Morning Colin, My K2 is #3255 and the KSB2 Build is Revision C-3. The envelope that contained the KSB2 crystals is marked 3.7 (as was the envelope containing the K2's IF filter crystals), and the KSB2 crystals are marked 4.9136. I have not made any modifications From 'swept' measurements the KSB2's filter -6db bandwidth is 2.1 kHz approx if I remember correctly Please note that this is not a 'noise loaded' measurement, e.g. Spectrogram. The exact figure is in my notebook which is packed away due to an invasion of plumbers, carpenters and others - sorry about that.
Using this data and the measured audio response, mic connector to and including the modulator, to set the carrier oscillator frequencies (BFO), the BFO is no more than 200 Hz away from the frequencies suggested in the KSB2 manual. With a Heil ProSet Plus and no audio mods, full specd PEP is obtained and unsolicited audio reports are complimentary. My personal opinion is that the 2.1 kHz bandwidth is satisfactory with the K2, for ragchewing and DXing. Because the same intermediate sized crystal ladder filter is used for both USB and LSB, increasing the bandwidth could result in problems with unwanted sideband suppression when the BFO is on the low frequency skirt of the filter. This assumes that the filter is properly designed and terminated. It is possible to fiddle things to steepen the LF skirt, but usually at the cost of increased ripple in the passband. 73, Geoff GM4ESD ----- Original Message ----- From: "m1bnw" <[EMAIL PROTECTED]> To: <[email protected]> Sent: Friday, May 27, 2005 7:18 PM Subject: [Elecraft] K2 XTALS I am buiding a K2 sn 004149 from an earlier non built K2 sn 000571 up to rev 'B' on the new 'B' pc boards. I also have an early KSB2 SSB unit. All the above has the original XTALS for the CW filter and SSB unit.ie 4.195MHz -20. I have read lots of comments on the audio quality because of the tight band pass of the original SSB unit. I know that Elecraft have produced some modifications in the form of 14 new XTALs and a capacitor upgrade kit. Does anyone have experience of these mods ? Is there a basic capacitor upgrade that one can do first of all? Or is changing all the XTALs and adding new capacitors the best solution? Or is the original configuration ok? Regards Colin M1BNW _______________________________________________ Elecraft mailing list Post to: [email protected] 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
