John, Please describe the quadrature phasing part of your receiver. On weak signals, I often find narrower filter settings of the K2 make the signal harder to copy. Part of that might be my bad hearing and the higher pitch sidetone I like... The noise and the signal seem to blend into one pitch...
I suppose a receiver with a 50 KHz or 100 KHz IF frequency would work quite well in regards to ringing....... > Mechanical filters, which operate in an acoustical domain, > may have somewhat > higher insertion loss and lower dynamic range than properly > designed crystal > filters. They operate at 455 KHz, I don't think even dogs can hear that high! > > However, I've heard some glowing on-air comments regarding > the performance of > the old Collins mechanical filters, especially with respect > to CW reception. > > Well-designed direct conversion receivers are often noted for > their superior > audio quality compared to highly filtered superhets. > > Recently, I've designed a highly filtered (100 Hz bandwidth) > quadrature phasing > direct conversion receiver, and was somewhat amazed by the > clarity of CW > reception. Was not the old heathkit hw7 a direct conversion receiver? I had a lot of fun with that rig... > > >From these observations I have concluded the following: > > Narrow-band reception requires sharp selectivity (obviously). > The higher the > frequency at which the selectivity takes place, the higher > the required 'Q'. > The higher the 'Q', the greater the amount of ringing and group delay > distortion that will occur. Ringing and group delay > distortion cause listener > fatigue. > > In a direct conversion receiver, a 100 Hz bandwidth can be > obtained at 1000 Hz > with a 'Q' of only 10. (Very low ringing) > > A 100 Hz bandwidth at an IF of 455 kHz, however, requires a > 'Q' of 4550. (More > ringing) > > A 100 Hz bandwidth at an IF of 5 MHz requires a 'Q' of > 50,000. (An RF "echo > chamber"!) Brett N2DTS _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
