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Re: Re: PICPOT Power!



G0MRF@aol.com wrote:
> In any event, the satellite should offer a "large"  U and S band signal
> (albiet 9600 baud noise) to monitor.

Well...

On 437 MHz they are transmitting a standard regular
9600 baud FSK AX.25 signal.

What exactly should we expect to hear on 2440 MHz?

I know a G3RUH 9600 baud FSK sounds like white noise,
but that's NOT what they're transmitting on 2440.
They're sending a ten kilobit per second GFSK signal
with a frequency deviation of one hundred twenty
five kilohertz.  Yes, one hundred twenty five
kilohertz deviation.

A new S-band signal in orbit is great, but it sounds
like few (if any) amateur radio operators are ready
to receive the bits the satellite is sending.

A quick reading of the PiCPoT telemetry PDF at

http://polimage.polito.it/picpot/documentazione/PiCPoTs_telemetry.pdf

has this very interesting paragraph:

>Due to the transceiver used for this link (Chipcon CC2400), 
>2440MHz communication link is based onto a GFSK modulation, 
>which uses a frequency deviation of +/- 125kHz, and a baud 
>rate of 10kbit/s. These parameters are not compliant with 
>standard ham-radio equipment, even if preceded by a down 
>converter for UHF or VHF frequencies. Consequently we 
>decided to not use both bit stuffing and scrambling, since 
>they introduce a great burden into the transceiver 
>software, but to use internal characteristics of 
>the CC2400.

Can someone tell me what that signal would sound
like in a typical NBFM amateur radio receiver,
if anything?

Will it require a Chipcon CC2400 chip to receive the
signal or is there another easy way to receive a signal
with a hundred and twenty five kilohertz of deviation?
The transceiver chip looks inexpensive in quantity,
but the development SDK boards I saw are not cheap.

I would like to listen for the PiCPoT signal and
demodulate the bits to receive the packets.

What other options exist for receiving this signal?

Demodulating the bits *without* bit stuffing and
scrambling might be easy enough, if we could get
the received signal through a wide enough receiver
and into a soundcard.  Ideas?

Douglas KA2UPW/5
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