Subject: Re: Needed: Kenwood TH-26A and TH-46A Mods

From: [email-masked] (Joakim Karlsson)
Date: 3 Oct 91 12:50:26 GMT

What follows below is the most extensive description of TH-27A mods
that I have ever seen.  Sorry about the ALL CAPS, it came that way.
I've performed the "snip-the-green-wire" mod on mine in order to be
able to use it for the Civil Air Patrol.  Works great.  ...Joakim

---- Cut here ----

The following info on the TH27A was posted before, just after Christmas,
and is reposted due to recent queries.  Please respond directly to the
author, Tom, at Internet: [email-masked],
		 Packet: N5OFF@K5ARH.#LFTLA.LA.USA.NA

I HAVE BEEN DOING SOME EXPERIMENTING WITH MY TH-27A, AND HAVE 
FOUND IT TO BE AN EXCELLENT AIRCRAFT RECEIVER AS WELL AS A FINE
TWO METER TRANSCEIVER.  IT WILL ALSO DO FULL 136-174 MHZ TX/RX,
BUT I HAVE NOT YET FOUND A MOD CONFIGURATION THAT WILL ALLOW
FULL TX/RX AND AIRCRAFT RECEIVE AT THE SAME TIME (EXCEPT THE
ASIAN CONFIG, TH-F27, WHICH I WILL DESCRIBE BELOW).

WHEN MODIFIED FOR FULL 136-174 TX/RX IN ANY OF THE WESTERN CONFIGS
THE AIRCRAFT AM IS DEFEATED (SEE CHART BELOW).  IN THE ASIAN CONFIG,
THE RIG BECOMES A VERSATILE WIDE BAND RECEIVER 118-174, 200-400 (DISPLAY
ONLY) AND WILL TX 136-174.  THE PROBLEM WITH THIS CONFIG IS THAT SOME
OF THE KEY POSITIONS BECOME RELOCATED (SEE CROSS REFERENCE).
THE KEY DIFFERENCES ARE OBVIOUS IF YOU COMPARE A JAPANESE 
KENWOOD BROCHURE WITH A YANKEE ONE.

SO, CAN ANYONE OUT THERE SHED SOME LIGHT ON HOW TO GET FULL
136-174 TX/RX AND PRESERVE THE RELATIVELY HIGH QUALITY 
AIRCRAFT RECEIVE PRESENT IN THE WESTERN STANDARD CONFIGURATION?
I HAVE INCLUDED BELOW MY SUMMARY OF THE POSSIBLE RESISTOR 
COMBINATIONS, ALONG WITH A PARTIAL RESULTS LIST.(DID I MISS
A RESISTOR SOMEWHERE?)

  R334      R335      R337     W301         REMARKS
    O        -         O        O          K,P US STOCK CONFIG
    O        O         O        O          E     144-146 TX/RX  NO AIRCRAFT
    O        O         O        -          E2    136-174 TX/RX  NO AIRCRAFT
    -        -         O        O          M     144-148 TX/RX NO AIRCRAFT
    -        -         O        -          M2    136-174 TX/RX NO AIRCRAFT
    O        O         -        O          X     144-148 TX/RX
    O        -         O        -          US MARS 118-174 RX 142-152 TX
    O        -         -        -          US MARS+ 136-174 TX/RX NO AIRCRAFT
    -        -         -        O          ASIAN STOCK
    -        O         O        -          ASIAN MOD 118-174,200-400 RX,
                                                     136-174 TX
    O        O         -        -                136-174 TX/RX NO AIRCRAFT
    O        -         -        O          NOT TRIED
    -        O         -        O          NOT TRIED
    -        O         O        O          NOT TRIED
    -        -         -        -          ASIAN RECEIVE MOD 118-174 RX,
                                           200-400 RX, 144-148 TX
    -        0         -        -          COMMERCIAL 136-174 TX/RX, 5.7 MHZ
                                           OFFSET, 150 DEFAULT

"O" MEANS RESISTOR OR JUMPER IN PLACE
"-"  MEANS OPEN
THE FIRST SIX CONFIGS ARE SHOWN ON THE KENWOOD SCHEMATIC
W301 IS OUR OLD FRIEND, THE GREEN WIRE.

TH-27A TO TH-F27 (ASIAN VERSION) KEY RELOCATIONS

       TH-27A KEY      =      TH-F27 KEY

      TONE/TONE SEL         CALL/C-SCAN
       CALL/C SCAN            BELL/STEP
       3 TALT                 3 TONE
       SHIFT/REV              REV/SHIFT
       MHZ/STEP               MHZ (NO F FUNCTION)

I HAVE SETTLED ON  THE ASIAN MOD FOR MY TH-27A, AND FIND THAT 
THE BUTTON  DIFFERENCES ARE EASY TO LIVE WITH.  ALL FUNCTIONS ON THE
RIG SEEM TO WORK IN THE ASIAN CONFIG EXCEPT I DON'T THINK THE
AUTO-DIALER WILL DIAL A * OR #.  NO BIG DEAL FOR ME. IT WILL MANUALLY
SEND A # OR * THOUGH.

AS STATED EARLIER, THE COVERAGE OF THE RIG IN THE ASIAN  CONFIG IS

        118-136 AM RX (WITH A REAL AM DETECTOR)
        136-174 FM TX/RX
        200-400 RX

I DON'T THINK THE 200-400 WORKS AT ALL BECAUSE I'VE COMPARED IT
TO STRONG LOCAL SIGNALS ON A SCANNER AND HEARD NOTHING ON THE 
TH-27A.  SEE THE SENSITIVITY MEASUREMENTS BELOW.

OTHER BUTTON DIFFERENCES NOT MENTIONED EARLIER ARE:

                        TH-27A                     TH-F27
           F1SEC,3      TONE ALT SOUND             TONE SELECT
            F MHZ       STEP                       BAND SWITCH 118/145/340
           
OTHER NOTES:

AUTOPATCH WORKS WELL

CTCSS TONES SENT OK, DTMF AND CTCSS SQUELCH WORKS

BAND SCANNING, ETC WORKS OK

PROCESSORR RESET DEFAULTS TO 145.000 INSTEAD OF 144.000

TX/RX NO PROBLEM ON VHF FM

RX AIRCRAFT, GREAT! AS GOOD AS A BEARCAT 100/200, BETTER THAN
ICOM 2SAT. THE TH-27A HAS A "REAL" AM DETECTOR/AGC (SEE SCHEMATIC).

WISH LIST, FOR SOMEONE ON THE NET TO FIGURE OUT THE MOD TO GIVE 
136-174 TX AND PRESERVE THE AIRCRAFT RECEIVE IN ONE OF THE STANDARD
US OR WESTERN CONFIGURATIONS. IS IT NECESSARY TO GO TO THE ASIAN
CONFIGURATION TO HAVE YOUR CAKE AND EAT IT TOO?

SENSITIVITY MEASUREMENTS			
TH-27A   12/18/90			
USING AN IFR MOD 1000S SERVICE MONITOR			
REFERENCE IS 1 LED SEGMENT LIT 			
1000 HZ TONE			
			
FREQ.	SIGNAL		
MHZ	MICROVOLTS		
			
118	1.7	AM	
120	1.5		
122	0.9		
124	0.9		
126	0.9		
128	0.9		
130	0.8		
132	0.8		
134	0.8		
136	0.8		
136	0.5	FM	
138	0.4		
140	0.4		
142	0.3		
144	0.3		
146	0.3		
148	0.4		
150	0.4		
152	0.4		
154	0.4		
156	0.5		
158	0.5		
160	0.5		
162	0.6		
164	0.8		
166	0.8		
168	0.8		
170	1.0		
172	1.3		
174	1.5		
200-400	NO RX		
			
INSERT USUAL WARNING/DISCLAIMER HERE.

DE TOM [email-masked]

-- 
-- James Dugal,	N5KNX		Internet: [email-masked]
Associate Director		Ham packet: n5knx@k5arh
Computing Center		US Mail: PO Box 42770  Lafayette, LA  70504
University of Southwestern LA.	Tel. 318-231-6417	U.S.A.

--
Joakim Karlsson            | [email-masked]
Flying Fanatic in Training | FAA: P-ASEL  CAP: Freedom 226 Mobile  FCC: N1JHW
                 "Oh, I have slipped the surly bonds of earth
                And danced the skies on laughter-silvered wings"