There has been at least two issues with the Baofeng mics:

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jeff.debes@...

Hi Rob,
I am not clear on what is going on here, is this the mike that comes with the uBitxV6? or some other Baofeng mic that you picked up to use? And you are just removing whatever surface mount resistor that you find inside so that the electret element inside gets fed with a higher voltage? Seems a little ill defined and vague, but seems you are having success. Are the internal workings of the supplied mics somewhat variable?
thanks
jer aa1of

Evan you asked;
Did you get a chance to measure the 3 leads of Q90?
What measurements do you want me to make to Q90
--
'72

Hi Evan, Ok on the mic capacitor and possible RF into the mic. As I mentioned my Baofeng mic did not have that capacitor installed! 

My Rf testing with an antenna and Dummy load did not have any RF issues.

So, some Baofeng mics like mine may not have that capacitor installed, installing one may be more trouble than its worth!

Evan, you are correct many Electret mics do have a .001 mfd capacitor connected across the mic element terminals.

If some users experience Rf in their transmit audio, that might be a place to look, amongst many other arears.

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Rob N8RT

Yes. That was an attempt at humor on my part. 😂

The Yaesu MH-31 mic works very well with the uBitx v6.
My audio reports have been “It sounds like you.”
Doesn’t get any better than that! 😀

It also drives my old Clipperton L amp to 110-120 watts, so it is turning out to be a great edition to the shack!

Nikhil,
I forgot to point out that if you are not hearing SSB signals correctly when receiving, that you could also have a BFO tuning issue.  If the BFO is too far off the SSB filter will attenuate the audio and you will also not get much output.

I would check it with this link:
https://www.hfsignals.com/index.php/bfo-tuning-aid/ 
it does require a mic connected to your PC and works best with the Chrome browser.

73
Evan
AC9TU

Nikhil,
It is common for SSB to show low values on a wattmeter.  Try providing a constant tone, or a long Heeeeeelloooooooow.  In another thread, there is a website that has an audio tone generator.  You can use that with a 1kHz and the mic close to the speakers.  Try different volumes and distances to see if the power out changes.  If so, then most likely you have a low audio drive from the mic.

I solved the low SSP audio by getting an amplified mic and using that. Others have gone to a preamp in the rig enclosure, and for the high end, a speech compression amp for maximum punch.  I have not that, so you will need to search the groups.io site or the internet for speech compression uBITX.
https://groups.io/g/BITX20/message/76912

Hope this helps a little
73
Evan
AC9TU

When i keep my other SSB reciver in the room and talk, i can hear my voice on that receiver. But watt meter show no power. What is the problem? Which part do i need to check?

Can anyone tell me what the problem is?

Hi Rob,

Glad you did it that way so we know!  I didn't get that from your original post.

73

Robert,
Thank you for the information on the lack of a part number for the uBITX model 6 mic.  The request was made because I knew that there is a variance in optimum voltage and max voltage for electret elements.  Having worked with Reed on the uBITX mic internals for another ham, I assumed that the wiring was done on purpose to limit the bias voltage.  It may have been just to reduce the current for the LED.  The result is a little less than 2 volts on the element.  Per your measurements, the voltage goes up to 8 volts.

I would not recommend removing the .001 capacitor across the mic, as that is to shunt any stray RF that can play havoc with the uBITX Nano.  In some cases another cap at the uBITX input, as well as snap-on ferrites are required depending on the RF in the shack and feed line.

You are correct in that a larger diameter mic would ten to have higher output, as there is more surface area to modulate the internal capacitor.
73
Evan
AC9TU 

That is great  investigative work Rob!

--
jeff.debes@...

-- hi mark  before I did the mod, I opened the mic hole and nothing changed! So increasing the voltage did.
So try the mod first before opening  the mic hole. See for yourself. 





Rob N8RT

Hi,

Normally electret condensor mike can operate at a range of voltages, but on average the rated voltage is usually pretty low.  Here's Digikey's list of electret condensor mics and their rated voltage by the numbers:

V     #Mics
.9          2
.93        3
1           1
1.1        2
1.3        281
1.5        67
2           308
2.1        10
2.5        3
3           32
4.5        17
9           2
10         1

The trouble with figuring out your change is that it seems that you did two things at once, removed the resistor and also opened up the mic hole.  So you really don't know which of the changes made the difference.

73,  Mark

Hello Evan,
Each manufacture has their own specifications for an electret mic. But from a list of companies that make these mics the average is about 10vdc. Some Electret mics use an internal 9vdc battery.
Evan there is NO part number on the mic on my Baofeng Mic.

I found that there are many many models on eBay and elsewhere, each one may be different regarding audio output and voltage.
I do know that the electret mics have a very good frequency range and are generally used by professional audio folks. 

I also think that the larger diameter mics may have a greater range of audio output voltages, then the smaller diameter ones. 

73 rob n8rt
--
Rob N8RT

A way to Check the audio SSB frequency response of your microphone.

There is a an audio ONLINE Tone Generator that is free and tunes covers 1Hz to 20,000 Hz .

The Generator is available here:

 https://www.szynalski.com/tone-generator/

Works on ANDROID and PC’s maybe others.

Connect your transmitter into a DUMMY LOAD, Connect a Wattmeter appropriate to your transmitter power.

Key the transmitter in CW Mode to make sure your wattmeter is showing at least ½ scale on the watt meter, this is not super important and is just a reference.

Now switch back to SSB and place the device you have downloaded the tone generator speaker next to your microphone, key your transmitter and on the Tone, Generator slide the button left and right and you can now see the PEAK frequency response of your SSB audio. ( The distance from the device speaker and the mic will only increase or decrease the power reading)

I wanted to check my UBITX Ver 6 , SSB Rf output power, frequency response of my  Modified Baofeng mic. (posted here) https://groups.io/g/BITX20/message/81778

 This frequency  measurement is very dependent on your UBITX  BFO adjustment, make sure that you have calibrated that before you do this test. My UBITX SSB power,   mic frequency peaked at about 900 hz , and fell off on each side of the 900hz frequency.

Rob N8RT

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Rob N8RT

Since I do not own a model 6 (model vs version for HW descriptions) I cannot get the electret cartridge part number to verify the correct bias voltage.  Based on the information in this thread, It would appear that the voltage is too low.  It would be nice to know the range that the cartridge expects.

Would someone please check as see what the part number is in the mic?

Thanks,
73
Evan
AC9TU