
Tracking Pico Balloons Using Ham Radio [pdf] - jah
http://www.harc.net/programs/wb8elk-balloon-tracking.pdf
======
i_am_proteus
Whenever I see things like this in light of the various threats to amateur
radio (usually from various interests who would like to get the frequencies
sold at FCC auction for commercial use), I'm reminded of the tremendous value
this hobby adds to engineering education. So many of the engineers I know who
work with radio got started by tinkering with amateur gear.

~~~
Stratoscope
Related discussion from yesterday:

[https://news.ycombinator.com/item?id=23795913](https://news.ycombinator.com/item?id=23795913)

------
bfirsh
The tracker is very cool: [http://habhub.org/](http://habhub.org/)

It’s a crowdsourced set of antennas around the world that upload data to
central server (think Flightradar24 for high altitude balloons). It’s been
running for 15 years or so.

Various bits of more reading if you’re interested in this stuff:
[http://picospace.net/](http://picospace.net/)
[https://ukhas.org.uk/](https://ukhas.org.uk/)

------
themodelplumber
Wow, that's amazing. 22 laps around the world over the course of one year. And
HF data rx in Australia from this tiny circuit board attached to a tiny
balloon over the mid-atlantic. Worth a read. Also bonus Windows XP points.

Btw how are they flying a circuit board in the raw without damaging
environmental effect from water? I'm new to this part of the hobby.

~~~
th0ma5
Maybe they just put on a thin layer of conformal coating?

~~~
sgt
What about clear coat paint you would get from a hardware store just before
launch?

~~~
0_____0
fwiw You can get urethane and silicone conformal coating in a spray can and
it's not _that_ expensive.

~~~
sgt
Agreed, and your wife won't be upset when she discovers all the nailpolish is
gone :)

------
pugworthy
As fascinating as the electronics tech is, I'm perhaps more interested in the
balloon tech.

Perhaps more reading will help me know the answer, but it doesn't seem like
these are just off the shelf Mylar party balloons. Nor do they seem to be
sized such that they can expand a lot as they rise.

The below linked article is kind of interesting in this area: it's about how
Death Valley is littered with Mylar party balloons. According to the
article...

"Mylar balloons do not go higher than about 3,000 feet to 7,000 feet before
they either explode or lose their “lift.” This is because of their inability
to expand to any great extent."

Read more here: [https://www.sanluisobispo.com/news/weather/weather-
watch/art...](https://www.sanluisobispo.com/news/weather/weather-
watch/article39489087.html#storylink=cpy)
[https://www.sanluisobispo.com/news/weather/weather-
watch/art...](https://www.sanluisobispo.com/news/weather/weather-
watch/article39489087.html)

~~~
trophyhead
There are several approaches that can be taken with balloons. By design, they
do not expand like a weather balloon does. One wants to put in enough lifting
gas to make it fly high (mostly to avoid clouds that will bring down a balloon
with such little free lift), but not enough that it will burst.

In the referenced article, an SBS-13 balloon is used. It's made from a clear
Mylar-like material and will fly at 40000ft+ when filled with helium (higher
with hydrogen). This is the 'gold standard' of balloons and can fly for months
at a time as it's over most weather. The downside is that they cost close to
$200.

Another approach is to buy a cheaper 36" diameter balloon made of similar
material from AliExpress that cost about $1. These are often pressurized to a
certain differential pressure to 'stretch' the balloon before launch and gain
some extra volume, as well as to QA the quality of the balloon (the QA on a $1
balloon isn't extensive). If filled with hydrogen, these can fly at 35000 ft+,
a bit lower for helium. Usually two of these cheap balloons are used for a
launch for more lift, though a single one can be used and a lower altitude
reached.

A light payload is desirable as it will increase altitude. I've seen as light
as 5 grams and the heavier ones are closer to 20g. One can calculate the free
lift where the differential pressure of the balloon at altitude will pop it,
but it's usually around 7g (so the balloon + payload + 7g will neither rise or
fall before launching).

------
hanoz
Why is the UK (in the unusual company of Yemen and North Korea) an important
"do not transmit zone"?

~~~
trophyhead
Airborne transmissions of this sort are not legal over the UK, North Korea, or
Yemen. Guessing it's a leftover rule from WW2 in the case of the UK, not sure.

These transmitters typically have geofencing routines that turn off the
transmission when flying over these countries.

~~~
hanoz
But in my brief attempt to answer my own question I only found pages detailing
pico balloon launches _from_ the UK.

~~~
trophyhead
I'm sure people in the UK are doing launches, but it's illegal for them to
transmit when flying in UK airspace.

In reality, it's an almost unenforcable law to begin with. Most of the WSPR
transmissions are on the order of 10mW (probably similar to the Bluetooth
output of your cell phone). It's not unusual for these transmissions to be
heard several thousand miles away, which is quite amazing!

~~~
kokey
If I remember right is the reason is that it’s illegal do use amateur radio
bands on something that is flying, so that excludes APRS. However, using the
ISM bands are fine so that’s what people in the UK tend to use, but it means
no APRS and you have to have people tracking you in other ways (e.g. sending
your telemetry over LoRa or RTTY)

------
JKCalhoun
This is the coolest thing I have seen this year. I think I always wanted to do
such a thing, circle the earth with a balloon — had no idea it was within
reach. I love all the ways in which they shaved weight on the payload.

I suppose having heard about the gas-powered model plane that crossed the
Atlantic decades ago started my obsession. Then learning about the Japanese
fire balloons that crossed the Pacific in WWII....

------
bernardv
How are these ballons flights managed, in relation to airspace? Given the
increasing restrictions on drone flight, I’m surprised such balloons are
allowed to wander and descend Without any control.

~~~
teraflop
In the US, a balloon with a total payload weight of less than 4 pounds doesn't
require any kind of clearance or approval.

------
mcculley
Can this frequency/protocol be used from sea level? I have some boats offshore
that I would like to track. We currently use a combination of AIS and SPOT
trackers.

~~~
trophyhead
You can, but you may not get the results you're looking for.

APRS is a line-of sight signal. In a balloon, you might be heard by
transmitters 200 miles or so away. On a boat, I'd expect that range to drop to
50 or less. So if you're out at sea, it's unlikely you'd be heard when you're
much outside the view of land.

WSPR has a very long range, but the density of information transmitted is very
low. Each transmissison takes about 2 minutes and the tx rate is around 5 baud
(not 5kb...5 baud!). The protocol was developed to test the range of ham radio
antennae and it doesn't give you much more than the transmission voltage and
the 'maidenhead' coordinates (which will give your location within a roughly
80 mile box depending on your latitude).

If that rough estimate of your position is good enough, WSPR may be useful to
you for tracking a boat. Some balloon trackers also transmit a secondary
signal under a different callsign with some more advanced telemetry
information, such as altitude, speed, more granular position within a 2 or 3
mile box.

Also, you'll need an antenna of some length. My balloons transmit on the 20m
bands, which means it has a 17 foot antenna both above and below the tracker
constituting a half dipole (it's 36 gauge magnet wire so weights almost
nothing. If your boats are big enough to cross oceans, you can likely mount
them in a way where you'd be heard.

------
jbuzbee
Do these balloons transmit any weather data along with their telemetry? Or at
the altitude they fly, maybe there's not much weather to report?

------
ECA_stax
[http://leobodnar.com/balloons/](http://leobodnar.com/balloons/)

more reading

~~~
jimnotgym
I love Leo Bodnar's stuff. I made a 'flight sim' joystick and pedals from one
of his boards

------
lxe
What's the purpose of that capacitor?

~~~
trophyhead
These are run by solar panels that only transmit during the day. The capacitor
just gives a half a minute or so in the event of brief cloud cover, panel not
facing the sun at a good angle, etc. Not strictly necessary, but since a WSPR
message takes almost two minutes to send, a good idea to not have it abort in
the middle of the transmission due to lack of power for a couple of seconds.

------
pugworthy
This kind of reminds me of CubeSats. I love the simple little design with the
side solar panel wings.

