weather station- what is being attached to the ballon--- mcu with temp probe?

Oh, thanks for the note. I wasn't aware. My distributor sells this stuff obviously a bit overpriced.

Rene

Hi The one I took apart as a kid was different. It had both a thermistor and a resistive humidity sensor. It had a barometer that caused a wiper switch to select either the thermistor or the humidity sensor. These to were used to FM modulate a carrier. Knowing the start signal, one could get the altitude by counting the alternate tones and the other info was the frequency of the tones. These units had two tubes that were battery powered. Dwight

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AFAIK, the transponder is not priced separately - it's an integral part of the sonde and it uses the data link used for weather data also.

The transponder does not decode the GPS signal - the calculation-intensive part is done at the ground receiver (which is not just the next-door Garmin). What is important to the position determination is where the signals from separate satellites meet. The combined signal can be sent with a data link elsewhere for final processing.

HTH

Tauno Voipio tauno voipio @ iki fi

You mean, you don't decode the spread spectrum signal ? You take the whole band where the spread spectrum is in and retransmit it at some other frequency. With the GPS signals burried in the noise ?

A bold approach.

I see some problems in just mixing it with a carrier also in the microwave bands because the mirror bands also appear unless you use single side band modulation with quadrature mixing. For wide bands there is the problem of phase errors.

Well, it is doable with SSB, I guess. But having a stabilized GUNN oscillator up there isn't cheap either, is it ?

Rene

The signal is not decoded, but it is partly detected using a clever new algorithm, which I'm not in a position to elaborate. The bandwidth of the down-link signal is much less than the original satellite signals.

Tauno Voipio tauno voipio @ iki fi

You can use GPS without decoding the code, just by using the carriers. One possible embodiment of such a system is described in the patent EP 0 732 596 A2. The patent documents can be found at, e.g.,

This makes the ground station rather complicated, but that is not an issue at it is not thrown away after use.

- Ville