Garry, The amount of the actual offset is small for the 8 pole filters. It is not important on wide filters, but with the more narrow ones, it becomes increasingly important - so yes, for maximum performance in diversity mode (and only in diversity mode) setting the offset midway between the measured offset of each filter is a prudent thing to do - although I would not bother with anything wider than a 1 kHz filter - the offset expressed as a percentage of the filter width is the 'telling' parameter - 10 Hz at 2.8 kHz is only 0.34% which is insignificant, but 10 Hz at 250 Hz is 4% which is significant.
It is easy to determine the actual filter center (the K3 has the AFV and dBV displays built-in) - just scan through the response to a constant signal input level to the K3 to see where the -3 (or -6) dB points are (the filter center is midway between those two points). Ifyou do not have an XG2 or other signal generator, run another transmitter into a dummy load and pick up an S-6 level signal with a short 'antenna wire' on the K3. Nothing exotic is needed with a little bit of thought put into what needs to be accomplished. 73, Don W3FPR Garry Shapiro wrote: > Apparently, from what has been previously discussed here, not all the > 8-pole filters are "no offset" in practice and some models in particular > might benefit from offset adjustments. And one should not forget that > these filters are roofers. Unless money is no object, I would say to > leave the stock filter in place and add another, narrower SSB filter. As > to what its BW should be, there have been scads of opinions expressed on > that subject, as well. > > Garry, NI6T > > On 4/12/2010 5:05 AM, David Ferrington, M0XDF wrote: > >> Since you seem to favour 8 pole, I'd say do it. You should be able to get a >> rebate on the 2.8kHz against the 2.7kHz. >> Also, if you are going to get the KRX3, it's simple to align the 8 pole >> filters - otherwise you need to tell Elecraft what the offset of your 2.7kHz >> is >> >> > ______________________________________________________________ > 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 > > ______________________________________________________________ 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
