All, I have a relatively new K3, s/n 4545; I just upgraded to the latest FW using the latest utility, but the problem predates that. I have 2.7 KHz, 5 pole filters, 1.8 kHZ and 250 Hz 8 pole filters in both the main and sub receivers. I have zero offset set for all of the 8 pole filters. When I first was learning my way around the radio in September, I noticed that the audio level would drop noticeably when I decreased the DSP filtering from 150 Hz to 100 or 50 Hz, both on the main and the subreceiver. A quick check with a friend indicates that his K3 doesn't do this. I hung a scope across the headphones to verify that it wasn't my imagination, and then I found the AFV readout. It confirms that the audio out drops by almost exactly 10 dBv going from 150 Hz to 100 Hz, and then does not drop further going to 50 Hz.
My test setup is a stable 8640B set to 14.100 MHz, -73 dBm sig level, AGC-S, centered up in the passband. When I switch in 100 or 50 Hz DSP filtering the audio drops, and slight retuning either side only make it worse. This is all with the 250 Hz 8 pole filter switched in. Because both the main and sub behave identically, I assumed it wasn't just an 8 pole filter with non-zero offset, but just to test, I offset the 250 Hz filter in the main rx by + and - 0.25 and the step audio change was still there, although the absolute audio level was lower with the filter offset from zero, indicating (to me) that zero offset was close to correct. I have also tried switching between FIR and IIR filtering to no effect. I keep thinking this is something I have accidentally changed somewhere in the initial setup of the K3, but several readings of the Menu and Config sections of the manual only made my headache worse. Please, what am I missing? 73, geo - n4ua ______________________________________________________________ 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
