N6CCH wrote: > I noticed the latest filter plots on the InRad W3 are a bit > different from those in the file. > > Which ones should we rely on for filter settings if the > filters were purchased in the last 3 months?
Measure your filter responses in the K3 using an XG-1 or XG-2. This can be done manually or using one of the automated scripts that third parties have written. Your specific filters may vary slightly from the published plots from either source. For example, the INRAD 8-pole filters are said to have zero offset, but several of mine do have a finite offset from the IF. This is especially critical on the narrow filters such as the 400 Hz where mine have offsets of 80 Hz. Although mentioned many times previously, the filter marketing names seldom reflect the exact -6 dB bandwidth, so again, measuring your actual filters is helpful in deciding what DSP bandwidth you choose to have them engage. Typically, the actual bandwidths of the INRAD filters are wider than their marketing label implies. Historically, these filters were used as the primary filtering in both the first and second Ifs of older-generation receivers. The resultant receiver bandwidth of two cascaded filters came close to the marketing label on each filter because each filter was actually wider by itself. For example, the so-called 250 crystal filter is closer to 370 Hz and the 400 is about 435 Hz. Accordingly, in their application as roofing filters for the K3, I see no reason to have both the "250" and the "400" in the same receiver. Ed - W0YK ______________________________________________________________ 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
