FT-736  Mods
 

1- Unplug the power from the radio
  2- Open the radio and locate the 144Mhz main unit.
  3- Locate diodes D24, D25, D26 and D27 See drawing.
  4- Remove or install the diodes per table 1.
  5- Reassemble the radio.

 1.) change the mic-phone in the handheld-case to a better one. (try several mic-phones at a resistance about 600 Ohms)
 2.) open the FT736 (upper case) and locate the TX-Board (on the left upper left side if the front is showing to You). On this TX-UNIT cut the Capacitor C 14 (Value 0.001uf) . The Capacitor is located in the right-bottom corner of the board. Adjust for FM-Mode the Potentiometer VR 01 just a little tick clockwise ( deviation-limiter).
If You can use a deviation-meter You can do this in a professional way. (about +- 5 Khz).
 3.) If You are using a preamp-microphone, make sure to adjust the level from this mike so that the mike-gain-potentiometer at the front panel from the FT736 are minimum in the 11 o'clock position for a good drive
of the power stage. Otherwise You will overdrive the first mic amplifier in the rig. This sounds like speaking in a train-station... When You are using a preamp-mike connect a small 600 Ohm resistor direct in the mike-plug between point 8 (middelplug) and point 7 (GND) So the rig always have the correct 600 Ohms resistance.
 4.) Best results I got whit a mike, that produces a strong signal in the higher audio-band (about 2000 Hz).

By the way, the PROC-Switch only works at SSB and only when You get down
with the drive-gain... if the ALC-Meter is on the right scale, the PROC-
switch has no affect !

ALWAYS think of loosing warranty if You modify something inside the FT736 !!
 

Kleine Modifikationen fuer ein besseres Audio-Signal beim Senden vom FT736R.

Hallo FT736 Fans,
Der FT736 ist ein prima Geraet, aber das Sendesignal ist von der Sprach-
qualitaet miserabel. Die Sprache klingt hohl und besonders in FM viel zu
tief. Bei SSB-Berieb schafft die Endstufe wie doll aber es werden nur die
tiefen Toene der Sprache uebertragen. Der QSO-Partner versteht bei schwachem
Signal meistens nicht sehr viel.
Hier nun einige kleine Aenderungen um dieses Problem zu mindern:

1.) werft die Mikrkabsel aus dem Handmikro in den Muell. Versucht es mit
anderen 600 Ohm-Kapseln.
2.) oeffnet den oberen Deckel des FT736 und sucht die TX-Baugruppe. Die
TX-UNIT ist auf der linken Oberseite wenn die Frontplatte zu Euch zeigt.
Entfernt den Kondensator C 14 am Mikeeingang hinter den 1 KOhm Widerstand.
Dieser Kondensator liegt in der unteren rechten Ecke auf der Platine.
Ich habe die Baugruppe deshalb nicht ausgebaut, habe die "russische
Methode" also Durchkneifen angewendet... Der C hat den Wert 0,001uF.
Fuer den FM-Betrieb dreht den Poti VR 01 einen kleinen Tick weiter
in Richtung Uhrzeigersinn (Hub-Begrenzung) Mit einem Hubmesser kann
man das auch professionell einstellen...
3.) Wenn Ihr ein Vorverstaerker-Mike benutzt, stellt den Pegel dieses Mikes
so ein, dass Ihr den Mike-Gain auf der Frontplatte auf Mnimum 11 Uhr
Position stehen habt und dann ein normales Signal sendet. Wenn Ihr den
Pegel des Mikrofons zu hoch einstellt wird der erste Mike-versterker im
FT736 uebersteuert, das erzeugt die Gieskannen-Modulation.
Ebenfalls sollte bei Benutzung eines VV-Mike im Mikestecker der Pin 8
(Mittelpin) und der Pin 7 (GND) mit einem 600 Ohm-Widerstand gebrueckt
werden. Der FT736 sieht dann immer die richtige Impedance.
4.) Beste Resul”tate habe ich mit einem Mike erhalten, das den oberen
Sprachbereich bevorzugt (ueber 2000 Hz).

Ach ja, moch was, der PROC-Schalter wirkt nur bei SSB und NUR wenn Ihr
gleichzeitig den DRIVE-Regler zurueckstellt. Wenn das ALC-Meter schon am
rechten Poller klebt, nuetzt der Proc-Schalter nichts mehr !!!

WICHTIG: Denkt an den Garantieverlust bei Aenderungen im Geraet !!!

I found the mod via a phone call to Yaesu and I talk to Chip(K7JA) who put
me in the right direction for the mod..What Chip told me was to tap off
between R-45 + R-96 for the receive end and between R-22 + C-16 for the
transmit end..You well have to change the RX filter to a wider filter
(CFW-455D) which I haven't done as of yet..Since there isn't much 9600 baud
packet on 2mtr in this area I have as of yet been able to check out the modem,
but I have notice an inprovement on the 1200 baud end..Still am testing this
mod out,so I am passing it on as such..Will send the final will tested mod in
a later message..If anyone else has something to add that I may need to do,
please pass it on to me...

I've received the modification information for the aforementioned radio.
Remember, this is for CAP/MARS use only - Amateurs are NOT permitted to
transmit outside of the Amateur bands without specific authorization.

The mods take place on the 144 main unit (No. 6XXX). The diode array is in the
lower left corner of the board, component side towards you, and the notches to
the left. No information was given as to diode type, but I assume any small
signal diode will work.
 

                D24 D25 D26 D27 X=Omit O=Installed
                  ___________________
                      X O O X                144.0 - 148.0 (Standard US)
                  ____________
                     X O O O                141.0 - 154.0 (Extended Rx/Tx)
                  ____________
                     X X O O                 144.0 - 146.0 (Non US)
                  ____________
 

If like me, one of the (many) features that attracted you to the FT736R
was the special DATA SOCKET, then you were probably very pleased to read
in the manual:
"This 3-contact mini stereo jack allows direct connection to the FM
receiver demodulator and FM transmitter modulator for digital equipment
such as a packet radio TNC. No pre-emphasis or de-emphasis is added to
the signals at this jack" (page 14).

Don't believe a word of it! A cursory inspection of the circuit diagram
shows that the TX side is simply merged with the microphone audio just
after the Mic Gain control, and is then murdered by several subsequent
filters. On the RX side the data audio output is similarly indirect.

My initial day with FO-20 was disastrous. (Yours too?)

So I looked at the FM signal on a calibrated monitor receiver when
transmitting FO-20/Microsat "Manchester" uplink signals. The waveform was
appallingly distorted.

The problem is that the TX LF response cuts off at 800 Hz. But the data
has substantial energy at 600 Hz and below. Indeed, when transmitting a
600 Hz square wave it was clear from the droop distortion that FO-20 or a
Microsat would almost certainly not decode the uplink reliably.

The cure is simple; modulate the FM varactor directly. Refer to the
circuit diagram; inject your TXaudio at the junction of R32/C29 on the TX
Unit. The signal level at this point should be 800 mV peak-peak, and will
give 3 kHz deviation. DO NOT EXCEED THIS LEVEL. Set Mic Gain to min.

The implementation is simple too.
1. Disconnect FT736R from the mains electricity. (Safety).
2. Remove top cover only.
3. TX Unit is the module flat on the left (not the one tucked down the
side vertically).
4. R32 is just to the left of the rectangular shielded enclosure. The
resistor is "on end". Scrape the paint off the free leg.
5. Your TXaudio lead should be a fine screened cable; connect the inner
to R32, and the outer braid to the adjacent enclosure.
6. Route the cable out though any convenient aperture in the case.

[ TXAudio of 800 mV pk-pk can be obtained from the G3RUH PSK modem by
adjusting the components C9= 1uf, R3=47k, R5=infinity (i.e. remove). C10
stays at 10nf (0.01uf).]

Modulating the FM transmitter this way you get an LF response down to
18 Hz (at which point the associated synthesizer PLL begins to track the
modulation), and an HF response which is flat to some 10 kHz.

*** FO-20/Microsat uplink modulation is now absolutely perfect. ***

 

 I bought a Yaesu FT736 about 6 months ago. It's a great radio but one
thing annoyed me about it. When I used in on FO-20 or the microsats with my
TAPR PSK modem, the PSK modem adjusts to the doppler frequency shift by sending
pulses to the up/down buttons on the microphone. Only problem is, every time it
sent a pulse the radio went BEEP. This beep didn't come thru the speaker,
instead it was emitted from a separate buzzer. As a result, even when using
the headphones, the beep would disturb the whole house. This was a particular
problem on late night passes. Thanks to a suggestion from WB2IBO and the folks
at Yaesu, I've discovered you can fix the problem.

If you remove the top cover you will find a circuit board right behind the
front panel. As you are facing the front of the radio on the top left corner
you will see capacitor C63 identified on the board with a red wire going into
the circuit board next to it. Clip the red wire and no more beep. You won't
actually see the beeper. To find the beeper you have to remove the top and
bottom covers (see the manual) and then loosen the screws on either side of
the front panel (see section 3.5.4 in the manual). At the bottom left of the
circuit board is the black buzzer, about the size of a quarter. The red wire
you need to clip starts from here. You don't actually have to remove the
bottom cover if you clip it where it goes back into the circuit board on the
top, however.

You could rig up a switch to turn the buzzer off and on, but I don't why
anyone would ever want to turn it back on. 73 de WA0PTV @WA0PTV


Here are some routines to drive a Yaesu FT736R CAT interface.

Note that the radio has TTL levels, so you need to build a circuit to
convert RS232 voltages to TTL voltages. You can do this with a MAX231 etc,
or a couple of NPN transistors. The latter can be mounted inside your
DB25 connector.

1. The Yaesu spec contains one or two typos which are herein connected.
2. It does not appear to be necessary to space out the 5 control
bytes by 50 ms.
3. The READ S-meter, squelch functions smetimes fail to return all 5
bytes, so the code (FNget) accomodates this.


REM
REM FT736R CAT Interface Drivers
REM ----------------------------
REM Last modified 1990 May 21
REM
REM (C)1990 J R Miller G3RUH
REM
REM Procedures and functions available are:
REM
REM PROCcat(on|off)
REM PROCmode(lsb|usb|cw|cwn|fm|fmn)
REM PROCptt(on|off)
REM PROCsplit(off|plus|minus)
REM PROCoffset(MHz)
REM PROCfreq(MHz) (* e.g. MHz = 145.6789 etc *)
REM PROCfull_dup(on|off)
REM PROCsat_mode(tx|rx , lsb|usb|cw|cwn|fm|fmn)
REM PROCsat_freq(tx|rx , MHz)
REM FNsqlch (* returns 0 if no signal *)
REM FNmeter (* returns S-meter value *)
REM
REM
REM Example - prepare FT736R for FUJI-OSCAR-20 satellite
REM
====================================================
PROCset_up: REM Do once only per session!
PROCcat(on)
PROCfull_dup(on)
PROCsat_mode(rx,usb): PROCsat_freq(rx,435.916)
PROCsat_mode(tx,fm ): PROCsat_freq(tx,145.850)
PROCcat(off)
END
:
REM Now follows procedures and functions
:
DEF PROCcat(F%)
IF F%=on B%(5)=0 ELSE B%(5)=&80
PROCput: ENDPROC
:
DEF PROCmode(B%(1))
B%(5)=7: PROCput: ENDPROC
:
DEF PROCptt(F%)
IF F%=on B%(5)=8 ELSE B%(5)=&88
PROCput: ENDPROC
:
DEF PROCsplit(F%)
B%(5)=&89: REM simplex
IF F%=plus B%(5)=&49
IF F%=minus B%(5)=9
PROCput: ENDPROC
:
DEF PROCoffset(F)
B%(5)=&F9
PROCfr(F)
PROCput: ENDPROC
:
DEF PROCfull_dup(F%)
IF F%=on B%(5)=&E ELSE B%(5)=&8E
PROCput: ENDPROC
:
DEF PROCsat_mode(F%,B%(1))
IF F%=tx B%(5)=&27 ELSE B%(5)=&17
PROCput: ENDPROC
:
DEF PROCfreq(F)
B%(5)=1
PROCfr(F)
PROCput: ENDPROC
:
DEF PROCsat_freq(F%,F)
IF F%=tx B%(5)=&2E ELSE B%(5)=&1E
PROCfr(F)
PROCput: ENDPROC
:
DEF PROCfr(F)
IF F>=1000 FX%=on ELSE FX%=off
F=(F+0.000005)/1000
FOR I%=1 TO 4: F=F*100: F%=INT(F): F=F-F%
B%(I%)=(F% DIV 10)*16 + F% MOD 10
NEXT
IF FX%=on B%(1)=B%(1)AND &F + &C0: REM 1200 MHz band
corrrection
ENDPROC
:
DEF FNsqlch
B%(5)=&E7: PROCput: PROCget
IF B%(1)=0 THEN =0 ELSE= -1
:
DEF FNmeter
B%(5)=&F7: PROCput: PROCget
=B%(1)
:
DEF PROCset_up
REM Establish constants etc
DIM B%(5)
off=0: on=-1
rx =0: tx=-1
plus=+1: minus=-1
lsb=0: usb=1: cw=2: cwn=&82: fm=8: fmn=&88
:
REM Most code after this is for controlling the BBC micro
hardware
REM and needs recoding for any other machine. Note "*FXn,m"
is
REM merely a BBC micro operating system call, no. n, parameter
m.
REM
REM Set up RS423 = 4800,8,N,2
*FX8,6
*FX7,6
*FX156,16,227
ENDPROC
:
DEF PROCput
REM Procedure sends five bytes to RS432c port, spaced by 50ms
REM bytes are in array B%(1) ... B%(5)
FOR I%=1 TO 5
REM Delay below is in the spec, but can actually be omitted
T%=TIME: REPEAT UNTIL TIME >= T%+5: REM Wait 50 ms/byte
REM Now direct output to RS423, o/p char, and restore o/p to
screen
*FX3,3
VDU B%(I%)
*FX3,0
NEXT
ENDPROC
:
DEF PROCget
REM Flush RS423 I/P buffer, then read bytes from input stream
REM until op code is detected. Previous value is result.
REM (straight reading 5 bytes found to be unreliable)
*FX15,1
*FX2,1
REPEAT B%(1)=B%: B%=GET: UNTIL B%=B%(5)
*FX2,0
ENDPROC
:
REM End of code
 

The 736R SAT switch has break-before-make contacts, which meanhat in between
switch positions the circuit is the same as if the SAT switch is in the OFF po
sition. If you have set up one of the modules to transmit for non-satellite op
erations (i.e., w
hen SAT switch is OFF), that module will be enabled between the RX-TX-NOR-REV p
ositions of the SAT switch.f you are transmitting while you move the SAT swi
tch between these positions you may accidently key up the unintended module and
send a burst of
RF down the antenna line into your pre-amp.

For example: VFO A happens to be set to operate on 2 meter FM. You don't give
this a second thought, since you are working Mode B CW with the SAT switch ON.
You are listening on 2 meters and keying your 70 CM transmitter trying tor
o your downlink f
requency. Changing the SAT switch positions under these conditions is perfectl
y normal.

However, if you happen to send a dot or dash during the open interval been s
witch positions it is not your 70 CM transmitter that gets keyed but your 2 met
er FM transmitter. This sends a burst of RF down the 2 meter coax that you hav
e configured for
receiving. If you have in that coax a preamp without adequate RF-sensed pin-di
ode switching, then say goodbye to the GaAsFETs in the preamp.

If you are using the FT-736R preamp switch and the 12 VDC on the coax to operat
e coax relays at the preamp, you might be lucky -- if the relays drop out fast
enough. I don't know if the control circuits operate fast enough to take car
e of this transie
nt condition, but I doubt it.

This cost me two MGF-1402 GaAsFETs in my unprotected homebrew 2 meter preamp be
fore I realized that they both departed this world under exactly the same circu
mstances of operation of the SAT switch while sending. Although I was on CW, t
he same thing cou
ld happen on SSB if you happened to be speaking and the VOX were to be operated
during the switch rotation.

Thanks to John, for clueing me to the real problemhe SAT switch while t
ransmitting.
(2) Use adequate RF sensed mp switching.

 

   English

  Frequency range 430 ?????? 450 MHz RX and TX.

1. Remove the top and bottom covers!
2. With the transceiver front facing towards you, locate the vertically mounted PLL board (covered by a metal box) on the right side panel! Carefully remove the PLL board by removing the six screws on the side panel!
3. Near the connectors, you should find a line of diodes. Diodes D8, D10 und D11 must be assembled! The European version should only miss diode D11! Assemble missing diodes!
4. Reassemble the transceiver and switch it on! The transceiver should now cover the frequency range of 430 - 450 MHz.

   German

  Frequenzbereich 430 ?????? 450 MHz RX und TX.

1. Unteren und oberen Geh+??usedeckel entfernen!
2. Wenn der Transceiver mit der Front gegen den OM steht, ist an der rechten Seitenwand ein stehender Print in einem Blechkasten zu erkennen, Dies ist der PLL - Print! Diesen mittels der sechs Schrauben an der Seitenwand l+??sen und vorsichtig ausbauen!
3. In der N+??he der Stecker befindet sich eine Reihe von Dioden, wobei hier die Dioden D8, D10 und D11 best++ckt sein m++ssen! Bei der Europaversion sollte nur die Diode D11 fehlen! Dioden dementsprechend einl+??ten!
4. Transceiver wieder zusammenbauen und einschalten! Jetzt sollte der Bereich 430 ?????? 450 MHz zur Verf++gung stehen

Designed to meet the needs of the most demanding VHF/UHF and satellite operators, the FT-736R covers up to 4 of the 50, 144, 220, 430 MHz and 1.2 GHz bands with .
installable band modules.

   Click Here for Module_installation.pdf

ATTENTION
The KB2LJJ takes no responsibility for any damage during the modification or for any wrong information made on this modification.