In a message dated 8/7/06 7:03:01 PM Eastern Daylight Time, [EMAIL PROTECTED] writes:
> I imagine one > could shift the bfo frequency along with the tuning to give the effect of IF > shift, if one had a place to put another knob. > The venerable Collins 75A-4 of a half-century ago, possibly the first receiver to have the feature, implemented the feature that way - mechanically! When you turned the knob, the PTO assembly rotated one way, changing the LO frequency and the BFO pitch control rotated to change the BFO frequency the same amount, but in the opposite direction. The method's success depended on the absolute linearity of the Collins PTO and BFO tuning. Quite a challenge even though the PTO and BFO tuned only single ranges for all bands. btw, Collins called it "bandpass tuning" IIRC. The same concept could be employed in the K-2, but it would require software that would figure out how to move the LO one way and the BFO the other way by exactly the same amount. And the software would have to do it on all bands and all frequencies on those bands! Most "other" rigs implement IF shift by an extra conversion step after the first fixed IF. This means there's a lot of gain and stages between the antenna and the sharp selectivity "knothole". No thanks. IMHO, IF shift is of limited use in a CW receiver, and not worth giving up having the filter right up against the first mixer. 73 de Jim, N2EY _______________________________________________ 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
