FDK MULTI7 User manual

Page 1 of 10
DM??C INSTRIJCTION MANUAL FOR MODEL
MULTI 7 ANATEXJR VHF/FM TRANSC'EIVFR
1- 1 1fMy Channeltf Function :
The model has 24 channels, namely 22 channels plus one fWy Channeltl
and VFO one.. "My Channel" is the function available easy &SY to your
private channel like a club one.
1-2 ttTunet' knob.
It tunes and varies receive frequency and is strong effectively for
noise interference owing to frequency slide.
1-3 Center Meter(M6criminator Meter 1.
The meter is switchable to S meter and Center meter. When it is on
Vreq.It position, namely as the center meter, you can watch an counter
station's freq. slide. So,
it can be used conveniently together with
1TunefI function.
1-4 A. F. B. (Audio Feed Back) Squelch Circuit.
We F. D. K. developed the particular 4FB sq. circuit. Comapared with
the usual noise-amp. squelch, the
AFB one can work stably, which does
not break owing to some change by counter station's modulation, etc.,
since audio signal
is returned. The two-step noise amplifiers are
employed and squelch points
is settled smoothly. Besides, it works
even if
it is against weaker signals.
1-5 Output Power Selection of ?OW(
HI ) and I\( LOW ).
By switching the Output Power Selector, you can select a suitable out-
put power from I0 or 1 Wtt, seeing distance or situation between you
and
a counter station. You do not interupt or interfere against any
other stations on
QSO at a selected output power.
1-6 Helical Resonator and Crystal Filter.
The former is used for RF stage of receiver circuit and the latter is
adopted to 1st IF stage with a ceramic filter. So, Multi 7 has the
. superior characteristics of band and cross-modula tion.
1-7 Speaker Position,
According to mounting space or situation, you can change and replace .
the position of speaker from the bottom to the top of the set so as to
listen clearly.
1-8 Transmitting Indicator,
The red lamp is put on when transmitting. You can watch mis-operation,
etc.
1-9 Accessory Terminal.
The +pin terminal is reserved at rear of the set. It is adaptable to
VFO connection, stand-by function, external microphone, ext. discremi-
nator meter and etc.

Page 2 of 10
1- 10 Professional Circuit Design.
1-70-1 For modulation circuit of the transmitter, the IDC splatter
filter
was employed. It prevents over deviation, namely over-
modulation and clears up interference against other stations.
Also
it can correspond to future tWarrow Band" modification easily.
1-10-2 Planned the drastical decrease of spurious by low-pass filter
adopted to antenna circuit.
7-10-3 used the perfect-shielded module system for driver and final
circuits.
1-10-4 The receiver circuit consists of each 2-step W, 1st IF, lirnitter
and 6-step 2nd IF.
1-10-5 The FET were adopted to the 2-step RF and the 1st Mixer, and
eievate two-signal characteristics.
1-10-6 Used the helical resonator, crystal filter and ceramic filter
effectively and they are workable to get high sensitivity and two-
signal characteristics. You can mofify Multi7 to 1lWarrowll band type
simply.
1-10-7 Adopted the reliable speaker. Size: 92 m/m Output: I-Watt
The speaker is housed in front-inclinated cabinet. This design
contributes to get clear sound and makes
a fine accoustic effect.
2. SPECIFICATION
2-1 General
semiconductors: 27-Transistor, SFET, 1-IC, 1-SCR and 18-~iode
Freq. Coverage: 144.00 - 146.00 MHz
Channel Capacity: 2Fchannel plus one external VFO channel
Power Sou.rce:
DC 13.5 V( operating range: 11.0 - 15 V , negative ground )
Power ~onsumpt'ion: 2.3 A approximately at
flHI" on transmit
1.2 A approx. at "LOW"
400 mA on receive
Dimensions: 134(~) 216(~) 58(~)m/rn( 75 dm max. )
Weight: Approx. 1.6 Kg
2-2 Transmitter
Wssion: F3
Ant. Impebnce: 50 ohms
Modulation: Vector Composite Phase Modulation
Freq. Multiplication: 12 times
Freq. Deviation: 12 KHz max.
Spurious Radiation:
-60 d~ or less
Output Power: 10W
at llHI", 1VI at 'lLON"
Mi crophone : 600-ohm, dynamic, press- to- tall type.
2-3 Receiver
Emission: F3
Receiver System: Double Super-heterodyne

Page 3 of 10
Intermediate Freq.: 1st - 10.7 MHz, 2nd - 455 KHz
sensitivity: S/N 30 dB or up at 1 uV input( at 7.5 KHz deviation
with
1 KHz AF .)
selectivity: 10 KHz ( - 6 dB),
19 KHz( - 50 d~)
Image Ratio: 60 dB or up
supurious Sensitivity: 60 d~ or up
1st Local Osc. Freq.'. P!ultiplication: 3 times
Audio output:
2 W ( at I& distortion, &ohm load
)
Speaker: 92 m/n$ &ohm
2-4 Accessories
1. Dynamic Microphone, press-to- talk type with curled cord and
4-pin plug . . . .. 1 pc.
2. Microphone Hanger ..... 1 pc.
3. Bracket and Fixtures for car dash mounting . . . . . 1 set
4. 2m long DC pwer cord with fuse and fuse holder( red-positive,
black-negative )
5. Fuse ( 3A ) ..... 1 pc.
6. External Speaker Plug .. . . . I pc.
7. Accesso'ry plug . .. . . 1 pc.
3. Features.
3-1 Power ON/OFF and Output Power Selector.
OFF at center, Power at HI or LOW.
3-2 Microphone Connector.
3-3 Meter
It warks as a S meter, center meter and output power one.
S meter arorks full-scale at approx. 20 dB inpu. Center meter shows
2 or 3 KHz at 1-scale range. Output power is indicated approx. 8 at 10
Watts and 50 ohms load. 'he meter is switched to S or Center by the
selector
at the rear of set.
3-4 Channel Indicator.
gdhen power on, A channel is shown illuminated. But it is put off when
you operate Multi
7 at
"My Channel".
35 Channel Selector
3-6 Squelch Control.
Tune clockarise and squelch is closed.
3-7 Vy'channel" switch-
You can do QSY to your own channel preset by onely one-touch to the
switch.. Try push
it and automafrically the channel is changed to the
'my Channel", regardless of the channel selector position. When the
above case
is, the channel indicator illumination is put off. Again,
push the knob and the original channel selector workso It is enough to
install the particular freq. crystals you specify into the
"Mu positions
for hc and Rx crystals in the set.

Page 4 of 10
3-8 Tune Knob.
~t mrks to revise freq. slide. Set the knob at a position that you
can listen most clearly.
If the knob is tuned clockwise, receive
frequency comes to higher. Other hand, the receive frequency comes to
lower when the knob ia tuned counter-clockwise.
3-9 Volume Control.
When you tune the knob clockwise, volume comes up.
3-10 ~ransrnittin~Indicator Lamp.
It puts on when transmitting, namely, you press the "Push-to-talkH
button on the microphone.
3-11 Meter Function Switch.
Set the switch at "S" position, the meter works as a S meter. Other
hand, when you set it at "Freq." position, it works as a Center meter.
3-72 Ekt. Speaker Jack.
When you use an external speaker, connect with Multi 7 by accessory
plug furnished.
3-13 Antenna Co~ector.Use a M type plug. Its impedance is 50-ohm
required.
3-14 Power Cord Connector. Use the accessory one.
3-15 Accessory Terminal. It is a 9-pin plug for the following purposes.
Temj.nal I: VFO receive-inpu Terminal 5: Positive Power Source( 13.5V
2: Stand-by signal(When grounded 6: Transmit Power Source
it comes to transmit)
7: Receive Power Source
3: Microphone
8: Discreminator Output
4: Grounding
9: VFO transmit-input
4. Notices prior to Power-on.
The Multi 7 was.designed so as to keep safety with various protection
circuits. But please read the following notices and confirm them to enjoy
your ham life.
4-1 Do not put on the power ON/OFF switch before connection with antenna and
at short-circuit of ant. terminal. Or, the fibal stage transistor mi&t
be broken.
4-2 Pay attention to the polarity of your car. Please refer to 6-3 on later
page. Other hand, in case you operat Multi 7 as a base station, you should
use the power source
at 13.5 Volts and available to get 2.7 A or up at less
than 10 mV ripple.
- ,
4-3 When being the power ON/OF'F switch put-on, do not connect or remove power
cord.
4-4 hploy 3A type fuse into the fuse holder belonged to DC power cord.

Page 5 of 10
4-5 The Multi 7 was designed to bear up against a long time transmitting,
but try "Stand-by" sometimes on a longer transmitting by way of pre-
caution.
4-5 Do not touch or modify the interior parts except the cores and trimmers.
All of them are adjusted or tuned p@rfectly.
5. Installation.
5-1 Antenna
The antenna output impedance is 50-ohm, so you can use any antenna of
50-ohm impedance. At mobile use, select antenna seeing type of. a car
and set
it so as to bear up against wind pressure. Antenna give greatly
influence to receive-sensi
tivi ty , power output and etc. So, pay attention
to the antenna circuit from the ant. connector of the transceiver.
Use the 50-ohm coadal cable. Please care for strain of the cable when
it is drawn into a car. Keep a reasonable tension and do not be it loosened.
5-2 Installation Place.
Mount the set at place not so as to disturb driver. Do not put the set at
the follwwing spaces.
. 1. Humid 2. Dirdct' rays of the sun, even if it is $iventhrough a
glass window, etc. 3. Direct heated blowing from the air conditioner.
4. High Temperature.
5-3 Setting.
The Multi 7 has the negative ground. If you can has the one, fix the set
directly wirh dash board mounting or so and connect the black colored
leadwire with body of car as a ground.
On the contrary, if it is a positive ground, the set ha8 to be free from
car body electrically
by an insulation washer, etc. In case of this, join
the red colored lead wire with car body
as a ground. Further, connect also
the outer core of antenna. coaxial cable through
a capacitor( 0.001 uF 1.
Fix the transceiver using the brackets and screws furnished. Set the rig
at desired angle. You
can select it at two anges of the bracket screws'
postition, And clinsh the fixtures attached to the transceiver.
According to situation, try to exchange the speaker ~ositionon the! top
or
at the bottom of the tmnsceiver. %hen you put the set on car seat,
it is convenient to fix the speaker on the top of the transceiver.
5-4 Power Cord connection.
Use the accessory cofd and confirm that the positive plug of the .DC power
cord connector of the set
is for the red lead wire of the cord and another
negative one
is for the black one. Do not be the cords slackened, but keep
a reasonable strain.

Page 6 of 10
6. operation Manner.
6-1 Setting.
Connect the poker cord, antenna cord and microphone to the prescribed
connectors. Care fore the polartity .of the power cord. The red one
is
for postitive and the black one is for negative.
6-2 Power-On.
Set the Power ON/OFF and HI-LOW switch at HI or LO\!] position.
The switch
is O?!, and tkie meter and channel indicator are back-lighted.
If they are not lighted, the channel
is placed at "FY" channel.
6-3 Receiving.
Set the channel selector at a channel lffiich is installed crystals and
no signal
is receiving. Tune the volume control clockwise and the squelch
control counter-clockwise, some noises
will be gotten gradually.
Set the volume control at desired point. Turn the squelch control knob
clock-wise, noise
is diminished. Zhe knob should be set at the position
that no noise
is heard.
After above tunings, you can
start QSO on other channels desired.
Inen you operate the transceiver with external speaker, earphone and
headphone, use the ext. speaker jack with the accessory plug. Ehploy
the external speaker of 4 to 8-ohm impedance.
6-4 Transmitting.
On pushing the press-to-talk switch of the microphone, the relay works
and begin transmitting.
On the action, transmitting indicater lamp puts
on. Seeing.the situation, select the output power from 1 ~att(~01~)and
10 ~atts(~1).
The Multi 7 is adjusted to show 118" on the meter scale at IOW, by a 5%
ohm power meter. men the SNT of antenna is fine, the meter pointer
indicates
?98,1 or so. It is the standard of antenna SWR.
Try to check antenna circuit when casually any RF power is not transmitted.
You can watch the case easily since the pointer of meter does not swung.
, .
This is due to working of protection circuit of final stage transistor re-
acted against
SXR soared up when short circuit is happened on the antenna
circuit or
a lead wire was snapped.
- -
When SWR is raised, The Automatic Power Control circuit, designed with
the
SCR, works to cut off the collector valtage of TR3 transistor of the
transmitter unit automatically and protects the breakage of final stage
transistors.
:&r~~fornot so as to operate at a blank channel. At the channel, of
-+, , course,.-po radio wave is transmitted.
.
rri-cas6:tkie- meter pointer swings dull extremly at 70 Watts output, the
antennematching is not enough. men the set is operating as it is no
matching, the final stap transistor miqht be broken or its life is
shortened.

Page 7 of 10
6-5 KY Channel.
You can select your own channel by push the button regardless of
the channel selector position. My channel has the priority.
It is enough to install crystals you desire into the 'TI" positions,
which are reserved in the set.
MY channel is good for a frequent
QSO channel, for example, your club channel, private or sevret one
and main channel.
6-6 Tune Knob.
On receive, you can adjust some slide of a counter station's frequency
by tuning the nob. Especially
it is effective for mobile station use,
because the set receives more poises if
a frequency is deviated, com-
pared with base station use.
6-7 Meter Function Switch.
Generally. it is used as a S meter. When you have it work to watch
frequency slide, set the switch at
lTREQ" position and it works as a
Center meter. Further, it is convenient for installment of additional
crystlas or adjustment of frequency by ?"Pune" knob.
6-8 Crystal Installation.
Zoosen 6 screws on the upper cover of the set and remove it.
There are the crystal sockets arranged four lines. Insert crystals
confirming
T( transmit ) or R( receive ) marked. The mark '(MT* is
reserved for My channel.
Regarding freq. adjustment, first set the meter function switch at
oFREQW position. Second, mke short circuit by some wires No. 6 for
transmit power source and No. 7 for receive power source of the
accessory terminal's pins. Third, tune the trimmer capacitor along
Tx crystals so as to be indicated 0 (zero) by the meter pointer.
During the above adjustment, put the
TUhTE knob on the center position.
The crystals are the HC-25 tfle and the following are their frequency
formulas. Transmit: Crystal Frequency
=+%-#+&Hz .F: - [L
Receive: Crystal Frequency = ( F-10.7 ) x 1/3 MHz
Please use the crystals made specially for the
Multi 7. Crystals vary
their oscillation intensity delicately due to their internal resistance,
C.I. and etc., and they happen drastical decrease of sensitivity, freq.
slide and etc.
7. Main Circuits.
Please refer to the black and circuit diagram drawn on the later pages.
7-1 Receiver Circuit.
The receiver circuit
is the crystal-controlled double super-herodyne.
The 1st IF is 10.7 MHz and the 2nd IF is 455 KHz.

Fage 8 of 10
7-1 The input si@al from antenna is amplified by RF amp., which consists
of 2-step ~T(~SKI~),through antenna relay. It is the helical resonator
that
is a tuning circuit between RF amplifier and the next stage.
'Fhe resonator is a good characteristic band-pass filter which is +step
coupledhigh IfQ1l factor tuning circuit by a slit applied to cavity reson-
mce.
~t is available to get 2 MHz of band vridth by the resonator. The frequency
side is clear and it is planned to level up two-signal characteristics
and 1 st image ratio. Further, you can have enough gain and high sensi-
tivity, because the two-stage RF amplifier
was adopted.
The signal passed the reeonator is forwarded to the 1st mixer which was
used FD(3SK39). .4nd it comes to the 1st IF signal of 10.7 MHz mixed with
the 1st Local Oscillator.
The first local oscilator is the circuit that oscilates 15 MHz band(14.811
- 15.033 MHZ)by a Pierce circuit, which consists of 2~~838,connected bet-
ween the base and the collector. After picked up the 3rd tuned frequency
of 45
MHz band(44.433 - 45.100 YHZ) factor by the L37 tuning circuit, a
signal is mulkiplied by 3 times at T~33(2~~1047)and is forwarded to the
1st mixer as a
1st local osc. signal of 135 MHz band(133.3 - 135.3 MHz)
&ich is 13.7 MHz lower, according to each signal frequency.
The 10.7 MHz 1st IF signal of the 1st mixer output is amplified at the
1st IF amplifier through the crystal filter and the ceramic one. By
combination 9f the two filters, it is very much effective to have good
image ratio, two-signal image characteristics and to avoid interference
by adjacent channels. Besides,
it has €he distinct side line over 15 KHz
of frequency. A signal is amplified by TR24 after passed the filter, so
there is no attenuation by filter and can get sensitivity fully.
At the 2nd mixer(~~25),the signals 11.155 and 10.7 MHz, which were
oscillated by the 2nd local osc.(T~34), are mixed
and come to a signal of
455 KHz 2nd IF signal.
The 2nd local osc. can vary oscillation freq. by variation of applied
voltage
at the vari-cap. diode which is located between the crystal
oscillator and the grounding. This variation can be made by *VI"I'heW knob
on the front panel of the set.
Through be ceramic filter, the 2nd IF signal is amplified and amplitude-
lindtted at the IF amp. ~~26, 27, 28, 29, 30, 31 and the limitter D2, 3,
4 and 5, and is forvmrded to the discriminator. At the 2nd IF stage,
desiped to employ 6-stage transistor amplifier, substituted for integrated
circuit one, to get full amplification and perfect limitter characteristics.
AF signal is multi-tuned by the discriminator which cansists of the two
diodes(0~90) ~6 and 7. And, after amplification by ~~38 4F amp. and passed
VR201 volume adjuster, it is amplified by AF power amp. 1~(~.47092) and is
fomrded to the speaker.

Page 9 of I0
7-2 A.F.R. ( Audio Feed Back
) Squelch Circuit,
The AF'i3 squelch is our otvn developed circuit. The usual noise amp.
type squelch control system often breaks voice when the counter
station's modulation changes.
It is the same as the case that signal
varies by fading, etco This
is caused by variation of noise level
accompanied signal change and squelch level
is shifted. On the
contrary, if variation of squelch-level
is lessened and a rated level
is kept, over-modulation and voice-break by fading are vanished.
It is the
AFB squelch that was realized the above theory.
The noise factor picked from the 2nd 1~(455 KHZ) is amplified by the
TR35 and
36 2-stage noise amp, through VR202 for squelch threshoid
level tuning.
4s signal amplified is forwarded to the base of ~~38
XF amp. after rectification by 38 and 9, and the signal erases mutually
with fhe
AF signal demodulated by the discriminator. Namely, if if is
settled the VRX)Z, at the point that noise is wiped out, by the squelch
knob, no signal is forwarded to ~~38, but, if noise factor is lessened
by input of receive signal, rectification signal level of the noise
amp. is down and a signal is sent to the ~~38. The signal is output
from the speaker.
~urther,by the TR37 amp., the AFT squelch amplified the iCF signals
demodulated
by the discriminator and applies the signal to the base of
~~38 after rectification of it. This signal has the reverse polarity
to the signal from the noise amp. and a signal from the
AFB amp. also
grow larger if
-4F signal does.
The AFT3 squelch erases the enlargement of rectification output from
noise amp. accompanied the increase of noise level and keeps always a
rated and stable squelch level.
7-3 Transmitter Circuit.
The oscillation is made by the non-tuned circuit which was used TRI
transistor connected with the crystal oscillator selected by channel
selector circuit and connected between the base and grounding.
The
oscil-lati on frequency is 12 MHz band(12.000 -
12.166 MHz). This osc.
output is made of vector composite phase modulation with 8 signal from
modulation amp., at TR
2.
The modulation AF amp. consists of the two-stage AF amp., IDC. Miller
circuit and splatter filter.
A signal through microphone is amplified
by the TR
8 and 9 .IF amp. and is forwarded to the D I and 2 IDC circuit.
The circuit clips a given level signal not so
as to excess the maximum
freq. deviation when the modulation level is soard up in a moment.
IDC output is integrated at TR 10 through VR 1 tuning semt-fixed resistor
and
is applied to the base of TR 2 modulator through the splatter filter.
Modulated signal is multiplied three times at TR3, 2 times at TR~ and
2-times at TR
5, and it comes to 144 MHz band. Further, it is forwarded
to TR
7 pre-drive amp. through TR 6 buffer. It is amplified approximately
0.5 W at TR 7 and is sent to the booster unit.

Page 10 of I0
7-3 The booster unit is assembled with the driver stage TR ll(2~C320)
and power amplifier ~~12(2~~1190)~The above 0.5W signal is ampli-
fied to
1.5 '$1 or so at TR11.
At the final transistor TR12,
it is available to gain 10 V!atts or
up by 1.5-Watt input. The
TC7 and 8 are the trimmer capacitors for
.
impedance matching.
When the output power selector is set at
"LOW1? position, the power
source voltage of TR7, 11 and 12 is lowered by the R201 voltage drop
resistor,
and output power is reduced to 1 Watt or less.
The signal power-amplified at the booster unit is forwarded to the
filter unit and passes the two-stage low-pass filter. Further,
it
is sent out to the antenna as 10 !Vatts output from the antenna
connector through the antenna change-over switch. In the filter unit,
D3Ol detecting circuit that selects transmit RF level meter and D302
detecting circuit as a final transistor protective circuit are
assembled.
The protectitive circuit ( APC circuit ) detects reflected wave when
SWR soared up md applied direct current signal detected by the diode
to the gate of the
SCR I. Further, it drops the collector voltage of
TR 3 through SCR 1 so that a signal does not go to the latter half
stage.
TheJttype filter is put between the antenna relay and ant. connector,
and
it supresses spu~Lousas 3 times harmonic wave by diode detection.

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