I would like to at least get the 4.2 khz mentioned - but in fact, I do not. My chief concern is that I should at least be able to use the full 4 khz waterfall that I can, in fact, get out of most other radios.
--- On Wed, 1/7/09, Joe Subich, W4TV <[email protected]> wrote: > From: Joe Subich, W4TV <[email protected]> > Subject: RE: [Elecraft] Mildly confused - Assumed filter width and what Isee > in waterfall do not match > To: [email protected], [email protected], "'Bob Cunnings'" > <[email protected]> > Date: Wednesday, January 7, 2009, 10:15 PM > > I guess my basic answer, is that should be my choice, > not the > > radio firmware. If I want to run 4 (or say, 10khz) > into my > > computer (and out) that should be my choice. > > The K3 does not support an audio bandwidth higher than 4.2 > KHz > in ANY MODE. If you do some checking you will find the > DSP's > digital to analog converter effectively includes a 4.2 KHz > "brickwall" filter ... even in AM mode with the > "bandwidth" > set to 5 KHz (10 KHz IF). > > If you expect audio response above 4.2 KHz, you will need > to > convince Wayne and Lyle to relax the upper frequency limit. > > HOWEVER, for digital modes I'm not so sure that is a > good > idea. With sound cards sampling at 11025 Hz, the input > audio > needs to be band limited to 5.5 KHz maximum and 4.5 KHz > offers > a fair margin for safety to handle the occasional > application > that runs at 8 or 9 KHz. > > For AM - since the digital modes are not a consideration - > it > would be nice to have 5.5 or 6.0 KHz response. > > 73, > > ... Joe, W4TV > > > > > -----Original Message----- > > From: [email protected] > > [mailto:[email protected]] On Behalf Of > Thomas > > Bingenheimer > > Sent: Wednesday, January 07, 2009 9:07 PM > > To: [email protected]; Bob Cunnings > > Subject: Re: [Elecraft] Mildly confused - Assumed > filter > > width and what Isee in waterfall do not match > > > > > > I guess my basic answer, is that should be my choice, > not the > > radio firmware. If I want to run 4 (or say, 10khz) > into my > > computer (and out) that should be my choice. After > all, how > > is an SDR all that different. Again, I suspect this is > a > > oversight in the firmware, not a design choice. Why > should > > such a flexible radio be hobbled in this manner? > (assuming, > > of course, that it is actually limited as such, as > opposed to > > me setting it up wrong :) ). > > > > > > --- On Wed, 1/7/09, Bob Cunnings > <[email protected]> wrote: > > > > > From: Bob Cunnings <[email protected]> > > > Subject: Re: [Elecraft] Mildly confused - Assumed > filter width and > > > what I see in waterfall do not match > > > To: [email protected] > > > Date: Wednesday, January 7, 2009, 8:59 PM > > > Disabling the AGC in the K3 certainly does > "do the > > > trick" in terms of > > > preventing strong signals in the passband from > reducing > > > receiver gain > > > and thus affecting the weaker signal I'm > decoding - > > > that's exactly why > > > I do it. > > > > > > As for ADC overload -that's a risk I'm > well aware > > > of but most of the > > > time it's a non-issue, for me at least. If it > happened > > > I would react > > > to it, but I rarely encounter signals in the > passband at > > anywhere near > > > the level to cause trouble of that sort. > > > > > > Bob NW8L > > > > > > On Wed, Jan 7, 2009 at 6:23 PM, Don Wilhelm > <[email protected]> > > > wrote: > > > > Bob, > > > > > > > > That will do the trick in an analog only > receiver, but > > > a receiver like the > > > > K3 has an analog front end followed by an > ADC and DSP > > > processor. The trick > > > > is to keep from overloading the ADC - should > that > > > happen, the copy will be > > > > garbage. > > > > > > > > That situation is not limited to the K3 - > overload of > > > the soundcard ADC is > > > > also a possibility with equally bad results. > > > > > > > > I have to admit that in many cases, one can > operate > > > with a wide bandwidth > > > > with no problem, but when that strong signal > enters > > > the passband, the wide > > > > bandwidth possibilities are "all > over". I > > > chose to take preventive measures > > > > before that happens. > > > > > > > > 73, > > > > Don W3FPR > > > > > > > > Bob Cunnings wrote: > > > >> > > > >> I simply disable AGC when I wish to run > a wide > > > receive bandwith with > > > >> PSK31 for "point and click" > tuning - > > > precisely to avoid such a > > > >> problem. > > > >> > > > >> Bob NW8L > > > >> > > > >> On Wed, Jan 7, 2009 at 5:44 PM, Don > Wilhelm > > > <[email protected]> wrote: > > > >> > > > >>> > > > >>> Thomas, > > > >>> > > > >>> I will not answer your questions > directly, > > > >>> BUT > > > >>> From an operational standpoint, > using a wide > > > bandwidth for data modes > > > >>> is *not* the best way to do it. > > > >>> The reason is AGC in the radio. Any > signal in > > > the receiver passband can > > > >>> activate the AGC - and that is fine > *if and > > > only if* the strongest > > > >>> station in the receiver passband is > the one > > > you are working - usually > > > >>> that is not the case. The strong > signal will > > > reduce the receiver gain > > > >>> due to its AGC action and the > station you are > > > trying to QSO with will be > > > >>> reduced along with it. Overload of > the DAC by > > > the strong signals is > > > >>> another similar consideration - > fortunately, > > > the K3 employs a hardware > > > >>> AGC ahead of the DAC to avoid just > that > > > possibility. The DSP ADC can > > > >>> handle an S9+20 signal without > overload, but > > > there are signals stronger > > > >>> than that even in the sub-bands > commonly used > > > for digital. > > > >>> > > > >>> Using a narrow passband for data > modes allows > > > one to avoid that > > > >>> situation. Yes, one must tune with > the VFO to > > > place the desired station > > > >>> inside the receiver passband, but > the > > > possibility of a QRM free QSO is > > > >>> much greater with the narrow > passband. > > > >>> > > > >>> Just because the software > application can > > > display a 4 kHz slice of the > > > >>> spectrum is not sufficient reason to > use a > > > wide receiver passband IMHO. > > > >>> > > > >>> Elecraft may well consider it just > because > > > some folks want to operate > > > >>> that way, but it certainly does not > make much > > > sense to me. > > > >>> _______________________________________________ Elecraft mailing list Post to: [email protected] You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
