Hello,
I posted the work below to an eHam forum and one reply suggested posting to this site. Thru another reply I have already verified that my interpreting of the K3-block-diagram is ok. So, left unanswered is the reason for the 2-pole crystal-ladder-filter. Hello, I'm to give a talk to our club next month about "roofing-filters". So, during my talk, I intend to show schematics for Yaesu's FT-5000 and Elecraft's K3; I choose these two because of their pristine locations on Sherwood's table. I'd have no problem explaining the 5000's block-diagrams; seems to follow the "expected script". But, with the K3's schematic: a) on its block-diagram (pg. 64), the five roofing-filters seem to not be in the expected location of immediately after the 1st-mixer. As I see it, the received signal-flow is...from the rec'r antenna, thru LC-bandpass-filters, attenuators, +12dB amp, then the 1st-mixer, a +17dB amp, the Noise-Blanker, finally the roofing-filters, and now an IF-amp, etc, etc. Am I interpreting the block-diagram correctly? b) on both dwg K3-RF-board and dwg KRX3-sub-rec'r, between the 1st-IF and the 2nd-mixer, a 2-pole crystal-ladder-filter is labelled as having a BW=14 KHz. I'm mystified why this part is there, especially since any of the preceding crystal-filters would have a significantly narrower bandwidth. Hopefully, someone could explain this conundrum. Also, I was not able to locate it on the block-diagram. That's about as far as I got trying to piece together an understanding of the K3-circuitry for now. Thanks in advance for any replies. 73 Jerry KM3K Thanks in advance for any replies. BTW, I'm only just a few hundred dollars short of buying the KX3. 73 Jerry-KM3K ______________________________________________________________ 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
