On Oct 14, 2014, at 6:35 AM, jsdroys...@nc.rr.com wrote: > Our panadapter regularly (but not always) shows wide green bands of "noise" > before the antenna is connected. When present, the bands are visible in the > same panadapter screen location regardless of wbich band the radio is turned > to, but the locations vary day to day (sometimes at the low end of the > screen, other times in the middle). The white line on the screen rises to > peaks above these green areas.
Are you using a PX3 or P3? Assuming it's a PX3, try this: - make sure RX I/Q is set to ON (KX3 menu) - make sure the PX3->KX3 cables are fully seated - connect an antenna to the KX3 - switch to 20 meters - turn the preamp ON and set the PREAMP menu entry on the KX3 to 20 dB - set the PX3's SPAN to 50 kHz or lower - adjust the REF level so the "grass" (noise floor) is close to the bottom of the spectral plot With the above setup, there will typically be no visible fixed spectral lines on the PX3. As described in the PX3 FAQ on our web site, very wide SPAN settings and low front-end gain (e.g., turning off the preamp) will reduce the signal-to-noise ratio of an RX I/Q-based pandapter, including making wideband spurs more apparent. The same limitations apply when using the KX3 (or other quadrature downconversion radio) with a PC sound card. Typically this doesn't impact usability, e.g. locating signals of interest. In fact most sound cards are limited to displaying about 48 kHz of spectrum, while the PX3 can go wider thanks to its high-performance/high-speed A-to-D converter. The P3 uses a completely different method of acquiring the signal for spectral display: It digitally down converts the K3's 8.2-MHz I.F. This provides a S/N and spur advantage over an RX I/Q approach, but requires much more complex circuitry -- hence the difference in cost between the two units. Wayne N6KR ______________________________________________________________ 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
