Has anyone ever used a NewQ Gold DSP in conjunction with digital ops? I was given one and don't really know if it usable for digital. 73, Rick W3BI
> Date: Tue, 21 Aug 2012 14:28:10 -0400 > From: [email protected] > To: [email protected] > Subject: Re: [Elecraft] USB sound dongle > > > On 8/21/2012 11:18 AM, Jim Brown wrote: > > On 8/21/2012 7:48 AM, Barry LaZar wrote: > >> However, 24 bits of quantization will get you a better dynamic > >> range. > > > > Not if the dynamic range of the analog electronics limits it, which > > is what Joe has pointed out. Often those extra bits are "advertising > > bits" -- they fool those who don't know any better into believing > > that more bits is better. > > There are two issues here - > > First most amateurs run their digital software from "line out" or the > demodulated audio from the transceiver. The demodulated audio has > generally been through at least one A to D to A cycle and the noise > floor is simply too high to take advantage of even the theoretical 96 > dB dynamic range of a 16 bit sound card. > > Now, if one is looking at the "raw" I/Q RF/IF or direct downconversion > audio 24 bits "might" be usable *IF* the noise floor is low enough (a > real *IF* with off the air signals) and any mixers and amplifiers are > really linear through the theoretical 138 dB dynamic range *without* AGC. > > None of this addresses the noise floor and dynamic range of any preamp > in the sound card ... it only looks at the theoretical dynamic range > of the analog to digital converter. > > Then there is an additional consideration pointed out by Chen in a > private e-mail - properly designed software can achieve dynamic range > (sensitivity) *better than* the A to D converter (that is, it can > "receive into the noise") by applying proper lowpass filtering and > decimation. I know Chen uses decimation even with 16 bit cards in > cocoaModem but it does not appear that any of the Windows centric > digital software does so since many are based on 11025 or 12000 Hz > sample rates and effectively throw away the potential processing gain > by not performing any lowpass filtering in the 44100/48000 to 11025 > or 12000 sample rate downconversion. > > 73, > > ... Joe, W4TV > > > On 8/21/2012 11:18 AM, Jim Brown wrote: > > On 8/21/2012 7:48 AM, Barry LaZar wrote: > >> However, 24 bits of > >> quantization will get you a better dynamic range. > > > > Not if the dynamic range of the analog electronics limits it, which is > > what Joe has pointed out. Often those extra bits are "advertising bits" > > -- they fool those who don't know any better into believing that more > > bits is better. Actually, it's far more important to optimize the > > signal level that the A/D converter sees. That's why I like the Tascam > > USB interface better than the Numark -- it has a much greater range of > > gain adjustment and a clip light on the front panel. That allows me to > > easily optimize the 90 dB or so of dynamic range that its 16 bits provides. > > > > Besides -- the 90 dB dynamic range provided by a decent 16-bit A/D is > > probably more than most hams will ever see at the audio output of their > > radios. While the radio itself has much greater dynamic range, the > > WORKING dynamic range is limited by noise received by the antenna that > > is often 30-50 dB greater than the electrical noise levels inside the > > radio. > > > > 73, Jim K9YC > > ______________________________________________________________ > > Elecraft mailing list > > Home: http://mailman.qth.net/mailman/listinfo/elecraft > > Help: http://mailman.qth.net/mmfaq.htm > > Post: mailto:[email protected] > > > > 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:[email protected] > > 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:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
