Hi John, The NPR test is, I agree, certainly a very useful method to expose IMD problems, but I think that when used as a *diagnostic* tool the requirements placed on the notch filter's bandwidth limits this method's versatility - unless one is prepared to build a set of band reject filters (probably crystal) that may be required, whose IMD contribution is much less that that of the receiver, device or sub-system being tested.
To obtain low phase noise from my IMD test arrangement I have been using low noise crystal oscillators followed by +40dbm output amplifiers, which is I admit a cumbersome approach, but it did provide useful results until I damaged the equipment while measuring the IMD generated by some types of RF transformer - a sad story! If Santa gave me a K3 I could stop speculating about its multi signal performance :-) 73, Geoff GM4ESD "juergen" <[email protected]> wrote on Saturday, December 11, 2010, at 6:18 PM: > Hi Geoff > The noise power ratio test(NPR) might show more clearly any mixer IMD > problems. The NPR test might also better characterize any roofing filter > IMD > as well. > The noise power ratio test better characterizes dynamic receiver > performance. The NPR test also does not require expensive low phase noise > signal generators. > 73 > John ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[email protected] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html
