[Milsurplus] Viz radiosonde ?

[Michael Bittner]

Yes, of course, the other two styli were for temperature and humidity.  I 
shoulda remembered that.  But on the AMT-3, the discs were translucent, 
i.e.., no aluminum base for the vinyl, and there was a speed bump rather 
than a speed dip. You could see the styli jump up when the raised part of 
the disc passed under them.

Mike, W6MAB
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----- Original Message ----- 
From: "David I. Emery" <die at dieconsulting.com>
To: <Milsurplus at mailman.qth.net>; <arc5 at ix.netcom.com>
Sent: Saturday, March 18, 2017 8:08 PM
Subject: Re: [Milsurplus] Viz radiosonde ?


> On Sat, Mar 18, 2017 at 11:29:25PM +0000, arc5 at ix.netcom.com wrote:
>
>>     What is the "record motor" and stylie all about?
>>     Sent from my Ain't Smart Phone.
>
> I once had access (way back in the mid 60s) to a then old (new
> stock) dropsonde (intended to be ejected from an aircraft and fall on a
> parachute through a storm while transmitting weather data).
>
> It had just what you described - a disk shaped  aluminum record
> platter coated with some kind of vinyl record material with a pie shaped
> radial wedge of maybe 30-40 degrees where the aluminum and record was
> bent down maybe 1/8 inch with little ramps back up to the plane of the
> rest of the record surface.
>
> And three swing "tone arms"  - one attached to an aneroid cell
> from a barometer, another to a bimetallic strip mechanism that responded
> to ambient temperature and a third driven by a hair hygrometer (human or
> animal hair under tension) to report relative humidity...  all of these
> tipped with a stylus and some kind of simple piezo-electric "cartridge"
> and arranged so that the tip of the stylus swung approximately on a
> radius of the disk at different angles of the clock so it did not
> interfere with the other swing arms... and was free to swing when the
> depressed "speed dip" went by the tip, but otherwise engaged in a grove
> on the raised part of the platter.
>
> The disk was driven by a motor with some sort of Governor and
> gear down arrangement...
>
> Each grove of the "record" contained recordings of Morse code
> sequences which encoded  a numeric distance for that grove from the
> center of the platter...
>
> IIRC there was a switch contact  mechanism to switch between the
> three "tone arms" and chose the output of one to feed a circuit that
> detected the recorded audio bursts and drove a relay which keyed a one
> tube crystal controlled HF transmitter (seems to me 3 MHz area)...
>
> I believe the switch had a fourth position that just turned the
> carrier on (or off) or maybe keyed a fixed CW ID... so the CW had either
> a long pause, or a period of carrier (or fixed CW ID) followed by
> temperature, pressure and humidity, then the pause again...
>
> The dropsonde operator would transcribe the strings of numbers
> and note the time and look the values up in a set of charts/nomographs
> to get actual humidity (or dew point), pressure, and temperature...
>
> I believe the parachutes were calibrated for a particular fall
> rate, but I also vaguely remember a radar corner reflector attached so
> the thing could be tracked by radar... which would allow the collection
> of wind information and perhaps correlation of pressure with actual
> altitude.
>
> The same thing is done today with cute little GPS based devices
> with MEMS sensors for pressure and humidity and temp and a one chip
> micro to run the whole thing... mostly transmitting around 400 MHz
> and of course not in CW...
>
>
> -- 
>  Dave Emery N1PRE/AE, die at dieconsulting.com  DIE Consulting, Weston, Mass 
> 02493
> "An empty zombie mind with a forlorn barely readable weatherbeaten
> 'For Rent' sign still vainly flapping outside on the weed encrusted pole - 
> in
> celebration of what could have been, but wasn't and is not to be now 
> either."
>
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