Mike element
VE7CWS WRSeiler <waltrseiler@...>
Recently I was browsing through the electronics cables section In our local thrift store, and found two Apple external microphones.
I dissected the subject microphones and tried it in my bitx40, The difference is outstanding, I no longer have to yell to get any decent output. I used the second element in my mbitx with similar results. I emailed a R&D fellow I know at Apple to get a part number and supplier for the said device but as of this week no reply. I will keep trying. cheers n 73 WRS VE7CWS


iz oos
That would be nice to know as I have tested other 3 mic elements and they gave lower output than the stock one.
Il 13/lug/2018 06:32, "VE7CWS WRSeiler" <waltrseiler@...> ha scritto: Recently I was browsing through the electronics cables section In our local thrift store, and found two Apple external microphones.


VE7CWS WRSeiler <waltrseiler@...>
The reply I got back, that component is no longer available,
I have tried several different mike types for various projects I have worked on and found that sometimes the most expensive are not always the best or vice versa, however, I also believe you get what you pay for.. I have developed and tested various acoustic arrays for underwater sonar applications. Using one of those transducers would raise the price of the bitx’s out of sight. I wonder what the R&D budget of Apple is,$$$$$$$$ In conclusion, the audio from both the bitx40 and ubitx is an improvement over the stock mike element I’m very pleased with the “Apple mike” cheers n 73 WRS VE7CWS


Karl Heinz Kremer, K5KHK
Do you have a picture of the original microphone before you removed the element? Or at least of what’s left?
 Karl Heinz  K5KHK


Gary Anderson
WRS,
Would it be possible for you to identify the Apple mic model you used? There are many on the reseller market, and many in junk boxes. I am aware of 2 basic Plain Talk model types from the 1990s. The older disc type (G2) being what I think is just a electret element (but I never opened one up). The newer (G3,G4) having an amplifier, and had a longer TRS connector. Regards, Gary


VE7CWS WRSeiler <waltrseiler@...>
Hello folks
I was told that it was developed for certain business class Mac computers and is very similar externally to the picture that Gary posted for the G2 mike. The element is about 2 millimeters larger in diameter to the stock mike and about 3 millimeters longer. My ship leaves on the next tide and Inmarsat email is cost prohibitive back in three weeks. cheers n 73


Greg Wasik
I have been playing with electret mics and using one that has has 24 dB output. This is :
https://www.mouser.com/datasheet/2/334/AOM5024LHDR1219369.pdf Note that 0dB = 1V/Pa. If you look at some of the specs of other elements, they have typical sensitivities from ~ 40 to 30dB. There is a huge range.... https://www.mouser.com/Electromechanical/AudioDevices/_/Nawp3d?Keyword=microphone&FS=True Greg K1YW


iz oos
I am now puzzled. Which gives more output? A mic with sensitivity  24db or one at  44db (as mine which still give some less output than the stock element)?
Il 13/lug/2018 23:05, "k1yw via Groups.Io" <k1yw=mail.ru@groups.io> ha scritto: I have been playing with electret mics and using one that has has 24 dB output. This is :


Greg Wasik
0 dB = 1 volt per Pascal
24dB = .0.063 V/Pa 44 db = 0.0063 V/Pa


Greg Wasik
this is a good explanation
http://www.analog.com/en/analogdialogue/articles/understandingmicrophonesensitivity.html


iz oos
So, would  24db be 20db more sensitive than  44db?
Il 16/lug/2018 22:26, "k1yw via Groups.Io" <k1yw=mail.ru@groups.io> ha scritto: 0 dB = 1 volt per Pascal


Jerry Gaffke
Yes, you have it right.
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For a given sound pressure into the mike, the 24 dB mike creates a voltage that is 10 times bigger than the 44 dB mike. A 10 times bigger voltage into a fixed resistance means 100 times more power, since power in watts = volts * amps = volts * volts/ohms. With 100 times more power, that's 10 * log(100) = 20 dB more power. If the mike were zero dB, we'd get 1 volt from the mike. Since the voltages we are dealing with are less than one volt, we get negative numbers when representing the values in dB. Jerry, KE7ER
On Mon, Jul 16, 2018 at 04:58 PM, iz oos wrote:


Gordon Gibby
With that level of sensitivity, perhaps no preamp at all is needed with the bitx series.
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Available for three dollars at digikey. Thanks for pointing it out and giving that educational lecture!
On Jul 16, 2018, at 21:51, Jerry Gaffke via Groups.Io <jgaffke@...> wrote:


iz oos
Thanks Jerry, I had always thought the opposite, the lower the more sensitive just like sensitivity in a receiver. So, I was wrong. What about sensitivity in headphones and speakers?
Il 17/lug/2018 04:29, "Gordon Gibby" <ggibby@...> ha scritto:


Jerry Gaffke
The receiver spec's how big of a signal goes in to give a desired result.
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The microphone spec's how big of a signal goes out given a specific input sound level. So the first gets a smaller number if more sensitive, the second increases if it's more sensitive. Totally different industries, totally different notions of how to go about it. A receiver's sensitivity figure in dBm tells us how much power must be coming in the antenna port to achieve a specific result, in this case the "minimum discernible signal". A power level zero dBm is arbitrarily defined as 1 milliwatt, and since typical signals at the receiver are much lower in power, the receiver sensitivity is a fairly large negative number. The microphone's sensitivity is defined as how big of a voltage signal we get coming out when the microphone is presented with a sound pressure of one Pascal, and zero dBV is arbitrarily defined as one Volt. Most of the speakers I buy state something like: "Response from 20 Hz to 20 kHz". Not very precise. They don't actually say what the response is, could be argued that catching fire is a response of some sort. Here's a webpage on speaker sensitivity: http://www.psbspeakers.com/articles/GuidetoSpeakerSpecifications "Sensitivity Sensitivity is most easily defined as the speakers’ ability to effectively convert power into sound. The traditional way of measuring a speakers’ sensitivity is using the standard of 1 watt/1 meter. Meaning a microphone is placed 1 meter away from the speaker to measure the sound output (in decibels) with 1 watt of sound played through it. " So like the microphone, they spec how big of a signal goes out (sound in dB) when given a specific input (1 watt of electrical power). Makes sense, as would have been the same engineers working with microphones and speakers back when these things were defined. Next question: What is 0 dB of sound, and shouldn't that dB have a letter following it to tell us what the baseline is when finding that ratio? Answer: Zero dB of sound is defined as the minimum discernible signal for the typical human ear. No final letter because, well, it's a different group of engineers who defined it and they didn't care about the resulting confusion. Jerry
On Mon, Jul 16, 2018 at 11:50 PM, iz oos wrote:


iz oos
Tnx Jerry for this valuable explanation in plain English. I learnt a lot from it. Hope this topic could become a question in the FCC exam if not included yet (I don't remember I have ever seen it).
Il 17/lug/2018 15:19, "Jerry Gaffke via Groups.Io" <jgaffke=yahoo.com@groups.io> ha scritto: The receiver spec's how big of a signal goes in to give a desired result.


Greg Wasik
Just to throw in another way of specifying microphoen sensitivities . 1V/Pascal is equal to 94 dB SPL. So you may see either terms when looking at mic specs.
Greg K1YW


Jerry Gaffke
The "dB SPL" gives the Pascal part of 1V/Pascal, but it does not specify the 1V part.
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94 dB SPL means 94 dB above the reference sound pressure level of 20 uPa, where 20 uPa is around the bottom threshold of human hearing. https://en.wikipedia.org/wiki/Sound_pressure When somebody says a rock concert has a sound level of 110 dB, they mean 110 dB SPL. So a complete spec for microphone sensitivity might say how many "dB SPL" to give 1V out. Or they might say how many "dB" to give 1V out, and mean the same thing. Those acoustic engineers only deal with one kind of dB, and assume any such figure is for dB SPL, and describes a measured sound pressure level, not a ratio. In radio work, "dB" refers to a ratio, perhaps the output power of an amp divided by the input power. To give a power measurement we might say 20 dBm, which is the ratio of the 100 milliwatts we measured divided by an inferred reference of 1 milliwatt: 10**(20/10) = 100. So dB is a ratio of two powers, and dBm is a specific power level. ###################### While I'm on a rant, here's a bit more for those still puzzled but vaguely curious. I've said that dB in radio work means a ratio. A good receiver might have a dynamic range that can simultaneously deal with incoming signals of both one microvolt and one volt at the antenna, and still allow us to hear the small signal. Since power is the square of voltage divided by resistance, that's a power ratio of 1,000,000,000,000 between the big and the little signal. These numbers quickly got out of hand, especially for those folks back in 1930 working with a slide rule. It might be easier to say that the big signal has 12 more zeros after it than the little signal. Though that isn't very precise, if the receiver front end was improved to deal with a big signal of up to 2 volts it would then have 12.6 more zeros than the little signal. (Those who remember high school algebra will understand how to deal with a fractional power of ten.) Rather than deal with fractional numbers like that, they decided to just multiply the zero count by 10, so we can now say that a receiver capable of dealing with signals between 1uV and 2V has a dynamic range of 126 dB. Through the magic of logarithms, when the gains of two amps in series are expressed in dB we can determine the total gain of the amp by adding a couple 2 digit numbers in our head instead of multiplying out a couple larger numbers. You don't see dB used much in hard science such as a physics textbook, they just deal with the big numbers. But radio engineers who live and breathe this stuff 12 hours/day needed an easier way to do the calculations in their head, and dB won out. The formula to go from a power ratio to dB is 10*log(P1/P2). Here, "log" is base ten, and log(1000) is 3. For even powers of 10, the log() function just tells us how many zeros. In the case above, we have 10*log(2000000*2000000/1) = 126 dB (where voltages are expressed in microvolts). I usually use python as my calculator when figuring out this sort of thing. It's available for almost every computer (unfortunately a Nano is too small) and fully interactive, highly recommended. The log function comes from an external library called "math", so we must first bring in that library to make it available. Here's a python session to test the above formula, it gives a more precise result than my approximation of "126 dB".: import math 10*math.log10(2000000*2000000/1) >>> 126.02059991327963 We can go from dB back to a power ratio with this: 10**(126.0206/10) >>> 4000000079872.417 and go back to the voltage ratio by taking the square root of the power ratio: math.sqrt(4000000079872.417) >>> 2000000.019968104 Jerry, KE7ER
On Wed, Jul 18, 2018 at 08:14 AM, <k1yw@...> wrote:
Just to throw in another way of specifying microphoen sensitivities . 1V/Pascal is equal to 94 dB SPL. So you may see either terms when looking at mic specs.


Ken Held KF7DUR
Greg,
I ordered a few of the 24 dB mic elements from Mouser. I put one in a cheapo Baofeng speaker mic and it works great! The stock mics element was very weak the 24 dB element made a huge difference. Good find. Ken KF7DUR


Kevin Rea
HI Ken, Would you happen to have the mouser part number for that element ?
Thanks, Kevin rea Lancaster, calif K6rea
From: BITX20@groups.io <BITX20@groups.io> On Behalf Of Ken Held KF7DUR via Groups.Io
Greg,

