The R2Pro has 5 circuit boards altogether, you can order only the downconverter board from Kanga US for 52 bucks http://www.bright.net/~kanga/kanga/KK7B/r2pro.htm
You will have to make some changes to the diplexer, it's made for a narrow band and low passes at aprox. 3khz if I remember right ... I had thought about using this but actually with the wider bandwidth needed for soft radio you are better off using a design with the bus switching ICs like the Flex Radio, you also gain dynamic range and a higher IP3 with a lower poweer LO I'm currently working on a front end design, mixer and wideband balanced amp, using Maxim ICs mainly because I can obtain samples for free but I won't be doing much with it until next fall .. the LO will use the I-Q DDS from American QRP, perhaps with a pair of PLLs to cut down on the spurs, perhaps not as the 9854 is cleaner that other DDS designs like the 9850 ... The Flex Radio uses a 9854 without the PLLs and seems to work fine Too many interests and hobbies and not nearly enough time John --- In [email protected], "Joe Rocci" <[EMAIL PROTECTED]> wrote: > These are ambitious design goals. I'm curious why you think the APRS > transmitter is a good start for a DSP radio platform. There's virtually > nothing in it that's applicable to the quest you described. Please feel free > to bash me here in public if you think I'm wrong though. > > There's also not much in the mini-R2 that would be applicable, except the > two balanced mixers. For a DSP 'soft-radio', you'd have to throw away the > audio phase shift networks (75% of the design) and come up with a stable, > tunable VHF/UHF quadrature LO system (which isn't included as part of the R2 > or mini-R2 designs as I recall). A good thing about DSP vs the hardware > phasing approach to single-signal detection is that the DSP can be > programmed to correct minor RF phasing errors. This makes the hardware > simpler to implement. > > If I read between the lines properly, I think what you're really looking for > is a simple, broadbandable, direct-conversion IQ downconverter/upconverter > for a multi-mode VHF/UHF DSP-based transceiver. Is that accurate? If so, I > think the most challenging aspect will be development of a programmable > broadband low-noise quadrature LO. This isn't too difficult at HF, but at > UHF the noise and jitter of the controlled oscillator can be a big problem > in a direct conversion receiver - especially for some of the phase-sensitive > digital modes. You might want to look at some of Analog Devices newer DDS > chips that can output almost 500 MHz. On the HF bands, DDS can be > troublesome for a receiver LO because of the many very low-level spurous > outputs, but on the less crowded VHF and UHF bands it would probably be just > fine. > > If you want a truly 'soft-radio' at the frequencies you're considering, I'd > consider a lineup that uses the aforementioned DDS-based LO, driving a pair > of diode balanced mixers. After each of the mixers you'll need some audio > frequency gain and some bandwidth limiting to keep strong nearby signals > from overloading the A-D converter in the PC soundcard. You'll have to be > careful to keep the phase shifts in the two audio paths matched, otherwise > there'll be more 'cleanup' work for the DSP software to do. > > An alternative would be to get an R2, strip out the audio phase shift > network, develop an inevitably narrow-band quadrature LO using LC or RC > phase shift networks, and feed the IQ audio outputs into a DSP of your > choice, possibly a PC sound card. But this wouldn't meet your need for > wide-band tunability. > > Keep us informed of what you come up with. > > Joe > W3JDR > > > > > ----- Original Message ----- > From: "kfiverud" <[EMAIL PROTECTED]> > To: <[email protected]> > Sent: Friday, April 15, 2005 12:29 PM > Subject: [soft_radio] Simple, Basic Data Radio > > > > > > > > QST recently ran an article about a simple APRS transmitter that was > > presented in QEX. That article is on the web at > > http://www.arrl.org/qex/qx9Hall.pdf. That simple transmitter started > > me thinking about a simple receiver to match. I have cycled through a > > lot of ideas since then. Here are my initial goals: > > > > 0. Transceiver for experimenting with data protocols. > > 1. Cost <$100 built. (Probably a big stretch goal.) > > 2. Audio is handled with a PC sound card interface for DSP processing > > on both TX and RX. > > 3. Work on 50 - 440 Mhz with minimal component changes, preferable > > only the RF filters. > > 4. Software control of frequency. > > 5. Adaptable to a full digital protocol RF modem with the addition of > > DSP processing. > > > > My latest thoughts are based still on the APRS transmitter which uses > > a digitally controlled PLL. The VCO is fixed frequency but acceptable > > for now. Some form of IQ mixer is needed. > > > > For the receiver, I am thinking of direct conversion using the > > transmitter VCO. Two designs that look interesting as starting points > > are the miniR2 and the BIQR by KK7B. The latter is the most > > interesting but I am unsure if the IQ phasing is tight enough for > > DSP. The design is intended for brain "DSP" so accurate IQ phasing > > was not critical. > > > > Anyone have thoughts? > > > > Rud > > K5RUD > > > > > > > > > > > > > > Yahoo! Groups Links > > > > > > > > > > > > > > > > Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/soft_radio/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
