Except the K3 i-f amplifier is fairly low gain, that gets even lower with hardware AGC. Noise filters are usually used at the end of a high-gain i-f strip.
Wes N7WS --- On Mon, 7/1/13, Al Lorona <[email protected]> wrote: > From: Al Lorona <[email protected]> > Subject: Re: [Elecraft] K3-schematic and 2-pole crystal-filter > To: "Jerome Sodus" <[email protected]>, "[email protected]" > <[email protected]> > Date: Monday, July 1, 2013, 11:48 AM > Hi, Jerry, > > That 2-pole filter is probably there to eliminate any > wideband noise that might be generated in the 1st IF amp. > It's a good receiver design technique. > > R, > > Al W6LX > > > > > > >________________________________ > > From: Jerome Sodus <[email protected]> > >To: [email protected] > > >Sent: Saturday, June 29, 2013 5:35 AM > >Subject: [Elecraft] K3-schematic and 2-pole > crystal-filter > > > > > >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:[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 > ______________________________________________________________ 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
