[Milsurplus] Viz radiosonde ?

Sun Mar 19 00:17:45 EDT 2017

Gang,

A couple of points RE AMT-3:

1)  The raised sector of the record covers 90 degrees.  So, the output 
is three 2-letter Morse groups followed by a long space.
2)  No special receiver is needed.  Just an HF RX and someone to copy 
the code.  I'm not sure if it's CW or MCW.
3)  Each unit came with a calibration sheet to translate the code groups 
into pressure, temperature, and relative humidity.
4)  An interesting characteristic of these things is that the styli make 
an audible buzz as they contact the raised sector.  So if you just apply 
3 volts to the motor, you can read the code.

I think I have one in storage.  I'll see if I can get it going and post 
a video.

Al

On 3/18/2017 11:31 PM, Michael Bittner wrote:
> 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
> -
> -
> ----- 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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-- 
Al Klase – N3FRQ
Jersey City, NJ
http://www.skywaves.ar88.net/