Re: [Elecraft] Sensitivity - Was K4 Observations
On Sun, May 19, 2019 at 12:06 PM Jim Brown wrote: > ... FT8 can work about 10 dB deeper into the noise than CW with good > radios and very good operators > on both ends. I've worked a lot of both modes. > > On 5/19/2019 6:50 AM, Wes wrote: > > FT8 reports negative SNRs number but we both know those are bogus > For those who care about the relative communications efficacy of various modes, here's a Joe Taylor document from the archives with some discussion and analysis, which provides theoretical confirmation of the comments made above by Jim and earlier by Joe W4TV. http://physics.princeton.edu/pulsar/K1JT/EME_Florence_2008.pdf As a side note, we all seen many occasions when FT8 or WSPR could decode signals that were completely inaudible and invisible on a pan. 73, Tony KT0NY __ 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] Sensitivity - Was K4 Observations
These techniques all end up using more bandwidth than a simple scheme, and the larger bandwidth itself increase the N in SNR. There is actually a theory for the case of idealised white noise and no other degradation (both of which are likely to be assumed in the cases previously discussed), that sets a theoretical limit to the error free digital communication rate of channel, based on bandwidth and SNR. This is the Shannon - Hartley theorem, and states that the capacity in bits per second is: bandwidth * log2 (1 + Signal / Noise) Note that this formula still has a positive result even if the signal is only minutely greater than zero. The holy grail of communications coding is to get as close as possible to this without having excessive latency. Maybe a better figure of merit for these, "below the noise" digital systems would be to quote the channel capacity as a percentage of the Shannon limit. I think the system used for 5G mobile phones get very close. One does have to be careful with bits per second, as I understand that FT8 relies on some parts of transmissions carrying less bits than needed to encode the characters in the standard code used, e.g. the number of bits actually represented by a call sign is log2 (number of possible callsigns) and the number encoded in FT8 is log2 (number of active FT8 callsigns). -- David Woolley Owner K2 06123 On 19/05/2019 19:15, Joe Subich, W4TV wrote: There is one place that digital modes (like those by Joe Taylor and associates) can improve the decoded SNR beyond simply reducing the detection bandwidth. If the modulation/encoding supports N states but the encoding only uses M of those states, the decoding software can make use of the "sparse constellation" to recognize states that are impacted by noise and select the "closest" valid state. This "coding gain" can improve the overall SNR beyond that provided simply by the "matched" (or optimal) noise bandwidth. However, with all amateur modes (CW to FT8 & FT4) the majority of the SNR improvement over SSB (or AM) is simply due to the use of optimal bandwidth to reduce extraneous noise in the detector bandwidth. Even with SSB, properly tailoring the IF bandwidth will make several dB difference in the detected SNR. For example, a 2 KHz bandwidth (500 - 2500 Hz) can provide significant improvement over a 2.8 KHz bandwidth (200 - 3000 Hz) under noisy conditions. __ 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] Sensitivity - Was K4 Observations
As Joe-W4TV nicely explained, digital modes excel due to occupying less bandwidth which also reduces noise bandwidth. There is some "high-tech" coding that adds to the overall sensitivity of the modes. CW eme operators are said to be able to reduce bandwidth "in their heads" to 50-Hz. When I ran CW eme, I found setting my radio to 100 to 200 Hz worked best for me. 50-Hz DSP filter caused too much ringing for me to discern the CW note. Radio sensitivity requirements are mostly set by band noise whose minimum is established by "celestial" (or sky noise). Such noise is commonly characterized as applicable sky noise temperature (in Kevin). Tsky (144-MHz) is thought to be about 250K. At 432 that lowers to 70K and above 1000 MHz approx 10K. Receiver sensitivity is tied to noise figure (which also can be thought of as a temperature (Trx). Overall receiving sensitivity Te = Tsky + Trx + Tant The last factor, Tant mostly refers to how much noise the antenna sees. Earth at 70F is 290K. So if your antenna sidelobes see the earth, that adds to minimum sensitivity one can achieve. A typical 144-MHz eme receiving system noise temp: Te = 250K + 70K + 29K = 349K. Trx=70 is roughly a noise figure of 0.5 dB. As one goes higher in frequency, sky noise is less so one wants the receiver to be less, to improve overall sensitivity. But as one goes lower in frequency sky noise rises a lot. Tsky (50-MHz) is roughly 2000K and Tsky (28-MHz) is 5000K (or more). Making a HF receiver super low noise (low noise figure and thus more sensitive) is severely limited by Tsky (which is in 10,000K to 100,000K). And note that I did not add any factor for human generated noise sources. Te = Tsky + Trx + Tant + Tman-made Sensitivity is measured in signal power which is related to system noise temperature b the formula: Pn = KTB. K is Botlzmanns constant. T is Te derived above. And B is detection bandwidth in Hz. If noise power, Pn is in terms of dBm, then Pn = -198.6 + 10Log(Te) + 10Log(B) SNR = Ps - Pn, where Ps is signal power in dBm. SNR=0 is at the noise level (where Ps = Pn). K3 (with PR6) is spec at Pn = -143 dBm at B=500,000 Hz which is very sensitive. That level would only make a difference on 10m or 6m due to lower sky noise. 73, Ed - KL7UW http://www.kl7uw.com Dubus-NA Business mail: dubus...@gmail.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] Sensitivity - Was K4 Observations
There is one place that digital modes (like those by Joe Taylor and associates) can improve the decoded SNR beyond simply reducing the detection bandwidth. If the modulation/encoding supports N states but the encoding only uses M of those states, the decoding software can make use of the "sparse constellation" to recognize states that are impacted by noise and select the "closest" valid state. This "coding gain" can improve the overall SNR beyond that provided simply by the "matched" (or optimal) noise bandwidth. However, with all amateur modes (CW to FT8 & FT4) the majority of the SNR improvement over SSB (or AM) is simply due to the use of optimal bandwidth to reduce extraneous noise in the detector bandwidth. Even with SSB, properly tailoring the IF bandwidth will make several dB difference in the detected SNR. For example, a 2 KHz bandwidth (500 - 2500 Hz) can provide significant improvement over a 2.8 KHz bandwidth (200 - 3000 Hz) under noisy conditions. 73, ... Joe, W4TV On 2019-05-19 11:19 AM, Tom Azlin W7SUA wrote: More like a "feel good" detection SNR? I think fldigi uses a few bins either side of the signal to determine the noise in the SNR measurement. When I narrow my K3 IF bandwidth down to just the, say Olivia, bandwidth the SNR number climb up to 30 dB high as the filter cut the noise in the adjacent "noise" bins. If I use a 600-700 Hz filter or wider for a 500 Hz wide Olivia then the SNR measurements stay the same. So I have always thought along the lines of your two emails Joe. Plus long time ago I discovered how I could add FFTs up and a coherent signal would "climb" out of the random noise. So for a signal with considerable time per bin measurement you get that gain as well. So have always thought of the WSJT type negative numbers as bogus. 73, tom w7sua On 5/19/2019 7:18 AM, Joe Subich, W4TV wrote: On 2019-05-19 9:50 AM, Wes wrote: FT8 reports negative SNRs number but we both know those are bogus. All of the modes that quote negative SNRs are doing so by using SNR in a voice (2500 Hz) bandwidth *NOT* SNR in the detector bandwidth (bandwidth of the final filter whether than be a narrow IF filter, the "ear-brain" filter or a software [computation] filter). If one looks at the SNR thresholds of the various Joe Taylor "slow" modes, 80% of the "negative" SNR can be attributed entirely to the difference between the occupied bandwidth and the [excess] measurement bandwidth. The remainder can be attributed to software processing algorithms that take advantage of the fact that noise is random while the signal is not - in essence reporting using a "peak noise" level while actually decoding against a "minimum noise" level (like copying CW through static crashes - one looses a dit/dah during the crash but fills that in from the context). 73, ... Joe, W4TV On 2019-05-19 9:50 AM, Wes wrote: I feel like I'm gonna be slappin' a tar baby by responding. Since we are discussion HF radios, I was assuming HF. I realize JT65(-HF) and JT9 have been used on HF, but the QSOs are hardly random. If your computer clock is off, sorry, no QSO. FT8 reports negative SNRs number but we both know those are bogus. Wes N7WS On 5/19/2019 5:58 AM, Ed W0YK wrote: JT65, JT9, FT8. 73, Ed W0YK ---- Original message ---- From: Wes Date: 5/19/19 07:49 (GMT-06:00) To: elecraft@mailman.qth.net Subject: Re: [Elecraft] Sensitivity - Was K4 Observations What current modes hear below the noise level? 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 __ 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] Sensitivity - Was K4 Observations
Regarding W0YK/Ed’s comment – The 8-ary FSK of FT-8 may be buried in the ambient noise at my/your/somebody’s QTH. Like LPI communications, knowing where to look in frequency and time allows the decoder to combine noisy samples and recover the original; in the case of FT-8, a 63 bit message. Your receiver does not hear the 63 bits, just the symbols used in statistically recreating the 63 bits. The real issue with sensitivity or receiver NF is making sure that the receiver is a weak contributor to the overall noise power entering the detection process which is generally dominated by ambient noise. Most of the radios in the top Sherwood top 10 are weak contributors in most locations, even in the CCIR-defined quiet rural environments. 73 Bob R – N7WY __ 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] Sensitivity - Was K4 Observations
On 5/19/2019 6:28 AM, Joe Subich, W4TV wrote: if the "effective" bandwidth for CW is on the order of 100 Hz a CW signal right at the noise in the 100 Hz "ear/brain filter" would be -14 dB in a 2500 Hz wide SSB filter. This estimate correlates well with my own that FT8 can work about 10 dB deeper into the noise than CW with good radios and very good operators on both ends. I've worked a lot of both modes. On 5/19/2019 6:50 AM, Wes wrote: FT8 reports negative SNRs number but we both know those are bogus. Not if you read the definitions within the WSJT-X docs. Joe has done that, and correctly interprets the numbers. 73, Jim 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] Sensitivity - Was K4 Observations
We all now (i guess) that decoding below the noise floor needs: Time, timing and repetition.. no formulas needed . 73's, Evert PA2KW -Oorspronkelijk bericht- Van: elecraft-boun...@mailman.qth.net [mailto:elecraft-boun...@mailman.qth.net] Namens Joe Subich, W4TV Verzonden: zondag 19 mei 2019 15:29 Aan: elecraft@mailman.qth.net Onderwerp: Re: [Elecraft] Sensitivity - Was K4 Observations Buck, New mode "hear below the noise" in a normal SSB bandwidth even though they may be as narrow as 16 to 50 Hz (in the case of JT9 and FT8). The largest part of the claimed -21 to -27 dB S/N threshold is based on the difference in noise bandwidth. The actual "filters" for each of the "tones" are just 1 - 2 Hz wide and there one still needs to "hear atmospheric noise." Using the standard 10*log(BWn/BWw) equation, one needs to hear ~20-25 dB atmospheric noise (4-5 S units in a K3/K3S) before reducing the RF gain! This is, however, not really any different than switching from SSB to CW ... if the "effective" bandwidth for CW is on the order of 100 Hz a CW signal right at the noise in the 100 Hz "ear/brain filter" would be -14 dB in a 2500 Hz wide SSB filter. 73, ... Joe, W4TV On 2019-05-19 7:42 AM, Buck wrote: > Here's a question about sensitivity. We used to say if you could hear > the atmospheric noise, that was enough. Time to reduce RF gain. > > New modes hear below the noise and DSP is getting better at removing it. > Does that mean our "old" wisdom is now wrong and sensitivity below > the noise level is useful? > > Buck, k4ia > Honor Roll > 8BDXCC > EasyWayHamBooks.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] Sensitivity - Was K4 Observations
I've often wondered what the effective bandwidth of a good CW operator was. I've noticed that, unless there's QRM, reducing the receiver bandwidth really doesn't help, so the limit factor is the "processing". On the other hand, neither does slowing down below perhaps 15 wpm, as if the processing just can't make the effective bandwidth any lower. Perhaps the real advantage of the JT modes is that they can take advantage of the lower noise bandwidth at very slow speeds, while our brains can't. It would be interesting to compare the performance at 15 wpm. 73, Scott K9MA On 5/19/2019 09:18, Joe Subich, W4TV wrote: On 2019-05-19 9:50 AM, Wes wrote: FT8 reports negative SNRs number but we both know those are bogus. All of the modes that quote negative SNRs are doing so by using SNR in a voice (2500 Hz) bandwidth *NOT* SNR in the detector bandwidth (bandwidth of the final filter whether than be a narrow IF filter, the "ear-brain" filter or a software [computation] filter). If one looks at the SNR thresholds of the various Joe Taylor "slow" modes, 80% of the "negative" SNR can be attributed entirely to the difference between the occupied bandwidth and the [excess] measurement bandwidth. The remainder can be attributed to software processing algorithms that take advantage of the fact that noise is random while the signal is not - in essence reporting using a "peak noise" level while actually decoding against a "minimum noise" level (like copying CW through static crashes - one looses a dit/dah during the crash but fills that in from the context). 73, ... Joe, W4TV On 2019-05-19 9:50 AM, Wes wrote: I feel like I'm gonna be slappin' a tar baby by responding. Since we are discussion HF radios, I was assuming HF. I realize JT65(-HF) and JT9 have been used on HF, but the QSOs are hardly random. If your computer clock is off, sorry, no QSO. FT8 reports negative SNRs number but we both know those are bogus. Wes N7WS On 5/19/2019 5:58 AM, Ed W0YK wrote: JT65, JT9, FT8. 73, Ed W0YK Original message From: Wes Date: 5/19/19 07:49 (GMT-06:00) To: elecraft@mailman.qth.net Subject: Re: [Elecraft] Sensitivity - Was K4 Observations What current modes hear below the noise level? Wes N7WS -- Scott K9MA k...@sdellington.us __ 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] Sensitivity - Was K4 Observations
More like a "feel good" detection SNR? I think fldigi uses a few bins either side of the signal to determine the noise in the SNR measurement. When I narrow my K3 IF bandwidth down to just the, say Olivia, bandwidth the SNR number climb up to 30 dB high as the filter cut the noise in the adjacent "noise" bins. If I use a 600-700 Hz filter or wider for a 500 Hz wide Olivia then the SNR measurements stay the same. So I have always thought along the lines of your two emails Joe. Plus long time ago I discovered how I could add FFTs up and a coherent signal would "climb" out of the random noise. So for a signal with considerable time per bin measurement you get that gain as well. So have always thought of the WSJT type negative numbers as bogus. 73, tom w7sua On 5/19/2019 7:18 AM, Joe Subich, W4TV wrote: On 2019-05-19 9:50 AM, Wes wrote: FT8 reports negative SNRs number but we both know those are bogus. All of the modes that quote negative SNRs are doing so by using SNR in a voice (2500 Hz) bandwidth *NOT* SNR in the detector bandwidth (bandwidth of the final filter whether than be a narrow IF filter, the "ear-brain" filter or a software [computation] filter). If one looks at the SNR thresholds of the various Joe Taylor "slow" modes, 80% of the "negative" SNR can be attributed entirely to the difference between the occupied bandwidth and the [excess] measurement bandwidth. The remainder can be attributed to software processing algorithms that take advantage of the fact that noise is random while the signal is not - in essence reporting using a "peak noise" level while actually decoding against a "minimum noise" level (like copying CW through static crashes - one looses a dit/dah during the crash but fills that in from the context). 73, ... Joe, W4TV On 2019-05-19 9:50 AM, Wes wrote: I feel like I'm gonna be slappin' a tar baby by responding. Since we are discussion HF radios, I was assuming HF. I realize JT65(-HF) and JT9 have been used on HF, but the QSOs are hardly random. If your computer clock is off, sorry, no QSO. FT8 reports negative SNRs number but we both know those are bogus. Wes N7WS On 5/19/2019 5:58 AM, Ed W0YK wrote: JT65, JT9, FT8. 73, Ed W0YK Original message From: Wes Date: 5/19/19 07:49 (GMT-06:00) To: elecraft@mailman.qth.net Subject: Re: [Elecraft] Sensitivity - Was K4 Observations What current modes hear below the noise level? 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 __ 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] Sensitivity - Was K4 Observations
On 2019-05-19 9:50 AM, Wes wrote: FT8 reports negative SNRs number but we both know those are bogus. All of the modes that quote negative SNRs are doing so by using SNR in a voice (2500 Hz) bandwidth *NOT* SNR in the detector bandwidth (bandwidth of the final filter whether than be a narrow IF filter, the "ear-brain" filter or a software [computation] filter). If one looks at the SNR thresholds of the various Joe Taylor "slow" modes, 80% of the "negative" SNR can be attributed entirely to the difference between the occupied bandwidth and the [excess] measurement bandwidth. The remainder can be attributed to software processing algorithms that take advantage of the fact that noise is random while the signal is not - in essence reporting using a "peak noise" level while actually decoding against a "minimum noise" level (like copying CW through static crashes - one looses a dit/dah during the crash but fills that in from the context). 73, ... Joe, W4TV On 2019-05-19 9:50 AM, Wes wrote: I feel like I'm gonna be slappin' a tar baby by responding. Since we are discussion HF radios, I was assuming HF. I realize JT65(-HF) and JT9 have been used on HF, but the QSOs are hardly random. If your computer clock is off, sorry, no QSO. FT8 reports negative SNRs number but we both know those are bogus. Wes N7WS On 5/19/2019 5:58 AM, Ed W0YK wrote: JT65, JT9, FT8. 73, Ed W0YK Original message From: Wes Date: 5/19/19 07:49 (GMT-06:00) To: elecraft@mailman.qth.net Subject: Re: [Elecraft] Sensitivity - Was K4 Observations What current modes hear below the noise level? 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 __ 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] Sensitivity - Was K4 Observations
I feel like I'm gonna be slappin' a tar baby by responding. Since we are discussion HF radios, I was assuming HF. I realize JT65(-HF) and JT9 have been used on HF, but the QSOs are hardly random. If your computer clock is off, sorry, no QSO. FT8 reports negative SNRs number but we both know those are bogus. Wes N7WS On 5/19/2019 5:58 AM, Ed W0YK wrote: JT65, JT9, FT8. 73, Ed W0YK Original message From: Wes Date: 5/19/19 07:49 (GMT-06:00) To: elecraft@mailman.qth.net Subject: Re: [Elecraft] Sensitivity - Was K4 Observations What current modes hear below the noise level? 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] Sensitivity - Was K4 Observations
Buck, New mode "hear below the noise" in a normal SSB bandwidth even though they may be as narrow as 16 to 50 Hz (in the case of JT9 and FT8). The largest part of the claimed -21 to -27 dB S/N threshold is based on the difference in noise bandwidth. The actual "filters" for each of the "tones" are just 1 - 2 Hz wide and there one still needs to "hear atmospheric noise." Using the standard 10*log(BWn/BWw) equation, one needs to hear ~20-25 dB atmospheric noise (4-5 S units in a K3/K3S) before reducing the RF gain! This is, however, not really any different than switching from SSB to CW ... if the "effective" bandwidth for CW is on the order of 100 Hz a CW signal right at the noise in the 100 Hz "ear/brain filter" would be -14 dB in a 2500 Hz wide SSB filter. 73, ... Joe, W4TV On 2019-05-19 7:42 AM, Buck wrote: Here's a question about sensitivity. We used to say if you could hear the atmospheric noise, that was enough. Time to reduce RF gain. New modes hear below the noise and DSP is getting better at removing it. Does that mean our "old" wisdom is now wrong and sensitivity below the noise level is useful? Buck, k4ia Honor Roll 8BDXCC EasyWayHamBooks.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] Sensitivity - Was K4 Observations
JT65, JT9, FT8.73,Ed W0YK Original message From: Wes Date: 5/19/19 07:49 (GMT-06:00) To: elecraft@mailman.qth.net Subject: Re: [Elecraft] Sensitivity - Was K4 Observations What current modes hear below the noise level?Wes N7WSOn 5/19/2019 4:42 AM, Buck wrote:> Here's a question about sensitivity. We used to say if you could hear the > atmospheric noise, that was enough. Time to reduce RF gain.>> New modes hear below the noise and DSP is getting better at removing it. Does > that mean our "old" wisdom is now wrong and sensitivity below the noise level > is useful?>> Buck, k4ia> Honor Roll> 8BDXCC> EasyWayHamBooks.com__Elecraft mailing listHome: http://mailman.qth.net/mailman/listinfo/elecraftHelp: http://mailman.qth.net/mmfaq.htmPost: mailto:elecr...@mailman.qth.netThis list hosted by: http://www.qsl.netPlease 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] Sensitivity - Was K4 Observations
What current modes hear below the noise level? Wes N7WS On 5/19/2019 4:42 AM, Buck wrote: Here's a question about sensitivity. We used to say if you could hear the atmospheric noise, that was enough. Time to reduce RF gain. New modes hear below the noise and DSP is getting better at removing it. Does that mean our "old" wisdom is now wrong and sensitivity below the noise level is useful? Buck, k4ia Honor Roll 8BDXCC EasyWayHamBooks.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] Sensitivity - Was K4 Observations
Here's a question about sensitivity. We used to say if you could hear the atmospheric noise, that was enough. Time to reduce RF gain. New modes hear below the noise and DSP is getting better at removing it. Does that mean our "old" wisdom is now wrong and sensitivity below the noise level is useful? Buck, k4ia Honor Roll 8BDXCC EasyWayHamBooks.com On 5/19/2019 6:58 AM, John Stengrevics wrote: Buck, Did you happen to discuss: 1. Noise blanker improvement 2. Improvement in sensitivity Relative to the K3S? 73, John WA1EAZ On May 18, 2019, at 11:09 PM, Buck wrote: The following is offered based on my observations and discussions at the Elecraft booth. I am *not* an official, or even unofficial, Elecraft spokesman and stand willing to be corrected. First, this is going to be another game-changer from Elecraft. The radio will have outstanding performance figures and an interface to die for. The screen is beautiful and functions can be controlled from either buttons or the touch-screen. There is band-stacking on the touch screen, a nit people have complained about on the K3. The radio is full SDR as opposed to the analog front end of the K3. However an option, the K4HD, is a superhet receive function. Like previous Elecraft radios, this can be added later if you think you need it. Preliminary is that it will not be necessary unless you operate in the presence of strong stations (multi-multi). Another option has a second set of band pass filters and ADC module that will allow the two receivers to operate on different bands or antennas (K4D). The radio contains a Linux computer so all this magic does not require an external computer except for logging or audio input. The rig will be addressable locally or over the internet with no additional software. I saw it operated from an iPad and Android is coming. The iPad screen looked exactly like the front panel, including the panadapter. There are multiple USB ports, an Ethernet port, RS232 and an HDMI port so you can project the front panel, or parts of it, to an external monitor. The panadapter looks awesome on the external monitor and you will be able to point and click to QSY the radio. The prices are targets but I got the impression the final will be very close. The cost is less than a fully loaded K3s. The kit version will be cheaper than factory-assembled and ship several months later to allow time to write the assembly manual. Target for the factory version is November. I suspect the K4 will replace the K3 series as K3s sales are sure to suffer because of product age and competition from the K4. I did not hear any talk about sun-setting the K3s when the K4 comes out. I am sure there are many people who will want to buy the basic K3s and upgrade over time (or not) rather than plunk down $4,000 for the K4. What does this do to the value of a K3 or K3s? I expect there will be some coming on the market. Anyone who buys, or retains, a K3 or K3s will still have one of the finest radios ever made. We are at the point where the difference among the top 5 or so on Sherwood's charts is a decibel or two, almost within the margin of error and certainly beyond the ability of the human ear to discern. So, don't panic. The demand for the K3 series will be strong for many years to come. Keep an eye on the website as more information comes from Watsonville. -- Buck, k4ia Honor Roll 8BDXCC EasyWayHamBooks.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
