Don, that's a great explanation. I came to the same conclusion in a recent RTTY contest. I built my K3 with the single stock filter based on advice from a number of folks to 'just operate for awhile til you get the feel for what other filters you need'. I think that's sound advice. Anyhow, I've been generally ok with the standard filter and relying on DSP filtering to narrow it as needed. However, in the RTTY contest, I often had issues working weaker stations when strong ones were very close by. It was easy to see what was going on by watching the P3- I'd start copying a signal inside the DSP bandwidth, and a strong one would pop up just above or below that station. Even though I couldn't hear the strong station, the weak one would go nearly silent as the AGC kicked in due to the strong signal in the IF passband. So, I think I've learned that I need a narrower filter for such situations. I'm thinking a 400hz filter is what I want. Any reason for a different selection in that scenario? 73 de W0ZF On Tue, Feb 21, 2017 at 8:52 AM Don Wilhelm <[email protected]> wrote:
> Mike, > > Think about it - if there are multiple signals in the passband, the AGC > will respond to the strongest, there is just no way around that fact. > If the signals can be separated by the DSP, and one is really strong, > that strong station may be activating the Hardware AGC. The only > solution for the latter is a more narrow roofing filter - put the > offending strong signal out of the passband of the roofing filter and > use shift to get your sidetone for the desired signal back in order. > > That may be too much "fiddling" for a run station in a contest, but it > is a viable way to operate when trying to copy a weak station working > close to a strong station. > > 73, > Don W3FPR > > On 2/21/2017 9:25 AM, W0MU Mike Fatchett wrote: > > We noticed again during the contest hat when 3 or 4 stations called, all > > those signals would be flattened to the same level. Once you got to > > where one or two stations were calling the signal level would pop up > > substantially. > > > > I have played endlessly with slope and threshold with little effect. > > > > My K3 has the new syn boards as well and filters from 2.8 to 2.5. > > Latest firmware etc. > > > ______________________________________________________________ > 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 > Message delivered to [email protected] > ______________________________________________________________ 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 Message delivered to [email protected]
