[1000mp] Pream Off ?

[Bill Tippett]

W7GP wrote:
"The MP menu has "tuned" and "flat" positions.  I think "tuned" means there
is a preamp in the signal path, and flat means it's not there.  Is it the
same thing to go to the menu and select "flat" vs. being in the "tuned"
position and then hitting the IPO button?  Or is it a different preamp, or
some other distinction between these two cases?"

        Tom, it's more complicated than that.  Take a look at the 
following Block Diagram from page 30 of the MP Operating Manual:

   Antenna - Bandpass - Attenuator - IPO - Flat/Tuned - Wide/Hi/Lo Preamps

Bandpass is a bank of 11 filters automatically set by frequency.

Attenuator is a passive 0/-6/-12/-18 dB attenuator...nothing to do 
with preamps.

IPO ON bypasses all preamps (OFF selects 1 of 3 different preamps based 
on other choices)

Flat (Menu 8-4) selects the Wide preamp (.1-30 MHz) for ALL frequencies

Tuned (Menu 8-4) selects (depending on frequency):

         Lo band preamp for 1.8-7.0 MHz bands
         Wide band preamp for 10 MHz-21 MHz bands (same as Flat above)
         Hi band preamp for 24-30 MHz bands

Lo band preamp is optimized for strong signal handling on the low bands
and has about 6 dB less gain than Wide which can be forced by selecting
Flat in Menu 8-4.

Hi band preamp has ~6 dB more gain than Wide on 12 and 10 meters.  

        I often switch Menu 8-4 from Tuned for 10 meters to Flat for
160 meters where I like a little more gain than the Lo band preamp which
is what I would get if Menu 8-4 were left in Tuned.

                                                73,  Bill  W4ZV