"You're both right," he mused, studying his own schematic (and inexplicably referring to himself in the third person).
The KNB3 *is* downstream of the pick-off point for the P3. But in the presence of very strong signals and with the KNB3 set to a long gate time, some of the gating artifacts could in theory back-propagate to the pick-off point, affecting the P3. Normally this effect would be highly suppressed because of the low impedance of the driving stage (the mixer post-amp). Wayne N6KR On Aug 17, 2014, at 11:54 PM, Jim Brown <j...@audiosystemsgroup.com> wrote: > Joe, > > I don't want to be confrontational and I greatly value your engineering mind, > but I'm quite certain that the wide K3 NB DOES affect the P3 display. I work > a lot of JT65 on 6M, and there are several strong signals (not of overload > magnitude) near me. The NB DOES create artifacts that result in multiple > decodes, and corresponding stuff that is quite visible in the P3 display, and > that is not visible when the K3 NB is off. > > 73, Jim K9YC > > On Fri,8/15/2014 2:35 PM, Joe Subich, W4TV wrote: >> >>> I often study the screen of my P3, which DOES show reduction of noise >>> when the wider NB is active. 2-4 dB is typical for the types of noise >>> for which it is effective. >> >> 2 - 4 dB may be due to upsetting the impedance at the IF feed but given >> the circuit topology it is not possible for the NB to provide effective >> blanking to the P3 with the noise gate *after* the IF pick-off point. >> >> 73, >> >> ... Joe, W4TV >> >> >> On 2014-08-15 5:13 PM, Jim Brown wrote: >>> On 8/15/2014 11:29 AM, Joe Subich, W4TV wrote: >>>> Jim, that information is incorrect. The K3 NB can not possibly have >>>> any impact on the P3 or P3SVGA as the IF pick-off is at the output >>>> of the first mixer - *before* any noise blanker gate. >>> >>> Joe, >>> >>> I've never studied the schematic or signal flow in the regard, but I >>> often study the screen of my P3, which DOES show reduction of noise when >>> the wider NB is active. 2-4 dB is typical for the types of noise for >>> which it is effective. >>> >>> I appreciate the alert to the existence of the P3 NB. I last updated >>> firmware about six months ago, and it was not in that version. It does, >>> indeed, work pretty well. >>> >>> 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
