Re: [Elecraft] K3 receiver desensing on CW during contest
N8LP wrote: ...Unless you live near a shortwave broadcast station, or have a high power ham nearby on the same band, you're not likely to need 130dB BDR anyway. Even in those cases, having 200dB BDR probably wouldn't help unless there is a LOT of improvement in transmitter spurious emissions, distortion and phase noise. This point is brought home all the time here in Albuquerque, where we have to deal with the radiation from ten or more TV/FM analog transmitters line-of-sight on top of Sandia Crest. While all these transmitters except Channel 2 have fundamentals well above 54 MHz (I run a DCI bandpass filter to keep it out of my preamp), the accumulated grunge from the transmitters' perfectly legal low-level spurious emissions and passive mixes are enough to render 6 meters unusable for weak-signal work in the direction of the mountaintop. Since the spurious gunk is actually radiated on hundreds of different frequencies within the 6-meter band -- not to mention the broad-band noise coming from the same mountaintop -- there is little filtering can do about it. Hopefully this will be alleviated to some degree when the last of the analog TV transmitters finally relocate to UHF digital come June (yes, they all elected to stay on the air past February 17th), but at least until then, there is little I can do about it except deploy longer and sharper yagis to minimize the unusable arc of the dead zone. Ergo, BDR isn't everything. It is still unfortunately necessary to take into account who your RF neighbors are. They may be operating perfectly legally on frequencies well outside your own area of interest, and still pollute the band with spurious RF that the FCC says is within acceptable limits for their class of operation. Bill W5WVO The highest signals I have seen here, during Field Day when there were several stations operating within a few miles of me, were 120dB above the noise floor. Of course, it's very important not to use any more front end gain than necessary for the band/conditions. 73, Larry N8LP Alan Bloom wrote: I agree this is something amateur equipment manufacturers like Elecraft should be keeping their eye on. If Analog Devices or someone came out with an under-$100 ADC with performance close to the K3, then you could save a lot of money and complexity by going to a directly-sampled RF front end architecture. But a lot of brilliant engineers have been working for many years trying to optimize ADC design. I just really have my doubts that they are going to make a 15-20 dB breakthrough any time soon. Al N1AL On Tue, 2009-02-24 at 09:55, Larry Phipps wrote: Not today... but give it a couple years. There is a lot of RD being poured into this by a number of competing chip manufacturers. Even if the next batch of designs falls a little short, an all digital design with BDR close to the best conventional designs would probably enjoy a very substantial market. 73, Larry N8LP Alan Bloom wrote: On Mon, 2009-02-23 at 18:40, N8LP wrote: ... I think the days of receivers with xtal filters are numbered. High speed ADCs capable of 140dB dynamic range without xtal filtering are on the horizon. A 20-bit ADC with enough processing gain would do it. I don't think you'll find a 20-bit ADC with a high enough sample rate to digitize the 3-30 MHz HF band (i.e. 65-70 MHz or so). At least not at a reasonable cost. I believe the best suitable, reasonable-cost ADCs available these days are able to achieve a 500-Hz blocking dynamic range in the low 120's dB, maybe 15-20 dB worse than the K3. That's significantly better than the previous generation of ADCs could achieve, and no doubt someday we'll get even better parts that are good enough to challenge the traditional superhet/crystal filter architecture. But I don't believe we're close to that level of performance today. Another issue, of course, is spurious responses. I'm pretty sure that current ADCs don't have good enough spurious-free dynamic range to challenge a state-of-the-art receiver like the K3. Al N1AL __ 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 receiver desensing on CW during contest
--- On Wed, 2/25/09, Bill W5WVO w5...@cybermesa.net wrote: This point is brought home all the time here in Albuquerque, where we have to deal with the radiation from ten or more TV/FM analog transmitters line-of-sight on top of Sandia Crest. While all these transmitters except Channel 2 have fundamentals well above 54 MHz (I run a DCI bandpass filter to keep it out of my preamp), the accumulated grunge from the transmitters' perfectly legal low-level spurious emissions and passive mixes are enough to render 6 meters unusable for weak-signal work in the direction of the mountaintop. Since the spurious gunk is actually radiated on hundreds of different frequencies within the 6-meter band -- not to mention the broad-band noise coming from the same mountaintop -- there is little filtering can do about it. Hopefully this will be alleviated to some degree when the last of the analog TV transmitters finally relocate to UHF digital come June ... [snip] I don't know how to break it to you but you're still going to have channels 7 and 13 after the transition. The alleged purpose of this transition was to free up spectrum that could be auctioned off. But a lot of broadcasters are going to wind up right back where they always were. Pity, as an over the air TV watcher, I was looking forward to needing only a UHF antenna, but n, I will still have to have a high band VHF antenna for local channel 9. Wes N7WS __ 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 receiver desensing on CW during contest
Although my contesting this past weekend was severely interrupted by a non-K3 related hardware failure, over the course of the contest I did use the K3 throughout all day and night segments on various bands. I did not call CQ except for a very little bit and the majority was SP on all bands except 10M which was for me, dead. There were the usual high powered stations crammed in tightly on all bands except for 15 where there were some spaces between CQs. I really put the K3 to the test with this one and made good use of the filtering and, considering the desensing thread have this observation to make: I noticed no desensing with the K3 in the presence of strong signals. I found that I was able to get rid of all but the most dead on of signals and those within those 50 Hz were not going to go away. Adjacent clicky signals were for the 99% of the time totally removed and for that 1% of the time the clicks remained, I was able to pull in the faintest signals. I know I must have P.O.ed more than a few people as I would scroll up the band and work a strong station and within 1Khz, work two others that were faint but clearly identifiable. Some of those faint ones, I had to call them for them to know I was hearing them. Thing is,as I'd tune up with fine tuning, I kept hearing station overlaying another and I had to be QRMing most of these other stations including the ones I just worked and the ones I would be working next. If the K3 has a liability, to me, it is not in any way related to desensing in the presence of strong signals. My old Omni V was a fine CW Rx but was nowhere as good as the K3 and I can say the same for my Corsair II which will be my backup rig for life. The K3 is stellar. Gary KA1J Any spelling ewrrors are the result of my laptop's keyboard... :) __ 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 receiver desensing on CW during contest
Agree, The K3 is stellar. Never any desensing in the presence of strong signals observed with my K3. I have found nothing that compares. 73 de KE4WY Jim -Original Message- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Gary Smith Sent: Wednesday, February 25, 2009 9:41 AM To: Elecraft@mailman.qth.net Subject: Re: [Elecraft] K3 receiver desensing on CW during contest Although my contesting this past weekend was severely interrupted by a non-K3 related hardware failure, over the course of the contest I did use the K3 throughout all day and night segments on various bands. I did not call CQ except for a very little bit and the majority was SP on all bands except 10M which was for me, dead. There were the usual high powered stations crammed in tightly on all bands except for 15 where there were some spaces between CQs. I really put the K3 to the test with this one and made good use of the filtering and, considering the desensing thread have this observation to make: I noticed no desensing with the K3 in the presence of strong signals. I found that I was able to get rid of all but the most dead on of signals and those within those 50 Hz were not going to go away. Adjacent clicky signals were for the 99% of the time totally removed and for that 1% of the time the clicks remained, I was able to pull in the faintest signals. I know I must have P.O.ed more than a few people as I would scroll up the band and work a strong station and within 1Khz, work two others that were faint but clearly identifiable. Some of those faint ones, I had to call them for them to know I was hearing them. Thing is,as I'd tune up with fine tuning, I kept hearing station overlaying another and I had to be QRMing most of these other stations including the ones I just worked and the ones I would be working next. If the K3 has a liability, to me, it is not in any way related to desensing in the presence of strong signals. My old Omni V was a fine CW Rx but was nowhere as good as the K3 and I can say the same for my Corsair II which will be my backup rig for life. The K3 is stellar. Gary KA1J Any spelling ewrrors are the result of my laptop's keyboard... :) __ 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 receiver desensing on CW during contest
Jim, Ditto here. #1129. AGC slope= 13, AGC THR =8. AGC set to fast. Never touched the RF gain control. I was totally amazed to be able copy weak ones under strong ones within the passband. Experienced none of the mushing reported here. However, when I first got the K3, I did manage to set the K3 AGC characteristics so that noise and all signals appeared to be at the same audio level. This made it difficult to separate signals. The rig sounded flat. 73 de Brian/K3KO Jim wrote: Agree, The K3 is stellar. Never any desensing in the presence of strong signals observed with my K3. I have found nothing that compares. 73 de KE4WY Jim __ 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 receiver desensing on CW during contest
KE4WY: Never any desensing in the presence of strong signals observed with my K3. KA1J: I noticed no desensing with the K3 in the presence of strong signals. I agree. 160 is the ultimate test for dynamic range (and desense or BDR) for any rig. Operating SOSB/160 I never experienced *any* desense this weekend in breaking the current USA record by 25%. If anyone experiences true desense (and some don't understand what that means), they don't have their K3 set up correctly. The simple way to do this on any band is to find the *minimum* gain combination which will result in hearing band noise when the antenna is connected (versus disconnected). On 160m, this usually means ATT ON and RF Gain backed off to 12-2 o'clock. For a Beverage only (not diversity), more gain may be necessary (i.e. ATT OFF but no PRE). For diversity, I like to balance the signal from my vertical TX array (about +5 dBi gain) with my Beverages (about -13 dBi gain following a splitter). In that case I use PRE for the Beverage side, but even on my Beverage port I never heard *any* desense this entire weekend. You can make the K3 desense by running with PRE ON and maximum RF Gain, but that's simply operator error and not the fault of the K3. 73, Bill -- View this message in context: http://n2.nabble.com/K3-receiver-desensing-on-CW-during-contest-tp2369819p2384234.html Sent from the Elecraft mailing list archive at Nabble.com. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto: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 receiver desensing on CW during contest
Those are impressive numbers, Eric. +5dBm would only be about 120dB above the background noise level on 40m here on a typical night, though. I am located in a relatively quiet area, but on the edge of suburban/rural. Of course, I don't have a Yagi currently, and I'm not on the East Coast or in Europe ;-) My comments were aimed at typical ham stations, not multi-multi contest stations. Even the best conventional receivers need help in that environment with external filters, tuned stubs, etc. I wasn't saying the front end should be wide open ;-) I would assume there would be bandpass filters for each band, and both high pass and low pass filters ahead of the ADC. I guess my point was that it seems like a reasonable compromise for most users to have 130dB BDR for all signals, as opposed to 140dB for signals outside the roofing filter, but only mid 90dB range for signals inside the roofing filter. I would like to see the variable BW xtal filters released, as that would improve the situation. It's all about compromises, and the K3 is as good as it gets in that regard, but so is the QS1R, which represents the state of the art in direct sampling DDC designs available to hams. Of course, I'm only talking receiver RF performance here, not the issue of knobs, buttons, QSK keying, etc. ;-) I would like to see how a QS1R with proper front end filters would perform in your environment. As an inveterate experimenter, I will be playing with the next generation of ADCs when they arrive. 73, Larry N8LP Eric Scace K3NA wrote: At the W1KM contesting site, we routinely see signals of +5 dBm or louder on/near 40m from SWBC stations (using a single Yagi). We also have two modest-power local AM stations (1 to 5 kW, a few miles away) just below 1500 kHz that show up even a bit stronger than that on our 160m antennas. Without taking into consideration signals from our own multi-multi transmitters, a receiver is already faced with 130 dB range between weak signals on 160m in mid-afternoon arriving from Europe and these other signal sources. WD3Q, a contester in Washington DC, has much stronger AM BC stations to deal with, including a 50 kW station on 1500 kHz. Wide-open receiver front ends attached to an A/D converter are not yet viable for these locations. -- Eric K3NA on 09 Feb 24 20:44 N8LP said the following: You may be right, Al. I think the improvements may be incremental, and distributed among various aspects of the design, not just the ADC. For instance, ultra-low jitter clock sources, faster FPGAs with improved IP cores, etc. I think most hams would be thrilled with an improvement to 130dB BDR, along with getting rid of phase distortion, ringing and other anomalies in the xtal filters and other analog components. Unless you live near a shortwave broadcast station, or have a high power ham nearby on the same band, you're not likely to need 130dB BDR anyway. Even in those cases, having 200dB BDR probably wouldn't help unless there is a LOT of improvement in transmitter spurious emissions, distortion and phase noise. The highest signals I have seen here, during Field Day when there were several stations operating within a few miles of me, were 120dB above the noise floor. Of course, it's very important not to use any more front end gain than necessary for the band/conditions. 73, Larry N8LP __ 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 -- View this message in context: http://n2.nabble.com/K3-receiver-desensing-on-CW-during-contest-tp2369819p2384507.html Sent from the Elecraft mailing list archive at Nabble.com. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto: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 receiver desensing on CW during contest
alsopb wrote: Ditto here. #1129. AGC slope= 13, AGC THR =8. AGC set to fast. Never touched the RF gain control. I was totally amazed to be able copy weak ones under strong ones within the passband. Experienced none of the mushing reported here. The mushing requires 10-15+ not-very-strong signals calling at once - i.e., a serious pileup. I experienced it many times on 40M/20M in ARRLDX and CQWW cw contests. The mushing has nothing to do with desensing and I don't think anybody ever implied that it did. Several threads have gotten intermingled here. 73, Barry N1EU -- View this message in context: http://n2.nabble.com/K3-receiver-desensing-on-CW-during-contest-tp2369819p2385080.html Sent from the Elecraft mailing list archive at Nabble.com. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto: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 receiver desensing on CW during contest
On Wed, 25 Feb 2009 01:50:18 -0700, Bill W5WVO wrote: While all these transmitters except Channel 2 have fundamentals well above 54 MHz (I run a DCI bandpass filter to keep it out of my preamp), the accumulated grunge from the transmitters' perfectly legal low-level spurious emissions and passive mixes are enough to render 6 meters unusable for weak-signal work in the direction of the Yes. Several decades ago, I was on the tech committee that maintained ham repeaters on 2M, 220, and 440. All VHF and UHF broadcasters in Chicago are located on two buildings downtown -- Sears and Hancock. Thanks to that grunge, a 2M receiver was completely useless anywhere near downtown. I did manage to make a 220 MHz receiver in a 101st floor window at Hancock sort of work to fill in holes caused by shadowing of the main RX. It was shadowed by the building from the transmitters for Ch 9 and Ch 11. I suspect that your 6M problem will be greatly improved when your Ch 2 goes away. I had a Ch 2 to deal with in Chicago too, but they were only running about 20-30kW ERP. One very large blessing of DTV is that nearly all the low- band VHF channels are going away (that is, Ch 2-6). The reason is that DTV is rather susceptible to impulse noise, and impulse noise is much worse at low VHF than at higher frequencies. 73, Jim Brown K9YC __ 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 receiver desensing on CW during contest
Larry N8LP wrote on 24 Februay 2009, at 02:40. I think the days of receivers with xtal filters are numbered. High speed ADCs capable of 140dB dynamic range without xtal filtering are on the horizon. A 20-bit ADC with enough processing gain would do it. -- Larry, You could be right, given an adequate amount of RD funding and time. When the performance of a state of the art HF receiver using xtal filters will be surpassed by one digitizing at signal frequency is an open question I think.. The performance standard in terms of Spurious Free 3rd Order dynamic range vs. time set in recent years by real HF superhet receivers using xtal filters, as I know it to be, is: Year 3rd Order SFDR3rd Order SFDRFilter Noise @ 2 kHzIn Passband BW Figure 1993 110 db 95 db 400 Hz 8 db 2007 122 db approx115 db 500 Hz 7 db So don't put the old horse out to pasture just yet :-) Sorry to have digressed from the subject matter. 73, Geoff GM4ESD __ 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 receiver desensing on CW during contest
Let's see: 122 to 140dB: only 15% increase! a walk in the park... ; - ) David G3UNA Geoffrey Mackenzie-Kennedy gm4...@btinternet.com wrote: Larry N8LP wrote on 24 Februay 2009, at 02:40. I think the days of receivers with xtal filters are numbered. High speed ADCs capable of 140dB dynamic range without xtal filtering are on the horizon. A 20-bit ADC with enough processing gain would do it. -- Larry, You could be right, given an adequate amount of RD funding and time. When the performance of a state of the art HF receiver using xtal filters will be surpassed by one digitizing at signal frequency is an open question I think.. The performance standard in terms of Spurious Free 3rd Order dynamic range vs. time set in recent years by real HF superhet receivers using xtal filters, as I know it to be, is: Year 3rd Order SFDR3rd Order SFDRFilter Noise @ 2 kHzIn Passband BW Figure 1993 110 db 95 db 400 Hz 8 db 2007 122 db approx115 db 500 Hz 7 db So don't put the old horse out to pasture just yet :-) Sorry to have digressed from the subject matter. 73, Geoff GM4ESD __ 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 receiver desensing on CW during contest
Geoffrey Mackenzie-Kennedy wrote: Larry N8LP wrote on 24 Februay 2009, at 02:40. I think the days of receivers with xtal filters are numbered. So don't put the old horse out to pasture just yet :-) I recall Icom's President Mr. Inouye saying something similar to Larry's comment just after the IC-756PRO was introduced (~10 years ago). Then Icom added even more crystal filters to keep the 7600/7700/7800 in the performance ballpark with Orion...and then the K3. I bet he wishes he had never said that. 73, Bill -- View this message in context: http://n2.nabble.com/K3-receiver-desensing-on-CW-during-contest-tp2369819p2377525.html Sent from the Elecraft mailing list archive at Nabble.com. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto: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 receiver desensing on CW during contest
Not today... but give it a couple years. There is a lot of RD being poured into this by a number of competing chip manufacturers. Even if the next batch of designs falls a little short, an all digital design with BDR close to the best conventional designs would probably enjoy a very substantial market. 73, Larry N8LP Alan Bloom wrote: On Mon, 2009-02-23 at 18:40, N8LP wrote: ... I think the days of receivers with xtal filters are numbered. High speed ADCs capable of 140dB dynamic range without xtal filtering are on the horizon. A 20-bit ADC with enough processing gain would do it. I don't think you'll find a 20-bit ADC with a high enough sample rate to digitize the 3-30 MHz HF band (i.e. 65-70 MHz or so). At least not at a reasonable cost. I believe the best suitable, reasonable-cost ADCs available these days are able to achieve a 500-Hz blocking dynamic range in the low 120's dB, maybe 15-20 dB worse than the K3. That's significantly better than the previous generation of ADCs could achieve, and no doubt someday we'll get even better parts that are good enough to challenge the traditional superhet/crystal filter architecture. But I don't believe we're close to that level of performance today. Another issue, of course, is spurious responses. I'm pretty sure that current ADCs don't have good enough spurious-free dynamic range to challenge a state-of-the-art receiver like the K3. Al N1AL __ 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 receiver desensing on CW during contest
I agree this is something amateur equipment manufacturers like Elecraft should be keeping their eye on. If Analog Devices or someone came out with an under-$100 ADC with performance close to the K3, then you could save a lot of money and complexity by going to a directly-sampled RF front end architecture. But a lot of brilliant engineers have been working for many years trying to optimize ADC design. I just really have my doubts that they are going to make a 15-20 dB breakthrough any time soon. Al N1AL On Tue, 2009-02-24 at 09:55, Larry Phipps wrote: Not today... but give it a couple years. There is a lot of RD being poured into this by a number of competing chip manufacturers. Even if the next batch of designs falls a little short, an all digital design with BDR close to the best conventional designs would probably enjoy a very substantial market. 73, Larry N8LP Alan Bloom wrote: On Mon, 2009-02-23 at 18:40, N8LP wrote: ... I think the days of receivers with xtal filters are numbered. High speed ADCs capable of 140dB dynamic range without xtal filtering are on the horizon. A 20-bit ADC with enough processing gain would do it. I don't think you'll find a 20-bit ADC with a high enough sample rate to digitize the 3-30 MHz HF band (i.e. 65-70 MHz or so). At least not at a reasonable cost. I believe the best suitable, reasonable-cost ADCs available these days are able to achieve a 500-Hz blocking dynamic range in the low 120's dB, maybe 15-20 dB worse than the K3. That's significantly better than the previous generation of ADCs could achieve, and no doubt someday we'll get even better parts that are good enough to challenge the traditional superhet/crystal filter architecture. But I don't believe we're close to that level of performance today. Another issue, of course, is spurious responses. I'm pretty sure that current ADCs don't have good enough spurious-free dynamic range to challenge a state-of-the-art receiver like the K3. Al N1AL __ 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 receiver desensing on CW during contest
You may be right, Al. I think the improvements may be incremental, and distributed among various aspects of the design, not just the ADC. For instance, ultra-low jitter clock sources, faster FPGAs with improved IP cores, etc. I think most hams would be thrilled with an improvement to 130dB BDR, along with getting rid of phase distortion, ringing and other anomalies in the xtal filters and other analog components. Unless you live near a shortwave broadcast station, or have a high power ham nearby on the same band, you're not likely to need 130dB BDR anyway. Even in those cases, having 200dB BDR probably wouldn't help unless there is a LOT of improvement in transmitter spurious emissions, distortion and phase noise. The highest signals I have seen here, during Field Day when there were several stations operating within a few miles of me, were 120dB above the noise floor. Of course, it's very important not to use any more front end gain than necessary for the band/conditions. 73, Larry N8LP Alan Bloom wrote: I agree this is something amateur equipment manufacturers like Elecraft should be keeping their eye on. If Analog Devices or someone came out with an under-$100 ADC with performance close to the K3, then you could save a lot of money and complexity by going to a directly-sampled RF front end architecture. But a lot of brilliant engineers have been working for many years trying to optimize ADC design. I just really have my doubts that they are going to make a 15-20 dB breakthrough any time soon. Al N1AL On Tue, 2009-02-24 at 09:55, Larry Phipps wrote: Not today... but give it a couple years. There is a lot of RD being poured into this by a number of competing chip manufacturers. Even if the next batch of designs falls a little short, an all digital design with BDR close to the best conventional designs would probably enjoy a very substantial market. 73, Larry N8LP Alan Bloom wrote: On Mon, 2009-02-23 at 18:40, N8LP wrote: ... I think the days of receivers with xtal filters are numbered. High speed ADCs capable of 140dB dynamic range without xtal filtering are on the horizon. A 20-bit ADC with enough processing gain would do it. I don't think you'll find a 20-bit ADC with a high enough sample rate to digitize the 3-30 MHz HF band (i.e. 65-70 MHz or so). At least not at a reasonable cost. I believe the best suitable, reasonable-cost ADCs available these days are able to achieve a 500-Hz blocking dynamic range in the low 120's dB, maybe 15-20 dB worse than the K3. That's significantly better than the previous generation of ADCs could achieve, and no doubt someday we'll get even better parts that are good enough to challenge the traditional superhet/crystal filter architecture. But I don't believe we're close to that level of performance today. Another issue, of course, is spurious responses. I'm pretty sure that current ADCs don't have good enough spurious-free dynamic range to challenge a state-of-the-art receiver like the K3. Al N1AL __ 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 -- View this message in context: http://n2.nabble.com/K3-receiver-desensing-on-CW-during-contest-tp2369819p2381481.html Sent from the Elecraft mailing list archive at Nabble.com. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto: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 receiver desensing on CW during contest
At the W1KM contesting site, we routinely see signals of +5 dBm or louder on/near 40m from SWBC stations (using a single Yagi). We also have two modest-power local AM stations (1 to 5 kW, a few miles away) just below 1500 kHz that show up even a bit stronger than that on our 160m antennas. Without taking into consideration signals from our own multi-multi transmitters, a receiver is already faced with 130 dB range between weak signals on 160m in mid-afternoon arriving from Europe and these other signal sources. WD3Q, a contester in Washington DC, has much stronger AM BC stations to deal with, including a 50 kW station on 1500 kHz. Wide-open receiver front ends attached to an A/D converter are not yet viable for these locations. -- Eric K3NA on 09 Feb 24 20:44 N8LP said the following: You may be right, Al. I think the improvements may be incremental, and distributed among various aspects of the design, not just the ADC. For instance, ultra-low jitter clock sources, faster FPGAs with improved IP cores, etc. I think most hams would be thrilled with an improvement to 130dB BDR, along with getting rid of phase distortion, ringing and other anomalies in the xtal filters and other analog components. Unless you live near a shortwave broadcast station, or have a high power ham nearby on the same band, you're not likely to need 130dB BDR anyway. Even in those cases, having 200dB BDR probably wouldn't help unless there is a LOT of improvement in transmitter spurious emissions, distortion and phase noise. The highest signals I have seen here, during Field Day when there were several stations operating within a few miles of me, were 120dB above the noise floor. Of course, it's very important not to use any more front end gain than necessary for the band/conditions. 73, Larry N8LP __ 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 receiver desensing on CW during contest
Mike I believe there are two separate parts to your post: At 50Hz width it was quite clear that many stations call off frequency. Using RIT, I could see that it was typical for them to be 70Hz or more away from the DX station but I could not hear them in my 50Hz passband. The real problem was when one of them was S9 or greater. They completely swamped weaker DX stations. Sound within the passband just blanked out. No band noise and no DX station. And there was no recovery between dits and dahs. It was actually easier to copy the DX station when people were calling directly on top of him. You could at least hear him between the dits. The K3 will desense for signals about S9+25 that fall *within* the roofing filter but *outside* the DSP WIDTH passband. Elecraft made a modification (hardware AGC in the mod kits list) about a year ago which improved this problem and raised the threshold from a little over S9 to S9+25 (or maybe +30). I don't know your S/N but if it's ~280 or less you should install this mod. In my opinion, the threshold for this mod could still be raised a little more based on my experience with Orion which has a very similar front end to the K3. You didn't mention which filter you were using but even if you had the 200 Hz filter installed, you could have desense from S9+25 signals about +/- 150 Hz from your center frequency. There's simply not much that can be done about this until SHIFT resolution is changed from 50 Hz to 10 Hz. Then you could possibly use SHIFT to put the strong interfering signal on the XFIL passband slope. For my style of operating this was a disappointment. I tried AGC-F and AGC-S but I forgot to try AGC off. I also varied the AGC THR and AGC SLP. I tried NR off and on. (I was not using NB). I tried PRE and ATT off and on. I tried riding the RF gain. I tried shifting the passband but shift doesn't work well when the width is only 50Hz. Nothing helped. I also tried opening up the passband. That didn't help either but I don't remember the results. This was not a one time thing. It happened at least 20 different times on different bands. I guess this is perfectly normal. I was just wondering what operational trick is available to compensate. This could be a second issue (i.e. separating multiple strong stations) which Dave K6LL has identified. I haven't experienced it as yet because unfortunately I haven't had many pileups of strong stations calling me! However I believe Dave W6NL has determined that AGC THR and AGC SLP settings of 5 and 5 are best for this separation issue. I leave my AGC PLS set to NOR and have not experienced any problems that I felt were related to it. As an aside, I never use AGC-S for any mode and have AGC-F set to 120. Using Extreme Isolation EX-29 headphones, I select AF GAIN LO in the CONFIG menu, set my front panel AF GAIN to 9 o'clock (NEVER higher than 11 o'clock), set PRE/ATT so I can hear band noise when antennas are selected and then back off the front panel RF GAIN to a comfortable audio level. In the contest this weekend with ATT on my TX array and PRE on my Beverages (using both antennas for diversity), I typically had RF GAIN for both Main/Sub set from 2 o'clock to noon. The K3 was wonderful on Topband in the contest, especially the first night when QRN was low enough to use both my directional TX array and Beverages in diversity. It appears I set a new USA record with 434 QSOs and 79 countries for 102,858 points, breaking the old record of 81k set by N4PN at W8JI's station in 2006. 73, Bill -- View this message in context: http://n2.nabble.com/K3-receiver-desensing-on-CW-during-contest-tp2369819p2371427.html Sent from the Elecraft mailing list archive at Nabble.com. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto: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 receiver desensing on CW during contest
Hi Wayne and all: My filters are 200, 400, 1.0, 1.8 and 2.7 and they are all CW enabled. I was using headphones and my sub RX was off. My serial number is 2208 and the radio was factory assembled (including the sub RX). I did not hear key clicks when this was happening. The off frequency transmissions were clean. I also made a point of observing the signal strength of the offending stations and they were usually S8 or S9. Not the 20db or 40db over S9 that I was expecting. I thought it was interesting that recovery was noticeably slow on the DX station's frequency when this was happening. However, under normal conditions when US stations were calling directly on top of the DX station, recovery was fast. Hence the ability to copy the DX station through the dits when the QRM was on frequency. Maybe a passband shift could of helped. I would like to see the shift limits changed to something less than 50Hz. Maybe 10Hz on CW and 50Hz on other modes. I appreciate the interesting ideas from K6LL and W4ZV. Unfortunately I'll have to wait for the next busy contest to try them out. This just isn't the type of condition you can experience under normal band conditions. 73, Mike K2MK wayne burdick Sun, 22 Feb 2009 18:26:03 -0800 Mike, The K3 is virtually desense-proof, with a BDR of ~140 dB. But to take advantage of this, you need a narrow crystal filter -- the closer to the DSP bandwidth the better. This is exactly the situation that we had in mind when we designed the 200-Hz 5-pole filter. For CW pileups, you can't beat it. What crystal filter were you using at the time? Of course if the transmitting stations are wide due to key clicks, there may be situations where no amount of filtering can help (for any receiver). The DSP noise blanker and NR may be useful sometimes -- you might give this a try. Wayne N6KR On Feb 22, 2009, at 4:45 PM, K2MK wrote: I had a great time with my K3 during the ARRL DX contest. I do SP and I was trolling around with my filter width at 50Hz. Absolutely outstanding. The auto spot is equally outstanding. At 50Hz width it was quite clear that many stations call off frequency. Using RIT, I could see that it was typical for them to be 70Hz or more away from the DX station but I could not hear them in my 50Hz passband. The real problem was when one of them was S9 or greater. They completely swamped weaker DX stations. __ 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 receiver desensing on CW during contest
K2MK wrote: I thought it was interesting that recovery was noticeably slow on the DX station's frequency when this was happening. However, under normal conditions when US stations were calling directly on top of the DX station, recovery was fast. Hence the ability to copy the DX station through the dits when the QRM was on frequency. Mike this definitely sounds like desense but I'm surprised you experienced it with only S8-9 signals. I'm not sure what you mean about differing conditions on and off the center frequency. Desense will affect everything inside the roofing filter. What speed AGC were you using (F or S) and what were your AGC-F and AGC-S CONFIG settings? I NEVER use AGC-S on either CW or SSB and like at least 120 dB/sec for AGC-F. Also, help your AGC do its job by not running RF GAIN fully clockwise (as mentioned in my previous message). 73, Bill P.S. As I said before my K3 worked extremely well coping weak signals in the midst of massive ones on 160 this weekend. I smiled when I saw the following comment from OL0W(OK1DSZ): Only for fun, when the band was already closing, I decided to try what I will be able to work with QRP. Using longer callsign OK1DSZ and the power reduced to 5W I spend about 10 minutes calling several east coast big guns. The award for the best ears goes to W4ZV, who was worked as easily as with the kilowatt earlier in the night. K8PO and W2FU were worked with several repeats. The others just kept CQing without any reaction with exception of K1TTT, who apparently heard something, but not enough for the QSO. -- View this message in context: http://n2.nabble.com/K3-receiver-desensing-on-CW-during-contest-tp2369819p2372087.html Sent from the Elecraft mailing list archive at Nabble.com. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto: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 receiver desensing on CW during contest
Hi Bill: Here are my CONFIG settings related to the AGC. The only ones I played with during the contest were SLP and THR. I always use AGC-F but did occasionally try AGC-S. AGC-HOLD 000 AGC-PLS NOR AGC-SLP 010 AGC-THR 005 AGC-F 120 AGC-S 020 The differing conditions I described were the situation of everyone calling the DX close to his frequency versus one strong station calling 70Hz off frequency. When even strong stations called the DX right on frequency I was able to hear signals through the QRM. When strong stations called 70Hz off of the DX frequency the receiver went quiet and took about 1/4 to 1/2 second to recover after he stopped sending. 73, Mike K2MK Bill W4ZV Mon, 23 Feb 2009 05:31:37 -0800 K2MK wrote: I thought it was interesting that recovery was noticeably slow on the DX station's frequency when this was happening. However, under normal conditions when US stations were calling directly on top of the DX station, recovery was fast. Hence the ability to copy the DX station through the dits when the QRM was on frequency. Mike this definitely sounds like desense but I'm surprised you experienced it with only S8-9 signals. I'm not sure what you mean about differing conditions on and off the center frequency. Desense will affect everything inside the roofing filter. What speed AGC were you using (F or S) and what were your AGC-F and AGC-S CONFIG settings? I NEVER use AGC-S on either CW or SSB and like at least 120 dB/sec for AGC-F. Also, help your AGC do its job by not running RF GAIN fully clockwise (as mentioned in my previous message). 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 receiver desensing on CW during contest
Aha. It sounds like the desense problem arises when the DSP filter is narrower than the roofing filter. A strong station within the roofing passband but outside the DSP passband will shut down the receiver through AGC. I think we all misled ourselves by the impression that desense was impossible in the K3. It's working just as it ought -- but operators need to widen out the DSP to the full width of the roofing filter, when there are strong stations every few Hz. A bit counter-intuitive, perhaps. Peter N8MHD On 2/23/09, K2MK k...@comcast.net wrote: Hi Wayne and all: My filters are 200, 400, 1.0, 1.8 and 2.7 and they are all CW enabled. I was using headphones and my sub RX was off. My serial number is 2208 and the radio was factory assembled (including the sub RX). I did not hear key clicks when this was happening. The off frequency transmissions were clean. I also made a point of observing the signal strength of the offending stations and they were usually S8 or S9. Not the 20db or 40db over S9 that I was expecting. I thought it was interesting that recovery was noticeably slow on the DX station's frequency when this was happening. However, under normal conditions when US stations were calling directly on top of the DX station, recovery was fast. Hence the ability to copy the DX station through the dits when the QRM was on frequency. Maybe a passband shift could of helped. I would like to see the shift limits changed to something less than 50Hz. Maybe 10Hz on CW and 50Hz on other modes. I appreciate the interesting ideas from K6LL and W4ZV. Unfortunately I'll have to wait for the next busy contest to try them out. This just isn't the type of condition you can experience under normal band conditions. 73, Mike K2MK wayne burdick Sun, 22 Feb 2009 18:26:03 -0800 Mike, The K3 is virtually desense-proof, with a BDR of ~140 dB. But to take advantage of this, you need a narrow crystal filter -- the closer to the DSP bandwidth the better. This is exactly the situation that we had in mind when we designed the 200-Hz 5-pole filter. For CW pileups, you can't beat it. What crystal filter were you using at the time? Of course if the transmitting stations are wide due to key clicks, there may be situations where no amount of filtering can help (for any receiver). The DSP noise blanker and NR may be useful sometimes -- you might give this a try. Wayne N6KR On Feb 22, 2009, at 4:45 PM, K2MK wrote: I had a great time with my K3 during the ARRL DX contest. I do SP and I was trolling around with my filter width at 50Hz. Absolutely outstanding. The auto spot is equally outstanding. At 50Hz width it was quite clear that many stations call off frequency. Using RIT, I could see that it was typical for them to be 70Hz or more away from the DX station but I could not hear them in my 50Hz passband. The real problem was when one of them was S9 or greater. They completely swamped weaker DX stations. __ 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 receiver desensing on CW during contest
Having 1/4 to 1/2 second recovery time does not sound like AGC-F. By chance, did you have the CW text decode feature engaged? Did you have NR engaged? - Keith N1AS - - K3 711 - -Original Message- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of K2MK Sent: Monday, February 23, 2009 11:00 AM To: btipp...@alum.mit.edu; Elecraft Reflector Subject: Re: [Elecraft] K3 receiver desensing on CW during contest Hi Bill: Here are my CONFIG settings related to the AGC. The only ones I played with during the contest were SLP and THR. I always use AGC-F but did occasionally try AGC-S. AGC-HOLD 000 AGC-PLS NOR AGC-SLP 010 AGC-THR 005 AGC-F 120 AGC-S 020 The differing conditions I described were the situation of everyone calling the DX close to his frequency versus one strong station calling 70Hz off frequency. When even strong stations called the DX right on frequency I was able to hear signals through the QRM. When strong stations called 70Hz off of the DX frequency the receiver went quiet and took about 1/4 to 1/2 second to recover after he stopped sending. 73, Mike K2MK Bill W4ZV Mon, 23 Feb 2009 05:31:37 -0800 K2MK wrote: I thought it was interesting that recovery was noticeably slow on the DX station's frequency when this was happening. However, under normal conditions when US stations were calling directly on top of the DX station, recovery was fast. Hence the ability to copy the DX station through the dits when the QRM was on frequency. Mike this definitely sounds like desense but I'm surprised you experienced it with only S8-9 signals. I'm not sure what you mean about differing conditions on and off the center frequency. Desense will affect everything inside the roofing filter. What speed AGC were you using (F or S) and what were your AGC-F and AGC-S CONFIG settings? I NEVER use AGC-S on either CW or SSB and like at least 120 dB/sec for AGC-F. Also, help your AGC do its job by not running RF GAIN fully clockwise (as mentioned in my previous message). 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 __ 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 receiver desensing on CW during contest
Peter Wollan-2 wrote: Aha. It sounds like the desense problem arises when the DSP filter is narrower than the roofing filter. A strong station within the roofing passband but outside the DSP passband will shut down the receiver through AGC. I think we all misled ourselves by the impression that desense was impossible in the K3. It's working just as it ought -- but operators need to widen out the DSP to the full width of the roofing filter, when there are strong stations every few Hz. A bit counter-intuitive, perhaps. Correct me if I'm wrong, but a strong station within the roofing passband but outside the DSP passband will NOT shut down the receiver through AGC unless the strength exceeds s9+25dB (when hardware AGC kicks in due to ADC dynamic range limits). 73, Barry N1EU -- View this message in context: http://n2.nabble.com/K3-receiver-desensing-on-CW-during-contest-tp2369819p2373077.html Sent from the Elecraft mailing list archive at Nabble.com. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto: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 receiver desensing on CW during contest
Hi Mike, On Mon, Feb 23, 2009 at 11:00 AM, K2MK k...@comcast.net wrote: Here are my CONFIG settings related to the AGC. The only ones I played with during the contest were SLP and THR. I always use AGC-F but did occasionally try AGC-S. AGC-HOLD 000 AGC-PLS NOR AGC-SLP 010 AGC-THR 005 AGC-F 120 AGC-S 020 These all look reasonable. I set my AGC-S to the max 040 but I actually never use AGC-S. If I were an AMer or 75m SSB ragchewer, I might. The differing conditions I described were the situation of everyone calling the DX close to his frequency versus one strong station calling 70Hz off frequency. When even strong stations called the DX right on frequency I was able to hear signals through the QRM. When strong stations called 70Hz off of the DX frequency the receiver went quiet and took about 1/4 to 1/2 second to recover after he stopped sending. This is what I'm having problems understanding: When even strong stations called the DX right on frequency I was able to hear signals through the QRM. 1. If two stations are exactly on frequency, the best ears in the world will not be able to separate them. I can distinguish pitch *differences* (i.e. one after the other) of about 0.4 Hz repeatably (see link below), but there's no way I could copy two simultaneous CW signals dead zero beat, so I don't understand your comment. The human ear's DSP has an effective bandwidth of ~50 Hz, so I could probably distinguish two signals 70 Hz apart if their amplitude was not too different (the human ear has AGC limits also!) http://tonometric.com/adaptivepitch/ (a fun test to take!) 2. The way the K3 and similar front ends (i.e. Orion, FT2000/9000, IC 7700/7800) work, strong signals inside the roofing filter passband will desense *all* signals within the passband...i.e. they will affect zero beat signals just as much as those 70 Hz away (which would be the case even if you were using the 200 Hz filter). So I cannot understand how signals off zero beat would be affected more than those zero beat. Anyhow, I'm clearly not understanding what you're saying. 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 receiver desensing on CW during contest
I believe the hardware AGC would be activated if the *combined* strength of all signals within the crystal filter passband gets above the threshold of S9+25 dB or so. This means that multiple unwanted signals don't have to reach the threshold strength *individually* for AGC pumping to occur, but there would have to be *a lot* of closely spaced unwanted signals at S8 to cause a problem if a narrow roofing filter is used. Also under those conditions, the operator would be unlikely to report that individual unwanted signals are no more than S8. I suppose one could also have a case where the wanted signal is almost strong enough to set off the hardware AGC, and a single, weaker signal gets through the roofing filter (but not the DSP) and adds just enough to the combined signal to cause hardware AGC action, resulting in an audible effect on the stronger wanted signal. 73, Erik K7TV - Original Message - From: Barry N1EU barry.n...@gmail.com To: elecraft@mailman.qth.net Sent: Monday, February 23, 2009 9:59 AM Subject: Re: [Elecraft] K3 receiver desensing on CW during contest Peter Wollan-2 wrote: Aha. It sounds like the desense problem arises when the DSP filter is narrower than the roofing filter. A strong station within the roofing passband but outside the DSP passband will shut down the receiver through AGC. I think we all misled ourselves by the impression that desense was impossible in the K3. It's working just as it ought -- but operators need to widen out the DSP to the full width of the roofing filter, when there are strong stations every few Hz. A bit counter-intuitive, perhaps. Correct me if I'm wrong, but a strong station within the roofing passband but outside the DSP passband will NOT shut down the receiver through AGC unless the strength exceeds s9+25dB (when hardware AGC kicks in due to ADC dynamic range limits). 73, Barry N1EU -- View this message in context: http://n2.nabble.com/K3-receiver-desensing-on-CW-during-contest-tp2369819p2373077.html Sent from the Elecraft mailing list archive at Nabble.com. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto: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 receiver desensing on CW during contest
Hi Bill: You stated it correctly. Here's an example. There are two US stations calling the DX. Me and you both within my 50Hz passband. I send my call once and you send your call twice. You are S9 at my receiver and the DX is S7. When I finish calling I can hear you and I can also hear the DX station. (If there is no pitch difference there are still differences in strength and speed). I may not hear every character he is sending but I might hear him come back immediately after I stop sending and I might hear parts of a number 2 and parts of a letter K in his response. So when I no longer hear him I take a chance and assume he called me and I respond with my info. This all happened while you were still sending your call. This was not an unusual situation this weekend. I had a good signal and was getting most stations in one or two calls so it was not really a big leap for me to respond. But I was only able to do it because I could still hear him through the QRM. Now take the same situation except you were calling 70Hz off of his frequency. My receiver was dead until you stopped sending. Once you stopped I might hear the tail end of his message but I wouldn't know if it was me unless he called me a second time. And of those 20 occurrences that I described earlier, maybe half of those times he was calling me but I had to wait for the re-call. Someone else asked if I had the text decode on and I did not. As for NR, I usually had it on. But I always try to keep the aggressiveness low. And I did experiment and I still had the same problem with NR off. 73, Mike K2MK Bill Tippett Mon, 23 Feb 2009 09:20:14 -0800 Hi Mike, On Mon, Feb 23, 2009 at 11:00 AM, K2MK k...@comcast.net wrote: Here are my CONFIG settings related to the AGC. The only ones I played with during the contest were SLP and THR. I always use AGC-F but did occasionally try AGC-S. AGC-HOLD 000 AGC-PLS NOR AGC-SLP 010 AGC-THR 005 AGC-F 120 AGC-S 020 These all look reasonable. I set my AGC-S to the max 040 but I actually never use AGC-S. If I were an AMer or 75m SSB ragchewer, I might. The differing conditions I described were the situation of everyone calling the DX close to his frequency versus one strong station calling 70Hz off frequency. When even strong stations called the DX right on frequency I was able to hear signals through the QRM. When strong stations called 70Hz off of the DX frequency the receiver went quiet and took about 1/4 to 1/2 second to recover after he stopped sending. This is what I'm having problems understanding: When even strong stations called the DX right on frequency I was able to hear signals through the QRM. 1. If two stations are exactly on frequency, the best ears in the world will not be able to separate them. I can distinguish pitch *differences* (i.e. one after the other) of about 0.4 Hz repeatably (see link below), but there's no way I could copy two simultaneous CW signals dead zero beat, so I don't understand your comment. The human ear's DSP has an effective bandwidth of ~50 Hz, so I could probably distinguish two signals 70 Hz apart if their amplitude was not too different (the human ear has AGC limits also!) http://tonometric.com/adaptivepitch/ (a fun test to take!) 2. The way the K3 and similar front ends (i.e. Orion, FT2000/9000, IC 7700/7800) work, strong signals inside the roofing filter passband will desense *all* signals within the passband...i.e. they will affect zero beat signals just as much as those 70 Hz away (which would be the case even if you were using the 200 Hz filter). So I cannot understand how signals off zero beat would be affected more than those zero beat. Anyhow, I'm clearly not understanding what you're saying. 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 receiver desensing on CW during contest
Is my summary of the issue correct? If both signals are within both the DSP and roofing filter bandwidths, then the receiver recovers instantly after each character. If the stronger signal is outside the DSP filter window (and you can’t hear him) but inside the roofing filter window, then there is de-sensing. Would passband tuning (shift) help to shift his signal outside of the roofing filter bandpass? John W2XS -- View this message in context: http://n2.nabble.com/K3-receiver-desensing-on-CW-during-contest-tp2369819p2373481.html Sent from the Elecraft mailing list archive at Nabble.com. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto: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 receiver desensing on CW during contest
It seems that this thread is VERY confused about how AGC works to control the RF gain. I also suspect that some are using the radio with too much RF gain. The settings that W4ZV posted are pretty much what I use, except that I regularly also run the RF gains (both main and sub) at about 2 o'clock when I hear signals getting buried in the background noise. I also think many do not understand the definition of desense. Desense occurs when a gain stage is driven into clip so badly that the bias point shifts and reduces the gain (worst case, to cutoff). So far, I've never heard my K3s desense. I have heard a strong station pump the AGC when I'm copying a weak station. I've also heard massive phase noise and clicks from a dirty transmitter (most recently, a JA who was only about 5dB over S9 when I was trying to run JAs 1 kHz away from him on 40M). And there's a JA who made it into my logbook on 80M with a power exchange of 1 watt! He wouldn't have with any other radio. One expansion of W4ZV's comments regarding perception of pitch. Human sight and hearing are logarithmic. Human hearing works on the basis of what acousticians call critical bands, which are logarithmic, and which are tied to the physical construction of the human hearing system itself. The filter between our ears is better able to separate a 50 Hz pitch difference at 300 Hz than at 900 Hz! That's one reason why some CW operators like to work at lower pitches when the going gets tough. 73, Jim Brown K9YC (Member Acoustical Society of America) __ 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 receiver desensing on CW during contest
Is this correct? If a cw signal falls within the DSP passband it should and will pump the AGC. If a CW signal falls outside the DSP passband it should not pump the DSP's AGC. The problem here is defining what the DSP's passband it. If a signal is just outside the audio range of the DSP (can't be heard) then I would consider it outside the DSP passband and it should not pump the AGC however this is never the case. I see moderate signals just slightly outside the audio passband that pump the AGC. This is partly what is confusing us. Signals that we can't hear pumping the AGC worry us. What we hear coming from the speaker doesn't match how the AGC is responding. If my WIDTH is set for 100hz and a signal is at 110hz, I won't hear him but my S-meter responds to him as well as my AGC desenses (reduces gain). All of this has nothing to do with the roofing filter. Steve Ellington n...@carolina.rr.com - Original Message - From: Jim Brown j...@audiosystemsgroup.com To: Elecraft List elecraft@mailman.qth.net Sent: Monday, February 23, 2009 1:46 PM Subject: Re: [Elecraft] K3 receiver desensing on CW during contest It seems that this thread is VERY confused about how AGC works to control the RF gain. I also suspect that some are using the radio with too much RF gain. The settings that W4ZV posted are pretty much what I use, except that I regularly also run the RF gains (both main and sub) at about 2 o'clock when I hear signals getting buried in the background noise. I also think many do not understand the definition of desense. Desense occurs when a gain stage is driven into clip so badly that the bias point shifts and reduces the gain (worst case, to cutoff). So far, I've never heard my K3s desense. I have heard a strong station pump the AGC when I'm copying a weak station. I've also heard massive phase noise and clicks from a dirty transmitter (most recently, a JA who was only about 5dB over S9 when I was trying to run JAs 1 kHz away from him on 40M). And there's a JA who made it into my logbook on 80M with a power exchange of 1 watt! He wouldn't have with any other radio. One expansion of W4ZV's comments regarding perception of pitch. Human sight and hearing are logarithmic. Human hearing works on the basis of what acousticians call critical bands, which are logarithmic, and which are tied to the physical construction of the human hearing system itself. The filter between our ears is better able to separate a 50 Hz pitch difference at 300 Hz than at 900 Hz! That's one reason why some CW operators like to work at lower pitches when the going gets tough. 73, Jim Brown K9YC (Member Acoustical Society of America) __ 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: 8.0.237 / Virus Database: 270.11.3/1967 - Release Date: 02/23/09 07:17:00 __ 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 receiver desensing on CW during contest
From what I though the original post was about the trouble copying signals in a pile up, it appears to me that thread has become at least 3 different topics. Seems there are people talking desense, AGC settings, and the pile up problem. To make mine clear, I do not have any desense problems with the K3, I can work within hundreds of HZ from very strong stations and have never had it blank the receiver when using narrow filters. AGC, I dont think it is the problem as I have it turned off most of the time and use the RF gain. The third problem is what I have had and apparently others, when there are many stations calling in a pile up that are a sig strength of say s4 to s5, the audio turns to mush and they all sound the same, no difference in strength, like they are all clipped somehow to the same level and distorted. Not a pure audio tone any longer, does not happen with just a couple stations in the pile up, only when maybe over 5 or 6 at a time are calling. Turns to mush as some one said. Have not tried turning the radio on and off when that happens, but will next time to see it that resets something. In an case dont lump all these comments that have come under the desense heading as one problem, it appears to be at least 3.. Perhaps the subject is incorrectly titled. Merv KH7C It seems that this thread is VERY confused about how AGC works to control the RF gain. I also suspect that some are using the radio with too much RF gain. The settings that W4ZV posted are pretty much what I use, except that I regularly also run the RF gains (both main and sub) at about 2 o'clock when I hear signals getting buried in the background noise. I also think many do not understand the definition of desense. Desense occurs when a gain stage is driven into clip so badly that the bias point shifts and reduces the gain (worst case, to cutoff). So far, I've never heard my K3s desense. I have heard a strong station pump the AGC when I'm copying a weak station. I've also heard massive phase noise and clicks from a dirty transmitter (most recently, a JA who was only about 5dB over S9 when I was trying to run JAs 1 kHz away from him on 40M). And there's a JA who made it into my logbook on 80M with a power exchange of 1 watt! He wouldn't have with any other radio. One expansion of W4ZV's comments regarding perception of pitch. Human sight and hearing are logarithmic. Human hearing works on the basis of what acousticians call critical bands, which are logarithmic, and which are tied to the physical construction of the human hearing system itself. The filter between our ears is better able to separate a 50 Hz pitch difference at 300 Hz than at 900 Hz! That's one reason why some CW operators like to work at lower pitches when the going gets tough. 73, Jim Brown K9YC (Member Acoustical Society of America) __ 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 receiver desensing on CW during contest
I'm at work and don't have time to check any of this ... But I was under the impression that it was not this way. Signals outside of the DSP passband but inside the roofing filter passband would activate the DSP. So, with a 2 KHz roofing filter and a 200 Hz DSP, you'd have very few signals being heard by the OP but lots of signals affecting the AGC. - Keith N1AS - - K3 711 - -Original Message- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Steve Ellington Sent: Monday, February 23, 2009 1:58 PM To: Jim Brown; Elecraft List Subject: Re: [Elecraft] K3 receiver desensing on CW during contest Is this correct? If a cw signal falls within the DSP passband it should and will pump the AGC. If a CW signal falls outside the DSP passband it should not pump the DSP's AGC. Steve Ellington n...@carolina.rr.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 receiver desensing on CW during contest
Hi John: You are correct. When there was no strong off center signal but two or more strong signals within the 50Hz passband it was possible to copy one signal, as we all do, in the presence of QRM. There was no noticeable AGC action. It was just a normal situation of trying to copy one signal out of several. Even at 50Hz you can't remove 100% of all QRM. When an S8 or S9 signal was around 70Hz away the signals inside the 50Hz passband were quiet until he stopped sending. I wanted to hear what was causing the problem so I used RIT to tune up or down until I could hear the off center signal. When I did I found that the offset was about 70Hz as read on the lower display. I could then also see his signal strength on the S meter. I wish I could say what happened when I opened up the passband but I don't recall. I thought a passband shift might help but the shift is limited to 50Hz increments. So one touch of the shift knob caused me to lose the signal of interest. 73, Mike K2MK John W2XS Mon, 23 Feb 2009 10:18:02 -0800 Is my summary of the issue correct? If both signals are within both the DSP and roofing filter bandwidths, then the receiver recovers instantly after each character. If the stronger signal is outside the DSP filter window (and you can't hear him) but inside the roofing filter window, then there is de-sensing. Would passband tuning (shift) help to shift his signal outside of the roofing filter bandpass? John W2XS __ 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 receiver desensing on CW during contest
There are two separate AGC functions: 1. Hardware AGC is activated when the combined signals that get through the roofing filter reach a certain level, about S9+25. When it is activated, all those signals, including the wanted signal, are attenuated before the DSP. AFAIK the hardware AGC cannot be turned off. 2. Software AGC implemented within the DSP. It can be turned on or off, and its parameters can be adjusted. I am not sure whether it is ever totally turned off, even when turned off. It reacts to the strenght of all that has passed through the DSP bandwidth. Signals outside the DSP passband but inside the roofing filter certainly enter the DSP, but the DSP bandpass filter should eliminate them before they can do anything to the software AGC. They can affect the hardware AGC, but only if they together (including the wanted signal) are so strong that the hardware AGC does anything at all. Erik K7TV - Original Message - From: Darwin, Keith keith.dar...@goodrich.com To: Elecraft List elecraft@mailman.qth.net Sent: Monday, February 23, 2009 12:22 PM Subject: Re: [Elecraft] K3 receiver desensing on CW during contest I'm at work and don't have time to check any of this ... But I was under the impression that it was not this way. Signals outside of the DSP passband but inside the roofing filter passband would activate the DSP. So, with a 2 KHz roofing filter and a 200 Hz DSP, you'd have very few signals being heard by the OP but lots of signals affecting the AGC. - Keith N1AS - - K3 711 - -Original Message- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Steve Ellington Sent: Monday, February 23, 2009 1:58 PM To: Jim Brown; Elecraft List Subject: Re: [Elecraft] K3 receiver desensing on CW during contest Is this correct? If a cw signal falls within the DSP passband it should and will pump the AGC. If a CW signal falls outside the DSP passband it should not pump the DSP's AGC. Steve Ellington n...@carolina.rr.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 __ 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 receiver desensing on CW during contest
This is an interesting subject. I've read several opinions on how the K3-AGC works here and MORE important: how it behaves. Can somebody from Elecraft shine a light on the AGC behaviour? I'm very curious now. 73, Arie PA3A __ 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 receiver desensing on CW during contest
This is what I was seeing too. I never had any issues with wide or clicky stations causing any issues. The radio is great to use. The K3 produced the least amount of listening fatigue that I have experienced. A good thing! Not being able to pull out callsigns out of a big pile is not a good thing. A slip of the foot you may soon recover, but a slip of the tongue you may never get over. Ben Franklin -Original Message- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Merv Schweigert Sent: Monday, February 23, 2009 12:15 PM Cc: Elecraft List Subject: Re: [Elecraft] K3 receiver desensing on CW during contest From what I though the original post was about the trouble copying signals in a pile up, it appears to me that thread has become at least 3 different topics. Seems there are people talking desense, AGC settings, and the pile up problem. To make mine clear, I do not have any desense problems with the K3, I can work within hundreds of HZ from very strong stations and have never had it blank the receiver when using narrow filters. AGC, I dont think it is the problem as I have it turned off most of the time and use the RF gain. The third problem is what I have had and apparently others, when there are many stations calling in a pile up that are a sig strength of say s4 to s5, the audio turns to mush and they all sound the same, no difference in strength, like they are all clipped somehow to the same level and distorted. Not a pure audio tone any longer, does not happen with just a couple stations in the pile up, only when maybe over 5 or 6 at a time are calling. Turns to mush as some one said. Have not tried turning the radio on and off when that happens, but will next time to see it that resets something. In an case dont lump all these comments that have come under the desense heading as one problem, it appears to be at least 3.. Perhaps the subject is incorrectly titled. Merv KH7C It seems that this thread is VERY confused about how AGC works to control the RF gain. I also suspect that some are using the radio with too much RF gain. The settings that W4ZV posted are pretty much what I use, except that I regularly also run the RF gains (both main and sub) at about 2 o'clock when I hear signals getting buried in the background noise. I also think many do not understand the definition of desense. Desense occurs when a gain stage is driven into clip so badly that the bias point shifts and reduces the gain (worst case, to cutoff). So far, I've never heard my K3s desense. I have heard a strong station pump the AGC when I'm copying a weak station. I've also heard massive phase noise and clicks from a dirty transmitter (most recently, a JA who was only about 5dB over S9 when I was trying to run JAs 1 kHz away from him on 40M). And there's a JA who made it into my logbook on 80M with a power exchange of 1 watt! He wouldn't have with any other radio. One expansion of W4ZV's comments regarding perception of pitch. Human sight and hearing are logarithmic. Human hearing works on the basis of what acousticians call critical bands, which are logarithmic, and which are tied to the physical construction of the human hearing system itself. The filter between our ears is better able to separate a 50 Hz pitch difference at 300 Hz than at 900 Hz! That's one reason why some CW operators like to work at lower pitches when the going gets tough. 73, Jim Brown K9YC (Member Acoustical Society of America) __ 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 receiver desensing on CW during contest
When I first received my K3, I too was disappointed with the BDR until I understood what was happening. In an effort to quantify the BDR of signals between the xtal filter bandpass and the DSP bandpass, I set up the following scenario... Two generators feeding the K3 through a hybrid combiner. One set to about -85dBm (S7 on my K3), and the other variable. I tuned in the -85dBm signal, with the xtal filter set to 500Hz, and DSP to 50Hz. With the interfering signal set to 200Hz offset (within the xtal filter passband) I started to see desense of the weaker signal at -34dBm output level for the stronger signal. With the interfering signal set to 2kHz offset, I started to see desense at +15dBm. The difference of 49dB shows the importance of the xtal filter to this design. Of course, different AGC settings would affect this test. The promised variable roofing filters would reduce the problem quite a bit, but that opens up other issues. I think the days of receivers with xtal filters are numbered. High speed ADCs capable of 140dB dynamic range without xtal filtering are on the horizon. A 20-bit ADC with enough processing gain would do it. 73, Larry N8LP Bill W4ZV wrote: K2MK wrote: I thought it was interesting that recovery was noticeably slow on the DX station's frequency when this was happening. However, under normal conditions when US stations were calling directly on top of the DX station, recovery was fast. Hence the ability to copy the DX station through the dits when the QRM was on frequency. Mike this definitely sounds like desense but I'm surprised you experienced it with only S8-9 signals. I'm not sure what you mean about differing conditions on and off the center frequency. Desense will affect everything inside the roofing filter. What speed AGC were you using (F or S) and what were your AGC-F and AGC-S CONFIG settings? I NEVER use AGC-S on either CW or SSB and like at least 120 dB/sec for AGC-F. Also, help your AGC do its job by not running RF GAIN fully clockwise (as mentioned in my previous message). 73, Bill P.S. As I said before my K3 worked extremely well coping weak signals in the midst of massive ones on 160 this weekend. I smiled when I saw the following comment from OL0W(OK1DSZ): Only for fun, when the band was already closing, I decided to try what I will be able to work with QRP. Using longer callsign OK1DSZ and the power reduced to 5W I spend about 10 minutes calling several east coast big guns. The award for the best ears goes to W4ZV, who was worked as easily as with the kilowatt earlier in the night. K8PO and W2FU were worked with several repeats. The others just kept CQing without any reaction with exception of K1TTT, who apparently heard something, but not enough for the QSO. -- View this message in context: http://n2.nabble.com/K3-receiver-desensing-on-CW-during-contest-tp2369819p2375849.html Sent from the Elecraft mailing list archive at Nabble.com. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto: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 receiver desensing on CW during contest
On Mon, 2009-02-23 at 18:40, N8LP wrote: ... I think the days of receivers with xtal filters are numbered. High speed ADCs capable of 140dB dynamic range without xtal filtering are on the horizon. A 20-bit ADC with enough processing gain would do it. I don't think you'll find a 20-bit ADC with a high enough sample rate to digitize the 3-30 MHz HF band (i.e. 65-70 MHz or so). At least not at a reasonable cost. I believe the best suitable, reasonable-cost ADCs available these days are able to achieve a 500-Hz blocking dynamic range in the low 120's dB, maybe 15-20 dB worse than the K3. That's significantly better than the previous generation of ADCs could achieve, and no doubt someday we'll get even better parts that are good enough to challenge the traditional superhet/crystal filter architecture. But I don't believe we're close to that level of performance today. Another issue, of course, is spurious responses. I'm pretty sure that current ADCs don't have good enough spurious-free dynamic range to challenge a state-of-the-art receiver like the K3. Al N1AL __ 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 receiver desensing on CW during contest
Thanks Larry, These measurements explain a lot of what's happening. 73, Arie PA3A -Oorspronkelijk bericht- Van: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] Namens N8LP Verzonden: dinsdag 24 februari 2009 3:41 Aan: elecraft@mailman.qth.net Onderwerp: Re: [Elecraft] K3 receiver desensing on CW during contest When I first received my K3, I too was disappointed with the BDR until I understood what was happening. In an effort to quantify the BDR of signals between the xtal filter bandpass and the DSP bandpass, I set up the following scenario... Two generators feeding the K3 through a hybrid combiner. One set to about -85dBm (S7 on my K3), and the other variable. I tuned in the -85dBm signal, with the xtal filter set to 500Hz, and DSP to 50Hz. With the interfering signal set to 200Hz offset (within the xtal filter passband) I started to see desense of the weaker signal at -34dBm output level for the stronger signal. With the interfering signal set to 2kHz offset, I started to see desense at +15dBm. The difference of 49dB shows the importance of the xtal filter to this design. Of course, different AGC settings would affect this test. The promised variable roofing filters would reduce the problem quite a bit, but that opens up other issues. I think the days of receivers with xtal filters are numbered. High speed ADCs capable of 140dB dynamic range without xtal filtering are on the horizon. A 20-bit ADC with enough processing gain would do it. 73, Larry N8LP Bill W4ZV wrote: K2MK wrote: I thought it was interesting that recovery was noticeably slow on the DX station's frequency when this was happening. However, under normal conditions when US stations were calling directly on top of the DX station, recovery was fast. Hence the ability to copy the DX station through the dits when the QRM was on frequency. Mike this definitely sounds like desense but I'm surprised you experienced it with only S8-9 signals. I'm not sure what you mean about differing conditions on and off the center frequency. Desense will affect everything inside the roofing filter. What speed AGC were you using (F or S) and what were your AGC-F and AGC-S CONFIG settings? I NEVER use AGC-S on either CW or SSB and like at least 120 dB/sec for AGC-F. Also, help your AGC do its job by not running RF GAIN fully clockwise (as mentioned in my previous message). 73, Bill P.S. As I said before my K3 worked extremely well coping weak signals in the midst of massive ones on 160 this weekend. I smiled when I saw the following comment from OL0W(OK1DSZ): Only for fun, when the band was already closing, I decided to try what I will be able to work with QRP. Using longer callsign OK1DSZ and the power reduced to 5W I spend about 10 minutes calling several east coast big guns. The award for the best ears goes to W4ZV, who was worked as easily as with the kilowatt earlier in the night. K8PO and W2FU were worked with several repeats. The others just kept CQing without any reaction with exception of K1TTT, who apparently heard something, but not enough for the QSO. -- View this message in context: http://n2.nabble.com/K3-receiver-desensing-on-CW-during-contest-tp236981 9p2375849.html Sent from the Elecraft mailing list archive at Nabble.com. __ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto: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 receiver desensing on CW during contest
What IF filters do you have installed? jim ab3cv __ 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 receiver desensing on CW during contest
This is more than likely due to dirty signals on the TX end. I was using a QS1R connected to the K3 IF and measured the width of some of the strong signals. Some were as wide as 2.6 kHz Not very good for a CW signal. In this case there is just not much you can do. 73 Greg AB7R On Feb 22, 2009, at 4:45 PM, K2MK wrote: I had a great time with my K3 during the ARRL DX contest. I do SP and I was trolling around with my filter width at 50Hz. Absolutely outstanding. The auto spot is equally outstanding. At 50Hz width it was quite clear that many stations call off frequency. Using RIT, I could see that it was typical for them to be 70Hz or more away from the DX station but I could not hear them in my 50Hz passband. The real problem was when one of them was S9 or greater. They completely swamped weaker DX stations. Sound within the passband just blanked out. No band noise and no DX station. And there was no recovery between dits and dahs. It was actually easier to copy the DX station when people were calling directly on top of him. You could at least hear him between the dits. (Obviously if I was calling CQ instead of SP I would have a wider passband and I would have just worked the stronger off frequency station). For my style of operating this was a disappointment. I tried AGC-F and AGC-S but I forgot to try AGC off. I also varied the AGC THR and AGC SLP. I tried NR off and on. (I was not using NB). I tried PRE and ATT off and on. I tried riding the RF gain. I tried shifting the passband but shift doesn't work well when the width is only 50Hz. Nothing helped. I also tried opening up the passband. That didn't help either but I don't remember the results. This was not a one time thing. It happened at least 20 different times on different bands. I guess this is perfectly normal. I was just wondering what operational trick is available to compensate. 73, Mike K2MK __ 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 receiver desensing on CW during contest
It seems that soundcard based AFCW has become popular with some contesters, for reasons which elude me. There is great opportunity to transmit wide, distorted cw signals if things are poorly adjusted. Bob W2WG -Original Message- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Gregory Fischer Sent: Sunday, February 22, 2009 7:59 PM To: K2MK Cc: Elecraft Reflector Subject: Re: [Elecraft] K3 receiver desensing on CW during contest This is more than likely due to dirty signals on the TX end. I was using a QS1R connected to the K3 IF and measured the width of some of the strong signals. Some were as wide as 2.6 kHz Not very good for a CW signal. In this case there is just not much you can do. 73 Greg AB7R On Feb 22, 2009, at 4:45 PM, K2MK wrote: I had a great time with my K3 during the ARRL DX contest. I do SP and I was trolling around with my filter width at 50Hz. Absolutely outstanding. The auto spot is equally outstanding. At 50Hz width it was quite clear that many stations call off frequency. Using RIT, I could see that it was typical for them to be 70Hz or more away from the DX station but I could not hear them in my 50Hz passband. The real problem was when one of them was S9 or greater. They completely swamped weaker DX stations. Sound within the passband just blanked out. No band noise and no DX station. And there was no recovery between dits and dahs. It was actually easier to copy the DX station when people were calling directly on top of him. You could at least hear him between the dits. (Obviously if I was calling CQ instead of SP I would have a wider passband and I would have just worked the stronger off frequency station). For my style of operating this was a disappointment. I tried AGC-F and AGC-S but I forgot to try AGC off. I also varied the AGC THR and AGC SLP. I tried NR off and on. (I was not using NB). I tried PRE and ATT off and on. I tried riding the RF gain. I tried shifting the passband but shift doesn't work well when the width is only 50Hz. Nothing helped. I also tried opening up the passband. That didn't help either but I don't remember the results. This was not a one time thing. It happened at least 20 different times on different bands. I guess this is perfectly normal. I was just wondering what operational trick is available to compensate. 73, Mike K2MK __ 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 receiver desensing on CW during contest
The behavior you are describing is almost the same thing I complained about a couple weeks ago. In my case I was trying to sort out several signals calling me in a pileup, but it's the same basic situation. Fast agc, even with the highest threshold and slp=0, compressed them all into an indecipherable mush. I'll tell you how I deal with it, but I'm not recommending this for everybody: agc off config af lim = 30 (tech mode) use preamp on 20m and higher no preamp on 40 no preamp + attenuator on for 80/160 plug headphones into speaker jack, so you don't hit the AF Limiter threshold. (There will be some hiss, but not too bad.) RF gain as low as possible AF gain as low as possible to protect your ears. WATCH OUT FOR YOUR EARS WITH THIS SETUP!! I am hoping that the Elecraft folks will raise the AF limiter threshold or allow disabling the limiter. If the limiter is activated, all signals are horribly distorted. Limiter threshold is abrupt and hard. This setup is probably not for everybody, but it works great for me. Dave Hachadorian, K6LL Yuma, AZ - Original Message - From: K2MK k...@comcast.net To: Elecraft Reflector elecraft@mailman.qth.net Sent: Monday, February 23, 2009 12:45 AM Subject: [Elecraft] K3 receiver desensing on CW during contest I had a great time with my K3 during the ARRL DX contest. I do SP and I was trolling around with my filter width at 50Hz. Absolutely outstanding. The auto spot is equally outstanding. At 50Hz width it was quite clear that many stations call off frequency. Using RIT, I could see that it was typical for them to be 70Hz or more away from the DX station but I could not hear them in my 50Hz passband. The real problem was when one of them was S9 or greater. They completely swamped weaker DX stations. Sound within the passband just blanked out. No band noise and no DX station. And there was no recovery between dits and dahs. It was actually easier to copy the DX station when people were calling directly on top of him. You could at least hear him between the dits. (Obviously if I was calling CQ instead of SP I would have a wider passband and I would have just worked the stronger off frequency station). For my style of operating this was a disappointment. I tried AGC-F and AGC-S but I forgot to try AGC off. I also varied the AGC THR and AGC SLP. I tried NR off and on. (I was not using NB). I tried PRE and ATT off and on. I tried riding the RF gain. I tried shifting the passband but shift doesn't work well when the width is only 50Hz. Nothing helped. I also tried opening up the passband. That didn't help either but I don't remember the results. This was not a one time thing. It happened at least 20 different times on different bands. I guess this is perfectly normal. I was just wondering what operational trick is available to compensate. 73, Mike K2MK __ 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 receiver desensing on CW during contest
I saw the same thing with a huge fairly weak pileup on 20m's today. This really needs to get fixed asap. It makes working a pileup almost impossible. A slip of the foot you may soon recover, but a slip of the tongue you may never get over. Ben Franklin -Original Message- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of Dave Hachadorian Sent: Sunday, February 22, 2009 6:26 PM To: Elecraft reflector Subject: Re: [Elecraft] K3 receiver desensing on CW during contest The behavior you are describing is almost the same thing I complained about a couple weeks ago. In my case I was trying to sort out several signals calling me in a pileup, but it's the same basic situation. Fast agc, even with the highest threshold and slp=0, compressed them all into an indecipherable mush. I'll tell you how I deal with it, but I'm not recommending this for everybody: agc off config af lim = 30 (tech mode) use preamp on 20m and higher no preamp on 40 no preamp + attenuator on for 80/160 plug headphones into speaker jack, so you don't hit the AF Limiter threshold. (There will be some hiss, but not too bad.) RF gain as low as possible AF gain as low as possible to protect your ears. WATCH OUT FOR YOUR EARS WITH THIS SETUP!! I am hoping that the Elecraft folks will raise the AF limiter threshold or allow disabling the limiter. If the limiter is activated, all signals are horribly distorted. Limiter threshold is abrupt and hard. This setup is probably not for everybody, but it works great for me. Dave Hachadorian, K6LL Yuma, AZ - Original Message - From: K2MK k...@comcast.net To: Elecraft Reflector elecraft@mailman.qth.net Sent: Monday, February 23, 2009 12:45 AM Subject: [Elecraft] K3 receiver desensing on CW during contest I had a great time with my K3 during the ARRL DX contest. I do SP and I was trolling around with my filter width at 50Hz. Absolutely outstanding. The auto spot is equally outstanding. At 50Hz width it was quite clear that many stations call off frequency. Using RIT, I could see that it was typical for them to be 70Hz or more away from the DX station but I could not hear them in my 50Hz passband. The real problem was when one of them was S9 or greater. They completely swamped weaker DX stations. Sound within the passband just blanked out. No band noise and no DX station. And there was no recovery between dits and dahs. It was actually easier to copy the DX station when people were calling directly on top of him. You could at least hear him between the dits. (Obviously if I was calling CQ instead of SP I would have a wider passband and I would have just worked the stronger off frequency station). For my style of operating this was a disappointment. I tried AGC-F and AGC-S but I forgot to try AGC off. I also varied the AGC THR and AGC SLP. I tried NR off and on. (I was not using NB). I tried PRE and ATT off and on. I tried riding the RF gain. I tried shifting the passband but shift doesn't work well when the width is only 50Hz. Nothing helped. I also tried opening up the passband. That didn't help either but I don't remember the results. This was not a one time thing. It happened at least 20 different times on different bands. I guess this is perfectly normal. I was just wondering what operational trick is available to compensate. 73, Mike K2MK __ 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 receiver desensing on CW during contest
Mike, The K3 is virtually desense-proof, with a BDR of ~140 dB. But to take advantage of this, you need a narrow crystal filter -- the closer to the DSP bandwidth the better. This is exactly the situation that we had in mind when we designed the 200-Hz 5-pole filter. For CW pileups, you can't beat it. What crystal filter were you using at the time? Of course if the transmitting stations are wide due to key clicks, there may be situations where no amount of filtering can help (for any receiver). The DSP noise blanker and NR may be useful sometimes -- you might give this a try. Wayne N6KR On Feb 22, 2009, at 4:45 PM, K2MK wrote: I had a great time with my K3 during the ARRL DX contest. I do SP and I was trolling around with my filter width at 50Hz. Absolutely outstanding. The auto spot is equally outstanding. At 50Hz width it was quite clear that many stations call off frequency. Using RIT, I could see that it was typical for them to be 70Hz or more away from the DX station but I could not hear them in my 50Hz passband. The real problem was when one of them was S9 or greater. They completely swamped weaker DX stations. --- http://www.elecraft.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 receiver desensing on CW during contest
I have the 200, 400, 1000 and 2.7 I do not recall which one I was using at the time. At least the 400hz. Keep in mind these signals were all s7 and below, most well below. I was fresh blood on 20m this morning and got spotted. It was an ugly pileup. The adjacent qrm was not an issue. When I could get one letter and had one or two people calling it was fine when 5 or more the signals all were the same strength and as Dave said mushy like. I did have to rit off and pick off those not zero beat. All my pileup training goes against having super narrow filters as you want to hear those on your sides too. This issue had nothing to do with wide signals or clicks. I don't think it is desense either it is more of an overload of the audio circuitry where all the signal levels are being capped or captured to a specific level. While the pileup was maybe S3 when I picked out station and he was all alone the signal would come up considerably. Why I don't know. There was no local noise issues and no hams close by causing issues. Just passing on what I experienced. Overall the radio is great on CW. I worked so many very weak stations easily that I contribute to the fine receiver in the K3. A slip of the foot you may soon recover, but a slip of the tongue you may never get over. Ben Franklin -Original Message- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of wayne burdick Sent: Sunday, February 22, 2009 7:27 PM To: K2MK Cc: Elecraft Reflector Subject: Re: [Elecraft] K3 receiver desensing on CW during contest Mike, The K3 is virtually desense-proof, with a BDR of ~140 dB. But to take advantage of this, you need a narrow crystal filter -- the closer to the DSP bandwidth the better. This is exactly the situation that we had in mind when we designed the 200-Hz 5-pole filter. For CW pileups, you can't beat it. What crystal filter were you using at the time? Of course if the transmitting stations are wide due to key clicks, there may be situations where no amount of filtering can help (for any receiver). The DSP noise blanker and NR may be useful sometimes -- you might give this a try. Wayne N6KR On Feb 22, 2009, at 4:45 PM, K2MK wrote: I had a great time with my K3 during the ARRL DX contest. I do SP and I was trolling around with my filter width at 50Hz. Absolutely outstanding. The auto spot is equally outstanding. At 50Hz width it was quite clear that many stations call off frequency. Using RIT, I could see that it was typical for them to be 70Hz or more away from the DX station but I could not hear them in my 50Hz passband. The real problem was when one of them was S9 or greater. They completely swamped weaker DX stations. --- http://www.elecraft.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 __ 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 receiver desensing on CW during contest
I think what they are seeing is this: Strong signals that fall slightly outside the DSP's audio passband are still pumping the S-meter and the AGC is desensing the receiver. The DSP is acting more like and audio filter than an IF DSP. In other words, the DSP's audio bandpass is very steep but it's IF bandpass is broad. This is with the 200Hz roofing filter installed but we are dealing with this 50Hz issue. To illustrate, tune in an S-9 carrier using the 50Hz filter. Tune off his signal 60Hz. The audio is gone but the S meter still reads S-9 telling me that the slopes for audio and IF are different. Also, at 50Hz BW the Passband tuning is indeed useless since it tunes in 50Hz increments. Can that be reduced? Steve Ellington n...@carolina.rr.com - Original Message - From: wayne burdick n...@elecraft.com To: K2MK k...@comcast.net Cc: Elecraft Reflector elecraft@mailman.qth.net Sent: Sunday, February 22, 2009 9:27 PM Subject: Re: [Elecraft] K3 receiver desensing on CW during contest Mike, The K3 is virtually desense-proof, with a BDR of ~140 dB. But to take advantage of this, you need a narrow crystal filter -- the closer to the DSP bandwidth the better. This is exactly the situation that we had in mind when we designed the 200-Hz 5-pole filter. For CW pileups, you can't beat it. What crystal filter were you using at the time? Of course if the transmitting stations are wide due to key clicks, there may be situations where no amount of filtering can help (for any receiver). The DSP noise blanker and NR may be useful sometimes -- you might give this a try. Wayne N6KR On Feb 22, 2009, at 4:45 PM, K2MK wrote: I had a great time with my K3 during the ARRL DX contest. I do SP and I was trolling around with my filter width at 50Hz. Absolutely outstanding. The auto spot is equally outstanding. At 50Hz width it was quite clear that many stations call off frequency. Using RIT, I could see that it was typical for them to be 70Hz or more away from the DX station but I could not hear them in my 50Hz passband. The real problem was when one of them was S9 or greater. They completely swamped weaker DX stations. --- http://www.elecraft.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 __ 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 receiver desensing on CW during contest
Have to ditto whats been said, I have to run with AGC off, audio set about 3 o'clock and use the RF gain. That seems to work fairly well, I use the 400HZ filter most of the time. Not sure what the problem is but the audio goes to pot in a hurry in a pile up. Sounds strange and no pure tone to the signals. Was beginning to chalk it up as my problem with old age, not knowing how to set parameters or ?? I have bought new headphones of several types thinking it was an audio problem here, but so far nothing works, I agree mine does not seem to be desense as I can get within a few hundred HZ of very strong signals and copy a single weak signal fine. Merv KH7C I have the 200, 400, 1000 and 2.7 I do not recall which one I was using at the time. At least the 400hz. Keep in mind these signals were all s7 and below, most well below. I was fresh blood on 20m this morning and got spotted. It was an ugly pileup. The adjacent qrm was not an issue. When I could get one letter and had one or two people calling it was fine when 5 or more the signals all were the same strength and as Dave said mushy like. I did have to rit off and pick off those not zero beat. All my pileup training goes against having super narrow filters as you want to hear those on your sides too. This issue had nothing to do with wide signals or clicks. I don't think it is desense either it is more of an overload of the audio circuitry where all the signal levels are being capped or captured to a specific level. While the pileup was maybe S3 when I picked out station and he was all alone the signal would come up considerably. Why I don't know. There was no local noise issues and no hams close by causing issues. Just passing on what I experienced. Overall the radio is great on CW. I worked so many very weak stations easily that I contribute to the fine receiver in the K3. A slip of the foot you may soon recover, but a slip of the tongue you may never get over. Ben Franklin -Original Message- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of wayne burdick Sent: Sunday, February 22, 2009 7:27 PM To: K2MK Cc: Elecraft Reflector Subject: Re: [Elecraft] K3 receiver desensing on CW during contest Mike, The K3 is virtually desense-proof, with a BDR of ~140 dB. But to take advantage of this, you need a narrow crystal filter -- the closer to the DSP bandwidth the better. This is exactly the situation that we had in mind when we designed the 200-Hz 5-pole filter. For CW pileups, you can't beat it. What crystal filter were you using at the time? Of course if the transmitting stations are wide due to key clicks, there may be situations where no amount of filtering can help (for any receiver). The DSP noise blanker and NR may be useful sometimes -- you might give this a try. Wayne N6KR On Feb 22, 2009, at 4:45 PM, K2MK wrote: I had a great time with my K3 during the ARRL DX contest. I do SP and I was trolling around with my filter width at 50Hz. Absolutely outstanding. The auto spot is equally outstanding. At 50Hz width it was quite clear that many stations call off frequency. Using RIT, I could see that it was typical for them to be 70Hz or more away from the DX station but I could not hear them in my 50Hz passband. The real problem was when one of them was S9 or greater. They completely swamped weaker DX stations. --- http://www.elecraft.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 __ 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 receiver desensing on CW during contest
I believe that I encountered this a couple of times while in VP5 last fall... there wasn't a roar of stations, the radio just sort of sat there and 'hummed'. I turned the radio off, then back on, rechecked all of the settings, and kept going. Brian N9ADG --- On Sun, 2/22/09, Merv Schweigert k...@flex.com wrote: From: Merv Schweigert k...@flex.com goes to pot in a hurry in a pile up. Sounds strange and no pure tone to the signals. Was beginning to chalk it up as my problem with \ __ 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 receiver desensing on CW during contest
Merv Try going into the Config and setting your AGC THR down to 003 and see if that improves. I had mine too high at one time and it caused stronger stations to distort. Steve Ellington n...@carolina.rr.com - Original Message - From: Merv Schweigert Cc: 'Elecraft Reflector' Sent: Sunday, February 22, 2009 11:31 PM Subject: Re: [Elecraft] K3 receiver desensing on CW during contest Have to ditto whats been said, I have to run with AGC off, audio set about 3 o'clock and use the RF gain. That seems to work fairly well, I use the 400HZ filter most of the time. Not sure what the problem is but the audio goes to pot in a hurry in a pile up. Sounds strange and no pure tone to the signals. Was beginning to chalk it up as my problem with old age, not knowing how to set parameters or ?? I have bought new headphones of several types thinking it was an audio problem here, but so far nothing works, I agree mine does not seem to be desense as I can get within a few hundred HZ of very strong signals and copy a single weak signal fine. Merv KH7C I have the 200, 400, 1000 and 2.7 I do not recall which one I was using at the time. At least the 400hz. Keep in mind these signals were all s7 and below, most well below. I was fresh blood on 20m this morning and got spotted. It was an ugly pileup. The adjacent qrm was not an issue. When I could get one letter and had one or two people calling it was fine when 5 or more the signals all were the same strength and as Dave said mushy like. I did have to rit off and pick off those not zero beat. All my pileup training goes against having super narrow filters as you want to hear those on your sides too. This issue had nothing to do with wide signals or clicks. I don't think it is desense either it is more of an overload of the audio circuitry where all the signal levels are being capped or captured to a specific level. While the pileup was maybe S3 when I picked out station and he was all alone the signal would come up considerably. Why I don't know. There was no local noise issues and no hams close by causing issues. Just passing on what I experienced. Overall the radio is great on CW. I worked so many very weak stations easily that I contribute to the fine receiver in the K3. A slip of the foot you may soon recover, but a slip of the tongue you may never get over. Ben Franklin -Original Message- From: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] On Behalf Of wayne burdick Sent: Sunday, February 22, 2009 7:27 PM To: K2MK Cc: Elecraft Reflector Subject: Re: [Elecraft] K3 receiver desensing on CW during contest Mike, The K3 is virtually desense-proof, with a BDR of ~140 dB. But to take advantage of this, you need a narrow crystal filter -- the closer to the DSP bandwidth the better. This is exactly the situation that we had in mind when we designed the 200-Hz 5-pole filter. For CW pileups, you can't beat it. What crystal filter were you using at the time? Of course if the transmitting stations are wide due to key clicks, there may be situations where no amount of filtering can help (for any receiver). The DSP noise blanker and NR may be useful sometimes -- you might give this a try. Wayne N6KR On Feb 22, 2009, at 4:45 PM, K2MK wrote: I had a great time with my K3 during the ARRL DX contest. I do SP and I was trolling around with my filter width at 50Hz. Absolutely outstanding. The auto spot is equally outstanding. At 50Hz width it was quite clear that many stations call off frequency. Using RIT, I could see that it was typical for them to be 70Hz or more away from the DX station but I could not hear them in my 50Hz passband. The real problem was when one of them was S9 or greater. They completely swamped weaker DX stations. --- http://www.elecraft.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 __ 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
