For me, at least, the purpose is twofold, to learn, and to get a better instrument. The idea of being able to discriminate between two inputs a few ps apart is fascinating and something I'd like to learn how it is done.
The VNA is a good comparison. I have a nice scalar nw but would like a VNA. So I built one of the n2pk VNAs. Great experience, great instrument. And I know a lot more than I did before. I think this project could be done sans prescaler, e.g. good to at least a hundred MHz, two inputs, 10mhz timebase input, rs232 out ( with ftdi USB option for a couple of hundred dollars in kit form. Would that be great for everyone? No. But would at least 10 people buy one and/or participate in the project? Probably. Could a design be done that could support all those options someone specified? Probably. Would one person be willing to design them all? No way. Would all that stuff be less than a 5370? No way. Would I want one of these and a 5370? Probably. But that what makes us nuts, isn't it? The other Bob On Dec 18, 2010, at 9:39 PM, Bob Camp <[email protected]> wrote: > Hi > > If you are going to do a full boat implementation and work out all the > isolation issues and packaging, the question becomes: > > Will it be better bang for the buck than a ~ $200 HP 5370? > > Bob > > > On Dec 17, 2010, at 9:29 AM, jimlux wrote: > >> Interesting discussion.. >> comments interspersed >> >> Chris Albertson wrote: >>> Jumping ahead to design. No one wants a serial RS232 interface. they >>> don't even make computers with RS232 ports much any more. Those guys >>> that designed equipment that forced people to load costom USB drivers >>> just did not think. There is no need for that. What you do is make >>> you project appear to be some "standard" USB class and then the OS >>> (Linux, Windows or Mac OSX) will already have a driver. That VNA >>> should have presented itself as a serial port. And then the software >>> could read from a serial port. But of course there would be not >>> physical RS232 device. >>> If you have to select an interface I'd rather have any wireless type. >>> WiFi or Bluetooth. >> >> wireless interface and RF test equipment is a bad combination. If you're >> trying to measure small scale performance (e.g. timing at 1E-10 levels), >> small amounts of RF leaking in/out causes problems. This is one of the >> things that separates good test equipment from great equipment. It's hard >> to get better than 100dB isolation from packaging, and if you're looking for >> things at the -150dBm level, something at 0dBm is huge. >> >>> But if you are building a modular system you do NOT want to pick one. >>> You just make a project standard to use (say) I2C, SPI, "two wire" ir >>> whatever. Then the counter module is controlled by i2c and if you >>> want to connect it to a computer you build the USB module but if you >>> want a stand alone no-computer instrument you build the "front panel" >>> that has LED numbers. >>> That is the entire ont is "modular", you avoid this kinds of decisions >>> and allow for easy upgrade as technology changes. >> >> >> IR/fiber optic interfaces are very intriguing. Too bad that the plastic >> fiber stuff costs more than conventional wires/connectors. >> >>> Other questions to resolve are "how many slices to cut the pie into". >>> I would argue for "very small" single funtions bulding blocks so we >>> don't have the HPSDR problem of years of time to design each one. >> >> Against that: every connection causes potential troubles. A better solution >> for the generalized case is to put multiple functions together, but don't >> necessarily connect them all. Think of the old IF strip chips. Oscillator, >> amplifiers, variable gain stages, detectors, all on the same chip but the >> ins and outs brought out to pins. I don't think you want to bring them out >> to connectors, but, rather, provide a way to do interconnections, etc. >> >> >> >>> Selecting a physical chassis to use willl take time. I like the idea >>> of using a disk enclosure because then you can buy a 1U or 8U rack or >>> an old PC chassis, If you modual looks like a disk there are plenty of >>> things it can fit into. >> >> "old pc chassis" is a very limited life item in a particular configuration. >> do you mean my old IBM PC? Or an AT? or a tower case? or a midsize case? >> When you say disk drive size, do you mean "5 1/4" floppy/CD-ROM/DVD" or >> something else. >> >> Packaging is going to be critical for high performance. Look at boxes from >> COMPAC, for instance. >> >>>> From my experience, for something like this to take off one person has >>> to take ownership of the project and run with it, make the web site, >>> write some golas and build "something" that works. Only then do other >>> jump in and help. >>> It really would be good to have a Time and Frequency Instrumentation >>> Project as currently the state of the art seem to be that you simply >>> buy something from a Chinese eBay reseller. This is hardly what I'd >>> cal "innovation." >> >> >> >> _______________________________________________ >> time-nuts mailing list -- [email protected] >> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts >> and follow the instructions there. > > > _______________________________________________ > time-nuts mailing list -- [email protected] > To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts > and follow the instructions there. _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
