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RS80 RadioSondes from Ebay

Some notes on the Vaisala RadioSondes that are currently doing the rounds on Ebay.

Written by: M0EYT ( Paul Marsh ) Monday, 26 January 2004

Click for full size imageRecently, some interesting looking units have appeared on Ebay. They are new sealed Radio Sondes originally used for weather measurements - visit ebay.co.uk and search for radiosonde. Here are a few notes compiled from Internet investigations and my own notes.

General description

The RS80 family of radio sondes are small light weight and tolerate well transportation, storage and field use. They are all equipped with the identical pressure, temperature, and humidity sensors as well as transducer electronics, thus ensuring uniform network data quality. They are supplied with either a 403 MHz or 1680 MHz transmitter, in either wide or narrow band versions to ensure compatibility with ground station and national radio regulatory authorities. GPS windfinding is achieved using a cordless 8-channel digital GPS receiver and the signal from all visible satellites with the GPS data being transmitted to the ground station using 1200 baud FSK modulation. The wind vector is updated at a rate of 2 Hz for raw and 0.5 Hz or 0.1 Hz for filtered data. The computation of the wind is done by the ground station.

The capacitive BAROCAP pressure sensor has a welded solid state design that consists of capacitive plates housed within a capsule, protected from humidity and dust. There are no mechanical adjustment and the sensor construction is friction-free for continuously variable measurements without discrete steps. Range 1060 mb to 3 mb Resolution 0.1 mb. The THERMOCAP temperature sensor is a small capacitive bead encapsulated in glass. A water repellant treatment and metallisation of the surface ensures minimum radiation sensitivity and excellent performance in rain. Range +60 C to -90 C Resolution 0.1 C. The HUMICAP is a capacitive thin film humidity sensor with good long-term stability and reliable response even at low temperature and after exposure to condensation. Range 0 to 100 % RH Resolution 1 % RH.

A solid state switch connects each sensor in turn to the transducer electronics. All parameters are measured at approximately 1.5 second intervals. Sampling Rate 7 samples/10 s for each parameter Calibration data content Polynomial for each with checksum Calibration data format 8 channel paper tape

The water activated 19V battery has an approximate 135 minute life and when activated the radio sonde has a total weight of approximately 220 g.

Some technical info on the GPS bit

Once you have stripped the sonde down, you'll see inside the polystyrene is the GPS receive board with it's QFH antenna. Looking at the circuit, you can see that the output from the QFH is amplified by a singal gaas-mmic device, then passed through a ceramic filter. The signal is then fed to an etched phase shift array, then into a Vaisala custom chip marked GPS-RF. The I/Q outputs from this chip are fed to another custom Vaisala IC marked GPS-I/Q. This chip examines the phase and signal strength and outputs a 1200baud ttl level and AFSK signal. The 1200bd signal is made up of up to 8 X 24bit words.

On the GPS receiver board is a nice crystal oscillator module that's encased in a nice 2 part injection moulded piece of polystyrene. This is for thermal stability.

Note: No actual decoding of any GPS data is in the sonde, therefore it's not possible to get standard NMEA type data out of this unit.

Modifications

After a considerable amount of time examining the GPS receiver board to see if it would be any use for navigational purposes, I decided that it would be too expensive in terms of time to attempt a conversion. I therefore decided that the GPS antenna and preamp could be used on their own with another of my GPS receivers. The preamp section was cut away from the receiver board, a SMA RF socket fitted and suitable adjustments were made to the power supply section. 5 volts is sufficient to run the preamp, so the modification takes power from the centre of the coax as provided by most GPS receivers. The preamp has a reasonable amount of gain, in the order of 17dB - 20dB.

Links:

  • Vaisala radiosondes [Click here]
  • DH9RS Sonde Site [Click here]

  • Attachments: (Click to view/download):
    1-1257-image-402 800 sonde.wav 1-1257-image-Dcp 9354.jpg 1-1257-image-Dcp 9355.jpg 1-1257-thumb-402 800 sonde.wav
    1-1257-thumb-Dcp 9354.jpg 1-1257-thumb-Dcp 9355.jpg 402 800 sonde.wav Dcp 9354.jpg
         
    Dcp 9355.jpg      

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