Re: [Elecraft] An AGC Story
Bob, Yes I did see your post thanks, but have not yet had the opportunity to digest your results - but I will. When you made these measurements, what settings did you use for the 'audio' Hi-cut and Lo-cut? My thinking was that I would first look at the SA612's output wile injecting multiple signals, and then do the same at suitable points along the signal path as it made its way to the audio output. By doing this it should be possible to find the weakest link in the chain (in terms of IMD), and then attempt to do something to improve the 'weak link's' performance. May I take this opportunity to stress that my comments were not intended to be any kind of criticism of the K3. 73, Geoff GM4ESD . Bob Henderson b...@5b4agn.net wrote on Sunday, December 12, 2010 4:11 AM: snip I made within DSP b/w IMD measurements on my K3 and comparable measurements on my K2. These were included in a post dated 5 December but you may have missed it. The following measurements relate to K3 S/N 4904 on 7MHz with 2.7kHz roofing filter and 2.7kHz DSP b/w. Default slow AGC was selected. The table shows input level at the K3 antenna connector for each of two carriers spaced 500Hz. At each input level, the level of the strongest IMD product observed at the AF output using an HP8568B is recorded alongside. snip __ 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] An AGC Story
Guy, have one (or several) on me for suggesting such a sensible idea :-) 73, Geoff GM4ESD Guy Olinger K2AV On Sunday, December 12, 2010, at 10:04 AM, Guy Olinger K2AV wrote: Thank you, Bob. But you have robbed Geoff of his favorite whipping boy. We will have to take Geoff out to a pub and help him drown his sorrows. What was your setup? 73, Guy __ 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] An AGC Story
Speaking of criticism, I've done my share of complaining about AGC pumping and pileup mush in the K3. That said, it's still the best contest receiver I've ever use, by a wide margin. It's sensitive, quiet and incredibly selective. In fact, I can get *too* close to adjacent stations without realizing it! In actual contest conditions, the AGC pumping can be reduced to more-or-less acceptable levels by using the 8-pole 400 Hz filter. It becomes a non-problem with the 5-pole 200 Hz filter. I suspect it could be reduced even more by increasing the HAGC threshhold, but evidently not without changing other components in the chain to avoid increased IMD. IMHO, the pileup mush is no worse than any other receiver I've used, and most of the time it's better (that sounds strange, but you know what I mean.) Considering that I had quite a few hours with my rate meter near 200/hr in CQ WW CW, I'd have to say the mush isn't reducing my rate a whole lot. One clue is that the mush effect is most noticable when there's a pileup of relatively weak signals and there's not a nearby strong station -- i.e., when the HAGC is not activated. If most of the signals are at the same pitch, it's mush. A bunch of really weak signals like that are simply darned hard to copy, and I'm beginning to think that no receiver can separate them unless AGC is turned off, with the attendant problem of ears being blown out when a strong station drops by. I have found, however, that the situation improves considerably with diversity reception using two antennas with opposite polarity. There's enough difference in the ever-changing arrival angles to be able to distinguish weak signals at the same pitch. No other receiver can do that for me. 73, Dick WC1M -Original Message- From: Geoffrey Mackenzie-Kennedy [mailto:gm4...@btinternet.com] Sent: Sunday, December 12, 2010 6:30 AM To: Bob Henderson Cc: Elecraft Discussion List Subject: Re: [Elecraft] An AGC Story Bob, Yes I did see your post thanks, but have not yet had the opportunity to digest your results - but I will. When you made these measurements, what settings did you use for the 'audio' Hi-cut and Lo-cut? My thinking was that I would first look at the SA612's output wile injecting multiple signals, and then do the same at suitable points along the signal path as it made its way to the audio output. By doing this it should be possible to find the weakest link in the chain (in terms of IMD), and then attempt to do something to improve the 'weak link's' performance. May I take this opportunity to stress that my comments were not intended to be any kind of criticism of the K3. 73, Geoff GM4ESD . Bob Henderson b...@5b4agn.net wrote on Sunday, December 12, 2010 4:11 AM: snip I made within DSP b/w IMD measurements on my K3 and comparable measurements on my K2. These were included in a post dated 5 December but you may have missed it. The following measurements relate to K3 S/N 4904 on 7MHz with 2.7kHz roofing filter and 2.7kHz DSP b/w. Default slow AGC was selected. The table shows input level at the K3 antenna connector for each of two carriers spaced 500Hz. At each input level, the level of the strongest IMD product observed at the AF output using an HP8568B is recorded alongside. snip __ 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] An AGC story
Chen, It is not really my place to comment on this subject not having a K3 to measure, but I would like to offer the following thoughts related to the naughty things you mention. Whereas measuring the receiver's audio output level vs.the level of a single signal injected into the antenna input port will obviously provide some good information about the AGC's control characteristics, unfortunately this measurement does not provide any hard data as to whether or not intermodulation generated in the IF stages will become or is an issue when two or more strong signals get through the roofer in use. Given that the 1db compression point of a typical SA612 mixer is reached when the *composite* power of all signals reaching its input is approximately minus 25dbm, and given that positive gain exists between the antenna port and the SA612's input when both the Preamp and Attenuator are OFF, in the region of 6db I believe when a 400 Hz roofer is in place, then in the *absence* of any HAGC action the SA612 would enter compression when the *composite* power of all signals at the antenna port that eventually get through the roofer is only minus 31dbm. At this level *without* HAGC applied there would be, of course, a large number of of strong odd order intermod products appearing at the SA612's output should multiple signals get through the roofer. Now bring in the HAGC. Because part of the method used to control IF gain by the HAGC involves current starvation of the J309 IF amplifier, it is *possible* that with HAGC applied the Output Intercept (OIP3) of this amplifier might decrease, thereby increasing the level of IMD products generated by this amplifier. So, even though the HAGC might prevent the SA612 from approaching compression, much of the HAGC's protective work in terms of reducing unwanted IMD products *might* be undone by the J309 when it is starved of current. Please understand that this is pure speculation on my part. If I had a K3, before I changed the HAGC threshold my *first* measurement would be to look at the output of the SA612 mixer (with a spectrum analyser) while introducing two or more very close spaced signals into the antenna port, so that these signals do get through the roofer - as in a pileup. The objective, of course, would be to obtain an acceptably clean output from the mixer with non intrusive products over a wide range of antenna input levels. IMHO the higher the HAGC's threshold can be the better, provided that its control is tight enough when activated to protect all what follows. 73, Geoff GM4ESD Kok Chen wrote on Thursday, December 09, 2010, at 7:05 PM: We know that the S9+ signals have to be kept from saturating the A/D converter (or even kept in check so the large signal doesn't do naughty things to the IF amplifier and the SA612 second mixer -- I don't know which of these three is the wimpiest in the chain). So some AGC is neccessary. __ 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] An AGC story
Hi Geoff The noise power ratio test(NPR) might show more clearly any mixer IMD problems. The NPR test might also better characterize any roofing filter IMD as well. The noise power ratio test better characterizes dynamic receiver performance. The NPR test also does not require expensive low phase noise signal generators. 73 John --- On Sat, 12/11/10, Geoffrey Mackenzie-Kennedy gm4...@btinternet.com wrote: From: Geoffrey Mackenzie-Kennedy gm4...@btinternet.com Subject: Re: [Elecraft] An AGC story To: Kok Chen c...@mac.com Cc: Elecraft Discussion List elecraft@mailman.qth.net Date: Saturday, December 11, 2010, 5:26 AM Chen, It is not really my place to comment on this subject not having a K3 to measure, but I would like to offer the following thoughts related to the naughty things you mention. Whereas measuring the receiver's audio output level vs.the level of a single signal injected into the antenna input port will obviously provide some good information about the AGC's control characteristics, unfortunately this measurement does not provide any hard data as to whether or not intermodulation generated in the IF stages will become or is an issue when two or more strong signals get through the roofer in use. Given that the 1db compression point of a typical SA612 mixer is reached when the *composite* power of all signals reaching its input is approximately minus 25dbm, and given that positive gain exists between the antenna port and the SA612's input when both the Preamp and Attenuator are OFF, in the region of 6db I believe when a 400 Hz roofer is in place, then in the *absence* of any HAGC action the SA612 would enter compression when the *composite* power of all signals at the antenna port that eventually get through the roofer is only minus 31dbm. At this level *without* HAGC applied there would be, of course, a large number of of strong odd order intermod products appearing at the SA612's output should multiple signals get through the roofer. Now bring in the HAGC. Because part of the method used to control IF gain by the HAGC involves current starvation of the J309 IF amplifier, it is *possible* that with HAGC applied the Output Intercept (OIP3) of this amplifier might decrease, thereby increasing the level of IMD products generated by this amplifier. So, even though the HAGC might prevent the SA612 from approaching compression, much of the HAGC's protective work in terms of reducing unwanted IMD products *might* be undone by the J309 when it is starved of current. Please understand that this is pure speculation on my part. If I had a K3, before I changed the HAGC threshold my *first* measurement would be to look at the output of the SA612 mixer (with a spectrum analyser) while introducing two or more very close spaced signals into the antenna port, so that these signals do get through the roofer - as in a pileup. The objective, of course, would be to obtain an acceptably clean output from the mixer with non intrusive products over a wide range of antenna input levels. IMHO the higher the HAGC's threshold can be the better, provided that its control is tight enough when activated to protect all what follows. 73, Geoff GM4ESD Kok Chen wrote on Thursday, December 09, 2010, at 7:05 PM: We know that the S9+ signals have to be kept from saturating the A/D converter (or even kept in check so the large signal doesn't do naughty things to the IF amplifier and the SA612 second mixer -- I don't know which of these three is the wimpiest in the chain). So some AGC is neccessary. __ 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] An AGC story
Hi John, The NPR test is, I agree, certainly a very useful method to expose IMD problems, but I think that when used as a *diagnostic* tool the requirements placed on the notch filter's bandwidth limits this method's versatility - unless one is prepared to build a set of band reject filters (probably crystal) that may be required, whose IMD contribution is much less that that of the receiver, device or sub-system being tested. To obtain low phase noise from my IMD test arrangement I have been using low noise crystal oscillators followed by +40dbm output amplifiers, which is I admit a cumbersome approach, but it did provide useful results until I damaged the equipment while measuring the IMD generated by some types of RF transformer - a sad story! If Santa gave me a K3 I could stop speculating about its multi signal performance :-) 73, Geoff GM4ESD juergen plebia...@yahoo.com wrote on Saturday, December 11, 2010, at 6:18 PM: Hi Geoff The noise power ratio test(NPR) might show more clearly any mixer IMD problems. The NPR test might also better characterize any roofing filter IMD as well. The noise power ratio test better characterizes dynamic receiver performance. The NPR test also does not require expensive low phase noise signal generators. 73 John __ 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] An AGC Story
Bottom posted for context. Geoff GM4ESD wrote If I had a K3, before I changed the HAGC threshold my *first* measurement would be to look at the output of the SA612 mixer (with a spectrum analyser) while introducing two or more very close spaced signals into the antenna port, so that these signals do get through the roofer - as in a pileup. The objective, of course, would be to obtain an acceptably clean output from the mixer with non intrusive products over a wide range of input levels. IMHO the higher the HAGC's threshold can be the better, provided its control is tight enough when activated to protect all what follows. I made within DSP b/w IMD measurements on my K3 and comparable measurements on my K2. These were included in a post dated 5 December but you may have missed it. The following measurements relate to K3 S/N 4904 on 7MHz with 2.7kHz roofing filter and 2.7kHz DSP b/w. Default slow AGC was selected. The table shows input level at the K3 antenna connector for each of two carriers spaced 500Hz. At each input level, the level of the strongest IMD product observed at the AF output using an HP8568B is recorded alongside. -73dBm Better than -55dBc (Input S9) -63dBm -55dBc -53dBm -50dBc -42dBm -45dBc -33dBm -42dBc -23dBm -37dBc (Input S9+50) These figures are good and IMHO entirely acceptable. Some older transceivers would struggle to provide -35dBc at S9. I made a similar set of measurements with my old K2 S/N 997 -73dBm -50dBc -63dBm -48dBc -53dBm -45dBc -43dBm -48dBc -33dBm -45dBc -23dBm -15dBc Broadly speaking the K3 is as good or better than the K2, which is itself good. It is possible later mods to the K2 may have made it even better. The most recent mods to my K2 were carried out over 5 years ago. 73 Bob, 5B4AGN __ 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] An AGC story
David Gilbert wrote: Nice program, but it doesn't run with LP-Bridge if I want to have more than one application (N1MM, CW Skimmer, K3_EZ, etc) interfacing with my K3. It is fine for simplifying the changing of AGC settings, but not on the fly during a contest. I strongly agree. There's a great need for some simple utilities for the K3 that will run with LP-Bridge or other CAT port sharing schemes: AGC/EQ management, expanded rig display, subrx control (avoid BSET), etc Barry N1EU -- View this message in context: http://elecraft.365791.n2.nabble.com/An-AGC-story-tp5817486p5822793.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] An AGC story
I have been talking with Dick Dievendorf about changes to the K3 Utility and LP-Bridge to allow most of the utility functionality to work (not including firmware revisions, however). This should benefit other utilities as well. The problem is finding time for changes and testing. Larry N8LP On 12/10/2010 12:00 PM, elecraft-requ...@mailman.qth.net wrote: Date: Fri, 10 Dec 2010 03:39:04 -0800 (PST) From: Barry N1EUbarry.n...@gmail.com Subject: Re: [Elecraft] An AGC story To:elecraft@mailman.qth.net Message-ID:1291981144656-5822793.p...@n2.nabble.com Content-Type: text/plain; charset=us-ascii David Gilbert wrote: Nice program, but it doesn't run with LP-Bridge if I want to have more than one application (N1MM, CW Skimmer, K3_EZ, etc) interfacing with my K3. It is fine for simplifying the changing of AGC settings, but not on the fly during a contest. I strongly agree. There's a great need for some simple utilities for the K3 that will run with LP-Bridge or other CAT port sharing schemes: AGC/EQ management, expanded rig display, subrx control (avoid BSET), etc Barry N1EU __ 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] An AGC story
Fred, For more on the K3 AGC system, please see the excellent study by Jack Smith, K8OZA at: http://cliftonlaboratories.com/elecraft_k3_agc_and_s-meter.htm Careful study of Jack's tables would tend to support your belief that the K3 could benefit from a higher threshold setting. Comparing the behavior of the K2 to that of the K3 as shown in Jack's charts, shows support for a threshold of some 20 dB higher than the present -100 dBm (~S4) that K8OZA measured for THR=8. That would place the threshold around S8 (-79 dBm) similar to that shown by the K2. 73, ... Joe, W4TV On 12/8/2010 8:01 PM, Cady, Fred wrote: After Team Vertical got back from our latest adventure in C6land, I was curious about how the AGC was working (or not). Kenny, C6ATA came away from the event really preferring his venerable TS850. Both Walt, C6ATR and I, C6AKX found turning AGC off was a way to increase the depth of the pileup and continue to rapidly pull signals out. I made some measurements and have posted the results for your perusal and information at www.ke7x.com. 73, Fred Ke7x __ 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] An AGC story
Very interested findings - Fred has a graph of AGC action with AGC THR=8 labeled figure 3 on http://www.ke7x.com/home/the-k3-agc-story : That graph is nearly identical to the information that Jack Smith, K8OZA originally presented two years ago: http://cliftonlaboratories.com/elecraft_k3_agc_and_s-meter.htm The following table comes from Jack's work: From the data, my estimate of the threshold settings is: AGC THRCorresponding Input Signal Level 2 -117 dBm 3 -110.5 dBm 4 -105 dBm 5 -103.5 dBm 6 -102.5 dBm 7 -101 dBm 8 -99 dBm The K2 AGC curve is also presented for comparison. K2 does not have a well defined threshold like that of the K3 but some AGC action (the curve departs from 1:1) begins at around -85 dBm and settles at slope similar to the K3 SLP=09 or SLP=10 (about 1.5 dB audio change for 10 dB RF change) at an RF level around -70 dBm. As a second point of comparison, Sherwood's Receiver Performance Table shows the FT-1000D has an AGC threshold nearly 10 dB higher than the K3 *with the FT-1000D preamplifier enabled*. Since the FT-1000D preamp is at least 10 dB, that represents an overall 20 dB higher ACG threshold (around S8/S9 with preamp off and S6/S7 with preamp on). It seems clear that the K3 would have much better pile-up performance if range of AGC THR were expanded by as much as 20 dB either by increasing the step (5/6 differ by only 1 dB) or by increasing the number of options. 73, ... Joe, W4TV On 12/9/2010 9:07 AM, Barry N1EU wrote: Cady, Fred wrote: I made some measurements and have posted the results for your perusal and information at www.ke7x.com. Very interested findings - Fred has a graph of AGC action with AGC THR=8 labeled figure 3 on http://www.ke7x.com/home/the-k3-agc-story : So I ask this group: is it possible to raise the AGC Threshold from s3 to s6 or s9 by simply reducing the RF Gain control? Can anybody estimate what settings of the RF Gain control would accomplish that? Barry N1EU __ 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] An AGC story
Chen, Imagine that there are three parameters, the current two, plus a upper threshold, after which the slope becomes 15 (i.e. flat at S0 to THR, then constant SLOPE until upper threshold and then flat from there until the front end starts to smoke),. The AGC is already a three piece curve. Below the AGC threshold (-117 to -99 dBm depending on THR) the audio:RF response is 1:1. Above the threshold the audio:RF ratio varies between 0.4 dB/dB to 0.05 dB/dB (according to K8OZA's measurements) until the HAGC activates between -43 and -48 dBm at which time the output becomes flat (no further increase). What this discussion appears to be asking for is the option to raise the level of first inflection point (AGC threshold) from approximately -99 dBm with THR=08 to somewhere in the mid -70 dBm range without using the attenuator and losing the weak signals. That is, nobody wants to give up the ability to receive a -128 dBm signal by using a 10 or 20 dB of attenuation when the receiver is easily capable of detecting a -130 dBm signal without use of a preamplifier but they do want reasonable level cues to use in separating signals close to the same frequency. What is needed is to broaden out the steps in THR from as little as 1 dB per step to something like a uniform 6 dB per step or adding more steps (e.g., 16 choices at 3 dB/step so that the threshold can be set over a -117 to -70 dBm range rather than the current limited -117 to -99 dBm range (K8OZA measurements). Since HAGC does not activate until the RF input reaches -48 to -43 dBm, one must assume that the IF amplifier, 2nd Mixer and ADC are capable of functioning properly well beyond the levels generated at -70 dBm input and raising the threshold even if it means using a flatter slope would not cause serious performance issues. 73, ... Joe, W4TV On 12/9/2010 2:05 PM, Kok Chen wrote: On Dec 9, 2010, at 12/99:17 AM, k...@aol.com wrote: But, since AGC works on every signal in the passband, if there are two signals - one S9 and the other S3 appearing at the same time, the S3 signal will disappear because the AGC is knocking down the S9 signal to an S3 level and thereby also reducing the S3 signal to the noise. My impression from reading what has transpired is that some people are more concerned that when the S9 signal is *not* there, that the S3 appears to be too loud? We know that the S9+ signals have to be kept from saturating the A/D converter (or even kept in check so the large signal doesn't do naughty things to the IF amplifier and the SA612 second mixer -- I don't know which of these three is the wimpiest in the chain). So some AGC is neccessary. Perhaps people will be happier if the AGC response is not as linear (in the log-log scale) as the one in the K3 once you have past the AGC threshold. I.e., perhaps people would care less if an S7 signal sound as loud as an S9 signal, but they do want the S3 signal to sound less loud as the S7 signal. A non-linear transfer function like that is certainly easy to implement (as long as I don't have to be the one to implement it :-), but will this make more people happy? Who knows? Basically, this is what I am simple-mindedly visualizing: currently, there are only two parameters to control a piecewise linear curve. Imagine that there are three parameters, the current two, plus a upper threshold, after which the slope becomes 15 (i.e. flat at S0 to THR, then constant SLOPE until upper threshold and then flat from there until the front end starts to smoke),. You then smooth out the piecewise linear curve using a pair of homotopy between those three partitions. You will end up with (1) a smooth curve instead of the piecewise linear one currently, and (2) a way to say I care more about distinguishing an S3 from an S9 signal than I do an S7 and S9 signal. Notice that if a simple homotopy is applied to smooth the AGC transfer function, and even if upper threshold is set to S7, you will still hear a difference between S7 and S9 -- just much less than between S3 and S9. Also, if the AGC curve is no longer piecewise linear you will still hear the S3 signal even if the lower threshold is set to an S3. I still think the only way to satisfy everybody is if everyone would homebrew their own rig, or sell an open commercial rig where you are allowed to make any mods -- hardware, firmware, or software. See first option :-) :-). 73 Chen, W7AY __ 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:
Re: [Elecraft] An AGC story
Cady, Fred wrote: I made some measurements and have posted the results for your perusal and information at www.ke7x.com. Very interested findings - Fred has a graph of AGC action with AGC THR=8 labeled figure 3 on http://www.ke7x.com/home/the-k3-agc-story : So I ask this group: is it possible to raise the AGC Threshold from s3 to s6 or s9 by simply reducing the RF Gain control? Can anybody estimate what settings of the RF Gain control would accomplish that? Barry N1EU -- View this message in context: http://elecraft.365791.n2.nabble.com/An-AGC-story-tp5817486p5818820.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] An AGC story
Barry, Without doing any measurements it may be difficult to say precisely, and I would think there would be a bit of difference from one K3 to another. However, there is a quick and easy way to accomplish that - note that the S-meter increases as the RF gain is reduced. So if you want to increase the AGC Threshold by (say) 3 S-units, disconnect the antenna, and reduce the RF Gain until you move the no-signal S-meter up by 3 S-units. That should be close to your goal. 73, Don W3FPR On 12/9/2010 9:07 AM, Barry N1EU wrote: Cady, Fred wrote: I made some measurements and have posted the results for your perusal and information at www.ke7x.com. Very interested findings - Fred has a graph of AGC action with AGC THR=8 labeled figure 3 on http://www.ke7x.com/home/the-k3-agc-story : So I ask this group: is it possible to raise the AGC Threshold from s3 to s6 or s9 by simply reducing the RF Gain control? Can anybody estimate what settings of the RF Gain control would accomplish that? Barry N1EU __ 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] An AGC story
Thanks Don. I just realized that I can do some quick experiments to get my answer using an XG2's s3/s9 capability and noting audio level increase with AGC Off and then with AGC On and reducing RF Gain until same audio increase is accomplished. An aside to KE7X and W4TV: I too wish we could try experimental firmware that significantly raised the max AGC THR value. And to K6LL: Yes, I too fear loss of weaker signals 73, Barry N1EU On Thu, Dec 9, 2010 at 3:00 PM, Don Wilhelm w3...@embarqmail.com wrote: Barry, Without doing any measurements it may be difficult to say precisely, and I would think there would be a bit of difference from one K3 to another. However, there is a quick and easy way to accomplish that - note that the S-meter increases as the RF gain is reduced. So if you want to increase the AGC Threshold by (say) 3 S-units, disconnect the antenna, and reduce the RF Gain until you move the no-signal S-meter up by 3 S-units. That should be close to your goal. 73, Don W3FPR On 12/9/2010 9:07 AM, Barry N1EU wrote: Cady, Fred wrote: I made some measurements and have posted the results for your perusal and information at www.ke7x.com. Very interested findings - Fred has a graph of AGC action with AGC THR=8 labeled figure 3 on http://www.ke7x.com/home/the-k3-agc-story : So I ask this group: is it possible to raise the AGC Threshold from s3 to s6 or s9 by simply reducing the RF Gain control? Can anybody estimate what settings of the RF Gain control would accomplish that? Barry N1EU __ 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] An AGC story
Thanks Barry for the suggestion to run some curves while changing the RF gain position. I've done that and I'm not sure I understand what is going on yet. Need to think about it a bit. I'll post the curves up on ke7x.com in a while. Fred Fred Cady fcady at ieee dot org -Original Message- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Barry N1EU Sent: Thursday, December 09, 2010 8:11 AM To: elecraft@mailman.qth.net Subject: Re: [Elecraft] An AGC story Thanks Don. I just realized that I can do some quick experiments to get my answer using an XG2's s3/s9 capability and noting audio level increase with AGC Off and then with AGC On and reducing RF Gain until same audio increase is accomplished. An aside to KE7X and W4TV: I too wish we could try experimental firmware that significantly raised the max AGC THR value. And to K6LL: Yes, I too fear loss of weaker signals 73, Barry N1EU On Thu, Dec 9, 2010 at 3:00 PM, Don Wilhelm w3...@embarqmail.com wrote: Barry, Without doing any measurements it may be difficult to say precisely, and I would think there would be a bit of difference from one K3 to another. However, there is a quick and easy way to accomplish that - note that the S-meter increases as the RF gain is reduced. So if you want to increase the AGC Threshold by (say) 3 S-units, disconnect the antenna, and reduce the RF Gain until you move the no-signal S-meter up by 3 S-units. That should be close to your goal. 73, Don W3FPR On 12/9/2010 9:07 AM, Barry N1EU wrote: Cady, Fred wrote: I made some measurements and have posted the results for your perusal and information at www.ke7x.com. Very interested findings - Fred has a graph of AGC action with AGC THR=8 labeled figure 3 on http://www.ke7x.com/home/the-k3-agc-story : So I ask this group: is it possible to raise the AGC Threshold from s3 to s6 or s9 by simply reducing the RF Gain control? Can anybody estimate what settings of the RF Gain control would accomplish that? Barry N1EU __ 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] An AGC story
As I understand the graphs and operation: AGC Threshold is the point at which AGC action starts. The higher the AGC THR number, the higher point at which AGC starts. The highest AGC THR (8) starts AGC action at S3. That is a pretty low level but any setting less than THR 8 starts the AGC action with even less signal. AGC SLP is how aggressive the AGC action is as signals rise. A highest AGC SLP number means the AGC flattens everyone. AT SLP = 15 all signals above S3 are brought to roughly the same level. Heard one at a time, two signals - one at S3 and one at S9 will sound the same level. But, since AGC works on every signal in the passband, if there are two signals - one S9 and the other S3 appearing at the same time, the S3 signal will disappear because the AGC is knocking down the S9 signal to an S3 level and thereby also reducing the S3 signal to the noise. Using a less aggressive (lower) slope number will help but the dynamic range between and S3 and S9 signal is compressed. The core problem is the AGC starts at such a low level. Background noise alone on 80 - 40 is almost always more than S3. The suggestion is an AGC THR setting to allow higher than an S3 level before AGC action starts. That makes sense but does it start to degrade the high-end dynamic range of the radio? Are we in danger of overloading the intermediate amplifiers/mixers generating IMD and other unwanted issues? Seems like there is a balancing act here. Another way to accomplish this is to use the Attenuator and/or reduce the RF gain to reset our starting point so that the S5 signal at the antenna becomes an S3 signal at the AGC level and our AGC action doesn't really begin until S5. I would like the ability to switch in even more attenuation for high noise conditions. Can that be done through the software? Still I would like to try a higher AGC THR setting and see how it plays. The beauty of this radio is its ability to adjust to different conditions - one size does not fit all. Unfortunately, its also complicated. It has taken me three years to figure this little bit out. Comments? Do I understand it right? Buck k4ia K3 #101 In a message dated 12/9/2010 10:11:19 A.M. Eastern Standard Time, barry.n...@gmail.com writes: Thanks Don. I just realized that I can do some quick experiments to get my answer using an XG2's s3/s9 capability and noting audio level increase with AGC Off and then with AGC On and reducing RF Gain until same audio increase is accomplished. An aside to KE7X and W4TV: I too wish we could try experimental firmware that significantly raised the max AGC THR value. And to K6LL: Yes, I too fear loss of weaker signals 73, Barry N1EU On Thu, Dec 9, 2010 at 3:00 PM, Don Wilhelm w3...@embarqmail.com wrote: Barry, Without doing any measurements it may be difficult to say precisely, and I would think there would be a bit of difference from one K3 to another. However, there is a quick and easy way to accomplish that - note that the S-meter increases as the RF gain is reduced. So if you want to increase the AGC Threshold by (say) 3 S-units, disconnect the antenna, and reduce the RF Gain until you move the no-signal S-meter up by 3 S-units. That should be close to your goal. 73, Don W3FPR On 12/9/2010 9:07 AM, Barry N1EU wrote: Cady, Fred wrote: I made some measurements and have posted the results for your perusal and information at www.ke7x.com. Very interested findings - Fred has a graph of AGC action with AGC THR=8 labeled figure 3 on http://www.ke7x.com/home/the-k3-agc-story : So I ask this group: is it possible to raise the AGC Threshold from s3 to s6 or s9 by simply reducing the RF Gain control? Can anybody estimate what settings of the RF Gain control would accomplish that? Barry N1EU __ __ 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] An AGC story
On Dec 9, 2010, at 12/99:17 AM, k...@aol.com wrote: But, since AGC works on every signal in the passband, if there are two signals - one S9 and the other S3 appearing at the same time, the S3 signal will disappear because the AGC is knocking down the S9 signal to an S3 level and thereby also reducing the S3 signal to the noise. My impression from reading what has transpired is that some people are more concerned that when the S9 signal is *not* there, that the S3 appears to be too loud? We know that the S9+ signals have to be kept from saturating the A/D converter (or even kept in check so the large signal doesn't do naughty things to the IF amplifier and the SA612 second mixer -- I don't know which of these three is the wimpiest in the chain). So some AGC is neccessary. Perhaps people will be happier if the AGC response is not as linear (in the log-log scale) as the one in the K3 once you have past the AGC threshold. I.e., perhaps people would care less if an S7 signal sound as loud as an S9 signal, but they do want the S3 signal to sound less loud as the S7 signal. A non-linear transfer function like that is certainly easy to implement (as long as I don't have to be the one to implement it :-), but will this make more people happy? Who knows? Basically, this is what I am simple-mindedly visualizing: currently, there are only two parameters to control a piecewise linear curve. Imagine that there are three parameters, the current two, plus a upper threshold, after which the slope becomes 15 (i.e. flat at S0 to THR, then constant SLOPE until upper threshold and then flat from there until the front end starts to smoke),. You then smooth out the piecewise linear curve using a pair of homotopy between those three partitions. You will end up with (1) a smooth curve instead of the piecewise linear one currently, and (2) a way to say I care more about distinguishing an S3 from an S9 signal than I do an S7 and S9 signal. Notice that if a simple homotopy is applied to smooth the AGC transfer function, and even if upper threshold is set to S7, you will still hear a difference between S7 and S9 -- just much less than between S3 and S9. Also, if the AGC curve is no longer piecewise linear you will still hear the S3 signal even if the lower threshold is set to an S3. I still think the only way to satisfy everybody is if everyone would homebrew their own rig, or sell an open commercial rig where you are allowed to make any mods -- hardware, firmware, or software. See first option :-) :-). 73 Chen, W7AY __ 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] An AGC story
I have no doubt that AGC adjustments are largely a matter of personal preference, and I congratulate Elecraft on making the K3 as adjustable as it is without overwhelming us with so many variations that we'd go crazy trying to figure it out. As an example of individual adjustments, I used the K3 as my run radio in CQWW CW from P49Y in 2009. Because I wanted help thinning out the pileup, I found that setting the SLP to 1, but leaving the AGC on worked well, and allowed me to ride the RF gain control to help distinguish signals while still offering some AGC protection against very strong signals. OTOH, in this years CQWW CW, where I was just doing some SP DXing from my home station, I set the SLP to 6, to allow me to turn the gain up higher to detect weak signals while still having protection against very strong ones. Using SLP 1 in that scenario with the RF gain all the way up was just too close to not having AGC at all. So I encourage everyone to experiment within the existing framework. 73, Andy ae6y - Original Message - From: Kok Chen c...@mac.com To: Elecraft Reflector elecraft@mailman.qth.net Cc: k...@aol.com Sent: Thursday, December 09, 2010 11:05 AM Subject: Re: [Elecraft] An AGC story On Dec 9, 2010, at 12/99:17 AM, k...@aol.com wrote: But, since AGC works on every signal in the passband, if there are two signals - one S9 and the other S3 appearing at the same time, the S3 signal will disappear because the AGC is knocking down the S9 signal to an S3 level and thereby also reducing the S3 signal to the noise. My impression from reading what has transpired is that some people are more concerned that when the S9 signal is *not* there, that the S3 appears to be too loud? We know that the S9+ signals have to be kept from saturating the A/D converter (or even kept in check so the large signal doesn't do naughty things to the IF amplifier and the SA612 second mixer -- I don't know which of these three is the wimpiest in the chain). So some AGC is neccessary. Perhaps people will be happier if the AGC response is not as linear (in the log-log scale) as the one in the K3 once you have past the AGC threshold. I.e., perhaps people would care less if an S7 signal sound as loud as an S9 signal, but they do want the S3 signal to sound less loud as the S7 signal. A non-linear transfer function like that is certainly easy to implement (as long as I don't have to be the one to implement it :-), but will this make more people happy? Who knows? Basically, this is what I am simple-mindedly visualizing: currently, there are only two parameters to control a piecewise linear curve. Imagine that there are three parameters, the current two, plus a upper threshold, after which the slope becomes 15 (i.e. flat at S0 to THR, then constant SLOPE until upper threshold and then flat from there until the front end starts to smoke),. You then smooth out the piecewise linear curve using a pair of homotopy between those three partitions. You will end up with (1) a smooth curve instead of the piecewise linear one currently, and (2) a way to say I care more about distinguishing an S3 from an S9 signal than I do an S7 and S9 signal. Notice that if a simple homotopy is applied to smooth the AGC transfer function, and even if upper threshold is set to S7, you will still hear a difference between S7 and S9 -- just much less than between S3 and S9. Also, if the AGC curve is no longer piecewise linear you will still hear the S3 signal even if the lower threshold is set to an S3. I still think the only way to satisfy everybody is if everyone would homebrew their own rig, or sell an open commercial rig where you are allowed to make any mods -- hardware, firmware, or software. See first option :-) :-). 73 Chen, W7AY __ 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] An AGC story
That is why it would be highly desirable to be able to quickly change AGC settings on the fly, especially when you consider the additional effect that different band noise has on the optimum AGC profile. I can understand Elecraft's reluctance to let users mess with the DSP code via macros, but I don't understand why it should not be possible to use macros to select from a few different AGC settings that have been preset using the CONFIG menu. It doesn't seem rational to me to build all that versatility into the AGC system so that it can be tailored to deal with all sorts of operating conditions ... different levels and types of band noise, different degrees of QRM, different levels of signal strengths, etc ... and then force you to choose only one setting for everything, especially during a contest. 73, Dave AB7E On 12/9/2010 12:20 PM, Andrew Faber wrote: I have no doubt that AGC adjustments are largely a matter of personal preference, and I congratulate Elecraft on making the K3 as adjustable as it is without overwhelming us with so many variations that we'd go crazy trying to figure it out. As an example of individual adjustments, I used the K3 as my run radio in CQWW CW from P49Y in 2009. Because I wanted help thinning out the pileup, I found that setting the SLP to 1, but leaving the AGC on worked well, and allowed me to ride the RF gain control to help distinguish signals while still offering some AGC protection against very strong signals. OTOH, in this years CQWW CW, where I was just doing some SP DXing from my home station, I set the SLP to 6, to allow me to turn the gain up higher to detect weak signals while still having protection against very strong ones. Using SLP 1 in that scenario with the RF gain all the way up was just too close to not having AGC at all. So I encourage everyone to experiment within the existing framework. 73, Andy ae6y __ 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] An AGC story
Dave, You can *effectively* increase the AGC threshold by 10 dB very quickly - just turn on the attenuator. Actually, that is more effective than reducing the RF Gain because it happens at the receiver input rather than at the IF. Yes, you can turn the attenuator of the K3 on whether or not the Preamp is on. And, if you have the S-meter set for abs (absolute) mode, it will not change with the attenuator or preamp. If you have signals high enough to produce greater than an S-3 level, you will still hear them when you turn the attenuator on, and the dynamic range of the K3 is retained. 73, Don W3FPR On 12/9/2010 3:02 PM, David Gilbert wrote: That is why it would be highly desirable to be able to quickly change AGC settings on the fly, especially when you consider the additional effect that different band noise has on the optimum AGC profile. I can understand Elecraft's reluctance to let users mess with the DSP code via macros, but I don't understand why it should not be possible to use macros to select from a few different AGC settings that have been preset using the CONFIG menu. It doesn't seem rational to me to build all that versatility into the AGC system so that it can be tailored to deal with all sorts of operating conditions ... different levels and types of band noise, different degrees of QRM, different levels of signal strengths, etc ... and then force you to choose only one setting for everything, especially during a contest. __ 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] An AGC story
This is exactly what I found useful during the CQ WW CW contest. I did some 500+ QSOs and found that it is easier to listen to the K3 with the Attenuator on in the 20 m band. In this band this is something I rarely do with the K2. This discussion on AGC threshold has perhaps told me the reason why this is so. Don Wilhelm-4 wrote: You can *effectively* increase the AGC threshold by 10 dB very quickly - just turn on the attenuator. - Sverre, LA3ZA K2 #2198, K3 #3391 http://www.qslnet.de/member/la3za/K2/mod.html LA3ZA Unofficial Guide to K2 modifications -- View this message in context: http://elecraft.365791.n2.nabble.com/An-AGC-story-tp5817486p5821194.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] An AGC story
OK, but that still doesn't address decay or slope ... parameters I might want to quickly change dependent upon the amount and type of band noise (such as when changing to the low bands or when thunderstorms are active) or the number (not only the level) of signals (pileup or QRM). I still say a few re-callable combinations of AGC settings would make sense, even if they had to be initially configured only through the CONFIG menu. 73, Dave AB7E On 12/9/2010 1:17 PM, Don Wilhelm wrote: Dave, You can *effectively* increase the AGC threshold by 10 dB very quickly - just turn on the attenuator. Actually, that is more effective than reducing the RF Gain because it happens at the receiver input rather than at the IF. Yes, you can turn the attenuator of the K3 on whether or not the Preamp is on. And, if you have the S-meter set for abs (absolute) mode, it will not change with the attenuator or preamp. If you have signals high enough to produce greater than an S-3 level, you will still hear them when you turn the attenuator on, and the dynamic range of the K3 is retained. 73, Don W3FPR On 12/9/2010 3:02 PM, David Gilbert wrote: That is why it would be highly desirable to be able to quickly change AGC settings on the fly, especially when you consider the additional effect that different band noise has on the optimum AGC profile. I can understand Elecraft's reluctance to let users mess with the DSP code via macros, but I don't understand why it should not be possible to use macros to select from a few different AGC settings that have been preset using the CONFIG menu. It doesn't seem rational to me to build all that versatility into the AGC system so that it can be tailored to deal with all sorts of operating conditions ... different levels and types of band noise, different degrees of QRM, different levels of signal strengths, etc ... and then force you to choose only one setting for everything, especially during a contest. __ 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] An AGC story
check out K3_EZ http://home.roadrunner.com/~n2bc/SW.htm then connect and check out the AGC Setup page GB 73 K5OAI Sam Morgan On 12/9/2010 8:49 PM, David Gilbert wrote: OK, but that still doesn't address decay or slope ... parameters I might want to quickly change dependent upon the amount and type of band noise (such as when changing to the low bands or when thunderstorms are active) or the number (not only the level) of signals (pileup or QRM). I still say a few re-callable combinations of AGC settings would make sense, even if they had to be initially configured only through the CONFIG menu. 73, Dave AB7E __ 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] An AGC story
Nice program, but it doesn't run with LP-Bridge if I want to have more than one application (N1MM, CW Skimmer, K3_EZ, etc) interfacing with my K3. It is fine for simplifying the changing of AGC settings, but not on the fly during a contest. Dave AB7E On 12/9/2010 8:18 PM, Sam Morgan wrote: check out K3_EZ http://home.roadrunner.com/~n2bc/SW.htm then connect and check out the AGC Setup page GB 73 K5OAI Sam Morgan On 12/9/2010 8:49 PM, David Gilbert wrote: OK, but that still doesn't address decay or slope ... parameters I might want to quickly change dependent upon the amount and type of band noise (such as when changing to the low bands or when thunderstorms are active) or the number (not only the level) of signals (pileup or QRM). I still say a few re-callable combinations of AGC settings would make sense, even if they had to be initially configured only through the CONFIG menu. 73, Dave AB7E __ 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] An AGC story
David Gilbert wrote: OK, but that still doesn't address decay or slope ... parameters I might want to quickly change dependent upon the amount and type of band noise (such as when changing to the low bands or when thunderstorms are active) or the number (not only the level) of signals (pileup or QRM). I still say a few re-callable combinations of AGC settings would make sense, even if they had to be initially configured only through the CONFIG menu. It might be more helpful to store the AGC threshold and slope per-band. The underlying problem is that many people will see a 30-40dB variation in antenna noise levels between 30MHz and 1.8MHz, and the K3 has only limited facilities to pre-set its front end gain (the one-step 10dB attenuator, the +12dB preamp and the manual IF gain control). After that, it's all down to the AGC. -- 73 from Ian GM3SEK http://www.ifwtech.co.uk/g3sek __ 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] An AGC story
After Team Vertical got back from our latest adventure in C6land, I was curious about how the AGC was working (or not). Kenny, C6ATA came away from the event really preferring his venerable TS850. Both Walt, C6ATR and I, C6AKX found turning AGC off was a way to increase the depth of the pileup and continue to rapidly pull signals out. I made some measurements and have posted the results for your perusal and information at www.ke7x.com. 73, Fred Ke7x __ 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
