[Yaesu] FT-1000MP: main rx AF hiss

[Steven J. Franke]

Hi All,
Just received a new FT1000MP and immediately noticed
that the main rx audio (without EDSP) exhibits what seems
to be an abnormally high level of AF hiss.  The sub-
receiver sounds much better in this respect.  
I have not measured absolute levels, but I would 
estimate that there is a 10dB (or more) difference 
in total AF noise between main and sub-receivers
(no antenna connected, 500 Hz filters selected,
CW mode, EDSP off).

This is not just a difference in audio gain
between the two receivers, as CW/SSB signals
are at approximately the same level at the 
outputs of both receivers.

The hiss level varies with the RF gain setting, 
so I suspect that it originates in the 455 kHz IF
stage, after the filters.  Turning the EDSP filter
on removes the out-of-band components of the hiss, 
but I can still hear an extra contribution to the 
in-band noise that is not present on the sub-rx.

The S-meter reading on live signals are identical
for both receivers, so I don't think that there is
a problem with RF/IF stage gains.

The overall effect is to make the main rx sound
deaf compared to the sub-rx, especially on a 
quiet band with narrow filters.

Has anyone else noticed these characteristics?

73, Steve  K9AN
Thanks/73 Steve, K9AN


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