150 watt "boots" for 160m
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In technical school after being a HAM for over 9 years I learned that it took 10Db change in level to perceive a doubling of audible signal level,,, 3 db hard to detect. I worked on modems during the Vietnam at a site for 1 year after tech school and all our old equipment was lab quality. I did this all day long for 6 days a week for a year. I know and heard what I write. Bill K9YEQ K2-#35 (2 more), KX1-#35, K3, TS2000, IC7000, etc. > From: [hidden email] > To: [hidden email] > Date: Fri, 11 Dec 2009 14:16:54 -0800 > Subject: Re: [Elecraft] [K3] 150 watt "boots" for 160m > > Quite right Bill, in an audio laboratory or perhaps in a very quiet > telephone circuit. > > But radio communications is different according to what I learned in school, > lo' these many years past. Over half a century ago most radio communications > engineers began using 3 dB (2:1 power ratio) as the minimum change in a > signal level that would normally be just discernable to the listener, > considering typical band noise and QSB. That was based in actual on-the-air > observations by a great many operators over time. > > When considering changing my power level, I never consider it worthwhile to > change less than 3 dB and more typically 6 to 10 dB as the minimum worth > bothering with (e.g. shifting from a K2/10 at 10-15 watts CW to a K2/100 was > a just worthwhile shift). > > When I was much younger and more "innocent" I used to scramble for each > little watt, exulting in running 30 watts instead of 20 watts from a 6L6, > for example, or tweaking my 6146 rig to run 90 instead of 75 watts and > feeling sure that made a big difference. It sure seemed to produce more > results from calls. But, looking back over logs over time, it was clearly an > illusion.. > > That's when I acquired the sign that still hangs over my desk to remind me > that "Believing is Seeing". > > So I don't argue with people who want to make what is a quantifiable silly > choice. Instead I say, "If you want to do it and you believe it's worth it, > do it." > > I'm no different. After all, we humans make most of our choices based on > emotion and then we use rational logic to justify the choice. > > Ron AC7AC > > -----Original Message----- > >From 100 to 150, for 1.7 dB, when Bell Laboratories research (with > huge capital investment and telephone maintenance dollars on the line) > determined that 3 dB was the signal strength change discernment for > most people? > > I'm not sure who said 3 dB was the minimum detectable by a listener but I > believe it's incorrect. 1 dB "roughly matched the smallest attenuation > detectable to an average listener". (see below) > > "The decibel originates from methods used to quantify reductions in audio > levels in telephone circuits. These losses were originally measured in units > of Miles of Standard Cable (MSC), where 1 MSC corresponded to the loss of > power over a 1 mile (approximately 1.6 km) length of standard telephone > cable at a frequency of 5000 radians per second (795.8 Hz) and roughly > matched the smallest attenuation detectable to an average listener. Standard > telephone cable was defined as "a cable having uniformly distributed > resistances of 88 ohms per loop mile and uniformly distributed shunt > capacitance of .054 microfarad per mile" (approximately 19 gauge)." > > http://en.wikipedia.org/wiki/Decibel#History > > 73, Bill > > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html _________________________________________________________________ Hotmail: Trusted email with Microsoft’s powerful SPAM protection. http://clk.atdmt.com/GBL/go/177141664/direct/01/ ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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Bill,
I do not dispute anything you say, but, I would like to offer the following: Recently I was having a QSO with a mobile station using a mono-band antenna on a motor home, he was able to switch between a Kenwood TS-480SAT (100w) and a TS-480HX (200w) radios. Both radios used the same antenna and repeated switches between them revealed the following: TS-480SAT @100w gave me S-3 on my K3 with no pre-amp TS-480HX @200w gave me S-4+ with no pre-amp Audio wise (ssb) I was able to hear the 480SAT but copy was not 100 percent. The 480HX was easier to copy and was 100 percent readable. I know this is less than Lab quality material, but it demonstrated to me that 200w is likely to be better a significant number of times more than using 100w The frequency we were on was 7.103 LSB where us "motorhomers" hang out in VK Land. I would opt for a 200w PA in a heartbeat and judging by the sales of the 480's in VK there is definitely a market for a 200w PA. 73's Gary VK4FD Sent via BlackBerry® from Telstra -----Original Message----- From: Bill Johnson <[hidden email]> Date: Mon, 14 Dec 2009 21:07:24 To: <[hidden email]> Subject: Re: [Elecraft] [K3] 150 watt "boots" for 160m In technical school after being a HAM for over 9 years I learned that it took 10Db change in level to perceive a doubling of audible signal level,,, 3 db hard to detect. I worked on modems during the Vietnam at a site for 1 year after tech school and all our old equipment was lab quality. I did this all day long for 6 days a week for a year. I know and heard what I write. Bill K9YEQ K2-#35 (2 more), KX1-#35, K3, TS2000, IC7000, etc. > From: [hidden email] > To: [hidden email] > Date: Fri, 11 Dec 2009 14:16:54 -0800 > Subject: Re: [Elecraft] [K3] 150 watt "boots" for 160m > > Quite right Bill, in an audio laboratory or perhaps in a very quiet > telephone circuit. > > But radio communications is different according to what I learned in school, > lo' these many years past. Over half a century ago most radio communications > engineers began using 3 dB (2:1 power ratio) as the minimum change in a > signal level that would normally be just discernable to the listener, > considering typical band noise and QSB. That was based in actual on-the-air > observations by a great many operators over time. > > When considering changing my power level, I never consider it worthwhile to > change less than 3 dB and more typically 6 to 10 dB as the minimum worth > bothering with (e.g. shifting from a K2/10 at 10-15 watts CW to a K2/100 was > a just worthwhile shift). > > When I was much younger and more "innocent" I used to scramble for each > little watt, exulting in running 30 watts instead of 20 watts from a 6L6, > for example, or tweaking my 6146 rig to run 90 instead of 75 watts and > feeling sure that made a big difference. It sure seemed to produce more > results from calls. But, looking back over logs over time, it was clearly an > illusion.. > > That's when I acquired the sign that still hangs over my desk to remind me > that "Believing is Seeing". > > So I don't argue with people who want to make what is a quantifiable silly > choice. Instead I say, "If you want to do it and you believe it's worth it, > do it." > > I'm no different. After all, we humans make most of our choices based on > emotion and then we use rational logic to justify the choice. > > Ron AC7AC > > -----Original Message----- > >From 100 to 150, for 1.7 dB, when Bell Laboratories research (with > huge capital investment and telephone maintenance dollars on the line) > determined that 3 dB was the signal strength change discernment for > most people? > > I'm not sure who said 3 dB was the minimum detectable by a listener but I > believe it's incorrect. 1 dB "roughly matched the smallest attenuation > detectable to an average listener". (see below) > > "The decibel originates from methods used to quantify reductions in audio > levels in telephone circuits. These losses were originally measured in units > of Miles of Standard Cable (MSC), where 1 MSC corresponded to the loss of > power over a 1 mile (approximately 1.6 km) length of standard telephone > cable at a frequency of 5000 radians per second (795.8 Hz) and roughly > matched the smallest attenuation detectable to an average listener. Standard > telephone cable was defined as "a cable having uniformly distributed > resistances of 88 ohms per loop mile and uniformly distributed shunt > capacitance of .054 microfarad per mile" (approximately 19 gauge)." > > http://en.wikipedia.org/wiki/Decibel#History > > 73, Bill > >______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html _________________________________________________________________ Hotmail: Trusted email with Microsoft’s powerful SPAM protection. http://clk.atdmt.com/GBL/go/177141664/direct/01/ ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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Yes, 200 watts is better than 100 and it may even be possible to put it in
the K3, but then you will want 400 or 600 and that is not the way to get it. IMHO, there is a lot to be gained by going from 100 to 400 or 500 watts (or pick your own number) and not really much benefit beyond that to go all the way to 1500 unless you are trying to bust pileups. There are several amplifiers out there, even new, that aren't really all that expensive. If you just want to talk mostly anywhere anytime, 400-600 watts will do the trick for all practical purposes. AL811, new list is 749 and will do better than 500 and the ALS500 if you want solid state (849 new list) from "12 volts" will do 500 watts just fine (battery close enough and mutiple short #10 wires to it). Used they are very reasonable. I am glad I have a SUPER Radio they put their time into and will put my own amp behind it. K3 #1442, 73, de Jim KG0KP ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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i am still looking for kpa800 or kpa1600. A kit serviceable by us is awaited.
73 Johnny vr2xmc Jim Miller KG0KP wrote: > Yes, 200 watts is better than 100 and it may even be possible to put it in > the K3, but then you will want 400 or 600 and that is not the way to get it. > IMHO, there is a lot to be gained by going from 100 to 400 or 500 watts (or > pick your own number) and not really much benefit beyond that to go all the > way to 1500 unless you are trying to bust pileups. There are several > amplifiers out there, even new, that aren't really all that expensive. If > you just want to talk mostly anywhere anytime, 400-600 watts will do the > trick for all practical purposes. AL811, new list is 749 and will do better > than 500 and the ALS500 if you want solid state (849 new list) from "12 > volts" will do 500 watts just fine (battery close enough and mutiple short > #10 wires to it). Used they are very reasonable. > I am glad I have a SUPER Radio they put their time into and will put my own > amp behind it. > K3 #1442, 73, de Jim KG0KP > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > This list hosted by: http://www.qsl.net > Please help support this email list: http://www.qsl.net/donate.html Yahoo!香港提供網上安全攻略，教你如何防範黑客! 請前往 http://hk.promo.yahoo.com/security/ 了解更多! ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Bill K9YEQ
In 1963's telephone school for newly employed wet-behind-the-ears AT&T
testboardmen, we were taught 3 db as the discernible change, and the reason why circuits that "toned out" more than a half db off had to be patched out of service and adjusted spot on. The only way to get from anywhere to anywhere with a long distance circuit was to switch shorter circuits together end to end, six times a half db was 3 db. You could plainly hear DC - Chicago - LA combos getting long and we'd make lists to pull out on midnight tours. Spent three years doing that. Until we got transistorized line bays later on that were more stable than the vaccum tube design, it was work a lot of overtime. Their maintenance schedule, the tens of thousands of of testboardmen they hired was based on the Bell Laboratories research on the matter. For that reason I may have an attachment to it, as ultimately it paid for my first house and car and put my kids through college, and is now paying retirement. If they'd said 2 dB maybe I never get hired. If one wants to dig up the research, it's found in the Bell System Technical Journal (BSTJ). This would be the stuff that everyone else refers to: 'C. F. Sacia and G. W. Beck, "The Power of Fundamental Speech Sounds," Bell Syst. Tech. J., vol. 5, pp. 395-403 (1926)' 'Harvey Fletcher and W.A. Munson, "Loudness, Its Definition, Measurement, and Calculation," Bell Syst Tech J., vol 12, issue 4 pp 377 ff.(October 1933)' Abstract: [Empirical formula for calculating loudness of any steady sound from analysis of intensity and frequency of its components developed; based on fundamental properties of hearing mechanism in such way that scale of loudness values results; in order to determine form of function representing this loudness scale, measurements were made of loudness levels....] 73, Guy. On Mon, Dec 14, 2009 at 10:07 PM, Bill Johnson <[hidden email]> wrote: > > In technical school after being a HAM for over 9 years I learned that it took 10Db change in level to perceive a doubling of audible signal level,,, 3 db hard to detect. I worked on modems during the Vietnam at a site for 1 year after tech school and all our old equipment was lab quality. I did this all day long for 6 days a week for a year. I know and heard what I write. > > > Bill > K9YEQ > K2-#35 (2 more), KX1-#35, K3, TS2000, IC7000, etc. > > > > >> From: [hidden email] >> To: [hidden email] >> Date: Fri, 11 Dec 2009 14:16:54 -0800 >> Subject: Re: [Elecraft] [K3] 150 watt "boots" for 160m >> >> Quite right Bill, in an audio laboratory or perhaps in a very quiet >> telephone circuit. >> >> But radio communications is different according to what I learned in school, >> lo' these many years past. Over half a century ago most radio communications >> engineers began using 3 dB (2:1 power ratio) as the minimum change in a >> signal level that would normally be just discernable to the listener, >> considering typical band noise and QSB. That was based in actual on-the-air >> observations by a great many operators over time. >> >> When considering changing my power level, I never consider it worthwhile to >> change less than 3 dB and more typically 6 to 10 dB as the minimum worth >> bothering with (e.g. shifting from a K2/10 at 10-15 watts CW to a K2/100 was >> a just worthwhile shift). >> >> When I was much younger and more "innocent" I used to scramble for each >> little watt, exulting in running 30 watts instead of 20 watts from a 6L6, >> for example, or tweaking my 6146 rig to run 90 instead of 75 watts and >> feeling sure that made a big difference. It sure seemed to produce more >> results from calls. But, looking back over logs over time, it was clearly an >> illusion.. >> >> That's when I acquired the sign that still hangs over my desk to remind me >> that "Believing is Seeing". >> >> So I don't argue with people who want to make what is a quantifiable silly >> choice. Instead I say, "If you want to do it and you believe it's worth it, >> do it." >> >> I'm no different. After all, we humans make most of our choices based on >> emotion and then we use rational logic to justify the choice. >> >> Ron AC7AC >> >> -----Original Message----- >> >From 100 to 150, for 1.7 dB, when Bell Laboratories research (with >> huge capital investment and telephone maintenance dollars on the line) >> determined that 3 dB was the signal strength change discernment for >> most people? >> >> I'm not sure who said 3 dB was the minimum detectable by a listener but I >> believe it's incorrect. 1 dB "roughly matched the smallest attenuation >> detectable to an average listener". (see below) >> >> "The decibel originates from methods used to quantify reductions in audio >> levels in telephone circuits. These losses were originally measured in units >> of Miles of Standard Cable (MSC), where 1 MSC corresponded to the loss of >> power over a 1 mile (approximately 1.6 km) length of standard telephone >> cable at a frequency of 5000 radians per second (795.8 Hz) and roughly >> matched the smallest attenuation detectable to an average listener. Standard >> telephone cable was defined as "a cable having uniformly distributed >> resistances of 88 ohms per loop mile and uniformly distributed shunt >> capacitance of .054 microfarad per mile" (approximately 19 gauge)." >> >> http://en.wikipedia.org/wiki/Decibel#History >> >> 73, Bill >> >> ______________________________________________________________ >> Elecraft mailing list >> Home: http://mailman.qth.net/mailman/listinfo/elecraft >> Help: http://mailman.qth.net/mmfaq.htm >> Post: mailto:[hidden email] >> >> This list hosted by: http://www.qsl.net >> Please help support this email list: http://www.qsl.net/donate.html > > _________________________________________________________________ > Hotmail: Trusted email with Microsoft’s powerful SPAM protection. > http://clk.atdmt.com/GBL/go/177141664/direct/01/ > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by hf4me
Gentlemen,
I am happy with the K3 in its present configuration that is either a 10W or 100W output transmitter. I only run a fraction of the output when using my Acom 1000 amplifier. The radio is very lightly loaded. A 200W K3 would be bigger and require a larger power supply and would be of no interest to me at all unless this was all that was on offer. Keep the K3 price down and let people source their amplifiers separately. I suspect this is the better philosophy if one wants the export market. The K3 has the best RX, can drive any amplifier and it sells at a competitive price. Now if we are talking external amplifiers well that is different. Boy is there a lot of competition out there. With respect I doubt many people will purchase 250 Watt amplifiers. A good kit for 800 Watts and another for 1600 Watts might be a seller. No one does a kit amplifier these days as far as I know. Please ignore or forgive me if my thoughts differ with yours. I am only an old dinosaur. One thing for sure I would not want Elecrafter to hurt itself with a product which does not sell. We are a fortunate group with such a fine radio and company service. Happy Christmas and New Year. 73 Doug EI2CN ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Guy, K2AV
http://www.audioholics.com/education/acoustics-principles/human-hearing-amplitude-sensitivity-part-1 "Speaking now in terms of dB SPL, the minimum discernable changes by the human ear/brain mechanism I've seen in the research that I've reviewed ranged from about 0.5 dB to 3 dB, depending on a number of factors." Table 1 (see the referenced link above or below) In Table 1 we see a collection of studies spanning 60 years. It should be kept in mind that in each case the results were obtained under laboratory-ideal conditions. Even so, we see a range of values from .25 dB to 3 dB. The resultant range is owing to varying methodologies used by the researchers and, of course, the response of the human hearing apparatus to the applied acoustic signals. <SNIP> From the third column of Table 1, we see the minimum detectable value, for the most part, hovers around 1 dB, +/- a fraction of a dB, and that attainable only with ideal (or at least as ideal as technology allowed for at the time the study was done) laboratory test conditions and test subjects. I tend to use .75 dB to 1 dB when considering minimums." http://www.audioholics.com/education/acoustics-principles/human-hearing-amplitude-sensitivity-part-1 73, Bill |
dB Changes, Loudness, and Signal to Noise Ratio
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On Tue, 15 Dec 2009 06:32:42 -0800 (PST), Bill W4ZV wrote:
>http://www.audioholics.com/education/acoustics-principles/human-hearing- amplitude-sensitivity-part-1 >In Table 1 we see a collection of studies spanning 60 years. It should be >kept in mind that in each case the results were obtained under >laboratory-ideal conditions. Even so, we see a range of values from .25 dB >to 3 dB. The resultant range is owing to varying methodologies used by the >researchers and, of course, the response of the human hearing apparatus to >the applied acoustic signals. I posted the following before, but somehow it appears to have been missed. The quotations above, and ALL of the discussions about what's perceptible and what isn't are talking about the LOUDNESS of a sound. Note the title in the link -- "amplitude sensitivity." That is VERY DIFFERENT from radio communications, where we are mostly concerned with SIGNAL TO NOISE RATIOS and INTELLIGIBILITY. There's nothing WRONG about the tutorial that Bill has posted, but it applies to a different problem. The first time I had this point driven home to me was around 1974, when I was balancing levels for an acoustic paging and background music system in a multi-story federal office building in downtown Chicago. In rooms where the background music was held just above the noise level, paging was significantly hotter. Changes in level of only a dB were quite obvious on the background music, and either "right" or "wrong" BECAUSE they were in reference to the background noise level! But that same dB change was hardly noticable on the paging, because the paging was at a higher level relative to the noise. When we make our transmit signal a few dB stronger with an amplifier or a better antenna, or when we add audio processing (compression, peak limiting), or when we run those multiple Beverages that Bill has talked about, or when we narrow up the RX bandwidth to pull out a weak signal, we are working on the signal to noise ratio, NOT LOUDNESS. It's apples and oranges! The only thing in common is that we're using a log ratio to describe it. 73, Jim Brown K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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On Dec 15, 2009, at 9:52 AM, Jim Brown wrote: > ...we are working on the signal to noise ratio, NOT LOUDNESS. It's apples and > oranges! The only thing in common is that we're using a log ratio to > describe it. I couldn't agree more with Jim on this one. In our "business," we are trying to get information across, instead of determining if one signal is louder than another. This is demonstrated especially well with digital modes, where we can measure with objective detectors instead of using the subjective gray matter between our ears. Take a look at this example for DominoEX 8: http://homepage.mac.com/chen/Technical/DominoEX/AWGN/AWGN/dominoex8.html The vertical axis is the percentage character error rate. Notice that for the primary DominoEX channel, a single dB of signal-to-noise ratio change, from a SNR of -13 dB to a SNR of -14 dB, moves the percentage character error from about 0.2% to almost 2%, a factor of almost 10 of errors. (In case you wonder how deep the signal is within noise and yet be copied reliably, it is really not. The noise in the above plot is measured within a 3 kHz bandwidth. In a 500 Hz noise bandwidth for example, the -13 dB SNR would correspond to about -5 dB SNR; albeit, still not too shabby. This is why you often see the SNR expressed as Eb/No in technical circles, but hams like to use SNR within 3 kHz noise bandwidth.) Steep sensitivity curves like this is very typical for digital mode demodulators. The curves do flatten out when you add multipath and Rayleigh fading. It can be seen in the example here: http://homepage.mac.com/chen/Technical/DominoEX/ITU/ITU/nvis.html That being said, there are cases where even a 10 dB increase in power will still not get you anywhere. In extreme propagation cases, some modes don't get through no matter how much power you use, see the case of non-FEC DominoEX 4 (blue curve) here, while the FEC versions will get through: http://homepage.mac.com/chen/Technical/DominoEX/ITU/ITU/highLatModerate.html 73 Chen, W7AY ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Bill W4ZV
Bill, W4ZV wrote:
"Guy, K2AV wrote: > > If one wants to dig up the research... > http://www.audioholics.com/education/acoustics-principles/human-hearing-amplitude-sensitivity-part-1 "Speaking now in terms of dB SPL, the minimum discernable changes by the human ear/brain mechanism I've seen in the research that I've reviewed ranged from about 0.5 dB to 3 dB, depending on a number of factors." Table 1 (see the referenced link above or below) ...SNIP..." That someone can, with certain individuals and certain conditions detect less than 3 dB, I would not dispute, any more than I would dispute a Beethoven or John Williams. This is taken into account in the same article you referenced above. ***EMPHASIS ADDED***: ----begin reference quote ----- "For example, Reisz in his 1928 study used two tones, close in frequency that beat slowly. The beating caused amplitude fluctuations and the minimum audible fluctuation was ~ 1dB. Toole and Olive, on the other hand, in their 1988 study used pink noise for their acoustic signal source and determined that a 5 kHz resonance, with Q = 1 was just detectible at .25 dB. They found pink noise to be the most revealing signal. ***THEY DID EMPLOY OTHER TYPES OF ACOUSTIC SIGNALS IN THEIR STUDY*** and discovered that ***WHEN USING THE LEAST REVEALING*** of these that ***JUST DETECTIBLE THRESHOLD INCREASED BY A FACTOR OF 5***. >From the third column of Table 1, we see the ***MINIMUM** detectable value, for the most part, hovers around 1 dB, +/- a fraction of a dB, and and that attainable ***ONLY*** with ideal (or at least as ideal as technology allowed for at the time the study was done) ***[IDEAL] LABORATORY TEST CONDITIONS AND [IDEAL] TEST SUBJECTS.*** I tend to use .75 dB to 1 dB when considering minimums." ----end reference quote---- When using the least revealing of these acoustic signals Reisz detectible threshold increased by a factor of 5. 5 dB or 5 times the voltage? Either way that's a huge handicap for not having ideal conditions. Show me something less ideal than QRN based noise varying 20 db on 80 or 160, a pile up half composed of hams that used ctrl-arrow/F4 and a spot to drop on exactly the same frequency as the DX. And then remember it's THEIR ears we're talking about, not ours. We are not talking about ideal laboratory test conditions, or ideal most talented test subjects or about the best possible result. Reisz' work was available to Bell Labs when the 3 dB maintenance standard was decided upon. The "lab" the phone company was going to have to spend money on (lots of it) was the real world. The Bell System decided that if it got to be 3 dB they would hire employees, buy test equipment, pay salaries and lay away for retirements to fix it. If it's 3 dB or leads to three dB it has to be fixed. In my experience in the phone company, they WOULD fix the 0.2 in a bad (wrapped but not soldered) connection, the 0.4 in a coil gone bad, the 0.9 in a soft tube, but they would find it looking for 3 dB or maintaining components to a 3 dB overall performance. Overall connections less than 3 dB off were in the "ain't broke don't fix it", let maintenance snug it up whenever it happens category. Maintenance was the least expensive way to stay inside 3 dB. And they had gain controls to suck up a fair amount of routine variation. This is no different than picking appropriate feedlines for antennas, soldering coax shields in PL259 connectors (be surprised how many don't), etc, etc. We COULD see 0.1 dB in our AT&T themocouples and line meters but we wouldn't patch a circuit out of service and ticket it for 1 dB. Wasn't that where we started this discussion, at what dB do we spend money on it? At the time, with Reisz' work in hand, the phone company that the rest of the world envied, that had the labs that gave us the transistor, picked 3 dB. And still, no one talks about the 27 dB between the ears. What was it they called a lid with an amp? A loud lid? How smart is it to ctrl-arrow/F4 and call DX on exactly the same frequency as ten other stations that did the same thing. What's that worth? Minus ten dB? Minus twenty? I've heard a QRO east coast multi, with 4 over 4 on forty at 100' and 200' braying zero beat to the F4 mob and getting beat six or seven times, including by one guy I know was running a wire antenna. There is some ancient wisdom still around that hasn't lost its lustre. YMMV and everyone entitled to spend their money however they want, but I'm saying it takes a smart op (one of those "ideals" that Reisz was talking about) to make 1.5 dB pay for itself 73 all, and may you always work the DX. Guy. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: dB Changes, Loudness, and Signal to Noise Ratio
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In reply to this post by Kok Chen
On Tue, 2009-12-15 at 11:14 -0800, Kok Chen wrote:
> On Dec 15, 2009, at 9:52 AM, Jim Brown wrote: > > > ...we are working on the signal to noise ratio, NOT LOUDNESS. It's apples and > > oranges! The only thing in common is that we're using a log ratio to > > describe it. > > I couldn't agree more with Jim on this one. I also agree. On the other hand, in actual on-the-air operation you almost never have a constant signal-to-noise ratio. With typical fading and interference coming and going, I seriously doubt you could ever notice a 1 dB change in power level. During 99% of the QSO the signal is either well above the threshold of copy-ability or well below. It would be very rare that a 1 dB increase in power could turn a non-contact into a valid QSO. On the other-other hand, even if 1 dB made the difference in only one contact in a thousand, that might be very important to a world-class contester. At that level of competition, a 0.1% increase in contacts could be the difference between winning and losing. So I think the bottom line is that 1 dB would make no discernable difference in casual operation. But for someone contesting at the highest levels. that is, someone who has a serious chance of winning a CQWW or a Sweepstakes, a 1 dB improvement is very worthwhile. Al N1AL ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Kok Chen
There was an interesting series of low power beacon receiving tests conducted in December 2004 through January 2005 by N2XE. John sent a beacon ID message including a unique code word at various power levels on 80m over a several day period. You had to correctly copy each code word correctly to verify reception. There's a lot of documentation on the Topband and QRP-L lists over that period, but here's a brief summary of the results: 80 uW - 8 stations correctly copied. 40 uW - 1 station 27 uW - 1 station 20 uW - 0 stations. The power difference in dB at each succeeding lower level was (top to bottom): -3 dB (i.e. the 80 uW to 40 uW test) -1.7 dB -1.3 dB I copied the beacon at both the 40 uW and 27 uW levels but could not decipher the code word at 20 uW even though I could detect presence of the signal. Unfortunately N2XE ran 20 uW only briefly (because at that point nobody else was hearing it). I believe I could have copied it if he had run it as long as he ran the other tests. The point of this is that small changes in dB do indeed make a difference in the ear/brain's ability to **copy** weak signals in noise, which is really what the discussion is about. Tom W8JI added the following interesting observation (which I also noticed and agree with): "Now for the curious effect I observed. While I didn't spend a large amount of time listening to 80 and I never listened to 40 at all, I did notice one thing that I found interesting. Listening to the very low power transmissions on 80 meters I observed a very pronounced signal peak just before sunrise. The effect was very much like the effect called "search light" or "spot light" propagation. While the signal was largely in the noise and unreadable from 0900 Z until 1120 Z, I observed a very clear "strong" peak between 1125 and 1135 Z where the signal was the equivalent of about a "559" or better DX report. By 1138 copy was back to nil with an increase that provided a short 2 minute long readable signal starting at 1143 Z . After 1145 Z that was it for the signal. I never really noticed this effect over the same path when power levels were higher and signal levels stronger, although I'm sure the path loss went through similar variations. This is why even one dB sounds like a large change when signals are in the noise, and is meaningless with "579" signals." http://lists.contesting.com/archives//html/Topband/2005-01/msg00023.html 73, Bill |
Re: dB Changes, Loudness, and Signal to Noise Ratio
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In reply to this post by Alan Bloom
On Tue, 15 Dec 2009 13:23:27 -0800, Alan Bloom wrote:
>So I think the bottom line is that 1 dB would make no discernable >difference in casual operation. Strongly agree. > But for someone contesting at the >highest levels. that is, someone who has a serious chance of winning a >CQWW or a Sweepstakes, a 1 dB improvement is very worthwhile. AND for working DX when conditions are marginal. I regularly run my Titan amp at 1kW or less to let the tubes and power supply loaf. But if I'm having trouble making a Q, I'll kick the drive up to get to 1.5kW. More than once it has made the difference. NCCC member Bill, N6ZFO, did some statistical analysis and came to the conclusion that 1 dB of signal strength was good for a 2.6% increase in Sweepstakes score. 73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: dB Changes, Loudness, and Signal to Noise Ratio
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Administrator
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[END of Thread (and all other related dB, 100-150-200w threads)]
Guys - Thought I ended this thread several days ago. Let's end it again now as we are beating it to death. :-) Must be a slow news day. (or no sun spots!) 73, Eric WA6HHQ elecraft moderator ---- Jim Brown wrote: > On Tue, 15 Dec 2009 13:23:27 -0800, Alan Bloom wrote: > > >> So I think the bottom line is that 1 dB would make no discernable >> ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Alan Bloom
> On the other-other hand, even if 1 dB made the difference in only one
> contact in a thousand, that might be very important to a world-class > contester. At that level of competition, a 0.1% increase in contacts > could be the difference between winning and losing. What you suggest sounds good, but.... At a world class contest station it's not how loud we transmit that is the maker/breaker. It's how well we receive. If the guy on the other end is running 100 watts to an antenna made of something metallic, shame on us if we don't work them. Working the QRP, basement noodle antenna crowd will make a difference. Getting the other station's call letters the FIRST time, in spite of pileups, noise, weak signal or whatever, ditto their exchange, will improve rate and make a difference. Who owns the last biggest tenth of a dB is a phallic symbol, testosterone thing. It's far easier to be loud. But RX is what wins contests. 73, Guy. ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Eric Swartz - WA6HHQ
At 03:19 PM 15/12/09, you wrote:
>Must be a slow news day. (or no sun spots!) > >73, Eric WA6HHQ As a matter of fact, there are some sun spots and the flux is over 80. Activity on 10 & 15 meters. John k7up ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Bill W4ZV
I'm sorry, but didn't you just prove that it took over 3 dB to make
the signal generally copyable from possibly copyable? Potentially copiable at 27 uW (because one did), generally copyable at 80 uW, a difference of 4.7 dB. Makes me wonder if a couple of threads on the merits of dB aren't being written in two languages, e.g. just barely copiable (by at least someone), and separately, generally copyable. 73, Guy. On Tue, Dec 15, 2009 at 4:33 PM, Bill W4ZV <[hidden email]> wrote: > There was an interesting series of low power beacon receiving tests > conducted in December 2004 through January 2005 by N2XE. John sent a beacon > ID message including a unique code word at various power levels on 80m over > a several day period. You had to correctly copy each code word correctly to > verify reception. There's a lot of documentation on the Topband and QRP-L > lists over that period, but here's a brief summary of the results: > > 80 uW - 8 stations correctly copied. > 40 uW - 1 station > 27 uW - 1 station > 20 uW - 0 stations. > > The power difference in dB at each succeeding lower level was (top to > bottom): > > -3 dB (i.e. the 80 uW to 40 uW test) > -1.7 dB > -1.3 dB > > I copied the beacon at both the 40 uW and 27 uW levels but could not > decipher the code word at 20 uW even though I could detect presence of the > signal. Unfortunately N2XE ran 20 uW only briefly (because at that point > nobody else was hearing it). I believe I could have copied it if he had run > it as long as he ran the other tests. > > The point of this is that small changes in dB do indeed make a difference in > the ear/brain's ability to **copy** weak signals in noise, which is really > what the discussion is about. Tom W8JI added the following interesting > observation (which I also noticed and agree with): > > "Now for the curious effect I observed. > > While I didn't spend a large amount of time listening to 80 > and I never listened to 40 at all, I did notice one thing > that I found interesting. Listening to the very low power > transmissions on 80 meters I observed a very pronounced > signal peak just before sunrise. The effect was very much > like the effect called "search light" or "spot light" > propagation. While the signal was largely in the noise and > unreadable from 0900 Z until 1120 Z, I observed a very > clear "strong" peak between 1125 and 1135 Z where the signal > was the equivalent of about a "559" or better DX report. By > 1138 copy was back to nil with an increase that provided a > short 2 minute long readable signal starting at 1143 Z . > After 1145 Z that was it for the signal. I never really > noticed this effect over the same path when power levels > were higher and signal levels stronger, although I'm sure > the path loss went through similar variations. This is why > even one dB sounds like a large change when signals are in > the noise, and is meaningless with "579" signals." > > http://lists.contesting.com/archives//html/Topband/2005-01/msg00023.html > > 73, Bill > > > > -- > View this message in context: http://n2.nabble.com/150-watt-boots-for-160m-tp4151943p4172347.html > Sent from the [K3] mailing list archive at Nabble.com. > ______________________________________________________________ > Elecraft mailing list > Home: http://mailman.qth.net/mailman/listinfo/elecraft > Help: http://mailman.qth.net/mmfaq.htm > Post: mailto:[hidden email] > > 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:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
Re: dB Changes, Loudness, and Signal to Noise Ratio
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In reply to this post by Guy, K2AV
On Tue, 15 Dec 2009 17:20:36 -0500, Guy Olinger K2AV wrote:
>It's far easier to be loud. But RX is what wins contests. It's certainly very important, but I don't think it's either-or, it's both. I know that my Beverages have made me a lot of Qs. Last night, I was trying to work ON4 on 160M. He was solid copy on my Beverage, but he couldn't pull me out of the noise to get my call right. 73, Jim K9YC ______________________________________________________________ Elecraft mailing list Home: http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/mmfaq.htm Post: mailto:[hidden email] This list hosted by: http://www.qsl.net Please help support this email list: http://www.qsl.net/donate.html |
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In reply to this post by Guy, K2AV
No Guy, I proved -1.3 dB (20 uW versus 27 uW) was the difference in one station and operator (i.e. yours truly) just detecting the signal versus having verified copy. End of thread per Eric's request. 73, Bill On Tue, Dec 15, 2009 at 4:33 PM, Bill W4ZV <btippett@alum.mit.edu> wrote: > There was an interesting series of low power beacon receiving tests > conducted in December 2004 through January 2005 by N2XE. John sent a beacon > ID message including a unique code word at various power levels on 80m over > a several day period. You had to correctly copy each code word correctly to > verify reception. There's a lot of documentation on the Topband and QRP-L > lists over that period, but here's a brief summary of the results: > > 80 uW - 8 stations correctly copied. > 40 uW - 1 station > 27 uW - 1 station > 20 uW - 0 stations. > > The power difference in dB at each succeeding lower level was (top to > bottom): > > -3 dB (i.e. the 80 uW to 40 uW test) > -1.7 dB > -1.3 dB > > I copied the beacon at both the 40 uW and 27 uW levels but could not > decipher the code word at 20 uW even though I could detect presence of the > signal. |
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