Bill: Nice job. I figured all along it was either due to a brain problem or being female.
Steve N4LQ ----- Original Message ----- From: "Bill VanAlstyne W5WVO" <[email protected]> To: "Bill W4ZV" <[email protected]>; <[email protected]> Sent: Wednesday, November 17, 2010 2:45 PM Subject: Re: [Elecraft] K3:New APF what happened? > Very good summary of the technical facts, Bill. > > It's IMPULSE noise, everybody, not white noise or pink noise or any other > kind of noise. Impulse noise is characterized by a very rapid transient > rise-time producing a large nearly instantaneous spike in amplitude. It's > literally the electrical equivalent of striking a bell sharply, as opposed > to rubbing it. > > The other thing that can make this feature seem magical (in the absence of > excessive ringing) is having it properly tuned, and by "properly" I mean > within a few Hertz. The K3's CWT/SPOT capability is good, but it's often > not > good enough for this degree of accuracy. Mine usually tunes to within +/- > 10 > Hz, but that's not always close enough for the APF to work at its best. > The > signal needs to be fine-tuned by ear, IMO, against the sidetone PITCH > frequency. Most people can hear the difference between two tones down to 1 > Hz or less. (BUT, some people CAN'T. It's a brain thing. Your brain can > either do this or it can't. My XYL couldn't do this if her life depended > on > it, as she is completely tone-deaf.) > > So maybe we can agree that there are a lot of variables at work here that > we > can't control for. I thought at first that the current release was "less > ringy" than the earlier release; I was fooled by a difference in band > noise. > Since then, I've seen the APF feature behave quite differently on > different > bands at different times. So, if it makes it easier to copy a given > signal, > use it, and if it doesn't, leave it turned off. It's a tool. All tools are > not appropriate for all jobs all the time. You have to choose your tools > and > when to use them. > > Bill W5WVO > > > > -----Original Message----- > From: Bill W4ZV > Sent: Wednesday, November 17, 2010 15:35 > To: [email protected] > Subject: Re: [Elecraft] K3:New APF what happened? > > > > N2TK wrote: >> >> John, >> Maybe the impact of the APF is a moving target influenced by the band >> conditions at the time? >> Yesterday morning 160M was very quiet. I could not hear the VK6 without >> the >> APF. When I turned on the APF the VK6 popped out of the band noise and >> was >> easily copyable. There was no hint of ringing even with the bandwidth >> down >> to 50HZ. >> >> Last night as usual in the evenings here 160M was noisy. When I turned on >> the APF it still did its magic. But there was almost a trace of >> "ringing". >> >> I need to play more with it to see if it is a definite pattern comparing >> between quiet and noisy band conditions. >> > > Ringing is a function of how much impulse noise (i.e. lightning induced, > electric fencer "ticks", key clicks, etc) hits the filter. No impulse > noise > = no ringing, lots of impulse noise = continuous ringing. As you said, > yesterday morning 160m was stone quiet and the background noise was > non-impulsive or white noise. Last night a strong cold front moved across > the Southeastern states which had lightning associated with the front. > The > lightning strikes created impulse noise which caused the filter to ring > more > than in the morning. This effect is present in any narrow filter, whether > analog or digital, and there's really not much that can be done to avoid > it. > Reducing AF Gain is about the only solution to attenuate the continuous > ringing sound but that also attenuates the signal you're trying to hear. > > 73, Bill > -- > View this message in context: > http://elecraft.365791.n2.nabble.com/RX-architecture-tp5746603p5748164.html > Sent from the Elecraft mailing list archive at Nabble.com. > ______________________________________________________________ > 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 > > > ______________________________________________________________ > 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 ______________________________________________________________ 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
