Paul, Looking at the Line Out with noise from an Elecraft N-Gen indicates the K3 audio is quite dramatically band limited.
With the maximum DSP high cut frequency and the 13 KHz first IF filter, broadband detected noise in either AM or SSB drops 45 dB between 4 KHz and 4.2 KHz with a further 15 dB roll off between 4.2 KHz and 9 KHz where it reaches the noise floor of the measuring device. The HF limit for data modes is also 4 KHz - depending on data sub-mode and center frequency. The HF limit for CW is approximately 2.5 KHz with the highest available "Spot" frequency and center frequency (shift). I think is it safe to treat the audio as band limited ... 73, ... Joe, W4TV > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of Paul > Christensen > Sent: Sunday, September 21, 2008 4:51 PM > To: Jack Smith; Jim Brown > Cc: Elecraft List > Subject: Re: [Elecraft] K3 related - non-linear audio > transformer behavior > > > > That's why I question the applicability of a ringing test with a > > square > > wave having a rise/fall time measured in nanoseconds, as > the audio that > > makes it through the K3's crystal and DSP will not remotely > resemble that > > waveform. > > Agreed Jack, if the DSP and/or AF stages truly limit impulses > through the > transformer. To Jim's point, ignore the modulation type for > the moment and > consider an impulse noise such as that created by the start > of light switch > or AC motor. If the system received BW is wide enough (e.g., > selecting the > K3's 6 kHz, or especially the 12 kHz filter), I suspect that > transient > impulse response becomes meaningful. I have not yet tried to > sweep the K3's > audio section beyond 4 kHz and the DSP and/or audio sections > may preclude an > audio response beyond that point. > > One way of testing this is to turn on/off various types of real noise > sources as a function of selected filter BW and while > observing a scope on > the output of the line-out transformer, record the > differences in peak > values with and without terminating resistance on the transformer > secondary -- taking into account any level difference created by the > addition of the terminating resistor. > > Paul, W9AC > _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net 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
