There has been a bit of discussion on the BITX20 Groups IO list about Baofeng mics, mods required to work with the µBITx, and what to do about a mic jack. This article tries to sum up thoughts on using the Baofeng mic.
Basics
The Baofeng Speaker/Mic can be obtained very cheaply, either direct from China (e.g. on Aliexpress.com or Banggood.com, or eBay.com) or via third parties in your country. Be warned that almost none of these will be a genuine Baofeng mic. There are many different varieties of “knock-off”, and they are of very varying quality. However, most are adequate for µBITx use.
The wiring in the microphone is not standardised (i.e the colour of the wires varies). In some cases the wiring simply doesn’t work. In this instance, you should throw away the Speaker-Mic as the wiring is non-repairable. Buy several to safeguard against the odd one that has wiring issues.
The microphone element is so-so, you can replace the one in the Speaker/Mic with the element that comes with the kit as required. You may also need to drill out the tiny hole to be a bit bigger to make a reasonable air passage to the element. The speaker is not high quality and will not give much volume. When using the speaker-mic in the µBITx, most of us don’t use the speaker at all.
Standard wiring will work on the BITx40, and the LED in the Speaker/Mic will even light up. It won’t on the µBITx, because the PTT line works differently. This is connected to +5v from an arduino line (messing up the bias on the microphone).
Disassemble the mic, and rewire (using a multimeter to test connections) so that the PTT switch is wired separately from the microphone element. You can use a common ground return for the mic, speaker and PTT. See the original circuit diagram for the speaker/mic here.
Panel jack mounting
A key question that those with a Baofeng Speaker/Mic, is whether you should retain the 3.5mm and 2.5mm plug, or cut it off.
John KG5WJQ observes that they sell a combined jack on Alibaba and the price is fine. The problem is that it is a PCB mount jack so that can result in some difficulties with mounting the jack in a case.
Craig KM4YEC uses panel mount mono jacks, one 3.5″ and one 2.5″, sourced from Radio Shack in store stock (but they could probably be ordered online). He says, “If you turn these back to back, and butt them against each other, with the ears turned out, it is a perfect fit for spacing.”
Craig uses only the PTT, and the Mic element in the enclosure. He enlarges the hole in front of the element, removes the speaker, and makes sure the only two circuits are PTT and Mic. He went as far as removing all the SMD components and unnecessary trace runs using exacto knife cuts.
Glenn VK3PE fitted standard 3.5 and 2.5mm jacks at the rear of his uBITX build. NOTE the 3.5mm jack needs to be insulated from the chassis to work as the PTT is connected to what is normally ‘ground’ on a stereo socket. Glenn used some plastic washers to insulate it.
The challenge with this approach is that the spacing between the two jacks needs to be reasonably precise.
There is nothing to stop you from cutting off the plug and wiring it directly into the circuit. This is a cheap option (no plug and socket required), but is a bit inconvenient when it comes to moving the rig, as the microphone is permanently attached.
The other option is to remove the plug altogether and use different connectors. Many constructors like to use a standard 4 pin mic jack or similar style 8 pin jack used by the big three Japanese amateur rig manufacturers as illustrated below:
Mike ZL1AXG uses Kenwood wiring on a standard 8 pin mic connector as shown below.
Is there a better choice of microphone?
Dave K8WPE felt his Baofeng speaker mike was of such poor quality that he went ahead and bought an almost identical microphone from Btech. This is a QHM22, a much better product, for US$23.00. The speaker is top notch and reports of his voice quality are also very good. So the Btech mike might be a better choice.