Topics

Why the Microphone Matters #v6 #audiocircuit #ubitxv6 #tx #microphone


Reed N
 

There have been a number of reports of issues with the baofeng mic that comes with the uBiTX v6, and some suggestions on how to fix the issue, but I haven't seen any measurements posted, so figured I'd show off what I found out.

For reference, here are some of the other threads already discussing microphone issues:
https://groups.io/g/BITX20/topic/71576826
https://groups.io/g/BITX20/topic/74673407
https://groups.io/g/BITX20/topic/75264904

I don't have calibrated test equipment, but I was able to produce relative measurements using the following setup:
I hooked up my radio to a dummy load, and used an AirSpy HF+ with SDR# to monitor the leaked output from the dummy load. I used my phone with the Function Generator app to produce an 800Hz, 50% amplitude sine wave on the right channel. I then turned my phone's volume up to max. Finally, I placed the mic pickup directly next to the phone's speaker, and moved the position around slightly until a maximum output was observed. I took a screenshot of SDR# showing this maximum for each configuration.

The stock mic is the baofeng mic I received with my v6. I measured it first, as it originally came in the mail.

Next, I modified the stock baofeng mic, by drilling out the plastic in front of the element using a 5/32" drill bit.


Finally, I measured the "Power Mic" that was suggested by a few people in the threads linked above, both with and without the battery for additional amplification.



Here's a table summarizing these values:
Mic Peak Signal (dB) Change (dB)
Stock -51.6 0
Stock, Mod -37.2 14.4
Power Mic -33.2 18.4
Power Mic, 9V -26.9 24.7


That's a 18.4dB increase purely from the microphone, and a total of 24.7dB with the amplification! What a difference!

It's worth noting that I believe the large harmonics peaks that are shown in the readout (especially the power mic 9V) are real, and not the power mic aliasing or whatnot. As I was moving the mic around, I could actually hear (and see) the harmonics increase and decrease, suggesting that the gaps between the phone and mic were acting as a resonating chamber, and that my phone probably wasn't producing as clean of a 800Hz sine wave as one would hope :P

It's also worth observing that there do appear to be a lot more spurs on the power mic, even without the amplification. I'm not sure where exactly these are coming from. Perhaps the power mic without amplification is already pushing "too hard"?


Reed


Gary Dumbleton
 

Although I have not done such exact measurements as below, I used the baofeng mic on 20 meters, and contacted someone in Virginia (I am near Toronto) and he gave me a 59.  My board says that it is a 6.2.  Is it possible that something was done to the mic amplifier circuit between 6.1 and 6.2.

I have not seen any list of changes made from version to version.

Gary

On 7/26/2020 4:26 PM, Reed N wrote:
There have been a number of reports of issues with the baofeng mic that comes with the uBiTX v6, and some suggestions on how to fix the issue, but I haven't seen any measurements posted, so figured I'd show off what I found out.

For reference, here are some of the other threads already discussing microphone issues:
https://groups.io/g/BITX20/topic/71576826
https://groups.io/g/BITX20/topic/74673407
https://groups.io/g/BITX20/topic/75264904

I don't have calibrated test equipment, but I was able to produce relative measurements using the following setup:
I hooked up my radio to a dummy load, and used an AirSpy HF+ with SDR# to monitor the leaked output from the dummy load. I used my phone with the Function Generator app to produce an 800Hz, 50% amplitude sine wave on the right channel. I then turned my phone's volume up to max. Finally, I placed the mic pickup directly next to the phone's speaker, and moved the position around slightly until a maximum output was observed. I took a screenshot of SDR# showing this maximum for each configuration.

The stock mic is the baofeng mic I received with my v6. I measured it first, as it originally came in the mail.

Next, I modified the stock baofeng mic, by drilling out the plastic in front of the element using a 5/32" drill bit.


Finally, I measured the "Power Mic" that was suggested by a few people in the threads linked above, both with and without the battery for additional amplification.



Here's a table summarizing these values:
Mic Peak Signal (dB) Change (dB)
Stock -51.6 0
Stock, Mod -37.2 14.4
Power Mic -33.2 18.4
Power Mic, 9V -26.9 24.7


That's a 18.4dB increase purely from the microphone, and a total of 24.7dB with the amplification! What a difference!

It's worth noting that I believe the large harmonics peaks that are shown in the readout (especially the power mic 9V) are real, and not the power mic aliasing or whatnot. As I was moving the mic around, I could actually hear (and see) the harmonics increase and decrease, suggesting that the gaps between the phone and mic were acting as a resonating chamber, and that my phone probably wasn't producing as clean of a 800Hz sine wave as one would hope :P

It's also worth observing that there do appear to be a lot more spurs on the power mic, even without the amplification. I'm not sure where exactly these are coming from. Perhaps the power mic without amplification is already pushing "too hard"?


Reed



Bob Lunsford
 

Thanks Reed for your measurements.

I drilled out the eletret hole in the mic to 1/8th inch which is only 1/32-in smaller than 5/32-in. Now I have to speak loudly and close-talk the mic to get through.

I also found a small SMD cap across the mic element and removed it after someone told me the transmitted audio needed to be "more crisp." I do not know what the cap value was/is since I could see no marking. I then listened to my signal on the "big rig" and could not detect a problem. I have yet to get an on-air check but from listening to the signal on the Yaesu, it does not sound bad.

I'll be interested in others' comments on this issue.

Bob — KK5R

On Sunday, July 26, 2020, 4:26:40 PM EDT, Reed N <greenkid336600+groupsio@...> wrote:


There have been a number of reports of issues with the baofeng mic that comes with the uBiTX v6, and some suggestions on how to fix the issue, but I haven't seen any measurements posted, so figured I'd show off what I found out.

For reference, here are some of the other threads already discussing microphone issues:
https://groups.io/g/BITX20/topic/71576826
https://groups.io/g/BITX20/topic/74673407
https://groups.io/g/BITX20/topic/75264904

I don't have calibrated test equipment, but I was able to produce relative measurements using the following setup:
I hooked up my radio to a dummy load, and used an AirSpy HF+ with SDR# to monitor the leaked output from the dummy load. I used my phone with the Function Generator app to produce an 800Hz, 50% amplitude sine wave on the right channel. I then turned my phone's volume up to max. Finally, I placed the mic pickup directly next to the phone's speaker, and moved the position around slightly until a maximum output was observed. I took a screenshot of SDR# showing this maximum for each configuration.

The stock mic is the baofeng mic I received with my v6. I measured it first, as it originally came in the mail.

Next, I modified the stock baofeng mic, by drilling out the plastic in front of the element using a 5/32" drill bit.


Finally, I measured the "Power Mic" that was suggested by a few people in the threads linked above, both with and without the battery for additional amplification.



Here's a table summarizing these values:
Mic Peak Signal (dB) Change (dB)
Stock -51.6 0
Stock, Mod -37.2 14.4
Power Mic -33.2 18.4
Power Mic, 9V -26.9 24.7


That's a 18.4dB increase purely from the microphone, and a total of 24.7dB with the amplification! What a difference!

It's worth noting that I believe the large harmonics peaks that are shown in the readout (especially the power mic 9V) are real, and not the power mic aliasing or whatnot. As I was moving the mic around, I could actually hear (and see) the harmonics increase and decrease, suggesting that the gaps between the phone and mic were acting as a resonating chamber, and that my phone probably wasn't producing as clean of a 800Hz sine wave as one would hope :P

It's also worth observing that there do appear to be a lot more spurs on the power mic, even without the amplification. I'm not sure where exactly these are coming from. Perhaps the power mic without amplification is already pushing "too hard"?


Reed


Reed N
 

Gary,

My uBiTX main board is also labeled 6.2. Maybe your baofeng mic is just better than mine!

---

Bob,

Did you not have to speak loudly and close-talk before drilling the hole, or are you just stating that you still have to, even with the mod?

I'm guessing you talking about the capacitor shunting the mic, labeled C2 on the baofeng microphone board. Did the person who told you your audio needed to be more crisp say that it was more crisp after removing the capacitor?

Even with the stock mic, in my early testing of the system, I sounded fine when listening to myself on a different rig. The problem for me has always been signal output level. With the stock unmodified mic, I made exactly 0 SSB contacts. Couldn't even be heard by a friend of mine a couple of kilometers away.


Reed


Bob Lunsford
 

Gary made a comment in the first paragraph about a possible change to the mic amp circuitry from V6,1 to V6.2. I have V6.1 and wonder if there is a change and if I should consider updating the mic. audio circuit, if there was a change.

Anyone having this info, please advise.

Bob — KK5R

On Sunday, July 26, 2020, 4:47:16 PM EDT, Gary Dumbleton <gary@...> wrote:


Although I have not done such exact measurements as below, I used the baofeng mic on 20 meters, and contacted someone in Virginia (I am near Toronto) and he gave me a 59.  My board says that it is a 6.2.  Is it possible that something was done to the mic amplifier circuit between 6.1 and 6.2.

I have not seen any list of changes made from version to version.

Gary

On 7/26/2020 4:26 PM, Reed N wrote:
There have been a number of reports of issues with the baofeng mic that comes with the uBiTX v6, and some suggestions on how to fix the issue, but I haven't seen any measurements posted, so figured I'd show off what I found out.

For reference, here are some of the other threads already discussing microphone issues:
https://groups.io/g/BITX20/topic/71576826
https://groups.io/g/BITX20/topic/74673407
https://groups.io/g/BITX20/topic/75264904

I don't have calibrated test equipment, but I was able to produce relative measurements using the following setup:
I hooked up my radio to a dummy load, and used an AirSpy HF+ with SDR# to monitor the leaked output from the dummy load. I used my phone with the Function Generator app to produce an 800Hz, 50% amplitude sine wave on the right channel. I then turned my phone's volume up to max. Finally, I placed the mic pickup directly next to the phone's speaker, and moved the position around slightly until a maximum output was observed. I took a screenshot of SDR# showing this maximum for each configuration.

The stock mic is the baofeng mic I received with my v6. I measured it first, as it originally came in the mail.

Next, I modified the stock baofeng mic, by drilling out the plastic in front of the element using a 5/32" drill bit.


Finally, I measured the "Power Mic" that was suggested by a few people in the threads linked above, both with and without the battery for additional amplification.



Here's a table summarizing these values:
MicPeak Signal (dB)Change (dB)
Stock-51.60
Stock, Mod-37.214.4
Power Mic-33.218.4
Power Mic, 9V-26.924.7


That's a 18.4dB increase purely from the microphone, and a total of 24.7dB with the amplification! What a difference!

It's worth noting that I believe the large harmonics peaks that are shown in the readout (especially the power mic 9V) are real, and not the power mic aliasing or whatnot. As I was moving the mic around, I could actually hear (and see) the harmonics increase and decrease, suggesting that the gaps between the phone and mic were acting as a resonating chamber, and that my phone probably wasn't producing as clean of a 800Hz sine wave as one would hope :P

It's also worth observing that there do appear to be a lot more spurs on the power mic, even without the amplification. I'm not sure where exactly these are coming from. Perhaps the power mic without amplification is already pushing "too hard"?


Reed



Bob Lunsford
 

I just checked with a few on the Kentucky Phone Net with my V6 with the Baufeng mic and was told it sounds a slight bit bassy but that the audio quality is fine, no need to try to improve it. That's what I hoped to hear.

Bob — KK5R

On Sunday, July 26, 2020, 6:38:46 PM EDT, Bob Lunsford via groups.io <nocrud222@...> wrote:


Thanks Reed for your measurements.

I drilled out the eletret hole in the mic to 1/8th inch which is only 1/32-in smaller than 5/32-in. Now I have to speak loudly and close-talk the mic to get through.

I also found a small SMD cap across the mic element and removed it after someone told me the transmitted audio needed to be "more crisp." I do not know what the cap value was/is since I could see no marking. I then listened to my signal on the "big rig" and could not detect a problem. I have yet to get an on-air check but from listening to the signal on the Yaesu, it does not sound bad.

I'll be interested in others' comments on this issue.

Bob — KK5R

On Sunday, July 26, 2020, 4:26:40 PM EDT, Reed N <greenkid336600+groupsio@...> wrote:


There have been a number of reports of issues with the baofeng mic that comes with the uBiTX v6, and some suggestions on how to fix the issue, but I haven't seen any measurements posted, so figured I'd show off what I found out.

For reference, here are some of the other threads already discussing microphone issues:
https://groups.io/g/BITX20/topic/71576826
https://groups.io/g/BITX20/topic/74673407
https://groups.io/g/BITX20/topic/75264904

I don't have calibrated test equipment, but I was able to produce relative measurements using the following setup:
I hooked up my radio to a dummy load, and used an AirSpy HF+ with SDR# to monitor the leaked output from the dummy load. I used my phone with the Function Generator app to produce an 800Hz, 50% amplitude sine wave on the right channel. I then turned my phone's volume up to max. Finally, I placed the mic pickup directly next to the phone's speaker, and moved the position around slightly until a maximum output was observed. I took a screenshot of SDR# showing this maximum for each configuration.

The stock mic is the baofeng mic I received with my v6. I measured it first, as it originally came in the mail.

Next, I modified the stock baofeng mic, by drilling out the plastic in front of the element using a 5/32" drill bit.


Finally, I measured the "Power Mic" that was suggested by a few people in the threads linked above, both with and without the battery for additional amplification.



Here's a table summarizing these values:
MicPeak Signal (dB)Change (dB)
Stock-51.60
Stock, Mod-37.214.4
Power Mic-33.218.4
Power Mic, 9V-26.924.7


That's a 18.4dB increase purely from the microphone, and a total of 24.7dB with the amplification! What a difference!

It's worth noting that I believe the large harmonics peaks that are shown in the readout (especially the power mic 9V) are real, and not the power mic aliasing or whatnot. As I was moving the mic around, I could actually hear (and see) the harmonics increase and decrease, suggesting that the gaps between the phone and mic were acting as a resonating chamber, and that my phone probably wasn't producing as clean of a 800Hz sine wave as one would hope :P

It's also worth observing that there do appear to be a lot more spurs on the power mic, even without the amplification. I'm not sure where exactly these are coming from. Perhaps the power mic without amplification is already pushing "too hard"?


Reed


Bob Lunsford
 

Reed, I have to speak loudly to get enough modulation. Did not get a before/after check on the air but listened to the audio on the big rig. When I speak loudly and closs-talk the mic, I get more S-Meter swing on the big rig. When they told me the audio sounded fine on the air tonight, I'll go with it. I do see more S-Meter swing with the hole drilled out, though.

Bob — KK5R

On Sunday, July 26, 2020, 6:58:48 PM EDT, Reed N <greenkid336600+groupsio@...> wrote:


Gary,

My uBiTX main board is also labeled 6.2. Maybe your baofeng mic is just better than mine!

---

Bob,

Did you not have to speak loudly and close-talk before drilling the hole, or are you just stating that you still have to, even with the mod?

I'm guessing you talking about the capacitor shunting the mic, labeled C2 on the baofeng microphone board. Did the person who told you your audio needed to be more crisp say that it was more crisp after removing the capacitor?

Even with the stock mic, in my early testing of the system, I sounded fine when listening to myself on a different rig. The problem for me has always been signal output level. With the stock unmodified mic, I made exactly 0 SSB contacts. Couldn't even be heard by a friend of mine a couple of kilometers away.


Reed


Reed N
 

Bob,

Did you look at your circuit board when you determined you had a v6.1, or did you look at the touch screen? Ashhar's stock software is currently at revision v6.1, and will display v6.1 on the screen. However, if you look near the antenna connector on the circuit board inside your radio, you should see a revision for the board.


Reed


Bob Lunsford
 

I have not yet looked to see if the revision number is on the board. Will do soon.

Bob — KK5R

On Sunday, July 26, 2020, 8:07:13 PM EDT, Reed N <greenkid336600+groupsio@...> wrote:


Bob,

Did you look at your circuit board when you determined you had a v6.1, or did you look at the touch screen? Ashhar's stock software is currently at revision v6.1, and will display v6.1 on the screen. However, if you look near the antenna connector on the circuit board inside your radio, you should see a revision for the board.


Reed