It seems that the
HM-151 microphone shipped with the IC-7000 has inadequate audio
output level. It also has too much bass response. They used a very
small condenser element which doesn't even fit into the silicone
keypad mount for it inside the mic. The 154T tone mic also suffers
from low audio drive.To make it function on SSB, you have to use the
compressor as an additional preamp and cut the low
frequencies with the DSP (TBW control). Without the compressor
turned on, it is almost impossible to get full modulation and output
level.
On FM there is no work-around. Even at 100% mic level setting, the
on-air audio is just plain low. It seems that the radio's internal
software makes it difficult to modulate over about 4KHZ deviation.
Add that to low microphone drive level and you have very low
over-all modulation on FM. AM is completely useless. Modulation
level is around 30%.
Being a modern firmware-run radio, there is no simple electronic
audio adjustment inside the radio. How and why this happened is not
important. How to fix it - that's our goal here.
PS: As of February 2010, I am still seeing low
audio on new IC-7000
HM-151 microphones. The latest one checked was serial # 0510201
In fact, the latest Chinese mics are dropping in
output.
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