Decibels are ridiculous - Page 1
Forum section: electronics / general

author: abeyer
author_rank: Frequent Contributor
timestamp: May 23, 2025, 10:58:34 pm
content: hot takehttps://lcamtuf.substack.com/p/decibels-are-ridiculous

author: TimFox
author_rank: Super Contributor
timestamp: May 23, 2025, 11:11:46 pm
content: Yeah, logarithms are hard.Yeah, the Weber-Fechner law is for losers.https://royalsocietypublishing.org/doi/10.1098/rspa.2022.0626Real physicists use Nepers, instead.Why do people post these ridiculous celebrations of ignorance?

author: tom66
author_rank: Super Contributor
timestamp: May 23, 2025, 11:24:02 pm
content: I kind of agree with the author, it would be better if there was a distinct prefix for the voltage-law decibels, versus the power-law decibels. Like a "volti-bel", but, a better name than that, I'm rubbish at naming things. But like lots of systems, it evolved organically without planning, and it's what we've got. It probably won't get replaced unless there is a compelling reason to replace it, and being a little awkward isn't enough (after all, imperial marches on.)

author: TimFox
author_rank: Super Contributor
timestamp: May 23, 2025, 11:37:52 pm
content: I find it easy to distinguish the meaning of "dBV" and "dBu" from "dBm" and other power measurements."u" may be confusing to those encountering it for the first time, but it is a voltage corresponding to the voltage across 600 ohms, when dissipating 1 mW.What is misleading in bad usage is just saying "dB" when a reference such as "dBm" is needed.One should be careful when using dB as a ratio to measure voltage gain between undefined impedances, such as in a normal audio signal amplifier that has a large (non-critical) input impedance and normally drives a large (very non-critical) load impedance, such as a hi-fi preamplifier. Saying "voltage gain" should suffice.The author also admits to ignorance of "pascal" as a unit: SI is for losers, too.Anyway, when using dB to measure monetary ratios, remember to use the factor 10, rather than 20, since money is power.

author: SiliconWizard
author_rank: Super Contributor
timestamp: May 24, 2025, 12:26:36 am
content: "You've been taught decibels wrong". That also works.

author: Smokey
author_rank: Super Contributor
timestamp: May 24, 2025, 12:28:35 am
content: I think I get why RF guys use dB. It's like mathematical transforms. In some situations, when used as a mathematical tool, they make the calculations much easier.But with that said, since I'm not a "real" RF guy, decibels are mostly just annoying for me and everyone else that just wants to know the absolute value for volts, or watts, or whatever so we can get on with our jobs. The worst part in my opinion is that, at least from the outside, even RF guys doing RF stuff actually care more about the absolute value of the quantity most of the time and it's only occasionally that the math is actually easier as opposed to doing the extra step of dB to abs value conversion in your head anyway.[when I say abs value, I'm talking about that as opposed to the relative values of dB quantities, not abs(value).... 0dBm is relative to 1mW for example. Just say 1mW]

author: TimFox
author_rank: Super Contributor
timestamp: May 24, 2025, 01:49:59 am
content: That doesn’t make dB “ridiculous”: only ignorance makes that.

author: jonpaul
author_rank: Super Contributor
timestamp: May 24, 2025, 05:39:44 am
content: Garbage post and substack.Read any text on acoustics, and check origins of the term.j

author: fzabkar
author_rank: Super Contributor
timestamp: May 24, 2025, 05:56:53 am
content: I agree with the author. Just express the quantity as an absolute unit, not some logarithmic ratio whose meaning depends on the context and can be misconstrued. I've always hated dBs for this and other reasons.

author: TimFox
author_rank: Super Contributor
timestamp: May 24, 2025, 02:23:01 pm
content: I must disagree.Decibels applied properly with appropriate suffixes are clear to those who pay attention.I learned about log10(x) and how to use it at age 14.For example, cascading amplifiers and attenuators is a good reason to express ratios in dB.Similarly, using anoise figurein dB is easier to understand than anoise factor(q.v.).I once worked on a project to improve noise performance for a client who disliked dB and wanted to set the goal in percent rather than dB. I pointed out that if one increased a value by, say, 20% and then reduced it by 20%, one did not get back to the original value. We compromised by saying “increase by ratio 1.20:1” and “decrease by ratio 1.20:1”, which satisfied both of us but was clumsier than 0.8 dB.

author: radiolistener
author_rank: Super Contributor
timestamp: May 24, 2025, 03:13:23 pm
content: Quote from: Smokey on May 24, 2025, 12:28:35 amWhile decibels can feel unintuitive at first, they serve a very practical purpose - not only simplifying calculations, but also making absolute values much easier to read and interpret.For example, it's far more readable and meaningful to express a signal level as -120 dBm than to write it as 2.23607e-7 Vrms or 0.000000223607 Vrms or as 1e-15 Watt or 0.000000000000001 Watt.As you can see, without the use of dB, such values become nearly unreadable and impractical to compare or work with - especially without a calculator. dB, on the other hand, allow for quick read, interpretation, easy comparison, and mental calculation, all without the need to count zeros or handle cumbersome numeric formats.As for the perceived complexity or ridiculous - this issue is largely exaggerated. The concept of decibels is actually quite simple, it requires only basic arithmetic and basic logarithm and power function understanding. With a small investment of time to understand the logic behind it, you'll find there's nothing to fear - and you'll likely come to appreciate how effective and efficient the dB scale really is.

author: TimFox
author_rank: Super Contributor
timestamp: May 24, 2025, 03:52:31 pm
content: When doing mental calculations late at night in the dark, away from my calculators or paper, I did some simple arithmetic to work out the power ratio for integer dB, to a measly two significant figures, starting from +3 dB is 2.0 (so -3 dB is 0.50), 10 dB is 10, and +5 dB is 3.2 (so -5 dB is 0.32).1 dB = 3 dB + 3 dB - 5 dB is 2.0 x 2.0 x 0.32 = 1.32 dB = 5 dB - 3 dB is 3.2 x 0.50 = 1.63 dB is 2.04 dB = 3 dB + 3 dB + 3 dB - 5 dB is 8.0 x 0.32 = 2.65 dB is 3.26 dB = 3 dB + 3 dB is 2.0 x 2.0 = 4.07 dB = 10 dB - 3 dB is 10 x 0.5 = 5.08 dB = 5 dB + 3 dB is 3.2 x 2.0 = 6.49 dB = 3 dB + 3 dB + 3 dB is 2.0 x 2.0 x 2.0 = 8.010 dB is 10

author: madires
author_rank: Super Contributor
timestamp: May 24, 2025, 04:07:52 pm
content: Let those ignorant 'experts' do link budgets for microwave PtP links or glass fiber links and they'll change their opinion quite fast.

author: TimFox
author_rank: Super Contributor
timestamp: May 24, 2025, 04:31:21 pm
content: Continuing to pile on:Simple R-C low-pass filters are usually described by the -3 dB frequency and the asymptotic slope as 6 dB per octave or 20 dB per decade.One could describe them otherwise in a cumbersome manner.

author: ejeffrey
author_rank: Super Contributor
timestamp: May 24, 2025, 04:46:45 pm
content: I am not going to watch the video so I don't know if the argument is sound but I mostly agree with the sentiment. dB and related dBx units are at the very least overused. They are basically a relic of an era before cheap calculators, before computerized spreadsheets, and before it was just as easy to plot linear data on a log scale as it is to plot log data on a linear scale.Logarithmic units are definitely easy for doing pen and paper or whiteboard link estimates, but I would argue that at the level of precision implied, scientific notation provides most of the benefit of log scales while interacting better with other units and formulas as well as being easier to handle when you move to a computer. I learned my multiplication tables in 3rd grade.Of course the reality is that the field uses dB. If you want to be fluent in electrical engineering you need to be comfortable with it. Instruments and equipment are specified in dB, and confirming to the standard is generally more useful than using what you might think is best.And yes, I regularly deal with link budgets with well over 100 dB of range. I don't think my life would be harder if I wrote that as 1e-10.

author: TimFox
author_rank: Super Contributor
timestamp: May 24, 2025, 04:49:24 pm
content: How do you parameterize the simple low-pass filter in my example?

author: radiolistener
author_rank: Super Contributor
timestamp: May 24, 2025, 05:01:06 pm
content: Quote from: ejeffrey on May 24, 2025, 04:46:45 pmdB units remain essential not just due to historical momentum, but because they offer clarity and practicality in ways that scientific notation often doesn’t, especially when dealing with relative comparisons, cascaded systems, and component specifications.For example, consider a receiver with a noise floor at -120 dBm and an incoming signal at -90 dBm. It’s immediately clear you have 30 dB of headroom. Now try expressing that in linear power terms: 1e-12 W vs 1e-15 W, calculating and comparing these mentally is far less intuitive, and certainly more error-prone when done quickly or without a calculator. Especially when dealing with values that are not neat integers, but rather long and unwieldy fractional numbers.More importantly, in real-world RF chains, you’re constantly adding and subtracting gains and losses (antenna gain, cable loss, amplifier gain, etc.). In dB, it’s just simple arithmetic add/subtract: +15 dB amplifier -3 dB cable loss. In linear terms, that’s requiring multiplication and division of fractional powers - something not exactly convenient, even with a spreadsheet.In addition, dB notation provides a compact and consistent way to express values across vastly different scales. Whether you're describing phenomena at the microscopic level or on a cosmic scale, decibels allow you to represent them using short, readable numbers that remain intuitive and manageable.

author: TimFox
author_rank: Super Contributor
timestamp: May 24, 2025, 05:07:08 pm
content: Yet another reason to use dB: This is a rule of thumb, not an exact result.In many applications, the minimum change that seems to be important or perceptible is approximately 1 dB.Roughly, this can be a result of the Weber-Fechner Law I mentioned in my first post.An informal definition in acoustics: if you tell a kid to turn down the sound on the TV, he will reduce it by 1 dB.

author: radiolistener
author_rank: Super Contributor
timestamp: May 24, 2025, 05:21:10 pm
content: One of the key advantages of using dB is that differences remain consistent across related physical quantities, such as voltage and power, since they differ only by a fixed offset in dB. This allows seamless comparison and interpretation, which isn’t possible in a linear scale where each quantity must be treated independently.

author: Siwastaja
author_rank: Super Contributor
timestamp: May 25, 2025, 07:02:06 am
content: Yeah, the problem isn't in using logarithmic scales in itself, but the fact how much hidden assumptions are being added, which must be guessed from context. I agree this happens more when decibels are being used.Those who are "in the club" don't see the issue at all, because they know the hidden context. But in my opinion, in science and engineering, variables and units used in formulae need to be defined. It is not a lot of work to do at all, and helps those who are stepping outside of their core expertise area.

author: Smokey
author_rank: Super Contributor
timestamp: May 25, 2025, 09:47:09 pm
content: Quote from: radiolistener on May 24, 2025, 03:13:23 pmIsn't this just a similar argument to why the units of capacitance are also "non-optimal"? I mean you never use a 1Farad capacitor unless you are working on something crazy.If you are working on an actual circuit you would never say 0.00000000012 Farads. You would also never say 1.2e-10 Farads. You would just say 120pF.If we used 1F as the 0dBf (for dBfarads) then 120pf would be -99dBf. (or if 1mF was the reference, it would be -69.21dBf)Which would be an absolutely crazy thing to put on a schematic or try to buy from Digikey.

author: TimFox
author_rank: Super Contributor
timestamp: May 25, 2025, 10:55:02 pm
content: Quote from: Siwastaja on May 25, 2025, 07:02:06 amHow is the concept of power ratios "hidden" in "dB", and how is the concept of a ratio to 1 mW hidden in "dBm"?The extension of dB to voltage ratios, done carefully, is understood by those skilled in the art.Behind a veil of ignorance?

author: radiolistener
author_rank: Super Contributor
timestamp: May 25, 2025, 11:05:54 pm
content: Quote from: Smokey on May 25, 2025, 09:47:09 pmNo, it's not a similar situation. In RF, used power levels span an extremely wide range, requiring the use of multiple unit prefixes: megawatts, kilowatts, watts, milliwatts, and for receivers even microwatts, nanowatts, picowatts, or femtowatts.Now try to compare, say, 1 MW to 10 fW directly - the numeric difference is vast, and switching between unit prefixes makes it harder to maintain clarity. Decibels solve this by expressing all values on a consistent logarithmic scale without the need for unit multipliers. This makes comparisons straightforward, differences easy to compute, and values more readable - something the linear scale just unable to handle well across such wide dynamic ranges.The beauty of the dB scale lies in the fact that you don't need to express megawatts in femtowatt units - doing so is impractical, as such precision is neither measurable nor meaningful in any real-world context. A linear scale becomes excessive and cumbersome in this regard.In contrast, decibels provide appropriate precision using concise, human-readable numbers across the entire relevant range of power and voltage levels. They allow you to maintain clarity and focus by eliminating unnecessary granularity and representing only what’s practically significant.Quote from: Smokey on May 25, 2025, 09:47:09 pmit will be -69.21dBmF, notdBF.if you use 1 Farad for reference, then:120 pF = -99.21 dBF1 mF = -30 dBFif you use 1 mF for reference, then:120 pF = -69.21 dBmF1 mF = 0 dBmFdBF and dBmF represent distinct units, so there’s no ambiguity between them. Converting from dBF to dBmF is straightforward - it simply involves adding 30 dB, making the transition very clear and easy to apply.From a practical standpoint, there’s no inherent issue with using such notation, as long as the reference units are clearly defined and consistently applied.

author: DimitriP
author_rank: Super Contributor
timestamp: May 25, 2025, 11:35:17 pm
content: QuoteTL;DR (typing this is as much time as I'll allot to it-since you asked) but as a general rule, you gotta come up with sumtn' eent'sting enough to get posted as a "lookie here what i found" ...and here we are !

author: Smokey
author_rank: Super Contributor
timestamp: May 25, 2025, 11:44:29 pm
content: Quote from: radiolistener on May 25, 2025, 11:05:54 pmDude. that was a great explanation. Thanks.

author: Siwastaja
author_rank: Super Contributor
timestamp: May 26, 2025, 09:33:02 am
content: Quote from: TimFox on May 25, 2025, 10:55:02 pmYou literally said the same. I was merely pointing out an observation of seeing careless use of units, and as a result, things being more difficult to those who are notthatskilled in the art. While I do appreciate skill, I don't believe in the idea of secret clubs with obfuscated communications.Especially in audio, dB is thrown around as a "unit of something", as shown in the opening article. RF folks are usually more careful, with dBm clearly defined and that definition easily checked, and rarely mixed with dB.Then again, none of this "now it's 1/10 log10, now it's 1/20 log10" stuff is necessary. Optical folks (film industry etc.) were happy to call the thing simply "log H = ..." or "log D = ...", resulting in consistent use of log10. Film density of "log D = 3.0" means that 1/1000 of light passes and 999/1000 is absorbed. dB folks would call that 60dB, and I see no benefit. Then again, it's just matter of learning. But I also think it's a good idea to question widely used notations, and sometimes look outside from one's own bubble: what others are doing, why, and how could we communicate better?I think the somewhat aggressive style in some of the replies is pretty revealing, confirming the cult-ness of this notation.

author: G0HZU
author_rank: Super Contributor
timestamp: May 26, 2025, 10:02:19 am
content: If it helps, power is (V^2)/R so if you want to use voltage, the voltage squared is achieved by adding two log results together as doubling the log is the same as squaring the voltage. So that’s why it is 20*log for voltage as this is 10*log + 10*log in order to square the voltage (to get the power ratio in dB).

author: Siwastaja
author_rank: Super Contributor
timestamp: May 26, 2025, 10:14:02 am
content: This is one of those systems designed to be so extremely simple to use, that it becomes too simple, and starts to confuse instead.I feel really comfortable calculating powers, voltages and resistances with the classic formulae U = RI and P = UI; I have done that since kid. When someone invents an "easier way" where multiplication is replaced by addition, I don't feel it's really any easier. This is why I feel the two different dBs, one for voltage and one for power, adds more confusion, than solves any actual problem for me. Things might have been different 100 years ago when having to calculate the multiplication on field.I also have no issues calculating logarithms, since a computer or calculator does that in a split second; things sure were different 100 years ago.Choosing suitable SI prefixes (micro, milli, etc.), or using scientific E notation for numbers, solves the range problem for me.This is all that I need to do all the timeanyway. The scope where dBs are used is limited so the remedy is also limited. I can't put everything in dBs: I'll be looking at large range linear scales, multiplications and logarithms all day anyway. So if voltage reference accuracy is given as 0.1%, why woudln't noise floor be defined as 0.1% as well?Therefore, all dBs have to offer to people like me is confusion. And I don't mean it's really that bad, not at all, I can deal with it, but the critique is still understandable. I could well talk about noise floor being at 1ppm of signal, for example (non-logarithmic scale).

author: TimFox
author_rank: Super Contributor
timestamp: May 26, 2025, 02:23:03 pm
content: I do not object to statements like:“I am confused about using dB for voltage and power ratios.”“Please explain what “dBu” means.”“I prefer non-log expressions such as scientific notation.”However, the original post by someone who doesn’t know what a pascal is, or how to use dB properly, therefore “decibels are ridiculous” is a show of aggressive ignorance.

author: Grandchuck
author_rank: Super Contributor
timestamp: May 26, 2025, 02:39:26 pm
content: Did the OP state his take on the decibel?

author: TimFox
author_rank: Super Contributor
timestamp: May 26, 2025, 03:45:19 pm
content: Clarification: I’m referring to the article the op posted (without comment).

author: abeyer
author_rank: Frequent Contributor
timestamp: May 26, 2025, 07:44:57 pm
content: Quote from: Grandchuck on May 26, 2025, 02:39:26 pmI didn't initially... partly because I had a bit of a knee-jerk reaction and was curious if others would too, without my muddying the water first. (and it seems like the answer is yes.)After I took a breath and re-read the article, I think I agree with most of it, but only because I think people are reading way to much into it...First, it's clearly a bit of a rant rather than any deep technical critique. If the style didn't make that obvious, the SNL skit video should have. Second, the fundamental gripe is actually about two things that absolutely are valid issues:1. People are often too lax about specifying what they are saying, and throw around bare "dB"s all over the place while mixing different meanings. (looking at you consumer audio equipment)2. A ratio scale depends on the definition of its zero point, and that is arbitrary. There are mostly "good reasons" for the arbitrary decisions that were made... but if you don't know them you don't know, and it all looks like a mess. Compare that to most physical units, where you could give a layman a brief one sentence explanation of what it measures and he could usually intuit what a zero would mean.

author: TimFox
author_rank: Super Contributor
timestamp: May 26, 2025, 08:01:57 pm
content: Quote from: abeyer on May 26, 2025, 07:44:57 pmIf I tell a novice technical person that 0 dBm means 1 mW, he should be able to understand that.For non-technical people, probably the most difficult dBs to understand are the often ill-quoted measurements of sound level, with different frequency weightings, often explained with respect to common nuisance levels such as leaf blowers.The original definition was tied to the threshold of hearing, but now it is quoted in pascals. However, for human perception and safety, different frequency weighting is applied to the measurement.Sound level, physically, is in W/m2. For meters that measure the pressure of longitudinal acoustic waves in air under normal conditions, 0 dBm (SPL) is set to 20 uPa rms, since the pressure and atmosphere determine the power per area.Frequency weighting is a filter between the microphone and voltmeter in the sound meter. Safety regulations include further consideration of maximum and average dosage.Now, the power is proportional to the square of the amplitude (pressure in Pa), so 140 dB SPL (a dangerous level) is then 200 Pa rms. This is small compared with the static air pressure, which is approximately 100 kPa.A good reason to use dB when discussing sound is that humanperceptionis approximately logarithmic for stimuli such as sound.

author: abeyer
author_rank: Frequent Contributor
timestamp: May 26, 2025, 08:34:54 pm
content: Quote from: TimFox on May 26, 2025, 08:01:57 pmReferenced into 600Ω? 50Ω? Maybe a mix of both in the same system while still calling them all "dBm" and really make it fun for said novice reader.

author: TimFox
author_rank: Super Contributor
timestamp: May 26, 2025, 08:42:51 pm
content: Quote from: abeyer on May 26, 2025, 08:34:54 pmNo, 0 dBm is a power measurement, independent of load impedance, meaning 1 mW.If you apply 0 dBm to a 600 ohm load, the voltage across that load is called 0 dBu.Many AC voltmeters, with high input impedance, are calibrated accordingly (usually stating dBm in 600 ohms).Don’t complicate things for the novice reader.One can express the output of an RF amplifier in watts, and the power drawn by a light bulb in watts, without confusion.

author: abeyer
author_rank: Frequent Contributor
timestamp: May 26, 2025, 09:17:36 pm
content: Quote from: TimFox on May 26, 2025, 08:42:51 pmAnd yet, what you see in the wild makes all sorts of "mistakes"/assumptions/shorthands like this.

author: baldurn
author_rank: Regular Contributor
timestamp: May 26, 2025, 09:47:39 pm
content: Quote from: ejeffrey on May 24, 2025, 04:46:45 pmScientific notation is just another way to write the log scale. It is literally the same, just with an offset and 10x multiplier:-30 dBm = 1e-6-20 dBm = 1e-5-10 dBm = 1e-40 dBm = 1e-310 dBm = 1e-220 dBm = 1e-130 dBm = 1e040 dbm = 1e1The trouble comes when you have a number that is not 1 in front of the 'e'.

author: TimFox
author_rank: Super Contributor
timestamp: May 26, 2025, 09:57:14 pm
content: Quote from: abeyer on May 26, 2025, 09:17:36 pmI am not responsible for the mistakes of others.I try to explain reality to those who will listen."dBm" and "dBu" are well-defined units for measuring power and voltage, respectively.Some people to measure force incorrectly in kg, rather than Nt: is that my fault?Other people prefer pressure in Pa or bar, but that is a matter of choice.

author: Analog Kid
author_rank: Super Contributor
timestamp: May 26, 2025, 10:54:59 pm
content: Quote from: TimFox on May 26, 2025, 09:57:14 pmDon't forget PSI.

author: TimFox
author_rank: Super Contributor
timestamp: May 26, 2025, 10:56:21 pm
content: In a free country, you can choose the conventional unit "PSI".Remember to distinguish PSIA from PSIG

author: TimFox
author_rank: Super Contributor
timestamp: May 26, 2025, 10:57:41 pm
content: Quote from: baldurn on May 26, 2025, 09:47:39 pmThe real trouble comes when you forget "W" to make 1e-3 W for 0 dBm.You can say 0 dB = 1e-3.

author: TimFox
author_rank: Super Contributor
timestamp: May 26, 2025, 10:59:49 pm
content: Question for those who dislike "dB":How do you express the attenuation of a coaxial cable, if not in "dB/m" or "dB/100 ft" ?

author: Fflint
author_rank: Frequent Contributor
timestamp: May 27, 2025, 08:01:37 am
content: dB are only confusing if you're new to the domain of use. I deal with them mostly in power context (RF and optical). It is difficult to imagine more convenient unit that as previous poster described in a very good post, puts the entire range you're likely to encounter on a single easy to visualise and understand linear number scale.It is extremely convenient all these things are on the same relatively small, east to understand at a glance scale:- kW and LNA amplifiers- filters- antenna vswr, gain, directivityHowever, let's not be too hard on the author. I believe the thought process that led to him writing this was something like: if I know math and physics I should be able to understand texts from whatever physical domain without having to search for and internalise these domain-context specific units.SI unit system is often reverred (in places that use it) exactly for the reason it gives anyone with sufficient foundational knowledge to understand any unit in any domain because its derivation is usually a simple operation on other basic units. This is not easy to "just know" how to do when domain specific dB units are used.

author: Someone
author_rank: Super Contributor
timestamp: May 27, 2025, 08:30:56 am
content: Quote from: TimFox on May 26, 2025, 10:59:49 pmOptics is more flexible between the two (linear and log dimensioning) and there are examples of % transmittance per unit length, or their own log scaled absorbance units “abs” (less annoying than decibels or Absolute magnitude).

author: TimFox
author_rank: Super Contributor
timestamp: May 27, 2025, 03:54:27 pm
content: Quote from: Someone on May 27, 2025, 08:30:56 amI do not like “% per unit length” for transmittance or attenuation of a transmission line or similar.Example: if the attenuation is 25% per meter, then the transmission of two meters is(0.75) x (0.75) = (0.5625), for an attenuation of 44%, not 50%.Furthermore, there is a basic problem with percents in this context: if you increase a quantity by 25%, then decrease the result by 25%, the final result is (1.25) x (0.75) = (0.94), not unity.There is also ambiguity, does a 25% decrease means a factor of (1 - 0.25) = (0.75), or (1/1.25) = (0..The difference is small for 1%, but important for larger values.In my example above, the second interpretation gives an attenuation of (1.25)2= 1.56, or 56%.Decibels give a clean result for this case.

author: Siwastaja
author_rank: Super Contributor
timestamp: May 27, 2025, 05:40:20 pm
content: Quote from: TimFox on May 26, 2025, 10:59:49 pmObviously %/m. Or even better, without % as bare multiplier, like 0.9999/m or 0.0001/m whether you look it from pass or stop viewpoint. It makes perfect sense to me. I understand the desire of field engineers to sum numbers instead of multiplying them, especially if they don't have calculators available, but I'm not in a such situation. To me, multiplication feelsintuitive. To me, it is intuitive that if I have a glass which absorbs half of the light, after two of them, I have quarter of light left, and after a third, I have one eighth of the light left. No addition; multiplication feels natural to me. A scale that enables multiplication to be replaced with an addition is a performance optimization (that of a primitive CPU, primitive electronics, or human brain which sucks at calculations); but premature optimizations are root of all evil.This is how we calculate steady state / low frequency / DC gains of opamps all day long anyway. Then we pseudo-randomly switch to dB for no real reason whatsoever, and mix the two systems.Why is transistor hFE not in dB?Icandeal with dBs just fine, but that's because I have had to learn to use them. It's extra work. Not some kind of epiphany of measurement system design.

author: TimFox
author_rank: Super Contributor
timestamp: May 27, 2025, 07:29:14 pm
content: 0.9999/m works, but %/m does not work.dB/m works well for me.Again, I find 1 dB to be useful as a "threshold of interest" when improving something.

author: fourfathom
author_rank: Super Contributor
timestamp: May 27, 2025, 09:45:01 pm
content: I definitely prefer to work in dB, dBm, dBc, and sometimes dBu. I even worked in dBA back when dinosaurs roamed the earth.Let's say I'm designing an elliptic RF filter and I want a deep stopband. I would much rather design for -62 dB than 0.0000006309573.... Also, all my RF test equipment is calibrated in dBm.

author: Infraviolet
author_rank: Super Contributor
timestamp: May 28, 2025, 02:19:16 am
content: I do have to agree with the substacker linked to in the original post somewhat, decibels do seem a pretty rotten choice compared to actually saying "amplified by 10^5 " or "attentuated by 10^8" ... I'm going to make a gues that the only reason people use decibels is because others were already doing so, when they're in use so widely one needs to understand them so as to convert in to more practical units (standard index notation is practical Z*10^Y is not a cumbersome way to express a number of whatever size)... but maybe if people had been using standard index notation from the start the decibel would never have been invented? I can see the point of decibels in graphing, just like log scales in graphing you can't show effects many orders of magitude different in strength without them, but as soon as something enters the realm of a written number standard index form makes a lot more sense (as does making use of all those wonderful prefixes, more added to either end every few years quetta and quecto at last count, that the SI units system gives us).

author: TimFox
author_rank: Super Contributor
timestamp: May 28, 2025, 02:31:18 am
content: Referring back to my point about “threshold of interest”, this is a good reason to use dB instead of Bels.I’m not aware of any actual use of Bels, but I did see a serious suggestion a few decades ago to use mB for improved resolution, but no real use thereafter.It’s convenient to express powers of 10 with scientific notation, but it’s less convenient when we get to two significant figures.

author: Tation
author_rank: Regular Contributor
timestamp: May 28, 2025, 06:59:03 am
content: 0.999/m works?So, to compute the signal level at the other end I need: raise 0.999 to the power of length, then multiply by input level.With dB: multiply by length (dBperm, the "natural" way is multiplying, not raising to a power) and then add it to the input level. Many times I can guesstimate the result and know where, more or less, will it be in the screen of the SA.

author: TimFox
author_rank: Super Contributor
timestamp: May 28, 2025, 03:10:43 pm
content: There are other logarithmic units for attenuation.In the late 1970s, I attended a guest lecture by the eminent professor Edward Purcell (1912-1997), who had just switched his research interest to interstellar dust (unrelated to dark matter).He said he started by converting the astronomers' unit of magnitudes per parsec to his favored dB/light-year.(Magnitudes are not ridiculous: they are well-defined in astronomic usage.)

author: UnijunctionTransistor
author_rank: Frequent Contributor
timestamp: May 28, 2025, 03:57:19 pm
content: Someone else is also quite upset about life.https://www.eevblog.com/forum/programming/littlebig-endian-the-most-stupid-term-ever-conceived/?topicseen

author: TimFox
author_rank: Super Contributor
timestamp: May 28, 2025, 04:25:50 pm
content: Quote from: UnijunctionTransistor on May 28, 2025, 03:57:19 pmNote that the terms "big endian" and "little endian" were first found in Swift'sGulliver's Travels(1726) as a parody on religious disputes.It is a rare example of computer architects adopting a literary term.' It began upon the following occasion.It is allowed on all hands, that the primitive way of breaking eggs before we eat them, was upon the larger end: but his present Majesty's grandfather, while he was a boy, going to eat an egg, and breaking it according to the ancient practice, happened to cut one of his fingers. Whereupon the Emperor his father published an edict, commanding all his subjects, upon great penalties, to break the smaller end of their eggs.The people so highly resented this law, that our Histories tell us there have been six rebellions raised on that account, wherein one Emperor lost his life, and another his crown. These civil commotions were constantly formented by the monarchs of Blefuscu, and when they were quelled, the exiles always fled for refuge to that Empire.It is computed, that eleven thousand persons have, at several times, suffered death, rather than submit to break their eggs at the smaller end. Many hundred large volumes have been published upon this controversy: but the books of the Big-Endians have been long forbidden, and the whole party rendered incapable by law of holding employments.During the course of these troubles, the emperors of Blefuscu did frequently expostulate by their ambassadors, accusing us of making a schism in religion, by offending against a fundamental doctrine of our great prophet Lustrog, in the fifty-fourth chapter of the Brundecral (which is their Alcoran). This, however, is thought to be a mere strain upon the text: for their words are these; That all true believers shall break their eggs at the convenient end: and which is the convenient end, seems, in my humble opinion, to be left to every man's conscience, or at least in the power of the chief magistrate to determine. '

author: Siwastaja
author_rank: Super Contributor
timestamp: May 29, 2025, 01:13:10 pm
content: Quote from: Tation on May 28, 2025, 06:59:03 amYes, you nailed it. Both representations take the same effort to plug into calculator. One is the "natural" representation of things (stacked attenuations, raising to the power), another is added abstraction layer on top of it, which sometimes applies and sometimes does not. I really would be fine without it; I don't understand the idea of decibels being somehow "a must", or even important, at all. We just use them because ... we use them.With very little computing power, pre-conditioning inputs to logarithmic scale and then summing is a useful optimization: this is how analog multipliers can be implemented for example (log-then-sum). Doing calculations "in head" on the field is another example of very little computing power. So maybe a good side of using dB scales is that it exposes us to this idea, so that we can apply it when it's useful.