When they built the FT-817, I think its such a shame they did not include a speech compressor. A good speech compressor makes such a huge difference to talk power and average RF power and is very helpful when using only 5w SSB. I did try a 'One Big Punch' speech compressor board that fits inside the MH-31 but I wasnt impressed with its performance, especially the noise gate. I found that with the MH-31 microphone, I have to have the mic gain set to 100 when using SSB and even then talk quite strongly within a few inches of the microphone. Even then I dont think the standard dynamic mic element sounds that good.
One great thing with the MH-31 is that there is an unused 5v supply connection. This allows an electret condenser microphone element to be used. I decided to experiment with this, and after some testing I came up with the circuit below.
Some photo's are below. I have stuck the electret element onto the front of the mic with some hot glue, then padded it with some foam before placing the PCB back in.
If you seem to share the same issues with the MH-31 microphone, I suggest giving this a go. Please let me know how you think it performs!