> I'm still wondering what the tolerance is on such published > curves.
I would not be so much concerned about tolerance as sampling error on the curves. Still, the Elecraft curves are generally similar to those given by INRAD for the same filter or those with a similar (e.g., 8215 or 8830 KHz) center frequency and bandwidth. For example, Inrad's curves for the KFL3A-2.1K & KFL3A-1.0 are identical to those from Elecraft ... Inrad's curves are wider for the KFL3A-6K & KFL3A-400 and Elecraft's cure is wider for the KFL3A-1.8K. (Inrad does not publish curves for the KFL3A-2.8K or KFL3A-250 ... nor do they have any information on the 1500 and 500 Hz "custom" filters) > My testing was done in CW mode with the pitch in the > low 300's (320 Hz, as I recall). The DSP begins to roll off at 200 Hz even if LO = 0.00. Any measurement where FC (Pitch) is less than [BW60/2 + 200] will be inaccurate on the skirts and any measurement where FC is less than BW6/2 + 200 will have essentially identical lower frequency responses. 73, ... Joe, W4TV > -----Original Message----- > From: ni0c [mailto:n...@earthlink.net] > Sent: Thursday, February 05, 2009 5:42 PM > To: li...@subich.com; elecraft@mailman.qth.net > Subject: Re: [Elecraft] [K3] Elecraft roofing filters > > > W4TV wrote: > > > > My source is Elecraft: www.elecraft.com/K3/K3_8_pole_plots.htm > > > > Look specifically at the last two plots which show: > > > > KFL3A-400 KFL3A-250 > > -6 dB 435 Hz 370 Hz > > -60 dB 935 Hz 785 Hz > > SF 2.15:1 2.12:1 > > > > INRAD do not publish the curves for the Elecraft (or Yaesu > > 8215 KHz) 250 Hz filter. However, they do show the curve > > for the 8830 KHz (Kenwood) version of the same filter and > > it shows a similar percentage bandwidth (367.5/845 Hz at > > -6/60dB). > > > > NI0C responds: > > I'm still wondering what the tolerance is on such published curves. > > > > Did you run those tests in a Data mode or with the CW pitch > > set to 800 Hz? If not, the low frequency skirts will be > > sharpened significantly and the measured bandwidth will > > less than the roofing filter. With a CW pitch of 560 Hz > > I measure 10% less bandwidth than in DATA (CF = 1500 Hz or > > 2210 Hz). If I reduce the pitch to 300 Hz, the measured > > bandwidth is further reduced (due to the DSP filter's low > > frequency cut-off). > > > > 73, > > > > ... Joe, W4TV > > NI0C responds: > > My testing was done in CW mode with the pitch in the > low 300's (320 Hz, as I recall). So, when I repeat the tests, > I'll vary the pitch and see what happens, say 300 Hz, 600 hz, > and 800 Hz. > > 73 & Thanks, Joe, for your info! > > Chuck Guenther NI0C > > > ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
