’ll conduct a "ground test" where we set the balloon up to transmit, and then drive away and see how far we can get before we completely lose the signal. 

It won’t be a very good simulation of the flight, but we believe that we’ll be able to pick the transmitter up when it’s flying at least as far as during the ground test (since we won’t have trees, buildings, and other obstructions to contend with during the former).  If nothing else, it will be the first opportunity for us to sort out how we will operate on the road, managing the computer, the SDR receiver, the antennas, and so on.

Beyond the ground test, we have a few major tasks left before the project, in no particular order:

  • build a radar reflector that will be suspended between the parachute and capsule
  • finalize the rigging that will hold the balloon, parachute, radar reflector, and capsule together
  • mount the transmitting antenna on the capsule (the final step in its construction)
  • conduct a few additional tests (full instrument pack endurance test, capsule shake test, camera shutter test)
  • dye the parachute either orange or red
  • identify a supplier for the helium
  • finalize details and authorization from the FAA
  • finalize the launch-day logistics

Several of these are in progress already, and while it will probably come right down to the wire, I think we have enough time to get everything done.

Stay tuned!