The HM-151 is a good solid mic, but it has a weak audio section. The element itself has low output and poor quality audio. Then, they use the wrong coupler cap. As well, they didn't dampen the mic with either acoustic foam or a ballast weight. Both these are in any decent microphone.
What I do to make this mic shine are:
1. Replace the element with a custom element which has the exact correct output and response for the 7000.
2. Change the SMD coupler cap to the correct value.
3. Increase the mic shell opening slightly.
4. Add a silk and foam pop filter.
5. Add acoustic foam in the rear shell.
6. Add 1oz of metal to deaden the shell (that plastic hollow sound) - and give it the correct
weight in the hand. This small detail makes a really nice difference.
The result is that you have perfect drive and response on FM and SSB.
50% mic level - no compressor - and your ALC will be right in the sweet spot. Prepare for unsolicited "great audio" reports.
I've shipped over 4000 of these upgrades and have all five-star ratings on Eham.com. Check out the reviews: