As of late 2009, it seems that Icom has gone over to shipping a
Chinese-made HM-151 microphone. This was an opportunity for them to
fix all the problems with the 151.
The circuit is identical.
Original Problems:
1.
Low output.
2. Hollow sound (no
acoustic damping)
3. Excessive low-end
causing SSB TX to be "muddy"
4. Lack of
pop-filter
5. No case weighting included
- way too light in the hand
My tests
show that output levels are slightly increased. I believe that the
small increase is due to just the difference in components used in
China to make the microphone, not
a conscious design change.
Now the
output is almost adequate to get full output on SSB. The internal circuit and coupling on the Chinese mic
is identical though -and the muddy / hollow sound is still there. My
type #2 element is about 30% higher in drive and much cleaner due to the modified
coupling arrangement I use. I correct all the other problems as
well.
(Use headphones if possible,computer speakers
are not the best at reproducing SSB)
My Youtube FM Bench-test of the new
Chinese HM-151
If you are like me, I want
every ounce of performance from my radios.
My goal with this upgrade is to do exactly that. Again, I appreciate your continued
support.
