I've got some questions for the receiver meisters. These are not K3 questions but will affect my understanding of the K3 specs when they appear.
IMD for the K3 (Orion, FTxxx, etc) refers to spurious signals produced by operation of a stage (or stages) in the nonlinear portion of its transfer curve (or whatever it's called)? The measurement "ground rules" imply two signals: one at fc and the other at fc+x, where "x" is 20khz, 10khz, ... ? The parameter usually being determined is referred to as the two tone dynamic range and indicates the point at which third order signals resulting from 2fc-(fc+x) and 2(fc+x)-fc begin to appear in the signal path? fc and fc+x are chosen to put (at least one of) the third order signals in the IF passband? I assume that receiver circuit characteristics before the roofing filters (or IF bandpass filter) essentially determine the dynamic range. However, dynamic range figures "always" seem to degrade for small separations of fc and fc+x. Is this because fc and/or fc+x are falling within the IF passband and are producing spurious signals in the stages following the roofing filters? For the case of strong signals in the IF passband, are the dynamic range tests run with the AGC disabled? In actual operation, wouldn't the AGC reduce signal levels below the point where distortion products were being generated (in the stages following the roofing filters)? The two tone test is only a proxy for the "real world". In actual operation, if any signal (or signals) in the RF passband or mixer passband exceeds the receiver dynamic range, will ALL of the signals in the passband begin contributing third order products? Is the magnitude of the third order distortion products a function of the "degree" of the nonlinearity? Can different receiver models with the same dynamic range numbers (operating under the same conditions) differ considerably in the "signal strength" of junk signals? When test results are "phase noise limited", what is going on? Is the phase noise acting simply as RF noise that masks the spurious signals being observed? Or is it acting as a "third signal" that mixes with fc and fc+x and causes the production of third order products at a lower signal level than fc and fc+x would alone? Mike W5FTD _______________________________________________ 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
