Hi Mike, I can probably scrounge up the original Lm and other specs for you.
Varactor capacitance vs. voltage for the parts I used in the design is readily available on the web. Just search for the part datasheet. Varactor tuning of the filter is great for varying the bandwidth, but it is a compromise in terms of loss and ripple. 73, Wayne N6KR > On Apr 17, 2020, at 12:55 PM, Mike Markowski <mike.ab...@gmail.com> wrote: > > For fun, I thought I'd make an archeological dig and take a look at how > things changed from NorCal 40a to K1 since they're easy to study. Then I > realized part of it is not so easy for me. The 40a uses a Cohn filter and I > thought I'd run through analysis (not simulation) of it. Again, just for the > exercise of it while cooped up during these viral stay-at-home days. > > However, the data sheets I downloaded for the HC-49 crystal don't seem to > have the motional capacitance and inductance. So, two questions arise: (1) I > thought these were provided by crystal makers, the experts. Are they expected > to be measured or is there some simplification in network analysis that > doesn't require them?, and (2) are there Cohn filter tables like there are > for Butterworth and Chebyshev? I can't find anything on analysis after a > fair bit of googling. > > Moving on to the K1, receive filter bandwidth is controlled by changing > capacitance via varactor diode voltage. But that comes from the DAC and > requires probing to determine voltage that in turn sets capacitance for the > filter. I can't find much on varactor controlled Cohn filters. So (3), is > there a place to read up more on it? > > Tnx es 73! > Mike ab3ap, suffering cabin fever > ______________________________________________________________ > 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 > Message delivered to n...@elecraft.com ______________________________________________________________ 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 Message delivered to arch...@mail-archive.com
