In article ,
N4RCC - Richard wrote:

Just received a brand FT-991 and the transmitted AM audio is horrible. I
noted a couple of other posts with the same issue, but did not note if anyone
has found a fix.

SSB mode seems to be fine.

Is there a fix or is it what it is?

Richard-

I've had my FT-991 for nearly a year. That includes a trip back to
Yaesu to repair damage caused by a transmitter lockup that was
discovered an hour later.

At the 2015 Orlando Hamfest, I talked with a Yaesu manager and provided
a list of the many problems I had found. I exchanged subsequent E-mail
messages with him. Yaesu is well aware that there is a problem with AM
transmission!

There have been several Firmware Updates that have solved most of the
problems. They changed ALC meter action during AM modulation, but did
not make any other improvement that I can detect. As I understand it,
you adjust audio gain so there is just an occasional downward power
kick, and that is the best you can do. That appears to produce about
ten percent modulation. Any higher audio gain only increases distortion.

I think Yaesu has failed to fix AM operation with firmware, and are not
willing to recall the radio for a hardware modification. Perhaps a new
FT-991A will be introduced with the needed modification.

AM operation is not the only problem the radio has. There are
occasional situations that may require a power cycling to correct.
Sometimes a change in a setting, followed by changing it back will fix a
problem. It is unfortunate, since the FT-991 is an impressive radio
most of the time!

73,
Fred
K4DII