¿ªÔÆÌåÓý

  1. BITX20
  2. Messages
Single Messages Topics Expanded Polls
 

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 ¡ª 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:
/g/BITX20/topic/71576826
/g/BITX20/topic/74673407
/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 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
Join [email protected] to automatically receive all group messages.