Mike for two tone dynamic range testing, both signals are located intentionally outside the detection passband (narrowest filter) of the receiver, and the receiver is tuned so that one of the third order intermods is within the passband.
you may find that this is a useful reference: http://www.arrl.org/tis/info/pdf/109435.pdf when the measurement is bounded by phase noise, it means that instead of introducing a distortion product or reducing the level of a weak signal, instead the phase noise introduced by the receiver itself (generally the local oscillators) has degraded detection of the weak signal. otherwise, you seem to be on the right track with your understanding. 73, curt --- [EMAIL PROTECTED] wrote: > 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 > ____________________________________________________________________________________ Got a little couch potato? Check out fun summer activities for kids. http://search.yahoo.com/search?fr=oni_on_mail&p=summer+activities+for+kids&cs=bz _______________________________________________ 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
