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

Re: Re: Proposal: SDR-DSP receiver



RS-485 uses +/-2V differential signalling and is limited to 10 MBPS. In this
case I would use slew-rate limited 250 KBPS RS-485 transceivers to prevent
interference with the radio.

I prefer Atmel 8-bit RISC MCUs or the ARM7 and ARM 9 32-bit RISC MCUs. When
writing in assembly language it is a big advantage to have a 2 or 3 address
instruction set and C complilers are more efficient. Also the Microchip parts
take 4 clocks to execute one instruction while the others execute one
instruction per clock.

I'm leaning towards a small device with a graphics display, two knobs, four to
six keyswitches, a connector for a headset and a couple of USB ports. It could
be connected directly to the SDR or two 802.11 adapters could be used to provide
remote control and the SDR could stay near the antenna and the power amplifier.

73,

John
KD6OZH

----- Original Message -----
From: "Achim Vollhardt" <avollhar@physik.unizh.ch>
To: "John B. Stephensen" <kd6ozh@amsat.org>
Cc: "AMSAT Bulletin Board" <amsat-bb@amsat.org>
Sent: Wednesday, 31 March, 2004 09:14 UTC
Subject: Re: [amsat-bb] Re: Proposal: SDR-DSP receiver


> Hi John,
> Well at least, I can comment on the MCU and RS-485 thing.. I have done
> already a DDS project with encoder, LCD display and math algorithms in a
> PIC16F877, so this was kind of a great board. If RS-485 is identical to
> LVDS, this should also be no problem.. I am working with LVDS on a daily
> basis in my lab..
>
> Alternatively, the PIC family also has devices with USB integrated by
> now.. but this is of course my biased comment, as I do only in PICs..
> any other MCUs to consider?
>
> I would strongly recommend to keep such a project stand-alone. Some
> people are indeed interested in signal analysis on a PC (there the USB2
> port is superb!) but the majority just want a knob to tune..
>
> 73s Achim, DH2VA
>
> John B. Stephensen wrote:
>
> > 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
> >>
> >
> >
> >
>
> --
>
> -------------------------------------
>      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



AMSAT Top AMSAT Home