![]() ![]() To test the filter, I started my N2PK VNA and took a measurement. When I was done playing, I looked up the appropriate schematic in the appendix of the manual, and started building it on a piece of PCB. ![]() Then I played a bit with the bandwidth and ripple, trying to find a 50 Ohm impedance point, but couldn’t find it so I ended up with 77 Ohm. I entered the average series frequency, Lm, Cp, number of crystals, and the desired passband bandwidth and ripple, and in a split second Dishal gave me all the capacitor values I needed. In the little bag of crystals, I had found a note with all the crystal parameters, so I didn’t need to measure them myself. I used Dishal from dj6ev, a windows program that luckily runs just fine under wine on Linux. No PCs either And no handheld calculators. To make a filter, there exist many software packages. Once again, something I’ve never done before. The purpose is to find a realization of the filter that meets each of the requirements to a sufficient degree to make it useful. My mission: to make a crystal filter for a Belthorn IF-module I’m going to build. Filter design is the process of designing a signal processing filter that satisfies a set of requirements, some of which may be conflicting. A few weeks ago, I was given some hand-matched crystals at the radio club. Technical Notes (Includes Filter Design topics) (29 April 2022) Stroke7-Ultra-Portable Amateur Radio (4Nov2021). ![]()
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