Kenwood TH-77 Extended frequency coverage and dual-band repeater

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relayed by n2ixl, from bitnet infohams digest,v90n433

Kenwood has made this radio compatible with the new ICOM S-Series radios
from what I can tell.  It has DTSS (Dual Tone Squelch System) which means
that your radio will not break squelch until it hears a particular
sequence of three DTMF tones (ICOM has this also and they call it
Coded Squelch which also use three tones).  The TH77A also has a paging
function that works *exactly* like the ICOM paging.  You program the
radio with a personal 3 digit DTMF code and someone pages you by
transmitting YOUR 3 digit code, followed by a * character and then
their own 3 digit code.  The ICOM will start to ring to let you know
that you have been paged and display the 3 digit code of the person
that has paged you.  The TH77A will beep once and open squelch as
long as the person that paged you does not drop carrier (I prefer
the ICOM method for this part, but there is a work around that I
will mention in a bit).  One thing the TH77A does at this point is
bring up a timer so you know how long its been since you've been
paged.  Maximum time is 99 hours and 99 minutes. 


Let's  see if your
battery can hold out that long!  The workaround so the TH77A will
ring, rather than just beep and open squelch is to put the radio
in the pager mode AND also put it in Tone Alert.  When you get
paged... the radio will "beep beep (pause) beep beep" five times
and start up the timer.  Kenwood has provided two different types
of BEEPS for you.  The second type is to ring like an electronic
telephone.  This one *REALLY* sounds nice!!  For those of you that
like autodial memories, there are 10 memories that can store 15
characters each.  There are 40 regular frequency memories in this
radio and you can make them all UHF if you like (no restriction).
NOW!  On to the *EXTRA* capabilities (there are other BASIC functions
that I didn't mention, those were just the highlights).
After making a few modifications to this radio, you can get it to
do the regular stuff that the IC24AT will do, such as AM aircraft,
expanded UHF (400-512 depending on PLL lock) and 800-950 (again,
depending on PLL lock) in addition to cross band repeat.
HOW DO YOU DO THIS!?

                  --       --       --
                  ||       ||       ||
                 /  \     /  \     /  \
                =========================-
                |                        |
                |                        \-\
                |                          |
                |       /=====----\        |
                |       |         |        |
                |       |         |        |
                |       |         |        |
                |       |         |        |
                |       \=====----/        |
                |                          |
                |       -- -- --           |
                |          || || <================== REMOVE THE RIGHT ONE
                |       -- -- --           |         FOR AM/800-950 RX.
                |    --                    |         REMOVE BOTH TO ALSO
                |    ||    -- -- --       -/         GET EXTENDED TX.
                |    --    || || ||      /
                |          -- -- --      |
                |                        |
                |       /==========--\   |
                |       |            |   |
                |       |            |   |
                |       |            |   |
                |       |            |   |
                |       |            |   |
                |       \==========--/   |
                |                        |
                |                        |
                =========================-

    Layout shown with electrolytic capacitor C124 removed
The best way to do this is to heat up both sides of the resistor and
push it out of the way with something small.  At least this was the
best way for me!  Once it's out, put the capacitor back in place and
close it up.  (Put the green wire back also, if you are making the
out of band TX mod too!)