[Date Prev][Date Next][Thread Prev][Thread Next] - [Date Index][Thread Index][Author Index]

Re: Re: Proposal: SDR-DSP receiver



I've been controlling my radios from a PC since 1991 and am getting tired of the
restriction so I designed the DCP-1 to operate standalone. For now the DCP-1 has
to be attached to a PC for software development, but after I'm done I want more
mobility.  I've got 25 keyswitches, two shaft encoders and a 40x121 dot graphics
display, but haven't decided how to use them.

A keyboard and display could attach to the DCP-1 through the SPI port, via the
USB port or via the RS-485 port. SPI is the cheapest option if the controls and
display are packaged with the DCP-1 board. However, for a few more dollars an
8-bit MCU and RS-485 transceiver would allow for a remote control head several
hunrded feet away. The last, and most expensive, option is to make a small PCB
with a 12MBPS USB hub, USB host controller, 32-bit RISC MCU and an SDRAM chip.
This last option would allow the most flexibility as it would allow the
integration of any USB device in a mobile environment.

Any suggestions?

73,

John
KD6ZOH

----- Original Message -----
From: "Achim Vollhardt" <avollhar@physik.unizh.ch>
To: "AMSAT Bulletin Board" <amsat-bb@AMSAT.Org>
Sent: Wednesday, 31 March, 2004 05:58 UTC
Subject: [amsat-bb] 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
>
> ----
> 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
>


----
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



AMSAT Top AMSAT Home