After thinking about what Yaesu is trying to achieve with the
Low-Band preamp, I concluded the following:
--the Low-Band preamp is primarily for cases where there are strong
local out-of-band (i.e. out of 1.8-7.5 MHz) signals which are causing
interference. Examples would be very close proximity to Broadcast
stations, multi-multis, etc.
--the Flat preamp is about 10 dB more sensitive than the Low-Band
preamp on 160.
--for very strong in-band IMD problems (i.e. a 160 contest), IPO is the
solution independent of whether Tuned or Flat is selected, since it
bypasses either preamp. I still have yet to hear my first IMD product
using Flat and I listened during a fairly good pileup on ZS8IR the
other evening, so the front end without IPO is fairly good.
My plans are to use Flat everywhere except 10 meters, where the Hi-Band
preamp has significantly more gain than the Flat preamp. If I had a
50 kW Broadcast station a few miles away, I suspect I would then see
an advantage to the Low-Band preamp. It might also be useful when at
a multi-multi. Too bad they did not make it possible to preselect the
preamp you wished to use in each frequency range so it would not be
necessary to switch from Flat to Tuned when changing bands in an all
band contest. However it is easy to do by going to menu 8-4.
The significant distortion in SPOT is a design problem in my opinion.
I'm going to let Yaesu know about it and maybe they can come up with a
simple modification. So far, this is the only major problem I've seen
with the radio (well, maybe the display COULD use a tinted filter to
remove the background stuff). Overall, I like the MP so far!
73, Bill W4ZV
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