Hi Wes: I took a look at the RF Gain Calibration on the K3 Utility and they offer two ways of doing it. One requires a signal generator and one uses factory default values. Is the factory default method satisfactory or is it necessary for us to purchase the XG2 to do the calibration properly.
Thanks, Mike K2MK Wes Stewart Thu, 17 Dec 2009 09:34:56 -0800 I believe I've written about this before, at least to a few, but perhaps it bears repeating. I have done a side-by-side comparison of my K3 with another K3 when "RF" (actually IF) gain was reduced with the AGC on. With my radio, tuned to a S9+50 dB BC station, even a slight decrease in gain was met by a large *decrease* in SNR. On the other this wasn't the case. IMHO, this results from the wide differences in the volts v. dB characteristic of the gain-controlled hardware, i.e. the FET/diode post crystal filter amplifier, from radio to radio. This is why one guy can write, "SNR is improved when I reduce RF Gain" and another can say, "SNR goes to pot when I reduce RF Gain." Both can be correct, depending on their hardware. It's not new knowledge that we want to delay the application of AGC to early stages in the radio so as to maintain SNR. But in this radio, one size of delay doesn't fit all. The RF gain "calibration" is an attempt to fix in firmware what is essentially a hardware problem and Lyle has done an excellent job doing this. If I understand correctly, (always a dubious proposition) he measures the gain v. volts of the FET amplifier and applies this new found correction to the gain control partitioning. This has made a remarkable difference in my radio, which must be a real outlier. Still, and this is conjecture, I have this nagging concern that there might be some latency in the process and under highly dynamic conditions, it "doesn't keep up." Wes N7WS ______________________________________________________________ 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
