Re: [Elecraft] K3 AGC Mush ... or "blur"
Awesome, Guy. I think your test will answer the questions I have about this problem. Please post the results of your test with a different title than above so we don't have to comb through a lot of posts to find it. 73, Dick WC1M -Original Message- From: Guy Olinger K2AV [mailto:olin...@bellsouth.net] Sent: Tuesday, December 06, 2011 3:17 AM To: David Gilbert Cc: elecraft@mailman.qth.net Subject: Re: [Elecraft] K3 AGC Mush ... or "blur" Not to argue but to move toward clarity... Low level signals are by definition closer to the noise. That would also mean that there would be more "stuff" between CW bauds. "Crisp" to some means that the artifacts which define the beginning and the ends of a baud are there. The extreme artifact is a key click. A normal artifact is additional bandwidth occurring at the edges of the baud, but reduced in level. These are down 6, 12, 18, 24 dB from the pure sine wave. Without these, the baud sounds soft, and the transitions on and off only excite the directly on-tone nerves in the ear, instead of some number of tones. Once the signal is close enough to the noise the baud start and stop artifacts become obscured by the noise, but the signal is still copyable by itself. If there are multiple signals in this state and the tones are close, our ears lose all clue of baud on/off other than slow (not "sharp") level transitions. We lose harmonic artifacts, and now must rely only on very soft level changes. Ancient Bell Labs studies on these issues for telephone would say that for most people, a change from one CW signal to another at close to the same frequency, less than three dB in amplitude, would not be a perceptible change. On these issues in that QRM situation, one would EXPECT that kind of "muddyness" in the S unit above the noise level. This would happen in a perfect receiver. This is why someone's signal sending fast when they go into the noise "blurs" the CW and the only way to overcome that is to slow down signficantly. **IF** the AGC was using settings that removed even those level differences from hearing, the muddying would begin at higher levels above noise. This would happen in a perfect receiver. **IF** the hardware AGC was exposed to significant CW signals outside the DSP skirts due to use of a much wider roofer than the DSP width setting (such as one listing of 500-800 Hz DSP under a 1000 roofer) the variable IF gain stage would be tracking the HAGC imposition on the gain, and raising and lowering the signal of the collective IN-DSP signals with foreign on/off information not related to any of the in-band signals. Muddle would be a good word to describe that effect. This is in a volume region where one is already losing clarity keying artifacts to the noise floor. ***This effect would occur the worst in the range between where the DSP AGC started to take up down to the noise***, and would otherwise be flattened back by the DSP AGC responding only to the in-band signals and treating the HAGC variations as "propagation changes". Slowing down the hardware AGC would prevent in-roofer-out-of-DSP baud-speed external signal gain modulation to weak, under AGC in-band signals. I should note for the record that in contests I am either running a 400 8 pole with DSP at 450 or a 250 8 pole with DSP at 350 or 150. When the offsets of the filters are carefully adjusted, these produce the sharpest composite skirts down 30 and 40 dB. There is never any signal outside the DSP limits making it to the hardware AGC. I always use slow AGC with the fastest possible decay. I always have my PRE/ATT and RF gain pushed back to match the band. There may be something else going on, but with my settings I have never heard any of the reported muddiness, other than the expected perfect RX conditions listed above. I am going to try the cap modification to my KRX3 only and listen in diversity to a single antenna. I will also set the main RX to keep the 400 8 pole as roofer all the way down. Then at 350 bandwidth, I will be listening to a wide roofer on one and an equal roofer on the other. Should be easy to put an XG3 + step attenuator tone IN band with a loud CW signal between the skirts and see what happens. Anything audio happening to one RX and not the other should be really obvious. 73, Guy. On Mon, Dec 5, 2011 at 12:39 PM, David Gilbert wrote: > > "The only time I heard mush on the K3 was when we had worked down the > pileup and only had very low strength guys all calling on the same > frequency (the packet/reverse beacon spotting phenomenon)." > > > Multiple low level signals close in frequency is EXACTLY the situation > that I and at least several others are concerned about. I don't > notice the problem on stronger signals either, and my low level > hearing is still pretty good. Operating from ZF-land where you > almo
Re: [Elecraft] K3 AGC Mush ... or "blur"
Not to argue but to move toward clarity... Low level signals are by definition closer to the noise. That would also mean that there would be more "stuff" between CW bauds. "Crisp" to some means that the artifacts which define the beginning and the ends of a baud are there. The extreme artifact is a key click. A normal artifact is additional bandwidth occurring at the edges of the baud, but reduced in level. These are down 6, 12, 18, 24 dB from the pure sine wave. Without these, the baud sounds soft, and the transitions on and off only excite the directly on-tone nerves in the ear, instead of some number of tones. Once the signal is close enough to the noise the baud start and stop artifacts become obscured by the noise, but the signal is still copyable by itself. If there are multiple signals in this state and the tones are close, our ears lose all clue of baud on/off other than slow (not "sharp") level transitions. We lose harmonic artifacts, and now must rely only on very soft level changes. Ancient Bell Labs studies on these issues for telephone would say that for most people, a change from one CW signal to another at close to the same frequency, less than three dB in amplitude, would not be a perceptible change. On these issues in that QRM situation, one would EXPECT that kind of "muddyness" in the S unit above the noise level. This would happen in a perfect receiver. This is why someone's signal sending fast when they go into the noise "blurs" the CW and the only way to overcome that is to slow down signficantly. **IF** the AGC was using settings that removed even those level differences from hearing, the muddying would begin at higher levels above noise. This would happen in a perfect receiver. **IF** the hardware AGC was exposed to significant CW signals outside the DSP skirts due to use of a much wider roofer than the DSP width setting (such as one listing of 500-800 Hz DSP under a 1000 roofer) the variable IF gain stage would be tracking the HAGC imposition on the gain, and raising and lowering the signal of the collective IN-DSP signals with foreign on/off information not related to any of the in-band signals. Muddle would be a good word to describe that effect. This is in a volume region where one is already losing clarity keying artifacts to the noise floor. ***This effect would occur the worst in the range between where the DSP AGC started to take up down to the noise***, and would otherwise be flattened back by the DSP AGC responding only to the in-band signals and treating the HAGC variations as "propagation changes". Slowing down the hardware AGC would prevent in-roofer-out-of-DSP baud-speed external signal gain modulation to weak, under AGC in-band signals. I should note for the record that in contests I am either running a 400 8 pole with DSP at 450 or a 250 8 pole with DSP at 350 or 150. When the offsets of the filters are carefully adjusted, these produce the sharpest composite skirts down 30 and 40 dB. There is never any signal outside the DSP limits making it to the hardware AGC. I always use slow AGC with the fastest possible decay. I always have my PRE/ATT and RF gain pushed back to match the band. There may be something else going on, but with my settings I have never heard any of the reported muddiness, other than the expected perfect RX conditions listed above. I am going to try the cap modification to my KRX3 only and listen in diversity to a single antenna. I will also set the main RX to keep the 400 8 pole as roofer all the way down. Then at 350 bandwidth, I will be listening to a wide roofer on one and an equal roofer on the other. Should be easy to put an XG3 + step attenuator tone IN band with a loud CW signal between the skirts and see what happens. Anything audio happening to one RX and not the other should be really obvious. 73, Guy. On Mon, Dec 5, 2011 at 12:39 PM, David Gilbert wrote: > > "The only time I heard mush on the K3 was when we had worked down the > pileup and only had very low strength guys all calling on the same > frequency (the packet/reverse beacon spotting phenomenon)." > > > Multiple low level signals close in frequency is EXACTLY the situation > that I and at least several others are concerned about. I don't notice > the problem on stronger signals either, and my low level hearing is > still pretty good. Operating from ZF-land where you almost always have > somebody strong calling you is not the typical situation many of the > rest of us experience from our home QTH's, and I would therefore expect > that you are less likely to experience the problem. Great sensitivity > and dynamic range are less useful if what you hear cannot be deciphered. > > By the way, it has been pointed out to me that "mush" may not be the > best descriptor for what I hear, and I agree with that. I think "blur" > might be a better term. When the problem shows up I can distinguish the > individual tones (the signals are not dead zero beat) but
Re: [Elecraft] K3 AGC Mush ... or "blur"
I think Mr. Harper has hit the nail squarely on the head with this comment: >I think our expectations of the K3 are based largely on >what we migrated to the K3 from. Its the same expectation that I have for transmit audio punch. It took me six months to feel comfortable with my audio settings on TX, and a lot of playing ensued. I learned a lot, too! While I would like to see some of my pet "additions" that I think are "important" be implemented, it doesnt sound so bad now, and reality states that there is just so much that can be implemented in the DSP; Im on my own to solve my perceived problems, real or imagined. There is no perfect rig. This one is close, but its not perfect, and never will be. Where once there was crackly receiver intermod products, now we hear clicking and "blur/mush". Not saying its not real, just saying it is an artifact of this technology's design and our own perceptions. If it can be fixed or mitigated, then great! If it cant, then we have to either live with it or buy something else. I had a boss who's favorite saying was "Perception is Reality". He is right. And I dont think a lot of this will be replicated in a lab either. Its as much perceived as it is real; we are all learning how to work in this new digital domain. Its going to take us a while to get our collective heads around it. I will record ARRL 10 as well, Im mixed mode, too. -lu-W4LT- __ 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
Re: [Elecraft] K3 AGC Mush ... or "blur"
On 12/5/2011 10:38 AM, David Gilbert wrote: > If I get the chance during the upcoming ARRL 10m contest I'll give it > another try. I'll also try to record the entire contest to see if I can > come up with a decent sound clip. That would be really cool, David. My K3 replaced my TS-850 [which I really liked], and I had them both [and my K2] on the desk for awhile. I easily found CW signals I could copy on the K3, could hear but not copy well on the K2, and that I couldn't hear at all on the 850. I'd sure like to hear the "mush" everyone is talking about. 73, Fred K6DGW - Northern California Contest Club - CU in the 2012 Cal QSO Party 6-7 Oct 2012 - www.cqp.org __ 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
Re: [Elecraft] K3 AGC Mush ... or "blur"
>Multiple low level signals close in frequency is EXACTLY the situation >that I and at least several others are concerned about. I don't notice Curiousity is getting the best of me...what transceiver(s) *don't* exhibit this problem and allow individual discernment of multiple weak signals near zero beat w/ each other? To a newbie contester like myself, it almost seems a herculean expectation... I'm mainly asking because I think our expectations of the K3 are based largely on what we migrated to the K3 from. John Harper http://www.ae5x.com/blog __ 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
Re: [Elecraft] K3 AGC Mush ... or "blur"
To be honest, I've never tried that very often. The one or two times I have done so (AGC off, RF Gain at max) have not been pleasant experiences. The only time I get a pileup of weak signals is working Europe from here in Arizona, and that means I have to point through some very loud signals on the East Coast ... it only takes one of them to cross my passband to teach me a lesson. If I get the chance during the upcoming ARRL 10m contest I'll give it another try. I'll also try to record the entire contest to see if I can come up with a decent sound clip. 73, Dave AB7E On 12/5/2011 10:57 AM, Wayne Burdick wrote: > David, > > Does turning AGC off (but leaving RF GAIN at max) ever "un-blur" the > signals? > > Wayne > N6KR > > > On Dec 5, 2011, at 9:39 AM, David Gilbert wrote: > >> >> "The only time I heard mush on the K3 was when we had worked down the >> pileup and only had very low strength guys all calling on the same >> frequency (the packet/reverse beacon spotting phenomenon)." >> >> >> Multiple low level signals close in frequency is EXACTLY the situation >> that I and at least several others are concerned about. > > > __ 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
Re: [Elecraft] K3 AGC Mush ... or "blur"
David, Does turning AGC off (but leaving RF GAIN at max) ever "un-blur" the signals? Wayne N6KR On Dec 5, 2011, at 9:39 AM, David Gilbert wrote: > > "The only time I heard mush on the K3 was when we had worked down the > pileup and only had very low strength guys all calling on the same > frequency (the packet/reverse beacon spotting phenomenon)." > > > Multiple low level signals close in frequency is EXACTLY the situation > that I and at least several others are concerned about. __ 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
Re: [Elecraft] K3 AGC Mush ... or "blur"
"The only time I heard mush on the K3 was when we had worked down the pileup and only had very low strength guys all calling on the same frequency (the packet/reverse beacon spotting phenomenon)." Multiple low level signals close in frequency is EXACTLY the situation that I and at least several others are concerned about. I don't notice the problem on stronger signals either, and my low level hearing is still pretty good. Operating from ZF-land where you almost always have somebody strong calling you is not the typical situation many of the rest of us experience from our home QTH's, and I would therefore expect that you are less likely to experience the problem.Great sensitivity and dynamic range are less useful if what you hear cannot be deciphered. By the way, it has been pointed out to me that "mush" may not be the best descriptor for what I hear, and I agree with that. I think "blur" might be a better term. When the problem shows up I can distinguish the individual tones (the signals are not dead zero beat) but the crispness of the keying disappears. It's as if something is filling in the spaces between the keying elements, and I tend to believe that the culprits are the sum/difference products of other nearby signals that happen to overlap the signal I'm trying to copy. 73, Dave AB7E On 12/5/2011 8:34 AM, K5WA wrote: > I really can't agree with the mush comment. I've just returned from ZF1A > where we put almost 8000 Qs in the log over the CQWW CW weekend. I took my > K3 and was able to evaluate it against the station's existing TS-850 since > we were M/S and rotated positions. In my opinion, the 850 WAS mushy and the > K3 was very clear however, K6AM, our host (who is a VERY serious contester), > prefers the 850 since he has been using it for 10 years. He also owns 4 K3s > but didn't bring them on the trip since the 850s "live" in Cayman and he > brought many pounds of other equipment. Personal preference plays a huge > part of this discussion. In this case, K6AM feels like his hearing is > limited to a frequency range of 6-7K while mine is still near 20K. Maybe > that is part of the puzzle. > > We regularly saw the 10 minute QSO rate meter in the 300 range and topped > 400 occasionally. I loved the way the K3 was able to plow through the > pileups which were calling us and work through them as fast as possible. > The only time I heard mush on the K3 was when we had worked down the pileup > and only had very low strength guys all calling on the same frequency (the > packet/reverse beacon spotting phenomenon). These must have been micro-watt > QRP'ers or stations with minimal/indoor antennas. I had my AGC on and > didn't have any time to try multiple settings but I am extremely happy with > the K3's receiver and think it is in the high end competition grade for me. > > I am sending Eric my configuration file as he requested in case he is able > to find an improvement but I will be amazed if one can be found. I've > always been extremely happy with Elecraft's commitment and motivation to > exceed expectations but they have already exceeded mine as it is. ;-) > > 73, > Bob K5WA > > __ 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
