[ICOM] 756 PRO II BCB sensitivity

[Don Moman]

The fixed attenuator built into that <1.6 mhz filter section isn't too hard
to bypass, if you can handle tiny smt work. I have done this on both of my
PRO's, but not the PROIII yet (it still needs it removed). There is a way to
trick the preamp -  Dallas Lankford came up with this idea - by cutting 2
traces and reversing them, so the preamp is on when you turn it off, you get
the idea.  I can see where to do it on schematic but haven't translated that
to where it actually needs to be done on the board.  In this respect, the
PROIII may be easier to mod as the preamps are mounted on a daughter board
above the main board. I have not yet attempted this mod on either the PRO or
PROIII.  It would have been so simple, at the design stage to allow the
preamps to be enabled, but as usual, we are stuck with what the designers
think should be sufficient.

At least if the internal att is bypassed, one can add external amplification
without loosing 10db of precious headroom, but letting the internal preamps
function would sure be handy.   I did break the RX line internally after the
TX/RX relay and bring it out to the rear, so I have true TX antenna OUT and
RX IN  (like older ICOMs with the little phone plug jumper) which adds a lot
of flexibility for external amplification and filtering.

73 Don

----- Original Message -----
From: "Cecil Acuff" <chacuff at cableone.net>
To: <icom at mailman.qth.net>
Sent: Friday, February 04, 2005 17:19
Subject: [ICOM] 756 PRO II BCB sensitivity


> Greetings,
>
>         Anybody been successful at restoring the full sensitivity on the
BCB
> and LW.  I would be interested in how it was done.  I have seen info on
how
> to do it on the 746...as well as managing to activate one level of preamp
> functionality.
>
> Things pretty deaf down on LF for us beacon chasers....
>
> Cecil...
>
>
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