"Reputable" companies also sell oxygen-depleted cables to audiophiles.
You can't cheat mother nature, no matter how hard you try. I don't doubt that they can display whatever they want, but as to actual, significant data displayed thereon, that's a different matter. A single channel of adc samples at 48ks/s can only display VALID unique frequency data up to 24 kHz before the spectrum "folds over". Since both I and Q can be used, they effectively double the sample rate, as if you were sampling at 96k. Not exactly correct, but close enough. Nyquist -who is still valid in the real world - theory says that you can only recover signals whose freq is up to one-half the sample rate. Again, I am generalizing, but close enough. So, one-half of 96k is 48k, not 96k. Factoring not involved. 48k total bandwidth before the spectrum folds over. Doesn't matter what the display says. Try it on Rocky, Powersdr, hdsdr, winrad, etc. I'm not saying that Joe or Larry are doing anything wrong, just that if your sound card (or DDC or other device) is providing I/Q samples at 48ks/s per I/Q pair, th best you can get is a total of 48k of valid, unique, and correct spectrum data points. That usually results in plus and minus 24khz being displayed around center frequency. To say that you can display 96k of unique, correct spectrum data from a 48ks/s rate I/Q pair is, well, not accurate (wrong). It's like depleting too much oxygen from your speaker cables. You end up with a hollow sound, like taking the oxygen away left too much room for the electrons to bounce around in. If you like fuzzy bass, that's ok. But, I've been wrong before. Sent from tfox iPad On Aug 19, 2012, at 9:54 PM, Don Wilhelm <w3...@embarqmail.com> wrote: > I don't know the advertized numbers, but Mr. Nyquist aside, there is a reason > that two independent experts with panadapter displays (Joe Subich W4TV and > Larry Phipps K8LP of LP-Pan fame) state that a soundcard with a 48 kHz rate > will produce a 96 kHz span on the pan display. > > I do not doubt Nyquist, but I think the treatment of the numbers are a bit > different (factor of 2) Could it be due to the two channels? I really don't > know the answers and do not have the energy to investigate such things > anymore, I just choose to trust the experts who deal with this I/Q stuff on a > daily basis. I guess my scientific curiosity has declined with advancing > years - it is no longer enjoyable to argue on the basis of observations vs. > theory to sort out the differences - that was "fun mind games" many years > ago. but today it is no longer a challenge. > > 73, > Don W3FPR > > On 8/19/2012 5:45 PM, WB4JFI wrote: >> Mr Nyquist would be happily surprised at that. With I&Q samples at 48kS/s >> each, you get a maximum of 48kHz, or one-half the total bandwidth. Not >> 48k+48k. >> >> So, with a 48k sample rate, you will get plus and minus 24k from center. >> >> Sent from tfox iPad >> >> On Aug 19, 2012, at 4:33 PM, "Joe Subich, W4TV" <li...@subich.com> wrote: >> >>>> The sound card's maximum sampling rate will determine how wide your >>>> panadapter display can be (in kHz); for example, a sound card capable >>>> of sampling at 48 kHz can display slightly less than 48 kHz of >>>> spectrum. If you want a wider display, you will have to ensure that >>>> your sound card can sample at higher rates. >>> A sound card capable of 48 KHz sample rate can display slightly less >>> than 96 KHz. With I/Q inputs and 48 KHz sampling you get +/- 48 KHz. >>> >>> 73, >>> >>> ... Joe, W4TV >>> >>> On 8/19/2012 4:20 PM, Richard Ferch wrote: >>>> Jeff, >>>> >>>> In addition to the cable, you will also need to be sure that your >>>> laptop's sound card accepts stereo input. Panadapter software requires >>>> stereo input (I and Q channels). Some laptop input jacks will only >>>> accept mono signals, even though the laptop's sound card itself is >>>> stereo. My newest laptop, for example, has a TRRS jack for the sound >>>> card with a single input line, two stereo output lines, and ground. >>>> I have no way to get stereo input into this sound card. An older laptop >>>> I have has separate input and output jacks, but while the output jack is >>>> stereo, the input jack is mono. If your laptop is like either of these, >>>> your only recourse may be to get an external USB sound card with stereo >>>> inputs. >>>> >>>> The sound card's maximum sampling rate will determine how wide your >>>> panadapter display can be (in kHz); for example, a sound card capable of >>>> sampling at 48 kHz can display slightly less than 48 kHz of spectrum. If >>>> you want a wider display, you will have to ensure that your sound card >>>> can sample at higher rates. >>>> >>>> Note that if you need to use an external (e.g. USB) sound card, it may >>>> or may not have 3.5mm inputs. For example, I have one with dual RCA >>>> phono jacks for its line inputs. With one of these cards, you would need >>>> to go from 2.5mm stereo for the KX3's RX I/Q jack to two separate RCA >>>> phono plugs for the sound card's input. >>>> >>>> I don't know whether Radio Shack has the specific cable you would need, >>>> but I am sure that they have cables and adapters that could be combined >>>> to achieve the desired result. >>>> >>>> 73, >>>> Rich VE3KI >>>> >>>> >>>> WW6L wrote: >>>> >>>>> Per the manual Iit looks like I would need one of these >>>>> >>>>> A cable with a 2.5 mm (3/32") plug on one end and >>>>> a plug that matches your sound card input on the >>>>> other end (typically 3.5 mm [1/8"] stereo) is >>>>> required. >>>>> >>>>> If I want to see a panadapter display on my laptop. >>>>> >>>>> Where do I get it? >>>> ______________________________________________________________ >>>> Elecraft mailing list >>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft >>>> Help: http://mailman.qth.net/mmfaq.htm >>>> Post: mailto:Elecraft@mailman.qth.net >>>> >>>> This list hosted by: http://www.qsl.net >>>> Please help support this email list: http://www.qsl.net/donate.html >>>> >>> ______________________________________________________________ >>> Elecraft mailing list >>> Home: http://mailman.qth.net/mailman/listinfo/elecraft >>> Help: http://mailman.qth.net/mmfaq.htm >>> Post: mailto:Elecraft@mailman.qth.net >>> >>> This list hosted by: http://www.qsl.net >>> Please help support this email list: http://www.qsl.net/donate.html >> ______________________________________________________________ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:Elecraft@mailman.qth.net >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html >> > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
