I hear it. I have always heard it. Its always been there. I think the "distortion" you are hearing and seeing in the waterfall you looked at is the notch in the audio itself and the ANF routine's "hunting around" for the frequency to notch as it samples the audio its being fed.
Within the audio spectrum of a voice there are many frequencies, and they are constantly changing as speech is being produced. The tone (of the carrier) you are trying to notch also falls within those frequencies. The notch produced by the ANF has a finite "width" and "depth" plus or minus several cycles, as you noticed in the waterfall, which has a rise time and a fall time. When that is superimposed over a voice, there is a "comb filter" like effect in some frequencies adjecent to the tone you are notching as the automatic notch routine samples and then attempts to blank the interfering tone. We are talking about notching audio here, ANF cant magically get rid of just the tone and leave what is being covered up by the tone alone, it has to get rid of ALL the energy in the spectrum occupied by the tone, plus or minus the notch filter width and depth, so there literally is a "hole" there, and it "moves" as the voice and the tone mix. You hear the hole, and notice that "something is missing". The hole "moves around" as the interference is blanked and the ANF refreshes its decision at whatever frequency it samples of what it needs to blank. That's why you dont see it in the manual notch, that one does not move around on its own. At least this is my long winded "guess" to what one hears here. K9YC may have a better way of explaining this than me (Im a duffer, he's a pro at this game). Ive always heard this to a greater or lesser extent in any radio or device that notches audio frequencies automatically. So called "feedback destroyers" in stage and studio audio have the same function as ANF, I hear this effect on them as well to a greater or lesser extent. They have gotten so good lately that it is barely preceptible, but its there, you can see it on a spectrum analyser. (Google Sabine Adaptive Audio to see a representative device, their older devices sound quite similar to what you hear in the K3 ANF; the newer ones are truly magical!). I dont think that it is *THAT* objectionable... It is there, I hear it, but I know why it is happening. Is it normal? Maybe. Could it be better? Possibly. I find it acceptable. Its a great aural reminder that you have the auto notch turned on! -lu-w4lt- ----------------------- -----Original Message----- From: elecraft-boun...@mailman.qth.net [elecraft-boun...@mailman.qth.net] On Behalf Of Tim Tucker Sent: Friday, May 18, 2012 10:57 AM To: Elecraft Reflector Subject: Re: [Elecraft] K3 - RX audio degradation with ANF ANF is the common use abbreviation for Auto Notch Filter. A lot of rigs use that nomenclature. The K3's ANF on SSB has not worked correctly IMO for several firmware releases. Someone posted a fix a while back that involved resetting back to factory settings, rolling back to a previous firmware, reloading all your settings and then loading the current firmware. That's a lot of work and I was hoping a more elegant fix could be implemented in a firmware update. In my experience, the issue isn't so much extreme distortion on the signal, it's that it doesn't notch the offending signal properly. To reproduce, watch your RX signal with a strong carrier on a waterfall with a computer application like MixW. Turn on the ANF and you'll see that the K3 notches on either side of the offending carrier, but not actually right on the carrier. If you have good ears, you can hear this yourself. The manual notch works fine, of course. I haven't tried the latest beta firmware, so I don't know if this issue has been addressed yet. It needs to be addressed, though. Tim ______________________________________________________________ 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
