[Milsurplus] Radiosondes

[Michael Kane]

Radiosondes have held a fascination for me since I was a kid and found one
of the early Australian 72 mhz units in a field. This unit used a 3A5 twin
triode. I actually built a receiver, a super-regenerative unit using acorn
valves. I never made any use of the transmitted information, but had worked
out the switching sequence, or so I thought.

Where I lived was no great distance from Williamtown RAAF base, the Met
Dept released them from here. Good signals same time every day. It amazed
me how long I could listen to the signals. One thing I did notice was that
after a certain time following release the switching sequence changed, only
many years later did I realize that Humidity sensing was not used above a
certain altitude.

Over the years more followed, eventually the frequency changed to 403 mhz,
these transmitters used a 6AF4 as osc and 6C4 as the blocking oscillator
modulator. Then came solid state, 2N3866 as TX and a locally made IC for
the tone generators. All these units used barometric driven switches to
switch between Temp/Humidity and internal reference resistor. The early
Australian units were obviously based on the US NBS design. All early units
used Radar reflectors for wind-speed,altitude and tracking. There were
quite a few Australian designs over the years, having started post war.

Australian Bureau of Meteorology now use the Finnish Vaisala models, we
started with the RS80 GPS analog version and the current model is the
RS92-SGPD digital unit. A large number of countries now use Vaisala. ( The
history of Vaisala is also a good study subject) There is a program
available for decoding the digital signals from Vaisala units including the
embedded GPS data

I have a collection of around thirty Radiosondes, my early Australian
models now just PCB assemblies , plus  US and German models.  These all
make good conversation pieces and evoke fond memories of my teenage years.

Cliff Lawson of North American Radiosonde Museum has a fascinating
collection, excellent Website. There is also a good French website
available, French only, but Google translate does a reasonable job and
provides a good laugh along the way. They have a good collection of audio
recordings and internal photos of many designs.

The Smithsonian also has a very good PDF available in the Studies of
History and Technology series, number 53..."The invention and development
of the radiosonde,........."    .This document is a must for anyone
interested in this fascinating subject. Simple schematics, diagrams and
photos from around the world.

I have done a lot of research on the subject of Radiosondes, information
regarding schematics of these is virtually non existent on Internet, some
photos I have found, although my main interest was on Aussie units. I have
a few schematics.

One thing that may interest US researchers was a series of USAF documents
explaining weather instruments, in an attempt to try and add a bit of
sanity to the Roswell phenomena. A few circuits of balloon beacons etc. I
can't find the URLs for these, but just use the word Roswell and weather
balloons, and be prepared
to wade through "the crazies".

Michael Kane..   VK4ZKT
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