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. > > 73, > Don W3FPR > > Thomas Bingenheimer wrote: >> This is the current state of the radio : >> the 6 khz filter is in FL2, the 2.7 khz filter is in FL3. ESSB is on, and >> set to 4.0, complete with the '+' displaying in the right of the display >> when USB/LSB is used (note that it is off during DATA modes). AM TX is set >> to FL2, SSB TX is set to FL3 (it will not allow it to be set to FL2, even >> with ESSB on). IN data A, I am setting the DSP to 4 khz. If the firmware is >> enforcing the use of FL3 for Data A, why would this be so? With software >> that can do 4.0 khz or greater waterfalls, why would we want to arbitrarily >> restrict the radio? For that matter, why restrict it at all for DATA modes? >> If the software on the computer would do it, why should we not be able to >> receive or transmit with say, the FM filter? If there is any such >> restriction, I would like to have the possibility of removing it considered. >> Thanks! >> >> > _______________________________________________ > 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 > _______________________________________________ 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
