Re: [Elecraft] K3 AGC THR doesn't go low enough
Nice writeup, Don. Thanks! But the one thing I haven't seen mentioned in this month's installment of the noisy K3 discussion is setting the RF gain control. I got into the habit long ago of using the RF gain to quiet the band noise to a reasonable level -- after setting pre-amp, attenuator, and AF gain appropriately. We didn't have AGC parameters to play with back then except maybe Fast/Slow/Off. If the K3's RF (actually IF) gain control works the way most rigs' do, it is providing a bias to the AGC control voltage. In other words, it is providing a maximum gain that will not be exceeded by the AGC's feedback action. Is that not an equally valid way to control the level of band noise? Apart from it being manual instead of automatic, is there any drawback to it? I can imagine that it could interact with AGC dynamics in some unpleasant way, but if so I haven't noticed it yet. The K3 is only the second HF rig I've owned in 23 years as a ham. My first was an Icom 735, and it is quite noisy on the low bands if the RF gain is all the way up. I've heard quieter rigs, but it never occurred to me to think of them as better just because of that. 73, Carl WS7L K3 #486 -Original Message- Go to www.w3fpr.com and click on the link in the left column referring to K3 noise and AGC settings. It is an expansion of the post I offered earlier today dealing with AGC settings and their relationship to K3 noise. 73, Don W3FPR __ 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 THR doesn't go low enough
Carl, Backing off the RF Gain will preserve the dynamic range of the receiver, and will move the AGC response further from the threshold (but it will do nothing for the slope). So, yes, that can be quite effective for reducing noise. Many do not like to back off the RF Gain. I have heard two valid reasons - one is that a modern receiver's AGC should take care of the need to change the RF Gain - and secondly, some object to the fact that the S-meter goes up when the RF Gain is reduced. Also, backing off the RF Gain is the best way to reduce the no signal band noise, but the AGC will handle things differently when there are signals on the band and pauses in the signal. If the AGC is set to be agressive (low threshold and high slope), there will still be little difference between the signal and the rise of noise during pauses in the signal. The only way to change that is to adjust the AGC parameters. 73, Don W3FPR On 10/8/2010 11:54 PM, Carl Clawson wrote: Nice writeup, Don. Thanks! But the one thing I haven't seen mentioned in this month's installment of the noisy K3 discussion is setting the RF gain control. I got into the habit long ago of using the RF gain to quiet the band noise to a reasonable level -- after setting pre-amp, attenuator, and AF gain appropriately. We didn't have AGC parameters to play with back then except maybe Fast/Slow/Off. If the K3's RF (actually IF) gain control works the way most rigs' do, it is providing a bias to the AGC control voltage. In other words, it is providing a maximum gain that will not be exceeded by the AGC's feedback action. Is that not an equally valid way to control the level of band noise? Apart from it being manual instead of automatic, is there any drawback to it? I can imagine that it could interact with AGC dynamics in some unpleasant way, but if so I haven't noticed it yet. The K3 is only the second HF rig I've owned in 23 years as a ham. My first was an Icom 735, and it is quite noisy on the low bands if the RF gain is all the way up. I've heard quieter rigs, but it never occurred to me to think of them as better just because of that. 73, Carl WS7L K3 #486 -Original Message- Go to www.w3fpr.com and click on the link in the left column referring to K3 noise and AGC settings. It is an expansion of the post I offered earlier today dealing with AGC settings and their relationship to K3 noise. 73, Don W3FPR __ 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 __ 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 THR doesn't go low enough
Note that my post referenced below sat in limbo for 4 days before showing up on the list. It's a bit stale. In the interim, one contributor gave some quantitative info about the noise measured between CW elements when running full QSK with the RF gain control set appropriately. If the noise between elements is rising above the level you had set with the gain control, that seems to be a malfunction. Is it maybe the case that some other rigs actually suppress the gain a bit between QSK elements, and are therefore perceived as having quieter QSK? I could imagine a good argument for a bit of gain suppression in that circumstance...but then my imagination runs amok quite frequently. 73 and thanks for listening, Carl WS7L K3 #486 -Original Message- [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Carl Clawson Sent: Friday, October 08, 2010 8:54 PM Nice writeup, Don. Thanks! __ 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 THR doesn't go low enough - SOLVED
Problem solved. When I built my K3 and came to the Owner's Manual setup procedures on Page 51 - 'S-Meter and RF Gain control'. Not being in possession of an XG2 I took the statement 'calibration is normally adequate using the factory settings' at face value - and didn't calibrate the rf gain. Anyway, some of the responses to my original post pointed to some more in depth reading from W3FPR, K6NA and others. I realised that my K3 simply wouldn't respond as described and had too much gain in the RF/DSP somewhere. So I re-visited the RF Gain Calibration procedure - still without XG2. Brought up K3 Utility Selected Calibrate RF Gain which brings up screen 'Welcome to RF Gain Calibration' which refers to using a calibrated signal source - Nevertheless, click Next Choose 'Use factory default' Click Next PROBLEM SOLVED The K3 now sounds and behaves as I would expect. What a revelation. It may be just my K3 slipped through some factory stage and needed the factory defaults loading. However, my two nearest K3 owners - also self builds - suffered with the same problem I described, as I had discussed it with them before posting my original. One has had similar success with the Utility Calibration the other less so. However, if you suffer the same issue it would certainly appear to be worth running through the procedure outlined above. It is a night and day transformation for my K3. Now to order an XG2 for a final tweak. 73 John G3XRJ I like to listen to a receiver with the rf gain set to just below antenna atmospheric noise and AGC on - and not raising the rf gain when it is switched on. My K3 is srl 46xx and the only way I get the quiet background I desire is to turn the AGC off. This necessitates having the AF limiter turned on to save my ears and hopefully the speaker output chip. I've played around with various AGC settings and in particular the AGC THR - which if it would go 2 or 3 points lower would appear to address the problem. __ 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 THR doesn't go low enough - SOLVED
RF gain calibration has to be done, whether one has an XG2 or not. Without the XG2 you can set it to factory defaults. The RF gain calibration has to be done after the K3 is assembled and can't be done to the board before shipping a kit version. Although it works without the cal, there are strange behaviors in the corners and fringes, probably some I ran into which you happily will never know. 73, Guy. On Tue, Oct 12, 2010 at 3:10 PM, John Chappell G3XRJ j...@g3xrj.com wrote: Problem solved. When I built my K3 and came to the Owner's Manual setup procedures on Page 51 - 'S-Meter and RF Gain control'. Not being in possession of an XG2 I took the statement 'calibration is normally adequate using the factory settings' at face value - and didn't calibrate the rf gain. Anyway, some of the responses to my original post pointed to some more in depth reading from W3FPR, K6NA and others. I realised that my K3 simply wouldn't respond as described and had too much gain in the RF/DSP somewhere. So I re-visited the RF Gain Calibration procedure - still without XG2. Brought up K3 Utility Selected Calibrate RF Gain which brings up screen 'Welcome to RF Gain Calibration' which refers to using a calibrated signal source - Nevertheless, click Next Choose 'Use factory default' Click Next PROBLEM SOLVED The K3 now sounds and behaves as I would expect. What a revelation. It may be just my K3 slipped through some factory stage and needed the factory defaults loading. However, my two nearest K3 owners - also self builds - suffered with the same problem I described, as I had discussed it with them before posting my original. One has had similar success with the Utility Calibration the other less so. However, if you suffer the same issue it would certainly appear to be worth running through the procedure outlined above. It is a night and day transformation for my K3. Now to order an XG2 for a final tweak. 73 John G3XRJ I like to listen to a receiver with the rf gain set to just below antenna atmospheric noise and AGC on - and not raising the rf gain when it is switched on. My K3 is srl 46xx and the only way I get the quiet background I desire is to turn the AGC off. This necessitates having the AF limiter turned on to save my ears and hopefully the speaker output chip. I've played around with various AGC settings and in particular the AGC THR - which if it would go 2 or 3 points lower would appear to address the problem. __ 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 __ 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 THR doesn't go low enough - SOLVED
John Chappell G3XRJ wrote: My K3 is srl 46xx and the only way I get the quiet background I desire is to turn the AGC off. SNIP Problem solved. When I built my K3 and came to the Owner's Manual setup procedures on Page 51 - 'S-Meter and RF Gain control'. Not being in possession of an XG2 I took the statement 'calibration is normally adequate using the factory settings' at face value - and didn't calibrate the rf gain. It's probably just as well that you didn't do the RF Gain Calibration. The most recent versions of the Utility (e.g. 1.3.9.xx) were not properly saving calibration parameters. I went through many pushups discovering this with #4717...not far past your #46XX. If you do get an XG2, be sure to download the latest K3 Utility (at least 1.3.10.11 or later) which correctly saves the parameters. If anyone else has done RF Cal recently (i.e. in September), you should redo it with the new Utility when released. 73, Bill -- View this message in context: http://elecraft.365791.n2.nabble.com/K3-AGC-THR-doesn-t-go-low-enough-tp5614723p5629218.html Sent from the [K3] 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: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 THR doesn't go low enough - SOLVED
On 10/12/2010 8:10 PM, Bill W4ZV wrote: be sure to download the latest K3 Utility (at least 1.3.10.11 or later) If it has been released I can't find it on the ftp site? GB 73 K5OAI Sam Morgan __ 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 THR doesn't go low enough - SOLVED
k5oai wrote: On 10/12/2010 8:10 PM, Bill W4ZV wrote: be sure to download the latest K3 Utility (at least 1.3.10.11 or later) If it has been released I can't find it on the ftp site? Still in beta but should be released soon. It works FB on two different units here so I believe the problem is solved. 73, Bill -- View this message in context: http://elecraft.365791.n2.nabble.com/K3-AGC-THR-doesn-t-go-low-enough-tp5614723p5629278.html Sent from the [K3] 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: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 THR doesn't go low enough - SOLVED
Bill, If you do get an XG2, be sure to download the latest K3 Utility (at least 1.3.10.11 or later) which correctly saves the parameters. If anyone else has done RF Cal recently (i.e. in September), you should redo it with the new Utility when released. Where does one get 1.3.10.11 or later? The last one on the web site is 1.3.9.12. 73, ... Joe, W4TV On 10/12/2010 9:10 PM, Bill W4ZV wrote: John Chappell G3XRJ wrote: My K3 is srl 46xx and the only way I get the quiet background I desire is to turn the AGC off. SNIP Problem solved. When I built my K3 and came to the Owner's Manual setup procedures on Page 51 - 'S-Meter and RF Gain control'. Not being in possession of an XG2 I took the statement 'calibration is normally adequate using the factory settings' at face value - and didn't calibrate the rf gain. It's probably just as well that you didn't do the RF Gain Calibration. The most recent versions of the Utility (e.g. 1.3.9.xx) were not properly saving calibration parameters. I went through many pushups discovering this with #4717...not far past your #46XX. If you do get an XG2, be sure to download the latest K3 Utility (at least 1.3.10.11 or later) which correctly saves the parameters. If anyone else has done RF Cal recently (i.e. in September), you should redo it with the new Utility when released. 73, Bill __ 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 THR doesn't go low enough - SOLVED
Did 1.3.7.26 have this problem? I just used it for RF cal a few minutes ago. Chuck, W5UXH Bill W4ZV wrote: If you do get an XG2, be sure to download the latest K3 Utility (at least 1.3.10.11 or later) which correctly saves the parameters. If anyone else has done RF Cal recently (i.e. in September), you should redo it with the new Utility when released. 73, Bill -- View this message in context: http://elecraft.365791.n2.nabble.com/K3-AGC-THR-doesn-t-go-low-enough-tp5614723p5629318.html Sent from the [K3] 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: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 THR doesn't go low enough - SOLVED
W5UXH wrote: Did 1.3.7.26 have this problem? I just used it for RF cal a few minutes ago. Probably OK. I used the oldest I could find which was 1.3.7.5 and it worked OK. -- View this message in context: http://elecraft.365791.n2.nabble.com/K3-AGC-THR-doesn-t-go-low-enough-tp5614723p5629327.html Sent from the [K3] 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: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 THR doesn't go low enough
For me, it is more than a perception. To demonstrate this to myself, I used the XG-2 set at 50 uV (so a good strong S9 signal) and for my normal operating setup I see a tone (from the XG-2) in the presence of very noticeable noise on an oscilloscope when looking at the K3 audio output. I believe I understand why this happens in my case. I believe it is because as a 100% CW 100% QSK type, I am not able to operate with the RF gain at maximum. If I do this, then when I am talking, the band noise is greatly amplified in between elements by the AGC, in the absence of other received signals. For this reason I have spent the last 50 years using the RF gain as my primary level control, keeping it as low as possible for the band conditions and signal I am in QSO with. With the K3, the received signal sounds great with RF gain at max. But it is not possible to think when transmitting with the RF gain at max, due to band noise. With the RF gain turned down to an appropriate level for decent QSK (and the AF gain subsequently set higher), the perceived extra noise is very real as seen on the scope, and typically, in the absence of signals, there is no change in the noise when I ground the antenna. Of course with RF gain at max there is a big change in noise when I ground the antenna. So, I really doubt there is any cure for me. I have played with the AGC SLP and THR parameters per suggestions in the main thread under this subject just in case. But I suspect clean QSK and RF gain at max are just mutually exclusive with the K3. If anyone can point me to a setup where this is not the case, I would be happy to investigate. This is not the case with my FT-1000MP. I have no idea what the reason for this difference is. Unfortunately the MP keying waveform leaves a bit to be desired. Maybe I will finally be forced to try one of the key click mods! Chuck, W5UXH Las Cruces, NM P.B. Christensen wrote: I had resigned myself to living with the AGC off because I can't stand the sound of the audio with it on in CW mode.. I have similar perceptions in CW mode and generally leave AGC turned off. -- View this message in context: http://elecraft.365791.n2.nabble.com/K3-AGC-THR-doesn-t-go-low-enough-tp5615857p5620257.html Sent from the [K3] 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: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 THR doesn't go low enough
I`ve been following this thread with interest as I have the same perceived problem as John - and think all K3s exhibit this symptom. I do not believe anyone has mentioned signal to noise ratio and surely this is fundamental ? I work a lot on 160m trying to dig out extremely weak signals using a K9AY loop array with pre-amp on (on the K3). I have tried lots of AGC settings with the K3 but my conclusion is that the best signal to noise ratio is achieved with the AGC off; turning it on in whatever combination of settings introduces noise and degrades the S:N. This conclusion means setting the AF limiter at a suitable level to protect my ears ! 73 Terry G4AMT On 08/10/2010 19:55, Don Wilhelm wrote: I seem to have trouble convincing some to raise the threshold to combat the noisy effect. Please read all below carefully, and I believe I can offer some explanation. Let's study what the AGC SLP and AGC THR settings do and try to relate them to the perception that the K3 is noisy. IF -- the threshold is so low that the noise triggers the AGC (and that will be happening if the noise is causing the S-meter to have a reading with no signal) AND -- If the slope is set to a high value which makes all the signals have more or less the same audio volume, THEN -- The noise will appear at about the SAME audio volume as the signals. RESULT -- A K3 that sounds noisy :-( ! It is a combination of both the threshold and the slope that create this condition. The cure for that situation is to increase the threshold and reduce the slope. How much? That is an individual decision, but I have mine set to the extremes of THR at 008 and SLP at 002. I really believe the defaults are OK for a band where the ambient noise level is lower, but certainly gives problems on a band that is inherently noisy. Please make your evaluation while listening to signals and the breaks between signals - if you are hearing only noise, you will naturally turn the AF Gain up, and yes the noise will increase - not only that, with only noise, the perception is that one should use a lower threshold setting. That is because as you lower the threshold, the AGC response to the noise gets stronger, and the audio level is reduced by the AGC - what you are perceiving is exactly the opposite of what you wish to achieve. In addition, turn the attenuator on and the preamp off - again, if you hear an increase in the band noise when the antenna is connected, you have all the sensitivity that you can use for that band and antenna. The K3 remembers those settings by band, so you don't have to make changes as you switch bands. 73, Don W3FPR On 10/8/2010 2:23 PM, Mike Scott wrote: I have thought about John's wish for more AGC control. The K3 has a lot of gain, I wonder if greater attenuator control would be more useful. I would like to rotate in another 10 or 20 dB attenuation at times when operating lower bands. I would guess my that wishes would require hardware modifications and John's may not. AE6WA Mike Scott K3, KX1 John G3XRJ said: I've played around with various AGC settings and in particular the AGC THR - which if it would go 2 or 3 points lower would appear to address the problem. __ 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 __ 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 THR doesn't go low enough
Don, Thank you for your responses and for your efforts on your webpage. However, I should have made it clear that I'm not in a noisy environment and just to make it absolutely clear I've made another recording without antenna connected to the K3. Main and RX antenna physically removed, pre Amp off. Att Off, SSB Bandwidth Normal Recording made in LSB mode rather than my normal CW because it demonstrates the point more clearly. Recording here http://www.g3xrj.com/Recordings/K3_agc_part2.mp3 Finally I must point out that I'm not saying the K3 is a noisy receiver but rather, whatever the AGC does in its present incarnation in the digital stream, has the effect of increasing the 'rf gain' from 12 o'clock to nearly 3 o'clock on overall system noise. 73 John G3XRJ In an effort to help those who perceive their K3 as noisy, and for those who are not certain their AGC slope and threshold settings are not right for their operation, I have added a page to my website. Go to www.w3fpr.com and click on the link in the left column referring to K3 noise and AGC settings. It is an expansion of the post I offered earlier today dealing with AGC settings and their relationship to K3 noise. 73, Don W3FPR __ 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 __ 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 THR doesn't go low enough
G3XRJ wrote: Finally I must point out that I'm not saying the K3 is a noisy receiver but rather, whatever the AGC does in its present incarnation in the digital stream, has the effect of increasing the 'rf gain' from 12 o'clock to nearly 3 o'clock on overall system noise. Rather than comparing the noise level at identical gain control settings, I believe you should be comparing the noise level at gain control settings that result in the same loudness for a fixed-strength signal (e.g. a 1 uV signal). After all, what matters is not the absolute level of noise at some arbitrarily-chosen gain control setting, it is the level of noise relative to the signals you want to listen to. In your original posting, you were comparing AGC off to AGC on. In order to reduce the disparity, you were requesting a lower AGC threshold. This would be counter-productive; reducing the AGC threshold increases the disparity between AGC on and off. To reduce the overall disparity between AGC on and AGC off, you must raise the AGC threshold so the AGC has as little effect as possible on weak signals. This may also require a re-adjustment of the RF gain control in order to make overall system gain on weak signals and noise the same between the two AGC settings (on and off, or low and high threshold). To put it another way, if you like the way the receiver operates with no AGC but would like to have AGC protecting your ears for very strong signals, set the AGC threshold as high as possible, adjust the rf gain controls for the desired noise (and weak signal) level at your ears, and then adjust the AGC slope setting to affect strong signals the way you want it to. The least aggressive AGC action overall occurs with the threshold set as high as possible and the slope setting as low as possible. There is a very good explanation of the effects of the K3's AGC settings at http://www.cliftonlaboratories.com/elecraft_k3_agc_and_s-meter.htm. 73, Rich VE3KI __ 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 THR doesn't go low enough
John, Your recording has substantiated the cautions that I have mentioned. First, attempts to evaluate the K3 AGC response with no signals on the band will lead you in the wrong direction. Secondly, you apparently have the AF Gain well advanced, perhaps even at maximum. Third, you have demonstrated that at low threshold settings the AGC can be activated on receiver noise alone. That fact is demonstrated by a reduction in noise when the threshold is lowered. Reducing the RF Gain has the effect of reducing the range of the AGC. If you want signals to pop out of the noise using real signals on a real band, try setting the Threshold to maximum and set the Slope to minimum. Set the attenuator on and preamp off for 160 meters (unless you are using an inefficient receiving antenna). Start with the RF Gain set at full clockwise and turn the AF Gain up only until you hear a moderate, but tolerable amount of band noise. You may wish to reduce the RF Gain a bit and advance the AF Gain, but keep the band noise received to a moderate level. Try it and see what happens. Again, reducing the AGC Threshold is going exactly the wrong way. 73, Don W3FPR On 10/9/2010 8:15 AM, John Chappell G3XRJ wrote: Don, Thank you for your responses and for your efforts on your webpage. However, I should have made it clear that I'm not in a noisy environment and just to make it absolutely clear I've made another recording without antenna connected to the K3. Main and RX antenna physically removed, pre Amp off. Att Off, SSB Bandwidth Normal Recording made in LSB mode rather than my normal CW because it demonstrates the point more clearly. Recording here http://www.g3xrj.com/Recordings/K3_agc_part2.mp3 Finally I must point out that I'm not saying the K3 is a noisy receiver but rather, whatever the AGC does in its present incarnation in the digital stream, has the effect of increasing the 'rf gain' from 12 o'clock to nearly 3 o'clock on overall system noise. 73 John G3XRJ __ 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 THR doesn't go low enough
Don, Thanks for response again. Recording was made from 'line out' so af gain not in play. Havn't had chance to try your suggestion yet but think I've already been there. 73 John John, Your recording has substantiated the cautions that I have mentioned. First, attempts to evaluate the K3 AGC response with no signals on the band will lead you in the wrong direction. Secondly, you apparently have the AF Gain well advanced, perhaps even at maximum. Third, you have demonstrated that at low threshold settings the AGC can be activated on receiver noise alone. That fact is demonstrated by a reduction in noise when the threshold is lowered. Reducing the RF Gain has the effect of reducing the range of the AGC. __ 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
[Elecraft] K3 AGC THR doesn't go low enough
I like to listen to a receiver with the rf gain set to just below antenna atmospheric noise and AGC on - and not raising the rf gain when it is switched on. My K3 is srl 46xx and the only way I get the quiet background I desire is to turn the AGC off. This necessitates having the AF limiter turned on to save my ears and hopefully the speaker output chip. I've played around with various AGC settings and in particular the AGC THR - which if it would go 2 or 3 points lower would appear to address the problem. Anyway, to save a thousand words, this recording sets the scene http://tinyurl.com/38qo9ud - made from Main Rx on 3670khz with 2.8khz filter passband set to Normal, NR and NB Off. Sub Rx is identical in performance in this respect. In all other respects that I use it the K3 is a stunner. John G3XRJ __ 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 THR doesn't go low enough
Interesting. Many of us have wanted just the opposite. The ability to hold off AGC action until even high levels than the THR value allows now. Perhaps in the future 73 de Brian/K3KO On 10/8/2010 12:22, John Chappell G3XRJ wrote: I like to listen to a receiver with the rf gain set to just below antenna atmospheric noise and AGC on - and not raising the rf gain when it is switched on. My K3 is srl 46xx and the only way I get the quiet background I desire is to turn the AGC off. This necessitates having the AF limiter turned on to save my ears and hopefully the speaker output chip. I've played around with various AGC settings and in particular the AGC THR - which if it would go 2 or 3 points lower would appear to address the problem. Anyway, to save a thousand words, this recording sets the scene http://tinyurl.com/38qo9ud - made from Main Rx on 3670khz with 2.8khz filter passband set to Normal, NR and NB Off. Sub Rx is identical in performance in this respect. In all other respects that I use it the K3 is a stunner. John G3XRJ __ 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 No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.862 / Virus Database: 271.1.1/3183 - Release Date: 10/07/10 18:34:00 No virus found in this outgoing message. Checked by AVG - www.avg.com Version: 9.0.862 / Virus Database: 271.1.1/3183 - Release Date: 10/07/10 18:34:00 __ 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 THR doesn't go low enough
John, I've noticed the same thing: the AGC does seem to make the receiver - in the absence of signals - roar quite a bit with my early (#770) K3. I've attributed a lot of the noise to computer and suburban hash, but listening with my old Drake receiver shows things much quieter. Noise reduction does help, but it would be nice to quiet this down as John suggests. My .02 Steve, W1ES -Original Message- From: John Chappell G3XRJ j...@g3xrj.com Sent: Oct 8, 2010 8:22 AM To: Elecraft@mailman.qth.net Subject: [Elecraft] K3 AGC THR doesn't go low enough I like to listen to a receiver with the rf gain set to just below antenna atmospheric noise and AGC on - and not raising the rf gain when it is switched on. My K3 is srl 46xx and the only way I get the quiet background I desire is to turn the AGC off. This necessitates having the AF limiter turned on to save my ears and hopefully the speaker output chip. I've played around with various AGC settings and in particular the AGC THR - which if it would go 2 or 3 points lower would appear to address the problem. Anyway, to save a thousand words, this recording sets the scene http://tinyurl.com/38qo9ud - made from Main Rx on 3670khz with 2.8khz filter passband set to Normal, NR and NB Off. Sub Rx is identical in performance in this respect. In all other respects that I use it the K3 is a stunner. John G3XRJ __ 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 __ 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 THR doesn't go low enough
Steve, The solution is to RAISE the threshold. I run mine at 008 which is the max. I also run the slope at 002 which makes the K3 AGC response more like my K2 - weak signals sound weaker than stronger signals. You can alter the slope without running into the situation where the K3 sounds noisy, but the signals will sound more nearly the same as the slope numbers get larger. If your local noise is high, increase the AGC threshold and the K3 will quiet down. There is yet another way - turn off the preamp, and even turn on the attenuator. You will have to increase your normal AF Gain a bit, but the noise will be reduced. If you can still hear an increase in the audio output when the antenna is connected, you can even reduce the RF gain. You are not increasing the USABLE receiver sensitivity by running everything at full right controls - in the presence of atmospheric noise, that will only reduce the usable dynamic range and will make the receiver sound noisy. 73, Don W3FPR On 10/8/2010 10:25 AM, Steve Wedge wrote: John, I've noticed the same thing: the AGC does seem to make the receiver - in the absence of signals - roar quite a bit with my early (#770) K3. I've attributed a lot of the noise to computer and suburban hash, but listening with my old Drake receiver shows things much quieter. Noise reduction does help, but it would be nice to quiet this down as John suggests. My .02 Steve, W1ES __ 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 THR doesn't go low enough
Ok, now I've done it... I had resigned myself to living with the AGC off because I can't stand the sound of the audio with it on in CW mode (I've come close to selling it because of that many times), but with all this chatter about the AGC settings, I got in there and messed around again (still not happy) but now when I shut of the AGC, my audio shuts off too... ARGHH. Can anyone tell me what I can do to undo my adjustments and get the option to shut of this cursed AGC off without losing my audio? Many thanks in advance and I better stop reading these postings :-) George WA1NTA...73 -Original Message- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Don Wilhelm Sent: Friday, October 08, 2010 11:03 AM To: Steve Wedge Cc: Elecraft@mailman.qth.net Subject: Re: [Elecraft] K3 AGC THR doesn't go low enough Steve, The solution is to RAISE the threshold. I run mine at 008 which is the max. I also run the slope at 002 which makes the K3 AGC response more like my K2 - weak signals sound weaker than stronger signals. You can alter the slope without running into the situation where the K3 sounds noisy, but the signals will sound more nearly the same as the slope numbers get larger. If your local noise is high, increase the AGC threshold and the K3 will quiet down. There is yet another way - turn off the preamp, and even turn on the attenuator. You will have to increase your normal AF Gain a bit, but the noise will be reduced. If you can still hear an increase in the audio output when the antenna is connected, you can even reduce the RF gain. You are not increasing the USABLE receiver sensitivity by running everything at full right controls - in the presence of atmospheric noise, that will only reduce the usable dynamic range and will make the receiver sound noisy. 73, Don W3FPR On 10/8/2010 10:25 AM, Steve Wedge wrote: John, I've noticed the same thing: the AGC does seem to make the receiver - in the absence of signals - roar quite a bit with my early (#770) K3. I've attributed a lot of the noise to computer and suburban hash, but listening with my old Drake receiver shows things much quieter. Noise reduction does help, but it would be nice to quiet this down as John suggests. My .02 Steve, W1ES __ 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 __ 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 THR doesn't go low enough
You guys are headed in the wrong direction ... crank the AGC threshold UP and you will come closer to getting what you want. I have mine set to 008 and if it would go higher I would set it there. 73, Dave AB7E On 10/8/2010 7:25 AM, Steve Wedge wrote: John, I've noticed the same thing: the AGC does seem to make the receiver - in the absence of signals - roar quite a bit with my early (#770) K3. I've attributed a lot of the noise to computer and suburban hash, but listening with my old Drake receiver shows things much quieter. Noise reduction does help, but it would be nice to quiet this down as John suggests. My .02 Steve, W1ES -Original Message- From: John Chappell G3XRJj...@g3xrj.com Sent: Oct 8, 2010 8:22 AM To: Elecraft@mailman.qth.net Subject: [Elecraft] K3 AGC THR doesn't go low enough I like to listen to a receiver with the rf gain set to just below antenna atmospheric noise and AGC on - and not raising the rf gain when it is switched on. My K3 is srl 46xx and the only way I get the quiet background I desire is to turn the AGC off. This necessitates having the AF limiter turned on to save my ears and hopefully the speaker output chip. I've played around with various AGC settings and in particular the AGC THR - which if it would go 2 or 3 points lower would appear to address the problem. Anyway, to save a thousand words, this recording sets the scene http://tinyurl.com/38qo9ud - made from Main Rx on 3670khz with 2.8khz filter passband set to Normal, NR and NB Off. Sub Rx is identical in performance in this respect. In all other respects that I use it the K3 is a stunner. John G3XRJ __ 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 __ 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 __ 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 THR doesn't go low enough
My first thought on comments about noise on a receiver is that the radio they are comparing it to just can't hear as well. 73, Jim - Original Message - From: Steve Wedge w1es1...@earthlink.net To: John Chappell G3XRJ j...@g3xrj.com; Elecraft@mailman.qth.net Sent: Friday, October 08, 2010 9:25 AM Subject: Re: [Elecraft] K3 AGC THR doesn't go low enough John, I've noticed the same thing: the AGC does seem to make the receiver - in the absence of signals - roar quite a bit with my early (#770) K3. I've attributed a lot of the noise to computer and suburban hash, but listening with my old Drake receiver shows things much quieter. Noise reduction does help, but it would be nice to quiet this down as John suggests. My .02 Steve, W1ES -Original Message- From: John Chappell G3XRJ j...@g3xrj.com Sent: Oct 8, 2010 8:22 AM To: Elecraft@mailman.qth.net Subject: [Elecraft] K3 AGC THR doesn't go low enough I like to listen to a receiver with the rf gain set to just below antenna atmospheric noise and AGC on - and not raising the rf gain when it is switched on. My K3 is srl 46xx and the only way I get the quiet background I desire is to turn the AGC off. This necessitates having the AF limiter turned on to save my ears and hopefully the speaker output chip. I've played around with various AGC settings and in particular the AGC THR - which if it would go 2 or 3 points lower would appear to address the problem. Anyway, to save a thousand words, this recording sets the scene http://tinyurl.com/38qo9ud - made from Main Rx on 3670khz with 2.8khz filter passband set to Normal, NR and NB Off. Sub Rx is identical in performance in this respect. In all other respects that I use it the K3 is a stunner. John G3XRJ __ 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 __ 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 __ 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 THR doesn't go low enough
Don, What I should have mentioned in my initial post was that the recording was made at midday on 80m and the noise from the antenna was only s1. For a given setting of the rf gain, increasing the threshold to 8 increases the noise, as can be heard in the recording. John G3XRJ The solution is to RAISE the threshold. I run mine at 008 which is the max. I also run the slope at 002 which makes the K3 AGC response more like my K2 - weak signals sound weaker than stronger signals. You can alter the slope without running into the situation where the K3 sounds noisy, but the signals will sound more nearly the same as the slope numbers get larger. If your local noise is high, increase the AGC threshold and the K3 will quiet down. There is yet another way - turn off the preamp, and even turn on the attenuator. You will have to increase your normal AF Gain a bit, but the noise will be reduced. If you can still hear an increase in the audio output when the antenna is connected, you can even reduce the RF gain. You are not increasing the USABLE receiver sensitivity by running everything at full right controls - in the presence of atmospheric noise, that will only reduce the usable dynamic range and will make the receiver sound noisy. 73, Don W3FPR __ 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 THR doesn't go low enough
John, I find that true too - but ONLY under the following conditions: 1 - the preamp is turned on 2 - the attenuator is off 3 - I set the K3 to hear only noise (no signal) If I set the preamp off and attenuator on (normal operation with my 80 meter antenna) and then set the AF gain to listen to normal signals, the K3 is less noisy with no signal than using other settings for the AGC Threshold. In other words, you cannot listen only to the noise level and make a valid comparison. 73, Don W3FPR On 10/8/2010 12:08 PM, John Chappell G3XRJ wrote: Don, What I should have mentioned in my initial post was that the recording was made at midday on 80m and the noise from the antenna was only s1. For a given setting of the rf gain, increasing the threshold to 8 increases the noise, as can be heard in the recording. John G3XRJ The solution is to RAISE the threshold. I run mine at 008 which is the max. I also run the slope at 002 which makes the K3 AGC response more like my K2 - weak signals sound weaker than stronger signals. You can alter the slope without running into the situation where the K3 sounds noisy, but the signals will sound more nearly the same as the slope numbers get larger. If your local noise is high, increase the AGC threshold and the K3 will quiet down. There is yet another way - turn off the preamp, and even turn on the attenuator. You will have to increase your normal AF Gain a bit, but the noise will be reduced. If you can still hear an increase in the audio output when the antenna is connected, you can even reduce the RF gain. You are not increasing the USABLE receiver sensitivity by running everything at full right controls - in the presence of atmospheric noise, that will only reduce the usable dynamic range and will make the receiver sound noisy. 73, Don W3FPR __ 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 __ 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
[Elecraft] K3: AGC THR doesn't go low enough
Re: ...the only way I get the quiet background I desire is to turn the AGC off.. and I had resigned myself to living with the AGC off because I can't stand the sound of the audio with it on in CW mode (I've come close to selling it because of that many times), AHA!!! Whenever I've posted a comment saying that my rx was noisy, it's generated a flurry of responses saying that I'm crazy, and don't know what I'm talking about or listening to. I'll never sell ol' #1823, but I did put her on the back shelf for a while until I added the DSPUPG board, and I'm giving her another critical listen. Considering this and my never-loud-enough speaker amp, I must come to the conclusion that NOT ALL THESE RADIOS ARE THE SAME! Tnx John, and George - I feel your pain (to quote an ex-president). VE7XF __ 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 THR doesn't go low enough
I had resigned myself to living with the AGC off because I can't stand the sound of the audio with it on in CW mode.. I have similar perceptions in CW mode and generally leave AGC turned off. The only problem I've encountered living in Florida is that on the 40m-20M bands, the 100 kHz/sec sweep from the Department of Homeland Security's ROTHR system nearly leaves me with permanent hearing damage. http://tinyurl.com/2egfnjo The sweeps occur at regular intervals, usually around 12 minutes apart from three ROTHR transmit facilities located in TX, VA, and PR. With the SDR-IQ running, I can usually react in time to activate AGC before the sweep appears on my listening frequency. However, when I'm not looking at the screen, the result is pretty painful. I know that the K3 firmware was updated some time back to include a peak-limiter function, but it seems to respond after the fact. Paul, W9AC __ 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 THR doesn't go low enough
I have thought about John's wish for more AGC control. The K3 has a lot of gain, I wonder if greater attenuator control would be more useful. I would like to rotate in another 10 or 20 dB attenuation at times when operating lower bands. I would guess my that wishes would require hardware modifications and John's may not. AE6WA Mike Scott K3, KX1 John G3XRJ said: I've played around with various AGC settings and in particular the AGC THR - which if it would go 2 or 3 points lower would appear to address the problem. __ 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 THR doesn't go low enough
I would concur with Don. I do not use the preamp unless the noise level is very low. I use the attenuator on load bands or when there is a substantial noise level. I use AGC as I don't want to damage my hearing accidentally. Bill K9YEQ John, I find that true too - but ONLY under the following conditions: 1 - the preamp is turned on 2 - the attenuator is off 3 - I set the K3 to hear only noise (no signal) If I set the preamp off and attenuator on (normal operation with my 80 meter antenna) and then set the AF gain to listen to normal signals, the K3 is less noisy with no signal than using other settings for the AGC Threshold. In other words, you cannot listen only to the noise level and make a valid comparison. 73, Don W3FPR On 10/8/2010 12:08 PM, John Chappell G3XRJ wrote: Don, What I should have mentioned in my initial post was that the recording was made at midday on 80m and the noise from the antenna was only s1. For a given setting of the rf gain, increasing the threshold to 8 increases the noise, as can be heard in the recording. John G3XRJ The solution is to RAISE the threshold. I run mine at 008 which is the max. I also run the slope at 002 which makes the K3 AGC response more like my K2 - weak signals sound weaker than stronger signals. You can alter the slope without running into the situation where the K3 sounds noisy, but the signals will sound more nearly the same as the slope numbers get larger. If your local noise is high, increase the AGC threshold and the K3 will quiet down. There is yet another way - turn off the preamp, and even turn on the attenuator. You will have to increase your normal AF Gain a bit, but the noise will be reduced. If you can still hear an increase in the audio output when the antenna is connected, you can even reduce the RF gain. You are not increasing the USABLE receiver sensitivity by running everything at full right controls - in the presence of atmospheric noise, that will only reduce the usable dynamic range and will make the receiver sound noisy. 73, Don W3FPR __ 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 __ 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 __ 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 THR doesn't go low enough
I seem to have trouble convincing some to raise the threshold to combat the noisy effect. Please read all below carefully, and I believe I can offer some explanation. Let's study what the AGC SLP and AGC THR settings do and try to relate them to the perception that the K3 is noisy. IF -- the threshold is so low that the noise triggers the AGC (and that will be happening if the noise is causing the S-meter to have a reading with no signal) AND -- If the slope is set to a high value which makes all the signals have more or less the same audio volume, THEN -- The noise will appear at about the SAME audio volume as the signals. RESULT -- A K3 that sounds noisy :-( ! It is a combination of both the threshold and the slope that create this condition. The cure for that situation is to increase the threshold and reduce the slope. How much? That is an individual decision, but I have mine set to the extremes of THR at 008 and SLP at 002. I really believe the defaults are OK for a band where the ambient noise level is lower, but certainly gives problems on a band that is inherently noisy. Please make your evaluation while listening to signals and the breaks between signals - if you are hearing only noise, you will naturally turn the AF Gain up, and yes the noise will increase - not only that, with only noise, the perception is that one should use a lower threshold setting. That is because as you lower the threshold, the AGC response to the noise gets stronger, and the audio level is reduced by the AGC - what you are perceiving is exactly the opposite of what you wish to achieve. In addition, turn the attenuator on and the preamp off - again, if you hear an increase in the band noise when the antenna is connected, you have all the sensitivity that you can use for that band and antenna. The K3 remembers those settings by band, so you don't have to make changes as you switch bands. 73, Don W3FPR On 10/8/2010 2:23 PM, Mike Scott wrote: I have thought about John's wish for more AGC control. The K3 has a lot of gain, I wonder if greater attenuator control would be more useful. I would like to rotate in another 10 or 20 dB attenuation at times when operating lower bands. I would guess my that wishes would require hardware modifications and John's may not. AE6WA Mike Scott K3, KX1 John G3XRJ said: I've played around with various AGC settings and in particular the AGC THR - which if it would go 2 or 3 points lower would appear to address the problem. __ 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 THR doesn't go low enough
Don, I tried your recommendations and it makes the setup sound better than where I had it. The threshold increase makes quite a listening difference for me personally. Thank you for sharing. Bill K9YEQ -Original Message- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Don Wilhelm Sent: Friday, October 08, 2010 1:56 PM To: m...@paxsen.com Cc: elecraft@mailman.qth.net Subject: Re: [Elecraft] K3 AGC THR doesn't go low enough I seem to have trouble convincing some to raise the threshold to combat the noisy effect. Please read all below carefully, and I believe I can offer some explanation. Let's study what the AGC SLP and AGC THR settings do and try to relate them to the perception that the K3 is noisy. IF -- the threshold is so low that the noise triggers the AGC (and that will be happening if the noise is causing the S-meter to have a reading with no signal) AND -- If the slope is set to a high value which makes all the signals have more or less the same audio volume, THEN -- The noise will appear at about the SAME audio volume as the signals. RESULT -- A K3 that sounds noisy :-( ! It is a combination of both the threshold and the slope that create this condition. The cure for that situation is to increase the threshold and reduce the slope. How much? That is an individual decision, but I have mine set to the extremes of THR at 008 and SLP at 002. I really believe the defaults are OK for a band where the ambient noise level is lower, but certainly gives problems on a band that is inherently noisy. Please make your evaluation while listening to signals and the breaks between signals - if you are hearing only noise, you will naturally turn the AF Gain up, and yes the noise will increase - not only that, with only noise, the perception is that one should use a lower threshold setting. That is because as you lower the threshold, the AGC response to the noise gets stronger, and the audio level is reduced by the AGC - what you are perceiving is exactly the opposite of what you wish to achieve. In addition, turn the attenuator on and the preamp off - again, if you hear an increase in the band noise when the antenna is connected, you have all the sensitivity that you can use for that band and antenna. The K3 remembers those settings by band, so you don't have to make changes as you switch bands. 73, Don W3FPR On 10/8/2010 2:23 PM, Mike Scott wrote: I have thought about John's wish for more AGC control. The K3 has a lot of gain, I wonder if greater attenuator control would be more useful. I would like to rotate in another 10 or 20 dB attenuation at times when operating lower bands. I would guess my that wishes would require hardware modifications and John's may not. AE6WA Mike Scott K3, KX1 John G3XRJ said: I've played around with various AGC settings and in particular the AGC THR - which if it would go 2 or 3 points lower would appear to address the problem. __ 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 __ 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 THR doesn't go low enough
Don, That's a good explanation. Hopefully those folks will read it however many times it takes for them to understand that lowering the threshold is the opposite of what they want to do. I suspect that MANY of the complaints about the K3 being a noisy rig are due to similar misunderstandings of how AGC actually works. It appears that many folks think of AGC as being only gain reduction, and while that's probably true technically, it's probably much better to think of AGC as being gain equalization when you're trying to use it. For anyone still unclear about how the AGC in the K3 works, I also recommend that study Jack Smith's page on the subject. It's a great explanation with several very informative graphs, and not surprisingly it is the very first link that is displayed when you Google K3 AGC. The page doesn't appear to have been updated to include the newer SOFT AGC mode in the K3, but even so it is highly relevant. http://www.cliftonlaboratories.com/elecraft_k3_agc_and_s-meter.htm I do a lot of contesting so I don't even want all signals to sound the same, and I certainly don't want the distortion issues that can sometimes be caused by AGC attack/decay slopes in the presence of multiple in-band signals. Linearity is my friend, and AGC is by definition not linear over the range of interest. I have my AGC THR set to 008 and I have my AGC SLP set to 000. Jack's curves show that at even those settings, there is still some AGC action at low signals and protection at high signals. For example, his data shows that even with AGC SLP = 000 it takes a 10 db increase in signal strength to give a 4 db increase in audio level. That works fine for me ... 73, Dave AB7E On 10/8/2010 11:55 AM, Don Wilhelm wrote: I seem to have trouble convincing some to raise the threshold to combat the noisy effect. Please read all below carefully, and I believe I can offer some explanation. Let's study what the AGC SLP and AGC THR settings do and try to relate them to the perception that the K3 is noisy. IF -- the threshold is so low that the noise triggers the AGC (and that will be happening if the noise is causing the S-meter to have a reading with no signal) AND -- If the slope is set to a high value which makes all the signals have more or less the same audio volume, THEN -- The noise will appear at about the SAME audio volume as the signals. RESULT -- A K3 that sounds noisy :-( ! It is a combination of both the threshold and the slope that create this condition. The cure for that situation is to increase the threshold and reduce the slope. How much? That is an individual decision, but I have mine set to the extremes of THR at 008 and SLP at 002. I really believe the defaults are OK for a band where the ambient noise level is lower, but certainly gives problems on a band that is inherently noisy. Please make your evaluation while listening to signals and the breaks between signals - if you are hearing only noise, you will naturally turn the AF Gain up, and yes the noise will increase - not only that, with only noise, the perception is that one should use a lower threshold setting. That is because as you lower the threshold, the AGC response to the noise gets stronger, and the audio level is reduced by the AGC - what you are perceiving is exactly the opposite of what you wish to achieve. In addition, turn the attenuator on and the preamp off - again, if you hear an increase in the band noise when the antenna is connected, you have all the sensitivity that you can use for that band and antenna. The K3 remembers those settings by band, so you don't have to make changes as you switch bands. 73, Don W3FPR __ 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 THR doesn't go low enough
John Chappell G3XRJ wrote: Don, What I should have mentioned in my initial post was that the recording was made at midday on 80m and the noise from the antenna was only s1. For a given setting of the rf gain, increasing the threshold to 8 increases the noise, as can be heard in the recording. It doesn't increase the noise, it just makes it sound louder. You need to turn down the AF gain to restore the noise to its original level. Or tune in a signal and adjust it to the same level as before, you should find you need less AF gain and the noise when the signal isn't present will be quieter. As Don stated you probably have too much front end gain because the reason increasing the threshold makes the noise louder is because the noise is strong enough to activate the AGC when the threshold is set low. Any receiver will sound noisy if you use preamplification when you don't need it. The important difference is that increasing the threshold and decreasing the slope increases the volume of signals relative to the noise and makes strong signals sound louder than weak ones. It's hard to explain and the adjustments are not very intuitive but a few months ago I tried different settings using my XG1 to generate 50uV and 1uV signals and observed the audio output on a scope, then it became clear what was happening and how the adjustments affected things. - Julian, G4ILO. K2 #392 K3 #222. * G4ILO's Shack - http://www.g4ilo.com * KComm - http://www.g4ilo.com/kcomm.html * KTune - http://www.g4ilo.com/ktune.html -- View this message in context: http://elecraft.365791.n2.nabble.com/K3-AGC-THR-doesn-t-go-low-enough-tp5614723p5616667.html Sent from the [K3] 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: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 THR doesn't go low enough
In an effort to help those who perceive their K3 as noisy, and for those who are not certain their AGC slope and threshold settings are not right for their operation, I have added a page to my website. Go to www.w3fpr.com and click on the link in the left column referring to K3 noise and AGC settings. It is an expansion of the post I offered earlier today dealing with AGC settings and their relationship to K3 noise. 73, Don W3FPR __ 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
