I failed to CC the group. ----- Original Message ----- From: "Richard Fjeld" <[email protected]> To: <[email protected]> Sent: Tuesday, July 12, 2011 2:03 PM Subject: Fw: [Elecraft] K-3 Roofing filter comment
> Don, > I realize that last reply seemed like a dumb question, but it's hard for > me to realize that the DSP can do that so well. > > Dick > > ----- Original Message ----- > From: "Richard Fjeld" <[email protected]> > To: <[email protected]> > Sent: Tuesday, July 12, 2011 1:47 PM > Subject: Re: [Elecraft] K-3 Roofing filter comment > > >> That's beautiful. Thanks for explaining. I'm coming from the non-DSP >> world. (The 'old world'.) >> So, would it have been the same with the 5 pole 2.7 Khz filter? >> >> 73, Dick n0ce >> >> ----- Original Message ----- >> From: "Don Wilhelm" <[email protected]> >> To: "Richard Fjeld" <[email protected]> >> Cc: "elecraft posting" <[email protected]> >> Sent: Tuesday, July 12, 2011 1:33 PM >> Subject: Re: [Elecraft] K-3 Roofing filter comment >> >> >>> Richard, >>> >>> You were not hearing the effect of the 2.8 MHz roofing filter, but >>> instead the DSP filter. >>> In order to hear the effect of the 2.8 kHz filter skirt, you would have >>> to widen out the DSP bandwidth to max or greater. The DSP forms the >>> ultimate filter, and does have nearly vertical slope. >>> >>> The purpose of the roofing filter is to keep adjacent strong signals >>> from activating the hardware AGC and causing the resulting AGC pumping. >>> It is the DSP that sets the actual filter width. >>> >>> 73, >>> Don W3FPR >>> >>> On 7/12/2011 2:22 PM, Richard Fjeld wrote: >>>> FYI, >>>> I don't want to open up a 'can of worms', and Rob Sherwood could better >>>> speak to this, but this is an observation I made using a P-3. >>>> >>>> Not long ago, there was quite a string of threads about the 5 pole 2.7 >>>> Khz roofing filter versus the 8 pole 2.8 Khz filter. Before I ordered >>>> my K-3, I had studied the filter skirts of each. I don't remember how I >>>> found the plot for the 5 pole filter, but I remember that the span of >>>> each was different. At the same span width, the 2.8 Khz filter skirts >>>> seemed to me to be considerably straighter when compared to the 2.7 Khz >>>> filter, so I ordered the 2.8 filter. >>>> >>>> The other day, I was on a qso with a group and while watching the SSB >>>> signal on the P-3, I noticed a carrier much taller appear right on the >>>> edge of the filter bandwidth as shown by the brackets at the bottom of >>>> the P-3. The carrier was on the far end of the filter, or 2.8 Khz away >>>> from the center frequency. >>>> >>>> I could not hear it, but expected to, so I tuned over slightly to get >>>> it within the filter bandwidth and heard it strongly. I seem to recall >>>> that a filter's width is rated at something like 6 dB down, so I >>>> thought I would have heard it within the skirts at their wider limits. >>>> I still wonder about that, but I'm very pleased. >>>> >>>> (Just a comment; I'd hate to do without the P-3) >>>> >>>> >>>> Richard Fjeld, n0ce >>>> >> > ______________________________________________________________ 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
