[VHFcontesting] Using battery bays for transverters in FT897

[jcplatt1 at mmm.com]

Hi Dave.   The key to the integration is the "large" battery bay area, the
good documentation that is available on the FT-897, and the design itself.
>From a system design perspective, there are three main "buses" that run
between the FT-897s main PCB and its PA board.   They are the RF Out, RF
In, and serial communication lines.    All the radios XMT and RCV signals,
from 1.8 through 440 MHz run through the RF In and RF Out lines .... much
like a split IF.   On transmit there is about 10 watts of RF in the RF Out
line (on HF).    The modification involves cutting the FT-897's RF In and
RF Out lines and inserting a RF relay in each.    The RF relays then
control when RF is routed through the normal radio path, or to the DEM
transverter (using it in its split IF mode).    The DEM board, its power
module, and the two RF relays will all fit inside the battery bay where
they are mounted to the radios removable battery shield plate.    This mod
DOES violate the warranty !    In addition, there is a small custom logic
board with a few logic gates on it that are used to sense the PA boards "28
MHz" and "XMT" control signals, and that are routed through the top panel
A/B Battery rocker switch.    When the rocker switch is in the A position,
the FT897 operates as normal.   When its in the B position, then 28 MHz
becomes 222.   This allows you to move from 222 (aka 28) to 50 to 144 to
432 with the band switch.    When operating on 222, the display still say's
28 .... not 222.   I do not use the radios transverter mode.

This mod may be applicable to other bands.    My 222 work here uses the DEM
222 PCB and power module not in its box.    The PCB is mounted to the
battery shield plate using the same mechanical mounting technic that is
used to mount it in its normal box.    Based on an N =1 (mine) its stable,
and power control is smooth and predictable.   I don't know if this same
open box approach could be used on 902 and up.    I would think that one
possible consideration is the DB6NT design as they are quite a bit smaller
and the whole transverter box could be installed inside.   It may be
possible to install more than one, say 902 and 1296, albeit you would have
to find a way to switch between them other than the A/B rocker switch that
is provided.

Hope this helps Dave.    Check out the full article with pictures in the
CSVHFS Proceedings in a few months !     Hope to see you in Mpls and
perhaps we can have an eye-ball QSO over the mod.   222 is a great band.

73, Jon
W0ZQ