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Re: Proposal: SDR-DSP receiver



Hello all,
nice thread started.. just to clarify: which of those projects are able 
to run without PC support, e.g. as a portable receiver for sat operations?

KD6OZH's project: probably yes , Audio Codc on board, needs perhaps some 
user knobs and buttons

USRP, DSP-10: not to my knowledge..

Please comment and correct where necessary.. the lead batteries for 
field ops are heavy enough, I don't want to take my laptop with me as 
well.. :)

73s Achim, DH2VA


John B. Stephensen wrote:

> Hello Achim and Kaj,
> 
> The dynamic range is determied by the level of the signal artifacts produced by
> the ADC and these get worse as the RF frequency goes up. The AD9244 has a 90 dB
> dynamic range when the input signals are limited to 45 MHz. By 240 MHz the
> dynamic range has dropped to 70 dB.
> 
> I was planning to convert the RF to 10.7 MHz and digitize there to get the best
> performance out of the ADC. I've got a partially assembled receiver board with a
> 350MHz 2MHz-wide first IF and an assembled but not yet tested 60-2150MHz LO
> board. Transmitting is easy. You can get quadrature modulator chips for
> 50-3500MHz so all that is needed are baseband I and Q signals. That's why my DSP
> board has two DACs.
> 
> 73,
> 
> John
> KD6OZH
> 
> ----- Original Message -----
> From: "Achim Vollhardt" <avollhar@physik.unizh.ch>
> To: <kaj.wiik@iki.fi>
> Cc: "AMSAT Bulletin Board" <amsat-bb@AMSAT.Org>
> Sent: Tuesday, 30 March, 2004 07:30 UTC
> Subject: Re: Proposal: SDR-DSP receiver (was: Re: [amsat-bb] Cube sat and DSPs
> (was Re: cube sat))
> 
> 
> 
>>Hello Kaj,
>>good comments.. i'll reply below.
>>
>>
>>>On 15:02 2004-03-30, Achim Vollhardt wrote:
>>>
>>>
>>>>Proposal is to is a 65 MSPS ADC with the digital down converter and
>>>>DSP.. so possible reception would be somwhere between 0.1 and 30 MHz.
>>>>Perhaps direct reception of the aliased image of 144 MHz (at 14 MHz)
>>>>would be possible as well.. a common problem like bad large signal
>>>>performace is negligible as we deal with sat-downlinks.. we don't
>>>>have large signals!!
>>>
>>>Huh, at two meters, you must be kidding!
>>>
>>>What's wrong about
>>>http://www.proaxis.com/~boblark/dsp10.htm
>>>with
>>>http://www.fidalgo.net/~wa7gxd/dspx.html
>>>
>>
>>DSP10: you need again a PC to control it.. That's not the idea.
>>DSPX: could be a building block for my proposal, I already spoke to Lyle
>>Johnson..
>>
>>
>>
>>
>>>The sample rate should be compatible with the signal bandwidth, not the
>>>signal frequency. You'll end up throwing most of the data away and will
>>>have to deal with nasty problems with high speed logic signals when
>>>using high speed converters (e.g. 65 MSPS, 10 bit only!).
>>>
>>
>>there is some thing called oversampling and coding gain.. I won't describe
>>this here, but actually you can increase system performance with a 65 MSPS
>>ADC.. at it is 14 bits, not 10 bits.. so dynamic range is over 80dB.. with
>>a variable gain amplifier(controlled by the DSP) , you end up with 125dB
>>range.. should be enough for Sat-operations.
>>
>>73s Achim, DH2VA
>>----
>>Sent via amsat-bb@amsat.org. Opinions expressed are those of the author.
>>Not an AMSAT member? Join now to support the amateur satellite program!
>>To unsubscribe, send "unsubscribe amsat-bb" to Majordomo@amsat.org
>>
> 
> 
> 

-- 

-------------------------------------
     Achim Vollhardt
     Universitaet Zuerich
     Physik Institut, 36H24
     Winterthurerstrasse 190
     CH-8057 Zuerich

     tel: 0041-1-6355742
	 0041-1-6355704 (fax)

     email: avollhar@physik.unizh.ch

----
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