More talkpower for the FT-817: a very simple microphone modification

Summary:

• By taking out the resistor R1 and replacing the capacitor C1 in the MH-31, audio and talkpower will improve.
• For an audio example of the difference between original mic and modified mic see here: https://youtu.be/DmAB0tLI__s

When it comes to punchy audio on SSB, the Yaesu FT-817 is notoriously weak. There are many solutions to this problem, from replacing the dynamic microphone capsule with an electret mic to HF clipper circuits.

I actually tried the electret mic mod, but with no luck – the audio sounded terrible, even though I tried different electret capsules. Other OMs assured me that it can work and that I just need to find the right capsule…

However, those electret mics are a little suspicious to me: first, unlike dynamic microphones, they require power – while the Yaesu radios can deliver it via the microphone cable, this strikes me as somehow inelegant. Worse yet, electret microphones decay! Yes, that’s right, they have an expiration date! Although Wikipedia claims that they will work for hundreds of years (how do they know?), this strikes me as very un-ham-spirit-like.

While I was looking for a solution to the talkpower problem of the FT-817, I came across this blog post (in German) where OM Anton presented an extremely simple modification of the MH-31 mic. All you need to do is take out the resistor and replace the 0.33uF capacitor with a 47nF (473) one:

Super-simple mod of the MH-31 for more talkpower on the FT-817

This will achieve two things:

• increase the output of the mic a little
• shift the frequency of the audio low-pass filter a little for more punchy audio

I think the MH-31 sounds great anyway, but after this mod, there’s just the little more punch and talkpower that the mic needs.

Remember also, as Anton rightly points out, that with dynamic mics, you need to speak directly into the microphone – that way they sound best, and you will even achieve some natural compression.

I also crank up the SSB mic gain setting on the FT-817 to 100, which works very well unless you are screaming into the microphone. The mic-radio combo is just a little on the weak side in terms of SSB modulation, but with the setting on 100 and this mod, it really shines. I got many spontaneous comments from my QSO partners that my audio sounds very good. This mod will of course also improve things when used with the FT-897 or FT-857…

Here are the steps:

Disassemble the MH-31…

…remove C1 and R1…

…put in the 47nF cap…

…assemble, and there you go!

Here you can see the MH-31 mod on video, including a comparison between the original mic and the modified mic:

 

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