IC24AT additional features (miscellany)
                =======================================

(Part 1)

This set of instructions originated from Icom America and was downloaded
from the Icom Library of HamNet (Compuserve).

The IC-24AT dual band handheld had three additional features that are not
described in the owners manual.  These have been left out of the owners
manual because some countries restrict the use of the radio in these modes.

AM AIRCRAFT RECEIVE PLUS 740 to 960MHz RECEIVE
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Remove D13 from the main logic board (this diode may already be removed by
ICOM in some units).  D13 is on the main logic board and is a discreet diode
(one of the two in the radio) near the center of the board.  It is the left
discreet diode of the two on the board when the radio is open and held with
the controls away from you.

Simultaneously hold "Light", "B", and "#" keys depressed and turn power on.

It is important to note that the radio will not meet specification on the out
of band receive frequencies that are enabled with this modification.

CROSS BAND REPEAT (simplex)
~~~~~~~~~~~~~~~~~~~~~~~~~~~
Remove D14 from the main logic board (this diode may already be removed by
ICOM in some units).  The diode is a discreet diode to the right of D13 and
directly beside it.

To turn on cross band repeat:
Hold "Funct" depressed then push "5" and then push "D".

To turn off cross band repeat:
Simultaneously hold "Funct" and "D".

Following the frequency expansion modification (as specified by Icom), a
sample IC-24 was recently tested for tuning range and input sensitivity for
an S9 signal.  While the sensitivity measurements should not be directly
compared with the manufacturer's specifications (usually measured reference
to a signal-to-noise quieting ratio), this "quick and dirty" data should give
you a good idea of the sensitivity to a medium-strength signal.

Tuning Range      Mode     Band      Sensitivity for S9 Signal

 74 - 107.995 MHz (fm)  VHF range    approx 1mV
108 - 136     MHz (am)  VHF range    10 - 30uV
138 - 240     MHz (fm)  VHF range    1uV - 1mV (1)
250 - 302     MHz (am)  VHF range    50uV - 1mV (2)
310 - 354.995 MHz (fm)  VHF range    50uV - 3uV (2)

355 - 409     MHz (fm)  UHF range    3 - 10uV
417 - 490     MHz (fm)  UHF range    1uV - 100uV (3)
805 - 955     MHz (fm)  UHF range    10uV - 100uV

Notes:

(1) The sensitivity from 138 - 150 MHz was 1uV.  From 150 - 240, the
    sensitivity decreased almost linearly from 1uV to 1mV (with input voltage
    plotted logarithmically).

(2) The sensitivity increased almost linearly for both these ranges (with
    input voltage plotted logarithmically).

(3) The sensitivity plot looked like a "U" with the bottom of the "U"
    corresponding to the range 440 - 450MHz (1uV).  The sensitivity then got
    worse below 440 and above 450.

(Tests courtesy of WB6GTM)

Cont'd in part 2

(Downloaded from GB7SYP)