Hi Roger,
--- Roger Rehr <[EMAIL PROTECTED]> wrote: > Hi Gian, > > This is what I had in mind! You could go one step > further than just > the 20 kHz filter and also have narrower IF filters > for once you had > 'zoomed in' on the signal in question, much like the > Orion has a bank > of selectible 'roofing' filters. Yes, additional filters .. I did not want to suggest too much ... hi No matter where > the signal of > interest was on the bandscope before zooming in, the > computer-radio > could shift the LO so that it is centered in the > narrower filter once > one zoomed in. When you unzoomed the computer could > remember the > original LO and switch to it and show the original > bandscope again so > that as the user the whole thing would appear > 'seamless'. I only used the Orion at W7AAZ .... but as a button pusher ..hi. Certainly intelligent control is necessary. > > I think this is the way to build a very high > performance 'SDR'; by > starting with a very strong analog front end, and a > set of > appropriately chosen IF 'roofing' filter widths, and > then using the > power of the computer to make it all work > seamlessly, so the 'user' > gets the best of both worlds. That's it... best of both worlds ... never close the door to what is new and to what is old ... hi I have another idea I started while at F5VGU in 2003 but never had the time to try it.... As the design technology is too advanced I do not want to release it yet ...(joking) ... first I want to be sure it works ... I do not want to be burning in Hell when I will go into Definitive QRT.... hi > > You are correct that I of course assumed the I7SWX > H-mode mixer would > be the one used when I did my gedanken-experiment, > as I wanted to use > the best design possible ;) > I need to do some free advertising ...hi > I hope that one of the currently very active SDR > programs makes use of > some of these concepts. It seems to me that without > the switchable > filters noted above, the hardware, while very > interesting and fun to > use casually, won't make a viable contest radio [at > least for me] > unless the strong signal handling capability is 50 > dB or so better than > current hardware. Yes ... today probably the real performer is G3XJP STAR that is the User Defined Radio taking the best of both worlds... now called STAR II ... > > Thanks again for the very cogent post, Gian. > Hopefully others will > read and appreciate ;) Thanks to you and hope others will appreciate these coments, we always learn and share something 73 Gian I7SWX > 73, > > W3SZ > Roger Rehr > http://www.nitehawk.com/w3sz > > > Quoting Giancarlo <[EMAIL PROTECTED]>: > > > Hi Roger, > > > > Vy nice to hear from you ... I believe you are > throwing not a stone > > in the pond but a lighted match in the petrol.... > hi > > > > I can share one of my ideas ... SDR still has a > lot to pedal before > > it can respond to all requirements of a contester > and VHF-SHFers > > looking for bouncing signals where IMD is > important. > > > > My few million $$$$ idea is to have one conversion > to a "not too > > expensive commercial filters" IF, as an example: > 10.7 MHz, usually > > with 20kHz BW. From 10.7 MHz or the like you will > need a strong QSD > > or possibly an I-Q Mixer (you could select Pericom > PI5C3125 and > > 74AC00 decoder (see Marco, IK1ODO QSD trial) or a > SR40 V7 like mixer) > > converting to I-Q baseband. > > > > You will need some intelligent front end control. > The system will > > look at the widest possible bandwidth, when > zooming into the > > interested signal, the IF filter will be inserted > and the DDS or PLL > > oscillator will be tuned to the signal. Your BW > now will be 20kHz in > > place of 100 or 250 or expected 400 kHz. A good > audio card like Delta > > or better and your SDR software will give you all > the power of > > filtering. > > > > You could have a similar set-up for HF up to 50MHz > with the best > > front end mixer guess what ??? A 2 or 3 > transformers H-Mode mixer > > followed by a good diplexer and post mixer amp > driving a good quality > > xtal filter (8 to 10 MHz) followed by a QSD or > I-Q Mixer and what > > necessary . In HF you may or may not need to have > a very large BW to > > monitor, maybe on 28 and 50 MHz yes. > > > > I have tested a similar set up for HF and it works > very nicely. I did > > not make any real measurement but I can send you a > Winrad screen > > print tuned on 7MHz > > > > These are ideas good or bad but you can still > send $$$$ hi. > > > > Maybe I am the one throwing the lighted match in > the petrol > > thank .boooom !!! > > > > BTW, I have replaced the second mixer with an > I7SWX 2T H-Mode Mixer, > > and re arranged 2nd IF gain in an FT1000MP ... > during a "strong" SSB > > contest with one splattering station at -3.5kHz > and a clean one at > > +2.5kHz they never missed any signal (low) they > could hear... no > > bubbling. > > > > 73 > > > > Gian > > I7SWX > > > > > > --- In [email protected], Roger Rehr > <[EMAIL PROTECTED]> wrote: > >> > >> Hello, All, > >> > >> Bob and Alberto's comments on the 'quality' of > sound in a DC-SDR > >> provide me to ask a generic question which I have > been pondering > > for a > >> while now. This forum has a lot of talent so I > am asking it here > > first. > >> > >> What was said about the exceptional 'clarity' of > signals derived > > from > >> direct conversion SDRs has been my experience as > well, whether the > >> radio was a simple homebrew design, a SoftRock, > an SDR14, or > > even 'The > >> Time Machine'. It has also been true whether I > was using Linrad, > >> PowerSDR, Winrad, Rocky, KGKSDR, Spectraview, > etc. as the software > >> backend. The 'old-style-radios I used for > comparison were FT1000MP > > Mk > >> V and Elecraft K2 [and before that IC735 and > IC970, but these last > > 2 > >> are not really in the same class at all]. > >> > >> So the sound effect is not limited to one type of > hardware or one > >> particular piece of software. I agree that it > likely relates to > > the > >> lack of crystal filters, etc. Unfortunately, in > some situations > > these > >> filters seem to be a 'necessity' and that is the > reason for this > >> email/question, as I ponder which course to take > as I upgrade my > >> [contest] station here. > >> > >> The problem that has made me unable to go totally > SDR, and for > > which I > >> really wish I had a solution, is that I do weak > signal contest work > > [50 > >> MHz to 24 GHz] but live in an environment where > during a [VHF and > > up] > >> contest I have more than 1 > full-legal-power-on-multiple-bands > === message truncated === ____________________________________________________________________________________ Never Miss an Email Stay connected with Yahoo! Mail on your mobile. Get started! http://mobile.yahoo.com/services?promote=mail
