Van     : LA8AK @ LA5IV
Datum   : 891222/0102
Betreft : IMPROVE IC-202 - PTT


SOME MODIFICATIONS FOR IC-202E, ALSO USEFUL FOR IC-202S
PROBLEM IS THAT VOLTAGE SWING ON PTT CIRCUIT WILL ONLY GO
UP TO +9V, AND IT IS VERY CRITICAL THAT IT GOES DOWN TO BELOW
+0.1V.  THIS CREATE DIFFICULTIES WHEN IC-202 IS A PART OF A 
LARGER STATION BUILD-UP, EXAMPLES: USING A POWER AMP, PRE-AMPLIFIER
LOGICS, CW-METEOR SCATTER TIMER, ALL CONNECTED /CONTROLLED VIA
PTT LINE:
MODIFICATION FOR IC-202 IS SIMPLE:
INSERT A DIODE 1N4002 IN SERIES WITH R54 22OHM TO 'STBY'(PTT)
REMOVE DIODE D17 1N60 FROM 'STBY'(PTT) INPUT TO BASE OF Q13 2SC945
REMOVE RESISTOR FROM BASE OF Q13 TO +13V LINE , R55= 22K
CONNECT A RESISTOR FROM EMITTER OF Q12(2SD355) TO BASE OF Q13 2SC945
VALUE: 22K. CONNECT A RESISTOR - 10K FROM BASE OF Q13 2SC945 TO GROUND
------
TRANSISTOR   IC202E  IC202S
               Q11    Q12
               Q12    Q13

C     I                                         C Q13 2SC945
 B----I---R54-->I----I-- BREAK --I------I-----B
E     I      1N4002  I           I      I       E
I               STBY(PTT)        I    10K       I
I----------22K NEW---------------I      I NEW   I
I +R9V                                 GND    GND
Q12    R:+9.45V
2SD355 T:+0.1 V                       

A NEW KEY JACK IS CONNECTED TO REAR, CONNECTIONS FOR PTT AND KEY.
PTT-LINE (STBY) IS REMOVED FROM CW-POSITION OF S3 'MODE SELECTOR' TO
AVOID 'MOX' AND USE REMOTE CONTROLLED PTT FOR METEORSCATTER CW.
A PNONO CONNECTOR(CYNCH BUCHSE) IS ALSO CONNECTED ON REAR FOR CONNECTION
TO POSSIBLE OTHER POWER AMPLIFIER, WHEN IT IS NOT MINE.....HI
-----RESULTS:-
PTT LINE NEED NOW ONLY GO DOWN TO +1V TO OPERATE THE TX FUNCTIONS, AND
IT MAY SWING UP TO 30V OR HIGHER, ALTHOUGH IT IS NOT GOOD FOR THE
COMPONENTS TO USE TOO HIGH VOLTAGE GOING INTO THE TRANSCEIVER

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

Van     : LA8AK @ LA5IV
Datum   : 900106/1435
Betreft : IC-202E


THE FOLLOWING LINE AMPLIFIER CAN BE USED FOR DRAKE R-4C AND ICOM IC-202E
THIS IS PARTICULAR USEFUL WHEN CONNECTING ACCESSORIES LIKE:
1) PACKET RADIO TNC
2) RTTY CONVERTER
3) TAPE-RECORDER
4) CW MS UP/CONVERTER 
5) LINE-EQUIPMENT (PHONE PATCH - ** WHEN LEGAL)
6) SIGNAL TO NOISE MEASUREMENT EQUIPMENT
7) CW DEMODULATOR
AND OTHER MEANS 
----
THE GREAT ADVANTAGE OVER USING THE SPKR /HEADPHONE OUTPUT SOCKET IS OF
COURSE THAT YOU CAN OPERATE THE AUDIO GAIN CONTROL ONLY WHEN YOU WISH
TO LISTEN TO, AND TURN IT DOWN AGAIN, WITHOUT UPSETTING THE SIGNAL LEVEL
TO THE AUXILLIARY EQUIPMENT.
-----
IN THIS EXAMPLE IS USED SOME GAIN. THIS IS IMPORTANT TO MAKE A GOOD RF
IMMUNITY. IF SIGNAL OUTPUT IS TOO STRONG IT IS EASY TO ATTENUATE IT.
-----

               I----------------I---------I----------+12V
               I                I         I 
               I         ------ 7 ----    0U1
              1M         I           I    I--GND
               I         I      OUT  6--I-------1UF---1K---AF OUTPUT
AF IN--22NF----I-22K---- 3           I  I                  CYNCH/PHONO
FROM           I         I           I 47K                 CONNECTOR
AF GAIN        I         I           I  I                  0.5V RMS
'TOP'         1M         I     F.B.  2--I                  1.4V P-P
80MV RMS       I         I           I  I
220MV P-P      I         I UA741     I 10K
               I         I-----------I  I
               I              4         I
               I              I       0U1 (0.1UF)
               I--------------I---------I-----------GND (0 V)

THIS LINE AMPLIFIER IS SUITABLE FOR THE FOLLWING RIGS:
DRAKE: R-4C
       RR-1
       SPR-4
ICOM:  IC-202E/IC202S
       IC-402(?)
SO FAR I HAVE NOT TESTED THE CIRCUIT FOR YAESU FT-7.


end item.