Newsgroups: rec.radio.amateur.misc

From: rfc
Subject: TH78A mod file, crossband repeat, extended RX/TX, cloning

Message-ID: <1992Oct25.051148.8822
Organization: AT&T Bell Laboratories, Murray Hill, NJ

Date: Sun, 25 Oct 1992 05:11:48 GMT

Lines:156



copied from packet:



  Msg# TSF   Size #Rd  Date  Time  Arrived Seq #      Msg ID      Route

  2182 BF    7214   2 22-Oct 1938z 22-Oct (019609 - 029771WT3V  ) []

  N2CZF  ==>  MODS
  "TH-78A Modification File"





Date: 22 Oct 92 15:38:10 EDT (Thu)

From: n2czf
Message-ID: <029771WT3V>

Reply-To: n2czf
To: mods
Subject: TH-78A Modification File



FILENAME:TH-78A.MOD                     June 25,1992

Revised:October 22, 1992

Modifications for the Kenwood TH-78A Dual Band Micro-HT.

By Rich Garcia N2CZF.   Packet Via N2CZF


Owner assumes all responsibility for modifying or using these

modifications!.



The following mods will provide for Crossband Repeat and extended

receive and transmit on the Kenwood TH-78A HT.



I believe other functions are also enabled by these mods. which I

have not found yet but I will update the file as news progresses.



Diode #4-  Crossband Repeat

Diode #5-  Extended Receive and out of band Transmit.



Remove all screws and open radio as explained in the Kenwood manual

for installing the memory expansion module.

On the back cover you will find the memory expansion module socket

and a copper shield to the upper left corner of it.

Under this shield their will be a row of SMC diodes which are

unmarked in a vertical configuration to the lower right portion

covered by the shield.



#1 Remove the shield at its four corners with a solder sucker and

SMALL! iron.



#2 Carefully count down from the 1st diode in the row to the fourth

one and remove for crossband repeat.

HINT:I found if you BRIEFLY touch the iron to the right side lead

while gently pulling up on the SMC diode it should completely come

off without needing to apply heat to the other side and further

risk board damage.

I used a pair of right angle surgical tweezers for this.



#3 Just as above you may remove the fifth diode to preform the

extended receive and transmit modification.



#4 Reset the CPU (yes you will loose all of your programed

memories! argh!) by pressing Function for more than one second and

then "0".

YOU HAVE NOW COMPLETED THE MODIFICATIONS!



#5 For 800Mhz go to the UHF band with the band switch and press

Function for more than one second quickly following with a press of

the Band switch again.  8---.-- will appear.



#6 For 300MHz go to the VHF band and repeat as above.  Original

bands are restored by repeating the "F Band" sequence.



MY observations...   All original functions have maintained the

same which is great.  Aircraft band which was accessible before the

mod remains with the same characteristics.  It seems that VHF-High

band has improved a bit on sensivity where it was dead as a dog

before the mod (above 155.000MHz) but the 162.000 MHz band where

weather radio is is still a bit deaf for reception at any distance

but about 20 Miles.  This depends on your (or my) terrain and

transmitter output power.



On UHF all public safety frequencies up to about 500 MHz seem to

come in well but sensivity greatly drops from there (we really

can't ask for more). Frequencies can be programed in up to the

920MHz ham band but I have no way of measuring sensivity.  800MHz

works but the signals are very weak, you must be near the

transmitter for reception.  Assuming you are in the town or city

where the transmissions originate it should work.



Transmit is enabled up to and incl. 500MHz but after testing this

on a frequency counter I find that a signal is only generated to

about 490 MHz, even though the trans. LED shows output in the

higher frequencies.



Crossband repeat seems to work fine but the audio is unacceptable

for use, BE AWARE the radio gets HOT!  Prolonged use or use on a

busy frequency would not be recommended.  Also remember this is a

dual band HT please use a proper antenna while in this mode to

avoid a high SWR, we should all know better... Right?



After first booting up the CPU in the mod I found that the message

screen showed "Cloning" so it seems that this radio now has cloning

capabilities. After searching I have found that holding the "0" key

and powering up the radio will display the clone feature, see below

for further explination.This leads me to believe that this HT may

have some more "Hidden" features that I am trying to find, some may

be useful.



Thanks to Gary KC8UD who sent me the following via packet .....



CLONING:

The TH-78 can be cloned without cloning cables or special equipment. It is done

entirely with RF, and, in fact, can be transmitted over the air, and even via

repeaters. This may be extremely useful for those users who do not have

the patience to program their own radios themselves. This application would

also be useful for clubs and user groups. (However, this can take as long as

50 minutes with the ME-1 expansion module. It is recommended that a dummy

load be used to prevent unwanted QRM.)



(1) Both radios must be on the same frequency.



(2) Activate both radios by pressing the "0" key while turning the power on.

The radios will display CLONE.



(3) Now, click the PTT of the "master" radio. The radio will transmit in the

conomy low power mode. This may take about 4 minutes for fifty channels.

hen the data has been transferred, both radios will revert back to the

riginal frequency.



(4) Turn both radios off and then on again. They will now operate normaly

     while the slave radio has the same memory contents as the master radio.



 ** I have not tried the following modification myself, try at your own risk **

                               *** Rich N2CZF ***

FREQUENCY EXPANSION



(1) You can receive from 340 - 399.987 Mhz FM by removing chip diode D8 on the

ontrol unit. To access this function, press the [F] key for one second, and then

the [LOW] key. This toggles between AMATEUR, AIR band (AM) and 360 Mhz.

AM and FM modes are selected automatically, depending on frequency.



    ** Since "F" for a second and "Low" toggles the power output, I wonder **

                               *** Rich N2CZF ***



    There is also a couple of arcade type games on the TH-78A. To start the

game you pres and hold [PTT] and [M] keys while turning the unit on. The first

game is a follow me type game. The radio beeps and shows a sequence of

numbers flashing on the screen. You have to match the same sequence on the

tone pad. Each time the sequence gets longer by one number. You have to

keep remembering the sequence as one gets added each time. Once you get to

a certain high score on that game, it breaks into a poker type game. To exit

the game mode press the LAMP key at any time. The receiver still works in

the game mode and you can adjust volume but no other features.



    RG>  The games seem to work fine and it is interesting that they have

inserted that into the programing of the chips.  Does anyone know of any further

features in the radio be it games or radio functions.

                                                            

                          73's Rich N2CZF Bricktown, NJ

=============================================================================

Note:I haven't tried or verified this, proceed at your own risk.  And

do not transmit outside of legal bands!  WA2ISE