Hi Al, Haven't tried it or observed it but I think that what you see is the switch to weaver mode demodulating. I thought this would only occurred when the filter was installed but from your observation I'd say that's not so.
I think what you're seeing is normal. There's an IF shift (or something similar) which moves the centre of the demodulated space up to 8KHz. This will also prevent the KX3 from switching to weaver mode and supress the hole in the centre of the demodulated audio but will confirm there's nothing un-natural going on. Weaver mode is essential to provide the minimal roofing filter width in direct conversion SDR architecture. In SSB mode the hole is of no consequence and not audible. In digital modes it can be supressed by keeping the IF bandwidth high. The 8KHz IF mode is really there to supress low frequency punch through from things like local AM broadcast station interference. 73's Peter VK4JD -----Original Message----- From: Elecraft [mailto:[email protected]] On Behalf Of Al Duncan Sent: Friday, 4 September 2015 12:56 AM To: [email protected] Subject: [Elecraft] KX3 PBT problem I have RX xFIL set to "normal" in the menu so that the PBT control adjusts bandwidth. When I use a BW of 1.8 KHz or higher in SSB mode, everything looks good on a waterfall display. But when I reduce the BW to 1.7 KHz or lower, a chunk approximately 250 Hz wide and centered at 1500 Hz is removed from the waterfall display. I originally thought it was related to the roofing filters as the effect happened at the same time that FL2 was selected, but after I set the roofing filters to "not installed" so that FL1 was used for all bandwidths, the problems still occurs. Any suggestions would be appreciated. KX3-K serial #1691 with latest production release firmware installed. The roofing filter option was ordered with the transceiver. 73, AL - VE3RRD ______________________________________________________________ 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 Message delivered to [email protected] ______________________________________________________________ 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 Message delivered to [email protected]
