On Mon,9/14/2015 10:10 AM, Adam Farson wrote:
As explained in my web article (and also in my QEX article), the optimum noise loading points for an ADC and a conventional receiver are different. In the conventional receiver, optimum noise loading is reached when the noise power induced in the IF passband within the notch (idle-channel noise) is equal to the DUT's intrinsic thermal noise power in the same bandwidth. At this point, the DUT's audio output rises by 3 dB.
I strongly disagree, Adam. If the test is designed to show response of the receiver to a lot of strong signals such as are present in a contesting or DX pileup environment, or as are present in a multi-transmitter site, the signal level should be consistent with that environment, NOT with the design of the receiver. In other words, if the input of the RX would be overloaded by those strong signals, the test should show it. This does (at least) two things -- it lets buyers know which radios perform best in this environment, and it also puts the manufacturer's feet to the fire to make the RX better. And this matters no matter what the architecture of the RX. It would also, for example, clearly show the difference between an RX with a preselector (or other selectivity) in front of the input and one without.
And finally, if you choose to test at a reduced signal level to stay below overload, the report should clearly state by how many dB the test signal had to be reduced.
I do appreciate your work and your dedication, but to be of value, it must be consistent with real world conditions, and it must expose the real differences between radios.
73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:Elecraft@mailman.qth.net This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html Message delivered to arch...@mail-archive.com
