Yaesu FT-901DM Manual

MAINTENANCE
SERVICE MANUAL
FT-901DM
YAESU
YAESU MUSEN CO.,LTD.
C.P.0. BOX 1500
YAESU ELECTRONICS CORP.
P.O. BOX 498
PARAMOUNT, CALIFORNIA, 90723

(Page)
FOREWORD)
26
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GENERAL
GENERAL
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FOREWORD
The
purpose
of
this
manual
is
to
provide
the
reader
with
the
information
required
to
keep
his
or
her
FT-
901
transceiver
in
top
operating
condition.
While
we
have
made
every
effort
to
provide
an
in-depth
technical
analysis
of
the
workings
of
this
equipment,
we
have
attempted
to
tailor
this
manual
toward
the
technician
or
owner,
rather
than
the
design
engineer.
To
this
end,
we
have
relied
heavily
on
drawings
and
diagrams.
Use of this manual is entirely at the owner’s risk. While we believe that the information presented herein
is correct and factual, we assume no responsibility for damage to your equipment when this manual is used
as reference.
Moreover,
if
your
test
equipment
is
not
equal
to
the
task
of
performing
alignments
the
right
way,
we
would
strongly
urge
you
to
refer
the
unit
to
a
qualified
service
center.
We
truly
hope
that
the
test
information,
parts
location
data,
and
modification
information
presented
herein
will
be
sufficient
to
your
needs.
The
author
wishes
to
express
his
gratitude
to
the
engineering
and
service
staffs
of
Yaesu
Musen
Co.,
Ltd.
and
Yaesu
Electronics
Corporation,
whose
skill
and
insights
have
contributed
significantly
to
the
completion
of
this
manual.
Special
thanks
go
to
Mr.
Y.
Morii
for
his
help
in
assembling
the
technical
materials
presented
herein.
CL
Muay
Chip Margelli, K7JA
Public Relations Manager
Yaesu Musen Company, Ltd.
Tokyo, Japan
Copyright © 1979
Yaesu Musen Co., Ltd.
All rights reserved.
No portion of this manual may be reproduced
without the permission of Yaesu Musen Co., Ltd.
Printed in Japan.

A BRIEF HISTORY OF THE FT-901 SERIES
The FT-901 transceiver first appeared in the USA early in 1978 and immediately established a position
of pre-eminence among “top-of-the-line” transceivers on the market. The FT-901 series has brought a
number of never-before-possible technical features to the amateur community, along with traditional
Yaesu quality design and purity of emissions.
The receiver section, in particular, has impressive credentials. A dual-filter variable IF bandwidth control
allows continuous variation of the IF passband, from 2.4 kHz down to 300 Hz. Also included is a
rejection tuning control, for nulling out of any interfering signal within the remaining IF passband. For CW,
and audio peak filter (APF) provides a significant reduction in background noise, in addition to razor-
sharp selectivity. The receiver dynamic range — typically well in excess of 85 dB in CW bandwidth — is the
best ever achieved in a production-line amateur solid-state receiver.
The transmit side includes RF negative feedback for purity of emissions. A Curtis 8043 IC keyer is built-in
on the FT-901DM/DE models, providing high reliability and immunity to RF interference. Another
innovation is the 10-second TUNE button, which activates the transmitter for 10 seconds for tuning
purposes, then returns the rig to receive, thus saving the final tubes from excessive key-down time.
The most exciting feature of the FT-901 series is the memory system, which provides for storage and
recall of any frequency for control on transmit, receive, or transceive. This one feature largely eliminates
the need for an external VFO in the traditional sense. That the FV-901DM synthesized scanning external
VFO is hardly traditional bears this point out.
With coverage on all modes (SSB, CW, AM, FSK, and FM) on all bands from 160 through 10 meters, the
FT-901 series is destined to maintain its position of dominance among top transceivers on the market. With
some 2800 components assembled in one box, for a finite price tag, the FT-901 offers more performance
per dollar than any other piece or collection of equipment on the market.

GENERAL
ALL MODE HF TRANSCEIVER
FT-901DM
GENERAL DESCRIPTION
The FT-901DM is a precision engineered, high-
performance HF transceiver of advanced design,
providing all band coverage (160 - 10 meters) on
all modes of operation: LSB, USB, CW, FSK, AM,
and FM. This transceiver operates at an input
power of 180 watts SSB/CW and 80 watts on AM,
FM, and FSK.
Advanced features include PLL (Phase Locked
Loop) frequency derivation, digital plus analog
frequency readout with large display LED digits,
a built-in Curtis 8043 IC electronic keyer, and
memory frequency control circuitry. State-of-the-
art receiver performance features include rejection
tuning, dual-filter variable IF bandwidth tuning.
and, for CW, an audio peak filter (APF) for un-
surpassed rejection of unwanted signals. Other
built-in features include VOX, semi-break-in
CW with sidetone, 25 kHz calibrator, advanced
noise blanker, RF speech processor, and a 20 dB
RF attenuator for protection against receiver
overload.
All circuits, except the transmitter driver and
final amplifier stages, are solid state, utilizing
modern plug-in printed circuit boards, thus per-
mitting easy maintenance.
The FT-901DM
tained, requiring only an antenna and power source
for operation. For base station operation, AC
es of 100/110/117/200/220/234 VAC
may be chosen, though the unit normally is sup-
plied with 117 volt capability. A DC-DC converter
unit provides for mobile or portable operation.
Selection of AC or DC power source is automati-
cally made when the proper line cord is inserted.
transceiver is entirely self-con-
power vo
For mobile operation a separate switch is provided
on the front panel to turn off the tube heaters
the receive mode. With the heaters off,
while in
current consumption is only 1.1 amp.
Among the available options on economy models
FT901D/SD/DE are the memory unit, the keyer
unit, the DC-DC converter, the FM unit, and the
cooling fan. Optional equipment on all models are
the 600 Hz CW filter and the 6 kHz AM filter.
The entire FT-901DM transceiver weighs approxi-
mately 18 kg., and is 342 mm wide, 154 mm high,
and 324 mm deep. A diecast front panel and
heavy-duty case provide maximum protection
against damage from shock and vibration during
travel use.

GENERAL
SPECIFICATIONS
GENERAL TRANSMITTER
Frequency coverage: Emission:
160m 1.8 - 2.0 MHz
80m 3.5 - 4.0 MHz
40m 7.0 - 7.5 MHz
20m 14.0 - 14.5 MHz
15m 21.0 - 21.5 MHz
10mA 28.0 - 28.5 MHz
10mB 28.5 - 29.0 MHz
10mC 29.0 - 29.5 MHz
10mD 29.5 - 29.9 MHz
WWV/JJY 15.0- 15.5 MHz, RX only
Power requirements:
AC 100/110/117/200/220/234 V, 50/60 Hz
DC_ 13.5 V, negative ground
(DC option FT-901D/SD/DE)
Power consumption:
(FT-901DM/D/DE)
AC 117V: 70 VA receive
(45 VA HEATER OFF)
320 VA transmit (max)
55 VA receive
(45 VA HEATER OFF)
105 VA transmit (max)
DC 13.5 V:
(FT-901S)
AC 117V: 55 watts receive
(45 watts HEATER OFF)
105 watts transmit (max)
3.8 A receive
(0.8 A HEATER OFF)
7.5 A transmit (max)
DC 13.5 V:
Size:
342 (W) x 154 (H) x 324 (D) mm
Weight:
18 kg
LSB, USB (A3j), CW (Al), AM (A3h), FM
(F3) (option FT-901SD/DE), FSK (F1)
PA input power:
FT-901DM/D/DE
SSB/CW: 180 watts DC
AM/FSK/FM: 80 watts DC
FT-901SD
SSB/CW/FSK/FM: 20 watts DC
AM: 5 watts DC
Carrier suppression:
Better than 40 dB
Unwanted sideband suppression:
Better than 40 dB @ 1000 Hz
Spurious radiation:
Better than 40 dB below rated output
Transmitter frequency response:
300 - 2700 Hz (—6 dB)
Third order distortion products:
Better than 31 dB below rated output
Stability:
Less than 300 Hz drift from a cold start; less
than 100 Hz drift over a 30 minute period
after warm-up
Negative feedback:
6 dB at 14 MHz
Modulation:
A3J: Balanced modulator
A3h: Amplitude modulation of a low power
stage
F3: Variable-reactance frequency modula-
tion, max. deviation #5 kHz (F3 fea-
ture optional on FT-901SD/DE)
Antenna output impedance:
50-75 Ohms, unbalanced
Microphone input impedance:
500 - 600 Ohms

RECEIVER
Sensitivity:
SSB/CW/FSK 0.25 pV for S/N 10 dB
AM 1 pV for S/N 10dB
FM 0.3 wV for 20 dB quieting
Image rejection:
1.8 - 21 MHz - - Better than 60 dB
28 MHz - - Better than SO dB
IF rejection:
Better than 70 dB
Selectivity, WIDTH control at “0”
SSB: -—6dB/2.4kHz —60 dB/4.0 kHz
*CW: —6dB/0.6kHz -—60 dB/1.2 kHz
*AM: —6dB/6.0kHz —60dB/12.0 kHz
**FM: —6 dB/12.0 kHz —60 dB/24.0 kHz
*AM and CW filters are optional, all models
**FM UNIT optional on FT-901SD/DE
GENERAL
Passband tuning:
Continuous from 2.4 kHz to 300 Hz
Two-tone dynamic range:
Typically well in excess of 85 dB (20 kHz
spacing, 14 MHz, 600 Hz bandwidth)
APF response:
Within 3 dB from 400 - 900 Hz
Audio output:
Better than 3 watts @ 10% THD
Audio output impedance:
4-16 Ohms
FT-901D/SD/DE/DM MODEL DIFFERENCES
O = Built-in feature X = Available option
FEATURE FT-901D FT-9018D | FT-901DE | FT-901DM
BAND CRYSTAL 160m ° ° ° °
BAND CRYSTAL 80m ° ° ° °
BAND CRYSTAL 40m ° ° O° °
BAND CRYSTAL 15m ° ° | ° °
BAND CRYSTAL __10mA eS i. 6 oi O
BAND CRYSTAL _10mB ° ° oe | °
BAND CRYSTAL 10m eo _ | ° ° °
BANDCRYSTAL —_10mD re) | ° ° °
BAND CRYSTALWWV/JY RCV. | OO 3 ° °
VOX/MARKER UNIT ° ° ° °
FM UNIT ° | x a. | °
RF SPEECH PROCESSOR [0 ° ° °
AM FILTER x x x X
CW FILTER x x x x
KEYER UNIT x | x lo) °
MEMORY UNIT x x x 3
DC-DC CONVERTER x x x °
COOLING FAN 3 x ° 3
POWER OUTPUT 100 W 10 W 100 W 100 W

GENERAL
TUBES AND SEMICONDUCTORS
TUBE COMPLEMENT FET: MSMSS01 1 Varactor diodes:
2SK19GR 15 MSM5562 1 1$2209 2
12BY7A 1 2SK19BL 8 MSMS564 1 182236 1
6146B 2. 2SK34E 1 SN75450B 1 FC63 1
3SK40M
14
SN76514N
1
MV
104
10
SEMICONDUCTOR
3SKS9Y
1
SN74LSOON
2
7
;
:
COMPLEMENT 3SKS9GR 1 SN74L04N 3 Silicon varistor diodes:
JF1033B 5 SN74LS90N 1 MVI3 !
Germanium transistors: SN74LS123N 1 Zener diodes:
T20A6 z Ic SN74LS192N 5 wz0s0 2
=n F BOD u TA7060P 1 WZ090 4
Silicon transistors: uPC78LOS 2
2SAS64A 2 uPC78L08 gi. — seiOa lee 5 Wzu0 ?
i TA7063P 2
2SA639 1 wPC14305 2 TA7080M | __ Light-emitting diodes:
2SA733 4 uPC14308 2 EAT205AP | GD4-203SRD Hl
peels 205
28C372Y
3
wPC14312
1
TA7310P
1
.
ase
28C373
10
F4024CP
1
TC5032P
i
Light-emitting
display:
2SC535A
1
F40192
2
mice:
HPS082-7740
6
2SC735Y 3 LM308 1 Germanium diodes:
2SC7850 5 MCI416P 1 IN60 17
28C945 3. _MC3403P 1 1S188FM 6
2SC1000GR 5 MC4044P 2 1$1007 (GB) 22
2SC1815GR 2 (HPC1008C) (1N270)
2SC1815Y 49 MC14011B 3
2N4427 I MC14042B 5 Silicon diodes:
MPSA13 1 MM74C90 1 181555 89
MSL980Y7 ! 10D1 7
MSL980Y4 1 10D10 8
MSMS61 3 VO6B 2
Specifications subject to change without notice.

GENERAL
RECOMMENDED ACCESSORIES
FV-901DM
FV-901DM SYNTHESIZED, SCANNING
REMOTE VFO
The FV-901DM external VFO provides a PLL-
synthesized control system for your FT-901DM
station. A three-speed scanner will take you
anywhere in the band instantly, and the auto-
scan feature will sweep the band until it finds a
signal, then it will halt.
PLL synthesis in 100 Hz steps is coupled to a 40-
frequency memory bank, allowing wide versatility
for contest, DX, or net operation. The TX/RX
clarifier allows offset from either dial or memory
frequencies, for precise tuning.
For the CW operator, the use of the FV-901DM,
along with the FT-901DM audio peak filter,
means that one step of the synthesizer will
eliminate a signal from the passband.
1-5
FTV-901R
FTV-901R VHF/UHF TRANSVERTER
In another Yaesu “‘first’, the FTV-901R brings
three bands in the UHF and VHF regions together
in one compact case. The basic FTV-901R comes
equipped for 144—148 MHz, and the 6 meter and
70 cm modules can be added as options.
The satellite 1—3 bands provide operation on
OSCAR Modes A/B/J, on full duplex, when an
external receiver is used. Of course, the FT-225RD
or FT-221R transceivers can also be used for
transmission on the OSCAR 145 MHz uplink.
In this case, your FT V-901R can be used for instant
QSY between 29 MHz, 145 MHz, and 435 MHz.
Repeater split is provided on 50 and 144 MHz.
This means that you can use the FM capability of
your FT-901DM to full advantage on these bands.

GENERAL
SSVs_—_7~“
SS s
YO-901
YO-901 MULTISCOPE
The
YO-901
Multiscope
provides
superb
monitor-
ing
capability,
with
instant
interface
to
your
FT-901DM
station.
Both
wide
and
narrow
band
IF
monitoring
can
be
performed,
as
well
as
trans-
mitter
trapezoidal
and
two-tone
tests.
The
two-
tone
generating
capability
is
built
in.
A
panoramic
adapter,
known
as
the
Bandscope,
is
an
available
option
for
the
YO-901,
allowing
quick
examination
of
the
band
for
activity.
For
a
variety
of
test
and
measurement
purposes,
the
YO-901
meets
your
requirements
with
ease.
SP-901P
SP-901P
SPEAKER/HYBRID
PHONE
PATCH
The
SP-901P
features
a
shaped-response
loud-
speaker,
and
the
hybrid
phone
patch
allows
easy,
efficient
operation
during
patches.
Styling
and
size
match
the
rest
of
the
901
series.
FC-901
FC-901 ANTENNA COUPLER
Present a 50 ohm load for your FT-901DM
transceiver all across the band with the FC-901
antenna coupler. You may select three coax-fed
and | random wire antenna. Included are an SWR
bridge and power output meter. Maximum power
handling capability is 500 watts.

GENERAL
CONTROLS AND SWITCHES
This transceiver has been specifically designed for
ease of operation and versatility. The operator
may. however. be unfamiliar with the operation
of the controls, and improper adjustment thereof
may result in poor transceiver performance. Thus,
be certain that you understand the function of
operating the
panel controls and switches
before
front
every control transceiver,
The various
ate
described in the following section.
(1) MODE
The MODE switch has six positions for selection
of the operating mode desired: LSB. USB. CW.
FSK, AM, or FM
(2) REJECT-WIDTH
The REJECT and WIDTH controls are mounted
on concentric shafts. The rejection tuning control
(REJECT). when activated by pressing the small
the left the REJECT
knob. provides a variable IF notch filter action
for nulling out a particular interfering signal
silver pushbutton to of
The WIDTH control varies the signal across the
passband of one of the two IF 8-pole crystal band-
pass filters used in this circuit, thus providing a
variable IF bandwidth for rejection of signals above
or below the desired signal.
(3) M
The M button is pressed to store a frequency in
the memory circuitry. Whatever
being read out on the
frequency is
ital display will be the
frequency stored when the M button is pushed.
(4) EXT
When pushed, the
T button transfers frequency
control from the FT-901DM to an external VFO,
FV-901
such the
VFO.
as fully synthesized scanning
(5) VFO
When the VFO button is pushed, frequency con-
trol is transfered from EXT or memory control to
the FT-901DM internal VFO.
(6) TX-MR-RX
Once a frequency has been stored by the memory
(M) button, that frequency may be recalled for
control of either the transmit or receive frequency
by pushing either the TX or RX MR button
respectively.
(7) MR
Once a frequency has been stored by the memory
(M) button, that frequency may be recalled for
control of the transceive frequency by pushing
the MR button.

GENERAL
(8) PRESELECT
This control pretunes the signal circuits for both
transmit and receive. The PRESELECT circuit
provides continuous permeability tuning through-
out the frequency range of the transceiver.
(9) BAND
The BAND switch provides selection of the band
desired, 160 through 10 meters plus WWV/JJY
(receive only).
(10) RF GAIN/CLARIFIER
The RF GAIN and CLARIFIER controls are
mounted on concentric shafts. The RF GAIN
control provides manual control of the gain levels
of the RF and IF amplifiers on receive.
The CLARIFIER control allows manual offset of
+2.5 kHz of either the transmit or receive fre-
quency. Selection of transmit or receive clarifier
is made hy the two silver pushbuttons to the
left of the CLARIFIER control.
(11) ATT
The ATT (RF attenuator) button provides inser-
tion of a 20 dB attenuator in the incoming signal
path to minimize receiver cross modulation caused
by extremely strong local signals.
(12) PROC LEVEL/AF GAIN
The PROC LEVEL and AF GAIN controls are
mounted on concentric shafts. The PROC LEVEL
control allows manual control of the output level
of the RF speech processor. The processor is
actuated by pressing the silver pushbutton to the
left of the PROC LEVEL control.
The AF GAIN control adjusts the audio output
level at the speaker and phone jack. Clockwise
rotation increases the audio output.
(13) TUNE
This pushbutton, when depressed, places the trans-
mitter in the “tune” condition for ten seconds
for tuning purposes. After ten seconds, the trans-
ceiver is returned to the receive mode so as to
prevent damage to the final amplifier tubes caused
by excessive “key down” time during tune-up.
(14) LOADING.
This control tunes the output circuit of the pi net-
work to match the antenna/feedline impedance.
(15) PLATE
This control tunes the plate circuit of the final
amplifier.
(16) CALIB
When the MARK switch is activated, the CALIB
knob provides manual control for zeroing the
calibration of the digital display with the cali-
brator signal.
(17) CARR/KEYER
The CARR and KEYER controls are mounted
on concentric shafts. The CARR control varies
the amount of carrier in the CW, AM, FSK, and
FM models of operation.
The KEYER control varies the speed of the
built-in Curtis 8043 IC electronic keyer.
(18) VOX GAIN
This control selects MOX/PTT/VOX transmitter
relay control as well as adjusting the sensitivity of
the VOX circuitry. The PTT position provides
push-to-talk operation from a microphone PTT
switch or a footswitch. The MOX position provides
manual transmit. It must be returned to the PTT
position for receiver recovery.
(19) APF FREQ
This knob, when actuated by turning on the APF
switch, provides manual control for peaking the
audio peak frequency (APF) circuit on the desired
signal. This control will find its chief usefulness
on CW, because its bandwidth is much too narrow
for normal SSB reception.
(20) SQL/MIC GAIN
The SQL and MIC GAIN controls are mounted on
concentric shafts. The SQL control sets the squelch
threshold level for FM reception.
The MIC GAIN control varies the audio level from
the microphone amplifier stage. The control has
sufficient range to permit the use of any low im-
pedance (500 - 600 Ohm) crystal or dynamic
microphone. Clockwise rotation increases the level
of output from the microphone amplifier stage.
(21) FUNCTION SWITCHES: AMGC, APF/MONI,
AGC, PO/IC/ALC, and NB/MARK
The AMGC switch activates a microphone gain
threshold circuit which requires a_ particular

minimum input level from the microphone to
trigger the microphone amplifier. Low-level back-
ground noise will not activate the transmitter
with the AMGC in operation. This circuit may be
considered a “microphone squelch” system. The
M GAIN control functions normally with the
AMGC system in operation.
When the APF/MONI switch is in the APF posi-
tion, the audio peak filter (APF) circuitry
is activated. The exact frequency of the audio
peak is set by the APF FREQ knob. When this
switch is placed in the MONI position, monitor-
ing of the microphone level may be accomplished
for operator convenience or tape recording both
sides of a QSO. In the CW mode, CW sidetone
will be heard regardless of the position of the
APF/MONI switch.
The AGC switch controls the length of the re-
covery time for the receiver AGC circuitry. This
switch provides slow or fast recovery, and will
also turn off the AGC if desired.
The
PO/IC/ALC
switch
will
hereafter
be
referred
to
as
the
METER
switch.
In
the
PO
position,
relative
transmitter
output
power
can
be
observed.
In
the
IC
position,
transmitter
final
amplifier
cathode
current
may
be
measured.
In
the
ALC
position,
transmitter
ALC
voltage
may
be
read.
When
the
FT-901DM
is
in
the
receive
mode,
the
meter
functions
as
an
“‘S”
meter.
The NB/MARK switch provides for actuation of
either the Noise Blanker (NB) or crystal calibrator
(MARK). The marker oscillator can produce cali-
bration signals at intervals of either 25 kHz or
100 kHz by proper positioning of a switch inside
the cabinet.
(22) POWER
This is the main on/off switch for the transceiver.
In the OFF position, the memory circuits are
disabled, so that when the transceiver is turned to
ON again, the memory circuits will have to be
reset.
(23) HEATER
With
the
HEATER
switch
in
the
down
position,
the
transmitter
tube
heaters
are
turned
off.
This
reduces
battery
drain
to
1.1
amp
and
thus
permits
long
periods
of
listening
without
excessive
battery
drain.
Placing
this
switch
in
the
up
position
pro-
vides
supply
voltage
to
the
tube
heaters,
and
after
30
seconds
of
warmup
the
transmitter
is
GENERAL
ready for operation. This switch operates in both
the AC and DC modes.
(24) PHONES
This is a standard 1/4” phone jack for accom-
modation of headphones. The internal speaker is
disabled when headphones are plugged into this
jack.
(25) MIC
This four-conductor jack accommodates the
microphone plug for microphone input as well as
for PTT actuation.
Headphone plug

GENERAL
REAR APRON CONNECTIONS
(1) GND
Threaded lug for ground connection.
(2) RF OUT
Signal frequency output from the driver stage
may be obtained at this jack for use with optional
equipment, such as the FTV-90IR VHF/UHF
transverter.
(3) ANT
Coaxial connection for antenna.
(4) PO ADS
Sets PO meter sensitivity
(5) RCV ANT
A second receiver receives its antenna connection
through this jack.
(6) ACC
Accessory socket. Provides access to transceiver
Operating voltages and relay contacts.
(7) KEY
Three-conductor jack for connection to keyer
paddle or external key.
(8) EXT VFO
Connections for external VFO.
1-10
(9) FUSE
Fuse holder requires 5 amp fuse for 117 volt or
3 amp fuse for 220 volt operation. For 12 volt
DC operation, a 20 amp fuse is installed in the
power cable. When replacing fuses, be certain to
install a fuse of the proper rating. The warranty
does not cover damage caused by improper fuse
replacement.
(10) POWER
Power receptacle. Both AC and DC cables are
supplied
(11) TONE
Sidetone output for second receiver (if used).
(12) IF OUT 2
Wide-bandwidth 8.9 MHz IF
to a spectrum analyzer, etc.
al for connection
(13) PATCH
Speech input terminal for phone patch connection.
Impedance is 500 ohms.
(14) A-TRIP
Anti-trip input from second receiver (if used).
(15) SP
Audio output is provided at this jack for an ex-
ternal speaker. Output impedance is 4 ohms, and

the internal speaker will be disabled when plug
is inserted.
(16) PTT
This jack may be used for external actuation of
the transmitter. As an example, a footswitch may
be connected to this jack to provide remote con-
trol of the transmitter relay, leaving the operator's
hands free for writing and tuning purposes.
(17) FSK
Input from the FSK terminal may be made
through this jack. The FT-901DM is set up for
170 Hz shift.
(18) IF OUT 1
Narrow bandwidth 8.9 MHz IF output is avail-
able for use with an IF monitorscope. etc.
(19) REMOTE
Provides switched 13.5 VDC for relay control
for external low-pass filter units, etc. As the band-
switch is rotated, 13.5 VDC will appear at various
Pins on the REMOTE jack. Use a VOM to deter-
mine the proper pin for the band in use.
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GENERAL
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GENERAL
INSTALLATION
This transceiver is designed to be a single-unit
station for fixed, portable, or mobile operation.
Consequently, power supply connections provid-
ing for operation from a variety of source voltages
are available. This system provides the flexiblity
required for changing locations or quick moves
from fixed to mobile operation.
BASE STATION INSTALLATION
The FT-901DM is designed for use in many areas
of the world using supply voltages that may differ
from the operator's local supply voltage. For this
reason, be sure that the voltage marked on the
rear of the transceiver agrees with the local AC
supply voltage. THIS INSPECTION MUST BE
MADE BEFORE CONNECTING THE AC POW-
ER CORD TO THE POWER OUTLET.
CAUTION
PERMANENT DAMAGE WILL RESULT IF IM-
PROPER AC SUPPLY VOLTAGE IS APPLIED
TO THE TRANSCEIVER.
The transceiver should be connected to a good
earth ground. The ground lead should be made
with a heavy braid wire and should be connected
to the GND terminal on the rear apron of the
transceiver.
We do not recommend the use of power con-
nectors other than the ones supplied by Yaesu. If
a rig brought in for servicing is blowing fuses every
time you plug it in, check to make sure that no
“improvements” have been made to the power
cord through substitution of or modification to
the power connector.
For base station installation, the only important
consideration that need be made is to ensure
adequate circulation around the unit. Do not place
books or papers on or around the cabinet, nor
should the unit be placed on top of another
heat-generating device such as a linear amplifier.
Avoid heat ducts and window locations which are
exposed to the hot sun, and you will keep your
transceiver running at full speed for a long, long
time.
Be certain to ground the transceiver through a
heavy, braided cable less than 10 feet long. Cold
water pipes in newer houses probably are unsatis-
factory as grounding posts; it is much better
practice to use a system of one or more ground
rods, with the ground line securely bonded to the
ground system.

MOBILE INSTALLATION
(Note: The DC-DC converter described herein is
built-in on the FT-901DM, and is an available
option on the FT-901D/SD/DE models)
The FT-901DM will operate satisfactorily from
any 13.5 Volt DC negative-ground battery source
by connecting the DC power cord to the rear
panel receptacle. For under-dash mounting, a
special mobile mounting bracket is available from
your dealer. In mobile installations the trans-
ceiver should be suited away from heater ducts.
No special precautions need be observed if ade-
quate ventilation space is available. A minimum
of two inches of air space above the cabinet top
and on all sides is recommended to allow proper
air flow around the cabinet. Never stack other
units above or below the transceiver since the
accumulated heat from both units could cause
damage.
The transceiver requires an average of 14 amps
on transmit, with 20 amps on voice peaks. The
DC power cable comes equipped with a 20 amp
fuse. When making connections to the car battery,
be absolutely certain that the RED lead is con-
nected to the positive (+) terminal and the BLACK
lead is connected to the negative (—) terminal.
Reversed connections could permanently damage
the transceiver.
The BLACK lead should, preferably. run directly
to the negative terminal of the battery. Using the
car
frame
as
a
negative
connection
or
connecting
the
RED
lead
to
a
positive
point
such
as
the
ig-
nition
switch
places
the
transceiver
in
the
same
current path as noise-creating devices, thus failing
to
take
advantage
of
the
filtering
action
of
the
battery. The power cable should be kept away
from
ignition
wires
and
should
be
as
short
as
Possible to minimize voltage drop and to provide
a
low
impedance
path
from
the
transceiver
to
the battery.
Before
connecting
the
power
cable
to
the
trans-
ceiver,
check
the
battery voltage
with
the
engine
running
(battery
charging).
If
the
voltage
exceeds
1S
Volts
DC,
the
regulator
should
be
readjusted
so
that
the
highest
charging
rate
does
not
ex-
ceed
15
Volts.
The
transceiver
should
always
be
switched
OFF
while
the
car
engine
is
being
started
to
prevent
voltage
transients
from
damaging
power
supply
components.
GENERAI
ANTENNA CONSIDERATIONS
The
FT-901
transceivers
are
designed
for
operation
using
an
antenna
system
presenting
a
50-75
ohm
resistive
load
at
the
antenna
jack.
Amateur
instal-
lations
seldom
meet
this
requirement
over
the
entire
spread
of
every
band,
but
the
final
amplifier
pi
network
is
sufficiently
forgiving
to
allow
for
minor
deviations
from
the
target
figure.
However,
significant
departures
from
the
50-75
ohm
range
will
result
in
seriously
degraded
transceiver
per-
formance.
If an open-wire feedline is used, or if the input
impedance of the antenna system presents a very
high or very low impedance at the coaxial input,
some sort of antenna tuner must be used to pro-
vide a SO - 75 Ohm unbalanced feedpoint for the
transceiver.
For mobile operation, most of the commercially-
available antennas on the market will provide
good results if care is taken to tune the antenna
for minimum SWR. The outer conductor of the
coaxial cable should be securely grounded to the
automobile chassis at the antenna mount.