[Space] Amateur Radio and Balloons

Mikolaj Habryn dichro at rcpt.to
Thu Dec 24 09:49:43 PST 2009


Hi Ed! There's some really intriguing labels on that map's pushpins -
totalPumpseconds and ballastmode? Are you already doing buoyancy
control?

On Thu, Dec 24, 2009 at 5:28 AM, Ed Moore <eam52 at cam.ac.uk> wrote:
> Hi All,
>
> Just by way of introduction, I thought I'd throw a brief comment upon some of the minutes of the meeting that you put up on your wiki.
>
> Specifically:
>
>    * HF ham stuff can reach a long way but takes lots of power
> with good enough buoyancy control, could dip down to 3g altitudes,
> download, re-ascend
>
> To share some of our experiences: we're legally limited to 10mW radios on the 434Mhz (70cm) amateur radio band in the UK. This is to say, they are 'license free' and intended for use in car key remotes and so on. It's annoying and a bit unenlightened, but it's not going to change any time soon, so we live with it. The last launch, using the 10mW 434Mhz modules that UKHAS now use as standard (radiometrix NTX2) had the following flight profile:
>
> http://spacenear.us/tracker/
>
> All of the data comes from the 10mW telemetry link. It's modulated at 50 baud, using the amateur radio standard RTTY. It transmits all the useful housekeeping data (lat/long/alt, temps, voltages, whatever) roughly every 10s. The ground stations were off the shelf amateur radio equipment (the Yaesu 817 being a particular favourite), With a yagi antenna for when it goes long range.

That is neat - did you have people in france take over tracking, or
were you doing everything from the UK?

> By way of contrast, my 3G USB dongle consumes about 2-2.5W, and it's reception is obviously dependant on local infrastructure.
>
> So I guess I would say not to write off ham radio stuff too early - you can do a lot with 10mW!

A number of people here have radio operator licenses (and I'm
intending to join them after the next hamcram in early January) to
allow transmission at higher power, but this conversation came up in
the context of image downloads. It seems using this kind of radio link
is the best option for telemetry, but getting bulk data (image/video)
back in real-time is harder (although I have wondered about 2.4 ghz
yagi mounted on a motorized telescope mount slaved to the GPS
co-ordinates that come back via radio).

>
>        - Ed
>
> P.S. Can I plug the #highaltitude channel on irc.freenode.net It's the UKHAS channel, lots of geeks, couple of the founders of London Hackspace, generally lots of like minded people.

Thanks! Also, the project list at the website in your sig sounds like
my research wishlist ;) Particularly intriguing - "Launching at this
altitude is much more efficient as air density is only around 1% of
its value at ground level, so much less energy is wasted by the rocket
in drag. The reduced pressure of the environment also allows further
expansion through the nozzle of the rocket motor, increasing the
thrust from a given motor." I wasn't really expecting the reduced drag
to make much difference to maximum ascent height, but the second point
is really interesting - have you been able to quantify the magnitude
of that effect?

m.

>
> _______________________________________________________
> Ed Moore,  CU Spaceflight (and UKHAS)   eam52 at cam.ac.uk    +44 (0)7789 933271
>
> www.cuspaceflight.co.uk
> flickr.com/cuspaceflight
> vimeo.com/cuspaceflight
>
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