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Manual #3222-06
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GEMINI II VHF/FM
Radiotelephone
KR-—25VN
OPERATION & SERVICE MANUAL
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TABLE OF CONTENTS
PART 1. GENERAL INFORMATION
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PART 11. OPERATING INFORMATION
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OTHER OPERATION CONTROLS - RADIOTELEPHONE UNIT ........... 4
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PART 111. INSTALLATION
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ae Pe LOY'S LEN Like ent hae byi.ieG se Ribs Woke dsm bia crate ale b 7
6. Transmitter Crystal Frequency Adjustment .........e.6. 8
PART IV. TECHNICAL INFORMATION
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eee 2 OWN, Leavole DG-POwer SUDDIY aus cece sk caed sewn oes ve 16
es heey oy VOlte UG Regulated Power Supply. .suexss ee ces e's 16
Seo b225/ Moonegudated AC Power SUDDVY oa ces coece vee acer he
QOnmmoroyY
PART V. TUNE-UP ALIGNMENT
GENERALS NEORIAIIOUN OE oe cc en ases ce sme neeaenssneveveeccese 20
1. Preliminary Test and Checks ...cccccsccansccsesssevsss 20
2. Test Equipment Required... .ccccceccsncscenececcercees 20
ALTGNMENT PROCEDURES @ 5 oie «0°} 656 » wimeseere. s ovsse a" areca ale oun 21
1. Receiver Alignment Touch-Up .....cccecvccscnnceccseces 21
2. Complete R.F. AlIGnMent 2... ccescccccscccececcscvvwecs 23
3. Receiver Sensitivity Measurement ........ceeececeeeces 26
TRANSMITTER: ALIGNMENT uve-ynctecc os pa hy * 40:5) Gmak ess. eee 26
b.. . Crystal. OSCTVVatOr «sac. oo Se cay eosin ote sie mieiacarmreiee ere 26
2. Multiplier Stages... 2.2... .ss5 cee s oc euiemus ce ot
3.5 Final) Power Amp] 1 $IGK oie ost 0c oo siea ene a sim ues elena eine es ab
4. Modulation Deviation Adjustment ......ccccceccccsseces 28
PART V1. MAINTENANCE
SERVICING se acs trcpsan Shereehee & hao carcue (o siel tateeetnnen aur Ney rom nonsncRetenereae 30
To PPeventi yew MarnEenance: <.. sso occ cis clenevere stetopeletenctereretenersnere 30
2.0 TroublesShoot ing: Guide. os ce< ope cg e see ee se see ernie 3]
PART VETS” PARTS LIST
CHASSIS. & FRONT PANEL ..c:ecweceecancscccesecceenesceson 34
RECEIVER P.C. BOARD, ASSEMBLY #4241- odie s4"h eteco eens eats, ahete 34
TRANSMITTER P.C. BOARD, ASSEMBLY #4242- ...cceessceeeees 34
CHANNEL CRYSTAL SWITCH, ASSEMBLY #4243- ...eeeeeeeceeees 35
POWER SUPPLY, 13.6 VOLT REAR PANEL’ ......ccccevescccecoces Be)
K-25/34 REGULATED POWER SUPPLY ....cceceeucevvccccevsccecs 35
K=25/115 REGULATED POWER SUPPLY... ..cececececcesccvceceves 35
LIST OF ILLUSTRATIONS
Channel Allocation Chart
KTG-33 V.H.F. Noise Generator Schematic
KTM-33 Radiotelephone Test Meter Schematic
KRV-6 Ringer Amplifier Schematic
RS-14M Remote Control Unit Schematic
K-25/32 Regulated 20 - 50 volt DC Power Supply Schematic
K-25/115 Regulated 100 - 150 volt AC Power Supply Schematic
KR-25VN/12 Chassis Wiring Schematic
KR-25VN/34 or 115 Chassis Wiring Schematic
KR-25VN Receiver Block Diagram
Receiver Voltage and Resistance Chart
Receiver P.C. Board Component Layout
Audio Power Amplifier - 3 Watt
Receiver P.C. Board Schematic
KR-25VN Transmitter Block Diagram
Transmitter Voltage and Resistance Chart
Transmitter P.C. Board Component Layout
Transmitter P.C. Board Schematic
Marine VHF Communication Range Nomograph
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PART 1. GENERAL INFORMATION
DESCRIPTION OF EQUIPMENT
B. EQUIPMENT
Equipment Furnished
Ris
nel model KR-25VN is a 12 channel plus weather marine VHF/FM a. sees (13.6 “et epee re vet
diotelephone capable of operation on any of the marine channels ne ye si ial e wi oa, ee ae ot a
Ssignated by the International Telecommunications Union in the antenna connector, or external regulate
6-157 and 161-162 MHz frequency ranges power supply, either 115 volts AC or 24/34 volt DC -
: : specify voltage when ordering) radiotelephone com-
2 equipment is suitable for installation aboard commercial or pie with interconnecting cable and antenna connec-
easure boats, and with ordinary care will provide years ou es or.
able service. The transmitter has been designed to exceed the E
quirements of intermittent marine service, which is defined as b. Microphone and hanger. .
50% duty cycle of two (2) minutes transmitting followed by a rs
riod.of two (2) minutes receiving. Operating the transmitter s
thin these limits will provide normal tube life.
Instruction book, warranty card and FCC license forms.
chanical construction: Chassis and cabinet are of heavy gauge | 2. Accessories Available
eated aluminum, with stainless steel hardware throughout. antrTest\Meter KTM: Shp luqstn skeet fever eres re iteae
ked Epoxy painted exterior: All exterior surfaces fully protected alignment and maintenance of receiver and transmitter.
th two coats of durable enamel. b. Remote Control Unit RS-14M: Remote unit permits full
: : : : : 2 F control (except channel changing) of the radiotelephone
aration engineered: Multiple tie points, safety staked rivets j | ,
d double grounds guard against vibration failure. from a second location (flying bridge, 'etc.). A
circuit diagram of the unit is shown at rear of manual.
Selective Ringer Amplifier KRV-6: This small inte-
grated circuit (1C) amplifier may be installed within
the radiotelephone unit to operate any type of Ringer
Receiving equipment. See your Konel dealer regarding
available Ringer Receiving equipment.
vironment protection: All wiring is varnished against marine _
rosion. Transformers are double vacuum impregnated, speakers :
ve mylar coated waterproof cones.
iversal mounting: The unit may be conveniently installed in any
sition; table top, bulkhead or overhead, and is easily removed
r service or storage by loosening four thumb screws.
nponentry: Highest quality electrical components are used : 3. Crystal Ordering Information
io i i i i of pe e e . e
ae The chassis design permits easy maintenance A chart is provided at the rear of the manual, which shows
| : the marine VHF channel allocation numbers as well as
cer_receptacle: A meter receptacle is provided which enables | channel and crystal transmit and receive frequencies.
rt i j i i i d with a KTM-33 |
Fae egal eee Gl ycuuts- Code monitored wit ] Crystals may be ordered by channel number from your Konel
; 3 dealer or from the following approved suppliers who have
note Control receptacle: A remote control receptacle is pro- | oleae correlation ae on file. When ordering
Seige ele aise lenhone to be operated (except crystals to sure to include:
innel changing) from two locations. amaalUGachaaneh nibhck
b. Transmit crystal part number
1. Land station, .0005%, part #2197
2. Ship stations, .001%, part #2194
c. Receive crystal part number 2199
d. Crystal frequencies
e. Statement that crystals are for Konel VHF model
KR-25VN. Be specific. Some channels are USA use
only. Note suffix letter in frequency list.
Approved Crystal Suppliers:
night, Inc. Sentry Mfg. Co. Sherold Crystals
Ache chil. Crystal Park 1510 McGee St.
60548 Chickasha, Okla. Kansas City, Missouri
73018 64108
Crystal frequencies are computed by the following formulas:
Receive crystal frequency (Mc) =
Channel Freq. (Mc) + 16.9 (Mc
3
Transmit crystal frequency (Mc) =
Channel Freq. (Mc)
12
TYPE ACCEPTANCE INFORMATION
KR-25VN radiotelephone has been type accepted for use under
following Federal Communications Commission ‘USA) Parts and
rtment of Transport (Canada) radio standards specifications ;
Par -Pere-ol s Stations on land when equipped with .0005%
transmit crystals (Konel Part #2197).
eo Fereoss Stations on shipboard when equipped with
.001% transmit crystals (Konel Part #2194).
Bo erabtelo. Receiver radiation.
4, R.S.S. 182, Stations on land when equipped with .0005%
transmit crystals (Konel Part #2197).
Stations on shipboard when equipped with
.001% transmit crystals (Konel Part #2194).
5. R.S.S. 126, Land and Mobile stations when equipped with
.001% transmit crystals (Konel Part #2194).
PART 11. OPERATING INFORMATION
A. FRONT PANEL CONTROLS
1. Volume Control: The volume control also turns the power ON when
rotated clockwise from a full counter-clockwise position. Clockwise
rotation will increase the receiver volume.
2. Channel Selector Switch: The channel selector switch selects
the appropriate transmit and receive crystals. The channel
positions are designated by letters A through L on the panel.
Operating channels should be identified on the front panel with
the channel number labels provided. The location of crystal
positions is shown along the edge of the. crystal sockets inside
the cabinet.
3. Squelch Control: The squelch control permits quieting of the
receiver background noise when no station is being received. lhen
the control is turned to its full counter-clockwise position the
squelch is "OFF" and background noise will be heard. Adjust the
volume control clockwise with the squelch off for proper listening
level, then adjust squelch control clockwise for the amount of
muting action desired (see squelch control operation).
4, Transmitter Power Switch: The transmitter power switch selects
the power output to the antenna. This switch also turns the trans-
mitter filaments "OFF" to conserve power when the radiotelephone
is used for receiving only.
5. Weather Station Switch: When depressed, the weather station
push button switch disconnects the receive channel selector switch
assembly and the microphone press-to-talk switch and connects a
weather station crystal to the receiver. When pressed again, the
receiver is returned to normal operating condition.
C. OTHER OPERATING CONTROLS - RADIOTELEPHONE UNIT
1. Front Panel Lamp: The front panel lamp is provided for i]]um-
ination at night (pull squelch control knob out from panel to turn
lamp on).
2. Press-to-Talk switch: When the press-to-talk switch on the
microphone is depressed, the receiver is disabled and the trans-
mitter turned on. When released, the receiver will operate.
3. Antenna Connector: The antenna coaxial connector is located
on the rear panel. This connector attaches to the UHF (S0-239)
type connector on the transmission line from the 50 ohm antenna.
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Remote Control: The "REMOTE" receptacle is located on the
ir panel. When the RS-14M remote unit cable is plugged into
s receptacle, the radiotelephone may be operated (except for
innel selection) from two locations.
: RS-14M volume and squelch controls operate in parallel with
: controls on the KR-25VN. For full volume and squelch control
either location, the volume control at the non-operating lo-
-ion should be in the "off" position (counter-clockwise) and
» squelch control in the "on" position (clockwise).
an emergency, the radiotelephone may be operated from either
both locations by turning either volume control "on" and oper-
ng in a normal manner.
Metering circuits: The KTM-33 test meter socket is located
the rear panel of the radiotelephone. The following circuits
f be monitored with this meter;
Receiver channel oscillator and multiplier
Receiver alignment
Receiver discriminator balance
Transmitter crystal oscillator grid current
Transmitter multiplier grid current
| Transmitter driver grid current
| Transmitter final grid current
Transmitter power output
Transmitter power input to final amplifier tube
OPERATING TECHNIQUES
» marine VHF frequencies on which the KR-25VN operates are shared
‘quencies. For this reason, the following operating procedures
iuld be followed:
a. Be sure the channel is clear before transmitting.
b. Keep all communications short; others may want to use
the channel.
c. Hold the microphone approximately one inch from your mouth,
depress the push-to-talk button and speak clearly. Don't
shout!
d. Identify your vessel: give your call sign and vessel's
name at beginning and end of each transmission.
e. Use channels for purpose designated.
f. Keep an accurate log of all emergency and safety commun-
ications.
g. Watch your language. Use of profane or obscene language
on the air is against the law!
PART 111. INSTALLATION
A. KR-25VN RADIOTELEPHONE
1. Factory Adjustments: The equipment has been aligned at the
factory to operate on any of the licensable VHF marine channels.
The radiotelephone is supplied with a limited number of transmit
and receive crystals installed. If additional channels are de-
sired, two crystals will be required for each channel. Install
in the proper crystal sockets and align each transmit crystal to
exact frequency. No resonant circuit alignment of the transmitter
or receiver will be necessary for operation on any of the VHF marine
channels since associated circuits are broad band tuned.
NOTE: All transmitter adjustments must be performed by an FCC
licensed technician.
2. Inspection of Equipment: The exterior and interior of the
radi Se TaunOWe sould be examined for any damage which may have
occured in transit due to improper handling. Report damage promptly
to the transportation company prior to disposing of the packing
materials.
3. Location of Equipment: The radiotelephone may be conveniently
mounted horizontally or vertically. It should be located in a
position convenient to the operator and the technician to make
routine inspections, and provide adequate ventilation. The mic-
rophone and hanger may be mounted in any location convenient to
the operator.
The cabinet may be removed, exposing all tuning and frequency
adjustments. Individual crystal frequency trimmers are provided
for each transmitting channel; trimmers are located along side the
transmitter crystal socket assembly. No receive crystal frequency
alignment is required due to the Automatic Frequency Control circuit.
4. Input Power
a. KR-25VN/12: The power leads between the ship's battery
source and the radiotelephone should be as short as
possible to minimize voltage drop.’ The following wire
sizes are recommended: #10 for cable runs up to ten
feet; #8 for cable runs from ten to twenty-five feet.
The input power plug and socket allows quick connect
and disconnect of the power circuit. The equipment
will not be damaged if the polarity is reversed, but
should this accidentally occur, the fuse located on
the rear panel of the equipment must be replaced.
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The KR-25VN is designed to operate on negative
grounded power systems. For optimum performance
and reliability the voltage at the power receptacle
on the rear panel should be between 13.0 and 14.0
volts under transmit conditions.
b. KR-25VN/115: The 115 volt power source wiring circuit
should be adequate to handle the transmitter power
requirements. The voltage regulator circuit within
this power supply will provide proper operation between
100 and 150 volts AC input.
c. KR-25VN/34: The power leads between the ships battery
source and the power supply should be adequate to
handle the transmitter power requirements of about
6 amps. The following wire sizes are recommended:
#12 wire for cable runs up to ten feet; #10 wire for
cable runs from ten to twenty-five feet.
Antenna System: The radio frequency transmitter power output
fed directly to the antenna through a 50-ohm coaxial transmission
e. Type RG-8/U transmission line (3 db loss per 100 feet) is
ommended. For transmission line lengths of twenty-five feet or
s, RG-58/U (6 db loss per 100 feet) transmission line may be
stituted.
ce VHF radio waves ordinarily do not reflect from the ionosphere
re iS no long-distance "SKIP". For all practical purposes the
munications range for VHF radio is considered to be "line-of-
nt" or about 20 miles for ship-to-ship and up to 50 miles or
e for ship-to-shore communications depending on antenna height
terrain. The most important single factor being the height
the sending and receivina antennas -- the higher the antennas,
greater the range.
a. Marine Antennas: For shipboard installation a low gain
50 ohm coaxial antenna should be used. This type of
antenna provides a steady signal when the ship is rolling
or pitching due to the broader beam lobes. Automobile
type antennas should NOT be used.
b. Base Station Antenna: The base station antenna should be
as high as possible, FCC Rules and Regulations permitting.
Local ordinances dealing with antenna height should be
checked before antenna installation.
Base station antennas should be of a high gain type,
exhibiting a low angle of radiation. This type of
antenna can provide gains of up to 12 dh which is equal
to increasing the effective radiotelephone power output
several times. High gain antennas also increase the
strength of the received signal by an equal ratio as
7
previously mentioned. At VHF frequencies height is a
most significant factor in determining communications
range. (See Range nomograph at rear of manual)
6. Transmitter Crystal Frequency Adjustment: The frequency of the
transmitter come. may be accurately adjusted with the series
trimmer condensers located on the crystal mounting assembly. Each
crystal socket and trim condenser is identified in accordance with
the channel selector switch position. The frequency of each crystal
and the channel frequency is listed in the Channel Allocation Chart.
When adjusting the transmitter frequency, disconnect the microphone
(red wire) to prevent frequency modulating the oscillator and ro-
tate the transmitter power switch to the 25 watt position. Connect
a 50-ohm RF load (or wattmeter) to the antenna connector on the
rear panel.
The Federal Communications Commission (FCC) and the Canadian
Department of Transport (DOT) both require that all marine land
station transmitters be within .0005% of the allocated channel
frequency and all shipboard stations within .001%. A frequency
meter or counter with an accuracy of 0.0001% or better, and cap-
able of frequency measurement in the 156 to 157 Mc range will be
required. The input of the frequency meter should be lightly
coupled to the output of the transmitter. The actual frequency of
the transmitter is computed by:
Transmitter frequency = Crystal frequency x 12
Turn the transmitter on by pressing the "push-to-talk" button
and measure the frequency. Adjust the associated trimmer condenser
for the precise operating frequency.
When all frequency adjustments are concluded, be sure to reconnect
the microphone lead. Then place the transmitter power switch in
the desired position. é
DO NOT MAKE CHANNEL FREQUENCY
ADJUSTMENTS WITHOUT INSTRUMENTS
OF KNOWN ACCURACY
IMPORTANT NOTICE
All crystals age during the first year. A new
crystal, placed on frequency, may age off fre-
quency as much as 10 ppm. (.001%) at the end of
the first year. For this reason, all transmitter
frequencies MUST BE CHECKED after the first year,
and should be checked annually thereafter.
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PART IV TECHNICAL INFORMATION
2. Receiver Circuitry
ECEIVER SPECIFICATIONS a. R.F. Circuits: The R.F. amplifier consists of a four tuned
circuit pre-selector and a dual gate FET (Q102) amplifier.
The inductive coupling of the pre-selector and inter-stage
lype Double conversion superh
f band front end. lcs a ee if coils are broad-banded (over coupled) to provide a 6 MC pass-
mee uency Range 156-163 MHz band (156-163 MC).
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ensi ee eri) acer (Shen: J Me fe RAE bs MC es oe
a te 5 : of a dual gate with signal applied to gate
ak eee Te arecie ae #1 and L.0. injection applied to gate #2. The 16.9 MC
me Freaheneics nas pe hes i ote 3uv tight) output of the first converter is fed through a 16.9 MC
Be iousehestnnse seid State 75 a nde TF .> 7 SoMHz crystal filter, which has a 6 db. bandwidth of 13 KC
lum and noise page er Thaar co! ab to a 16.9 MC I.F. stage (Q104). The output of the
Idjacent Channel Atten.(EIA) Better than 80 d 16.9 MC I.F. ‘stage is fed to gate #1 of the second
ludio Response a Rtiia2 tor Ln sa ‘ b converter (16.9 MC to 1.75 MC). Gate #2 of the second
th Gk of true 6db per octave converter (Q105) functions as a Pierce crystal oscil-
e-emphasis characteristic from 300 to 3000 Hz lator which provides the injection signal.
‘requency Stability .0005% (with AFC lock)
The 1.75 MC output from the second converter is fed
Transistors and Integrated Circuits to the input of the PA-189 integrated circuit I.F.
a. R.F. circuits amplifier and limiter. The output of the I.F. amplifier
5é 1.C. drives a conventional double diode (1N3064) dis-
| - 40673 R.F. amplifier criminator.
it Wess ster Wan Roane 2 The first converter (Q103) receives its L.0. injection
1 - 40673 Pade tonverte ae signal from the crystal oscillator (Q107) and multiplier
1 - PA189 1.75 M a se (Q108) circuits. The multiplier transistor (Q108)
at; c I.F. amplifier (1.C.) functions as a tripler with an output frequency 16.9 MC
b. Channel Oscillator Circuits above the channel frequency.
b. Audio Circuits: The audio output of the double diode
] “i 2N54 if —er——eneS oo . ° ‘re
yrs eae Boe aren discriminator is fed to the first audio amplifier
1 - 2N5180 yee scillator (Q115) through a D.C. volume control transistor (Q114)
iplier (x3) and audio de-emphasis network (ua & C150). The D.C.
ees : F volume control transistor (Q114) functions as a vari-
SECU pc able resistor, whose value is controlled by the forward
- 2N5485 Noise Amplifier bias voltage applied to its base.
Suisse Fiahete eee The audio output signal from the D.C. volume control
- 9N3565 Trigger circuit is applied to the gate of the first audio amp-
~ 2N5305 Squeich "OFF" lifier and squelch controlled transistor (Q115). The
quelch "OFF" control output of the first audio amplifier is applied to the
input of the audio power amplifier integrated cirucit
PA-237. The one watt power output of PA-237 is connected to
the input of a 3 watt complementary power amplifier P.C. board
ed ad ed el
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d. Audio Circuits
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1] - )42C2 Audio power output amplifier
1 - D43c¢2 Audio Power Output amplifier
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Squelch Circuits: The KR-25VN receiver is equipped
with a differential triggering circuit which permits
the operator to set the received signal level required
to open the squelch, independently of the signal level
required to re-set the squelch. This type of circuit
prevents audio "popping" when the received signal fades -
below the squelch opening level.
The squelch circuit is formed by a high pass audio
filter L103, noise amplifier Q109, noise rectifiers
CR102 and CRI03, differential triggering cirucit Q110,
Q111, Q112 and Q113 and squelch controlled audio amp-
lifier Q115. The squelch circuit operates by detecting
the effect a received radio signal has upon the noise
output of the discriminator. In the absence of a
Signal, maximum audio noise is present. When a signal
is received, this noise level is reduced in proportion
to the strength of the carrier. The triagering sen-
sitivity of the squelch circuit is controlled by the
setting of the front panel squelch control.
In the absence of a signal, noise from the discriminator
output is amplified by transistor Q109, rectified by
diodes CR102 and CR103 and applied as a negative DC
voltage to the gate of transistor Q110 to turn it off.
A positive. voltage is applied to the drain of audio
transistor Q115 through resistor R152 and diode CR105
which permits audio to reach the loud speaker through
audio power amplifier -PA-237.
When the front panel squelch control is turned slightly
"ON" (clockwise) a small positive voltage is applied
to the base of transistor Q111 through resistor R147
thereby causing it to conduct. When Q111 conducts the
positive drain voltage to Q115 is removed and the
receiver audio output is silenced. This is the most
sensitive setting of the squelch control (threshold).
When a carrier signal }. received, the negative DC
noise output from diodes CR102 and CR103 is reduced, .
proportional to the strength of the carrier, until 4
Q110 conducts. When Q110 conducts, Q112 becomes forward |
biased and also conducts.. When Q112 is turned on,
Q113 becomes forward biased, through resistor R151,
and audio transistor Q115 is turned on permitting ’
audio to pass through to the loud speaker.
As the squelch control is advanced past the threshold
point, an increasing positive voltage is applied to
the source of Q110 through resistor R146. The higher
this positive source voltage is set, the stronger the
carrier signal must be to lower the negative DC noise
11
voltage on the gate of transistor 0110 to cause it to conduct.
The maximum carrier signal level required to open the squelch is
set by variable resistor control (Sq "B") on the board. Once tran-
sistor Q110 is turned on, transistor Q113 also conducts which
removes the positive voltage from the emitter of Q110. This per-
mits the D.C. noise voltage on the base of Q110 to rise to a high
level before Q110 cuts off, thereby, re-setting the squelch and
silencing the receiver. This action eliminates squelch "popping"
as signals fade.
The threshold sensitivity of the squelch circuit is set by
variable resistor control (Sq "A") on the P.C. board. This
control adjusts the gain of the noise amplifier Q109.
To adjust the triggering levels of the squelch circuit, proceed.
as follows:
1. Turn front panel squelch control full "OFF" (counter clockwise).
2. Disable AFC circuit by shorting AFC terminal (located at front
of P.C. board behind speaker - violet wire) to ground with
clip lead.
3. Attach VTVM (10. volt scale) between squelch rectifier (test
point "T" on bottom of P.C. board) and ground. Set for
negative voltage.
4. Connect signal generator to antenna terminal, tune to channel
frequency and then set attenuator to zero output.
SQUELCH CONTROL "A", THRESHOLD SENSITIVITY
1. With no signal input, set control "Sq A" on top of P.C. board
until VTVM indicates maximum negative voltage (-3 volts or
more). This is most insensitive setting.
2. Turn front panel squelch control clockwise until receiver
just quiets (threshold).
3. Advance signal generator attenuator until squelch opens (about
.3 to .5 microvolts). Note VTVM reading, then return attenuator
to zero output.
4. To increase threshold sensitivity, rotate (Sq A" control until
VTVM voltage approaches the reading noted in 3 above. Advance
signal generator attenuator until squelch opens (about .1 to
.2 microvolts). This is most sensitive setting.
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LCH CONTROL _"B", MAXIMUM RANGE
Turn front panel squelch control full "ON" (clockwise).
Set control "Sq B" on top of P.C. board for maximum
resistance (toward red wire).
Advance signal generator attenuator to about 5 microvolts and
set frequency deviation control to + 5KC deviation.
Adjust tuning slug in T1104 and T1095 for minimum VTVM voltage
reading (minimum crystal filter ripple).
Rotate "Sq B" range control back toward minimum resistance
until squelch opens safely.
Turn signal generator attenuator back toward zero and note
level where squelch re-sets (about .1 to .3 microvolts) then
advance attenuator until squelch opens (about .5 to 2 microvolts).
12a
Automatic Frequency Control (AFC) Circuit: The KR-25VN
receiver 1S equipped with an AFC circuit which auto-
matically tunes the receiver to the frequency of the
transmitting station. This function is accomnlished
by slightly moving the frequency of the receiver channel
crystal oscillator in accordance with the D.C. un-
balance voltage developed by the discriminator.
When a station is received that is on a frequency
slightly different than the frequency of the receiver,
a positive or negative D.C. voltage is developed at
the output of the discriminator. The magnitude and
polarity of this voltage depends upon the amount of
frequency difference and whether this difference is
higher or lower than the receiver frequency. If the
frequency of the station is higher than the receiver,
the discriminator output voltage will be positive and
if lower the voltage will be negative.
This discriminator output voltage is applied to the
gate of junction FET Q106 through a two section RC
filter. When the frequency of the station is higher
than the receiver, a positive voltage is applied to
the gate of Q106 causing more drain current to flow
thereby reducing the forward bias on the crystal
oscillator transistor Q107. Lower forward bias on
Q107 increases the crystal oscillator frequency,
thereby causing the frequency of the receiver to
approach the frequency of the transmitting station.
To adjust the AFC circuit for proper operation,
proceed as follows:
1. Disable AFC circuit by shorting AFC terminal
(located at front of receiver P.C. board behind
speaker - violet wire) to ground with a clip lead.
2. Connect positive lead of voltmeter (20,000 ohms
per volt) or VTVM to test point marked "AFC Set"
on bottom of P.C. board, Use 5 volt scale. Con-
nect negative lead to ground.
-3. Press "Weather" push button and ver caretuy
tune top slug in oscillator coil T108 (#0931-18)
for maximum meter reading.
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. .Release "Weather" push button and rotate channel
selector switch to chan. #6 or #16. Very carefully
adjust A.F.C. control R129 (jocated near oscillator
transistor, Q107) for maximum meter reading.
NOTE: The crystal oscillator frequency changes very
rapidly when tuning slug and control are varied
at maximum meter reading, therefore use care
when making these adjustments.
Set KTM-33 function switch on "meter set zero" and
adjust meter control for center zero. Advance func-
tion switch to "Rec. Disc. Bal." position.
Using the weather station as an accurate frequency
source, slightly adjust top slug in oscillator coil
(T108) until KTM-33 reads center zero.
If available, a 60MC frequency counter may be con-
nected to the "AFC set" test point (thru a D.C.
blocking capacitor) in place of the voltmeter.
Slightly adjust top slug in oscillator coil (T108)
until counter reads 59.8166 MC.
Release "Weather" push button and check frequency
of other channel crystals. All crystal frequencies
should be within +1200 cycles of their correct
frequency.
The operation of the AFC circuit may be checked as
follows:
a
Connect VHF signal generator to antenna connector
on rear of radiotelephone.
Set KIM-33 function switch on "meter-set zero"
and adjust meter control for center zero. Advance
function switch to "Rec. Disc. Bal." position.
Tune signal generator to center of channel (KTM-33
meter reads center zero).
Tune signal generator until meter reads 2 on either
Side of center zero, disconnect AFC short clip
lead on AFC terminal and note if meter returns
toward center zero.
Repeat test by tuning signal generator until meter
reads 2 on opposite side of center zero, remove AFC
short and note if meter returns toward center zero.
NOTE: If a voltmeter is connected to "AFC Set" test
point, the reading may drop slightly when the
AFC short is removed. The meter reduction
should be about equal for step #4 and #5 above.
If reduction is unbalanced, slightly re-adjust
control R129 for balanced reduction.
TRANSMITTER SPECIFICATIONS
Frequency Range..........- 156 - 157 Mc
Chanriels évawe. oo 2. eats fagede i
PA Power sOWwtpit =... 2 sis ..25 watts & 1 watt - -10%
Modu tation. «aus ac. @ ania Phase type, 100% capability,
tapered audio
Frequency Stability.... .0005% or 0.001% @ -30° to +60°C
(When supplied with approved crystals)
Frequency Multiplication..12 times
Deviabionan. H810. «teehee +5 Ke (adjustable)
Spurious EmisSions......e. Less than 50 uw
Power Amplifier Tube...... GE Compactron-type 8156
Frequency Adjustment...... Series padding condensers
Tube Line-up:
1
Ne
6CL8A (tetrode) crystal oscillator
(triode) phase modulator
6CL8A (triode) frequency tripler
(tetrode) frequency doubler
12GN7A pentode doubler/driver
8156 power amplifier
Transmitter Circuitry: The transmitter tetrode crystal
oscillator tube (6CL8A) uses 13 Mc fundamental cut crystals.
The oscillator output is resistance-capacity coupled to
the grid of the triode phase modulator. The output of
the phase modulator is tuned to the crystal frequency and
capacity coupled to the grid of a triode frequency tripler
(6CL8A).
The output of the tripler is tuned to three times (3x) the
crystal frequency and capacity coupled to the grid of the
tetrode doubler. The output of the tetrode doubler is
tuned to six times (6x) the crystal frequency and capacity
coupled to the grid of a pentode doubler/driver (12GN7A).
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The plate circuit of the doubler/driver is tuned to twelve
times (12x) the crystal frequency, and inductively coupled
to the grid of the final amplifier (8156). The output of
the final amplifier is also tuned to twelve times (12x)
‘the crystal frequency and coupled to the 50-ohm antenna
circuit through a two-section harmonic filter.
The transmitter audio circuitry consists of a carbon type
microphone and a microphone-to-grid transformer. The
microphone transformer in turn drives the speech clipper
circuit consisting of 2 back-to-back Zener diodes. The
output of the deviation control is fed to the grid of the
phase modulator through an "LC" and "bridge T" low pass
audio filter.
POWER SUPPLY CIRCUITRY
KR-25VN/12 volt DC Power Supply: The receiver DC power
is obtained directly from the 13.6 volt primary source
through the input power fuse. The transmitter plate
supply is provided by a DC to DC converter consisting
of two 2N3772 transistors, a power transformer and a
filter circuit. A B+ voltage and negative bias are pro-
vided by the supply. The high voltage for the final power
amplifier and driver stages is 420 volts. A negative
bias voltage of 30 volts is applied to the final grid and
negative 6 volts to the tripler and doubler grids. This
bias protects the transmitter tubes should the excitation
fail or the radiotelephone be operated on a channel with-
out a crystal.
K-25/34 volt DC Regulated Power Supply: The KR-25VN 34
volt DC power supply is regulated by two switching type
regulators, one for operating the 13 volt transmitter
filaments and the receiver (continuous operation) and one
for operating the transmitter high voltage and bias power
supply (intermittent operation). The dual switching
regulator will accept any input voltage from 20 through
50 volts.
c. Q507 and Q516 - Voltage sensitive trigger.
d. Q504 and Q513 - Buffer-driver.
When the radiotelephone front panel power switch is turned
"ON", Q512 conducts (due to forward bias through R514)
which turns on Q511 and Q510. When A510 is turned on,
current flows through choke L502 developing a voltage
across potentiometer R521. When the output voltage from
potentiometer R521 exceeds 6 volts, zener diode CR508
conducts causing Q516 to conduct. When Q516 conducts,
Q515 turns off causing mono stable multi Q514 and vuffer-
driver Q513 to conduct. When the buffer-driver Q513
conducts, series elements Q510, Q511 and Q512 turn off
and current ceases to flow to the output.
When mono stable multi Q514 conducts, capacitor C507 is
discharged which determines the "OFF" time of series
elements Q510, Q511 and Q512. When capacitor C507 is
discharged, Q515 again conducts permitting series elements
Q510, Q511 and Q512 to again conduct. The ratio of "OFF"
time to "ON" time is determined by the primary power line
charge voltage on capacitor C507 thereby controlling the
regulated output voltage.
Inductor L502 and capacitor C508 filter the switched out-
put voltage of the regulator and diode CR507 provides a
DC return path for the inductive current from L502 when
the series regulator elements Q510, Q511 and Q512 are
turned off.
The transmitter switching regulator operates when the
primary power line relay K501 is actuated by the press-
to-talk button on the microphone. The output voltage of
the transmitter regulator is set for 16 to 18 volts which
operates the inverter transistors Q508 and Q509. The
transmitter high voltage is obtained from a full-wave
rectifier and filter and the bias voltage is obtained from
a half-wave rectifier and filter.
To adjust the output voltage of each regulator, proceed as
A switching type regulator is an efficient device since follows:
it delivers to the load only the amount of power required,
A. Receiver Regulator
therefore when the supply voltage goes up, the supply
current goes down.
+ 1]. Connect the positive lead of a voltmeter (25 volt
scale) to terminal #3 or #4 of TB502. Connect neg-
ative lead to terminal #1 of TB502 (NOTE: The power
supply chassis is not connected to ground or negative).
Both regulators consist of the following elements:
ao OU is oe, Os03 and GS1t0,0511 , 0512.—- Series
regulator elements.
b. Q505, Q506 and Q514, Q515 - Mono-stable multivibrator “e
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2. Connect input power to TB501 (24 to 48 volts). Turn
on power supply (advance volume control knob on Radio-
telephone).
3. Adjust control R521 (Rec.) on P.C. board until meter
reads 13.6 volts.
Transmitter Regulator
1. Connect positive lead of a voltmeter (500 volt scale)
to terminal #6 of TB502. Connect negative lead to
terminal #1 of TB502.
2. Connect input power to TB501 (24 to 49 volts). Turn
On power supply (advance volume control knob on Radio-
telephone).
3. Set "Transmitter" switch on front panel of Radio-
telephone to "25 watt" position and allow about 1]
minute for transmitter tubes to heat.
4. Connect 50 ohm load to antenna connector on rear
panel of Radiotelephone.
5. Press "Push-to-talk" button on side of microphone and
adjust control R510 (Transmitter) on P.C. board until
meter reads 420 volts.
K-25/115 Regulated AC Power Supply: The KR-25VN regulated
AC power supply will automatically compensate for power
line voltage variations between 100 and 150 volts. The
regulator operates by automatically selecting the ap-
propriate primary voltage tap on power transformer T1402.
The voltage regulator is entirely contained on P.C. board
assembly number 6074-01 and functions in the following
manner: A power line voltage sensing transformer (1401)
is connected to the unregulated power line. The secondary
voltage will vary from 10 to 15 volts for power line
variations of 100 to 150 volts. This secondary AC voltage
is applied to the anodes of two silicon unilateral switches
(2N4987) through two voltage adjusting potentiometers
(R401 & R402). Potentiometer R401 (low voltage) is ad-
justed so that its silicon switch conducts when the line
voltage reaches 120 volts and R402 (high voltage) is
adjusted so that its silicon switch conducts at 135 volts.
The silicon unilateral switches conduct when the peak
positive cycle voltage reaches 8 volts, thereby, applying
a half-wave rectified positive voltage to the base of
transistors Q403 or Q404. When Q403 or Q404 has a positive
voltage applied to its base, it conducts, thereby, closing
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relays K401 or K402.
Transformer T402 provides all voltages for the operation
of the KR-25VN. These voltages are: 13.6 volts AC for
the transmitter filaments, 13.6 volts DC for the receiver,
-30 volts for transmitter bias. and +380 and +420 volts
for transmitter plate power.
To set the two voltage adjusting potentiometers on the
regulator P.C. board, proceed as follows:
Ws
Connect an A.C. voltmeter (25 volt scale) between
terminal #3 and ground on terminal strip TB401.
Connect a variable voltage transformer between the
power line and the power supply.
Set both voltage adjusting potentiometers to "OFF"
position (counter-clockwise).
Turn on power supply by advancing volume control
knob on Radiotelephone.
Advance variable voltage transformer control until
A.C. voltmeter reads 14.6 volts.
Turn "Low voltage" potentiometer (clockwise) until
low voltage relay just closes. The AC voltmeter will
drop to 12.6 volts.
Advance variable voltage transformer control] until
AC voltmeter again reads 14.6 volts.
Turn “High voltage" potentiometer (clockwise) until
high voltage relay just closes. The AC voltmeter
will again to 12.6 volts.
At these control settings the A.C. filament voltage will vary
between 12.6 and 14.6 volts (15%) and the transmitter power
output will vary between 20 and 30 watts over a power line
voltage range of 100 to 150 volts.
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PART V__TUNE-UP ALIGNMENT
penERAL INFORMATION
Konel KR-25VN receiver contains a number of unique design
tures.
KR-25VN was accurately aligned at the factory and will not
nally require anything more than alignment "touch-up" in
vice to compensate for minor changes in component character-
ics. However, in cases where major components have been re-
ced or where the over-all sensitivity of the receiver falls
ow .5 microvolts for 20 db quieting, the RF and IF sections
uld be carefully realigned in accordance with the procedure
-lined in the following paragraphs. Do not attempt to align
s radiotelephone unless precision instruments are available.
Preliminary Tests and Checks: Any tuning adjustments to the
transmitter must be made by an FCC licensed technician.
Frequency and modulation adjustments may be made at time of
installation or on a service bench provided the bench load
conditions are equivalent to those of actual operation. The
result of this adjustment should be entered in station loa
or radio log section of this Instruction Manual.
(See FCC Rules Part 83-111).
Test Equipment Required: For complete receiver and transmitter
alignment, including frequency adjustment, the following
equipment will be required:
a. Signal Generator: A good, stable VHF signal generator
with an accurately calibrated attenuator usable at
Signal levels of 0.5 microvolts or less. Frequency
range, 156 to 162 Mc. Frequency modulation capability
+8 Ke or greater.
b. Signal Generator: A general coverage signal generator
with accurate attenuator, for frequencies of 1.75 and
16.9 Mc.
c. Noise Generator: Silicon diode type with output in
150 to 170 Mc range (KTG-33 circuit shown at rear of
manual).
d. Frequency Meter: A frequency meter with 0.0001% or
better accuracy or a frequency counter is required
for transmitter frequency alignment.
e, Wattmeter: 50 ohm load type
ta
B.
f. Volt-ohm meter: With 2.5 volt AC scale, or less.
g. Deviation Meter: Frequency modulation capability t5 Ke
or better.
h. Test Meter KTM-33: Plug in test meter for checking
receiver and transmitter circuit operation.
i. Alignment Tools: Screw driver for slotted screws,
two plastic hex alignment tools for #10 powdered iron
cores in front end coils and one hex alignment tool
for, 1/4 cores nil tsa cols.
ALIGNMENT PROCEDURES
All measurements and meter readings are correct only when the
radiotelephone primary power voltage, as measured at the power
input connector, is as specified on the rear panel of the radio-
telephone or external power supply.
ie
Receiver Alignment Touch-Up: The receiver in the KR-25VN
radiotelephone was accurately aligned at the factory using a
special Sweep Generator and Noise Source. Becuase of the
high selectivity and critical over-coupling of the front end
R.F. coils, it is recommended that only touch-up procedures
be used to obtain optimum receiver performance. A Noise
Generator (KTG-33), Test Meter KTM-33 and a V.0.M. are the only
alignment instruments required for this procedure.
Before starting alignment, short AFC terminal (front of
receiver P.C. board behind speaker - violet lead) to ground
with clip lead.
a. I.F. Alignment Touch-Up
1. Plug test meter KTM-33 into meter socket on rear
panel and place function switch in the "Align"
position.
2. Rotate the channel selector switch to a position
without a crystal.
3. Turn Radiotelephone on. Test meter should read
about 1.5 for properly aligned and operating
receiver. Touch-up tuning slugs in all I.F. coils,
starting with the crystal filter input coil, for
maximum test meter reading. (T1104, T105, 1106,
T107 and bottom slug in T1110).
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To adjust discriminator balance, unscrew top. tuning
slug in coil T110 to top of coil. Rotate meter
function switch to "Meter-Set Zero" position and
set meter pointer to center zero (with center
zero control on KTM-33). Rotate function switch
to "Receive Disc. Bal." position and, with no in-
put signal to the receiver, slowly adjust the top
tuning slug into the coil to the first position
where the meter pointer reads zero.
Connect the output of a VHF signal generator to
the rear panel antenna receptacle and tune to the
receiver channel frequency. With a generator
output of about 100 microvolts slowly tune across
the channel frequency while observing the test meter.
The test meter pointer should swing from about 2
on one side of the scale to the same reading on
the other side of the scale. (With no signal in-
put the meter need not read center zero for the
equipment to function normally; a no signal un-
balance of 12 scale divisions is acceptable).
R.F. Front End Alignment Touch-Up
{.
Connect an A.C. voltmeter (2.5 volt scale - use
"output" terminal or .01 mfd. D.C. blocking cap-
acitor) to test point marked "TP" on bottom of
P.C. board near I.C. PA-189. Connect other lead
to chassis ground.
Rotate channel selector switch to any channel in
the 156 MC band.
Connect the output of a diode noise generator
(KTG-33) to the antenna terminal of the radio-
telephone.
Turn noise generator "ON" and advance its level
control. Note the amount the test meter reading
increases. (If an increased test meter reading
is not obtained, use procedure described under
"Complete R.F. Front End Alignment").
Rotate channel selector switch to any channel in
the 161 MC band. Again advance the noise generator
level control while noting the amount the test
meter reading increases. If there is more than a
slight difference between the two increased test
meter readings (about one or two scale divisions),
the antenna and R.F. amplifier coils (T1901,
T102 and 7103) should be touched-up as follows:
Ze
2.
6. Rotate channel selector switch between 156 MC and
161 MC crystal positions while observing Ist
mixer L.O. drive on KTM-33 test meter (Rec. Osc."
position). If drive is not balanced (within 5 scale
divisions) touch-up tuning of bottom slug in oscil-
lator coil (1108) and top and bottom slugs in mult-
iplier coil (T109) until a balanced reading is
obtained. Do not adjust top tuning slug in oscil-
lator coil (T1108). This tuning adjustment is part
of AFC circuit and described under "AFC Circuit”
procedures.
7. Rotate channel selector switch between 156 MC and
161 MC crystal positions while simultaneously ad-
justing top and bottom tuning slugs in each R.F.
coil (T1101, T102 and T103) for maximum A.C. volt-
meter reading. Because of the high selectivity of
these R.F. coils, DO NOT turn slugs more than 1/8
turn at a time. Since these three coils are in
cascade, a slight mis-alignment of any one of the
six high Q tuned circuits can drastically reduce
the sensitivity in either the 156 MC or 161 MC
bands, resulting in unbalanced test meter readings
thereafter. If the front end is seriously out of
alignment, the "Complete R.F. Front End Alignment"
procedure should be used.
Complete Receiver Alignment: All tuned circuits in this unit
are iron core slug tuned and should require only touch-up
tuning (if any) during the life of the equipment. Factory
alignment procedures are outlined in the following two
paragraphs.
a. Complete I.F. Alignment
1. Plug test meter KTM-33 into socket on the rear
panel and place function switch in "Align" position.
Apply a 1.75 MC unmodulated signal to gate #1 of
Q105 the second mixer, through a .001 mfd capacitor
and increase the generator output until the test
meter reading increases. Adjust the tuning slug
in the 1.75 Mc I.F. transformer (1107) and the
lower slug in the discriminator transformer (1110)
for maximum meter reading. Keep reducing the in-
put signal level below the limiting level of PA-189
I.F. amplifier I.C. so the meter will indicate level
change with tuning.
23
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2. Apply a 16.9 Mc signal to gate #1 of the first
mixer (Q103) through a .001 mfd capacitor. In-
crease signal generator output to 100 microvolts
and carefully tune generator around 16.9 Mc until
a meter reading is obtained. Reduce signal gen-
erator output until meter reading drops about 50%.
Adjust tuning slug in 16.9 Mc I.F. coils (T1104,
T105 and top and bottom slugs in T7106) for maximum
meter-reading (continue to reduce the signal gen-
erator output as the receiver response increases.
3. Remove signal generator from mixer (Q103) and check
if R.F. front end is within range to receive a
"noise signal". (Check by shorting gate #1 of Q103
to ground and noting if meter reading drops to a
lower level). Assuming a “noise signal" is received,
adjust tuning slugs in crystal filter input and out-
put transformers (T104 and T105) for maximum meter
reading. If the R.F. front end is not capable of
producing a "noise signal" return to this step
after R.F. front end alignment has been completed.
4. If the R.F. front end is aligned, the discriminator
transformer, T110, may be balanced according to
procedures described in paragraph 4 of I.F. Align-
ment Touch-Up Procedure. If the R.F. front end is
not aligned return to this step after R.F. front
end alignment has been completed.
Complete R.F. Front End Alignment
The KR-25VN contains a highly selective R.F. front end
consisting of one R.F. stage and mixer. Three double
tuned and over-coupled R.F. transformers provide the
necessary broad-banding to permit reception in both
the high frequency band (161-162 Mc) and the low fre-
quency band (156-157 Mc). Because of the balanced
selective nature of this R.F. front end, complete
alignment should not be attempted unless absolutely
necessary. If the R.F. front end touch-up procedures
previously described are ineffective, the following
procedures should be followed:
1. Disable the AFC circuit by shorting the AFC
terminal (located at front of P.C. board
behind speaker - violet wire) to ground with
clip lead.
2. Connect an A.C. voltmeter (2.5 volt scale -
use “output" terminal or .01 mfd. D.C. block-
ing capacitor) to test point marked "TP" on
bottom of P.C. board near I.C. PA-189.
24
8.
Connect other lead to chassis ground.
Rotate function switch on KTM-33 test meter
to "Rec. Osc." position.
Rotate channel selector switch between 156 Mc
and 161 Mc crystal positions while observing
lst mixer L.0. drive on KTM-33 test meter. If
drive is not balanced (within 5 scale divisions)
touch-up tuning of bottom blug in oscillator
coil (T108) and top and bottom slugs in mult-
iplier coil (T109) until a balanced reading is
obtained. Do not adjust top tuning slug in
oscillator coil (T108). This tuning adjustment
is part of AFC cirucit and described unde
"AFC Circuit" procedures.
Rotate channel selector switch to 161 Mc band
channel crystal, tune signal generator to this
frequency and advance attenuator until an in-
creased test meter reading is obtained on A.C.
voltmeter.
With receiver placed on edge, tune top and
bottom tuning slugs in each R.F. transformer
simultaneously (T1101, T102, and T103). Start
with any one of the three R.F. transformers
and peak both tuning slugs to the high band
channel frequency. Be sure that the tuning
slugs. are on the outside of the transformer
coils. Reduce signal generator output as
alignment progresses for unsaturated meter
reading.
Rotate channel selector switch to 156 Mc band
channel crystal, tune signal generator to this
frequency and advance attenuator until an in-
creased test meter reading is obtained on A.C.
voltmeter.
Very carefully turn the top and bottom tuning
slugs of each transformer, simultaneously,
further toward the center of the transformer
until a peak is obtained on the A.C. voltmeter.
Be sure neither tuning slug is turned past the
peak thereby compensating for the position of
the opposite tuning slug. ;
At this point the R.F. front end should be
virtually aligned, permitting the I.F. and
R.F. touch-up procedures to be followed.
25
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/Receiver Sensitivity Measurement: After all receiver stages
/have been accurately aligned with a noise generator, the
overall sensitivity for 20 db quieting should be checked.
Measure receiver sensitivity as follows: Disable the AFC
circuit by shorting the AFC terminal (located at front of
P.C. board behind speaker - violet wire) to ground with
clip lead. Connect a VHF signal generator through a 6 db
pad attenuator and a 40 inch length of RG-58/U cable, to the
rear panel antenna receptacle, Connect a db meter across the
speaker voice coil and advance the receiver volume control
(squelch control “off") until a convenient noise level read-
ing is obtained on the db meter. Carefully tune the signal
generator to the channel frequency until a minimum noise
reading is obtained on the db meter. Adjust the signal gen-
erator output attenuator until the db meter reading is 20 db
lower than the reading obtained with no input signal. The
signal generator output attenuator including the pad attenuator
loss, will indicate the microvolt input signal to the receiver
required to obtain 20 db quieting. A properly operating
receiver should require .5 mv or less for 20 db quieting with
full input voltage.
——
TRANSMITTER ALIGNMENT
or to making any transmitter tuning adjustments, place the trans-
‘ter power switch in the 1 watt position. Connect a 50 ohm
ixial R.F. load (or wattmeter - 30 watts or higher) to the
‘enna connector on the rear panel. Allow one minute for the
insmitter tubes to warm up. All meter readings and alignment
rcedures will be described using accessory test meter KTM-33.
1. Crystal Oscillator: Place the test meter function switch
in the “Trans. Osc." position. Plug a channel 16 (156.80 Mc)
crystal into one of the transmitter crystal sockets and
rotate the channel selector switch to this position.
CAUTION: In keying a detuned transmitter only key for
approximately 10 seconds at a time to aviod possible
overload conditions which could result in loss of tube
life.
The transmitter has fixed bias on all R.F. amplifier stages
to protect the tubes if keyed on a channel without a trans-
mitter crystal installed.
Turn the transmitter ON by pressing the push-to-talk
button on the microphone and observe the test meter to
verify that the crystal is oscillating (approximately
mid-scale reading).
26
Multiplier Stages: Advance the meter function switch to
the "Mult. arta position. Press the push-to-talk button
and tune the 39 Mc coil (1201) for maximum meter reading.
Advance the meter function switch to the "Driver Grid"
position and tune 78 Mc coil (1202) for maximum meter
reading.
Advance the meter function switch to the "Final Grid"
position and tune the driver plate (top) and final grid
(bottom) tuning slugs (1203) for maximum meter reading.
Final Power Amplifier: Turn the meter function switch to
the
Power Output’ position and place the transmitter
power switch in the 25 watt position. Press the push-
to-talk button and tune: the final plate (1204) tuning
slug and antenna capacitor (C222) for maximum meter
reading.
The test meter should read about 25 on the 0-100 scale
and a watt-meter should indicate 25 watts power output.
The power output is dependent upon power line voltage.
The KR-25VN/12 is designed to give rated power output
with 13.6 volts DC measured at the power input connector
under transmitter load conditions. The regulated power
supplies used with the KR-25VN/115 and /34 will provide
rated power output over a very wide range of input volt-
ages.
a. TO measure the transmitter plate power input,
place the test meter function switch in the
"External 2.5V (250 Ma.) position. Plug a pair of
test leads in the pin jacks marked - (black) and
+ (red). Connect the probe ends of the test leads
across the 10 ohm resistor, located near the relay
on the transmitter P.C. board, witn the negative
lead closest to the relay.
BE EXTREMELY CAREFUL, as 400 volts is connected to
the 10 ohm resistor. Be sure the transmitter
power switch is in the desired position.
Press the push-to-talk button on the microphone
and note the reading on the 0-250 Ma. scale of
the test meter. A reading of about 135 Ma. (50
watt input) is normal with full supply voltage. A
reading of about 20 Ma. should be obtained in the
1 watt position.
b. Rotate the meter function switch to the "External-
1000 volt" position. Remove the probe end of the
black test lead from the 10 ohm resistor and con-
nect to chassis ground. Press the push-to-talk
27
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button on the microphone and note the reading on
the 0-1000 scale (1000 volts full scale) of the
test meter. A reading of about 420 volts is nor-
mal with full input supply voltage.
The transmitter plate power input to the final
amplifier tube may be calculated as follows:
Watts = Plate voltage x Plate current in amperes
Modulation Deviation Adjustment: All frequency modulated
transmitters (marine, mobile, FM broadcast, etc) use
phase modulation. Phase modulation is the only type of
frequency modulation permitted by international law.
With phase modulation, the frequency deviation doubles
as the frequency of the audio signal doubles.
All communication type FM radiotelephones are required,
by law, to contain a "speech clipper", to prevent over-
modulation, and an “audio roll-off filter" to reduce the
speech clipper harmonics above 3000 cycles.
Due to the excellent audio frequency response of the
KR-25VN transmitter, the modulation deviation must be
adjusted to +5 KC at an audio frequency of 2600 cycles.
To adjust the modulation deviation, proceed as follows:
i:
As the frequency of the audio signal generator is reduced,
Connect the low impedance output (500 ohms or less)
of an audio signal generator between the micro-
phone terminal on the transmitter P.C. board
(red lead) and ground.
Connect a 50 ohm R.F. load (50 ohm wattmeter - 30
watts or higher) to the antenna connector on the
rear panel of the radiotelephone unit.
Key the transmitter and tune a suitable deviation
meter to the 156-157 MC output frequency.
Set the audio signal generator for an output of 4
to 5 volts R.M.S. at 2600 cycles.
Adjust the "Deviation" control on the transmitter
P.C. board for +5 KC maximum peak deviation. The
sum of both plus and minus deviation should not
exceed 10 KC maximum.
the modulation deviation will decrease. At frequencies
higher than 3000 cycles, the audio roll-off filter will
cause the deviation to decrease at a rate of about 12 db
per octave.
28
High level audio at frequencies below 1500 cycles will
produce considerable distortion due to:
a. The speech clipper produces distortion overtones
at multiples of the fundamental audio frequency.
b. These distortion frequencies are below the 3000
cycle roll-off frequency of the audio filter.
c. These high distortion frequencies produce more
frequency deviation than the fundamental - hence
they are amplified more.
These distortion characteristics are normal for all FM
radiotelephones and should cause no concern. The de-
emphasis network in the receiver's audio circuitry equal-
izes the phase modulation characteristics of the transmitter
and the listener hears a normalized audio signal. Most
deviation meters provide an earphone output which includes
a 750 microsecond de-emphasis network similar to the net-
work in F.M. receivers. An oscilloscope connected to this
output will provide a true picture of the transmitter's
audio fidelity.
29
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PART VI MAINTENANCE
SERVICING
riodic checks should be made by properly qualified technical
rsonnel to ensure optimum performance at all times and to cor-
ct any condition which could later result in equipment failure.
nce the Konel VHF receiver differs considerable in its design
om conventional marine receivers, no attempt should be made to
rvice the equipment until a thorough understanding of the basic
rcuits and the characteristics of FM radiotelephones: is acquired.
rvicing may be simplified by reference to the block diagrams
d schematic diagrams at the end of this manual.
e approach is to localize the source of trouble and eliminate
ose sections of the equipment which are operating normally.
ways check the entire installation for defective antenna con-
>ctions, loose or broken microphone wires or some other condition
pmpletely external to the set before actually removing the equip-
ant for servicing.
Preventive Maintenance: To ensure maximum performance, a
routine program of preventive maintenance shotild be established,
and should include the following points:
a. Check plugs, connectors, tubes and fasteners for proper
seating.
b. Check for dust accumulation. Remove dust with smal] brush
or dry compressed air.
c. Check relay contacts. Use a relay burnish tool or clean
by drawing a small strip of ordinary bond paper between
contacts while holding gentle pressure on relay armature.
DO NOT USE FILE OR SANDPAPER ON CONTACTS. Disconnect the
input power before attempting to clean the relay.
d. Check battery connections. Add water and clean terminals
when required.
e. Check antenna system carefully. Look for corroded coaxial
plug or socket connections. Check continuity of center
coax conductor and outer shield. Check resistance between
connections.
f. Check input power system and remote control wiring. Check
for loose connections and corrosion of plugs and receptacles.
Check wiring for kinks, pinches and abrasions from other
moving parts.
30
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g. Check radiotelephone for minimum performance. Receiver
sensitivity - better than .5 microvolts for 20 db quieting.
Transmitter output better than 20 watts at rated input
voltage.
h. Check transmitter input to antenna system. Use thru-line
type R.F. wattmeter.
Power input to antenna should be
better than 20 watts at rated input voltage.
i. Check antenna "reflected" power with thru-line type watt-
meter when transmitting.
most negligible if antenna and coaxial transmission line
and transmitter are in proper order.
Reflected power should be al-
Trouble-Shooting Guide: To locate trouble use KTM-33 test
meter to isolate the section of the set which is causing the
trouble. Refer to the block diagram and voltage/resistance
chart, and the schematic diagrams.
a. Power Supply (isolated from all loads)
Inoperati ve
Blown fuse
Low output voltage
defective fuse
defective ON-OFF switch
defective transformer
defective transistors
reversed battery polarity
defective transformer
defective rectifier (s)
defective filter capacitor
low supply voltage
defective rectifier (s)
defective filter capacitor
defective voltage regulator
b. Transmitter (power supply satisfactory)
Inoperative
(no output)
Operative
(low output)
ail
defective tube (s)
defective control relay
defective crystal or no crystal
defective tube (s)
out of alignment
faulty antenna system
Transmitter power switch in
] watt position
Modulation deviation
low (1)
(3)
(4)
(5)
Modulation distorted (1)
(2)
(3)
(4)
eitciceiccbaee aE
(2)
defective microphone or
microphone cable
low microphone voltage
defective speech limiter,
Zener diode
defective modulator tube
(6CL8A)
check deviation control set-
ting and percent modulation
check receiver and trans-
mitter frequencies
check deviation control set-
ting and percent modulation
check transmitter frequency
alignment
defective modulator tube
(6CL8A)
defective oscillator tube
(6CL8A)
defective crystal
faulty crystal padding con-
denser
Receiver (power supply satisfactory)
Inoperative (
Squelch inoperative (
Operative, low
sensitivity
32
defective transistor (s)
defective volume control
circuit
defective components
‘check "B" voltage
check control relay and
antenna circuit
defective squelch transistors
check adjustment of squelch
triggering level controls
(Sq A & Sq B)
defective squelch diodes
(1N3064)
defective component (s)
defective transistor (s)
check "B" voltagé
defective antenna system or
cable
defective receiver crystal (s)
out of alignment
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Operative, audio
distorted
Limited communication
range
check transmitter frequency
defective audio IC (PA237)
defective transistor (s)
defective volume control
circuit
faulty discriminator adjust-
ment
out of alignment
defective loudspeaker
) check antenna system thor-
oughly
check power into antenna and
SWR with "Thru-line" type
wattmeter
check position of transmitter
power switch
check transmitter frequency
check modulation deviation
check terrain and expected
range (see range chart)
A. Chassis & Front Panel
Ss ss ws ss I os we Os SO
PART VII
0437-05
0443-01
4254-01
1422-50
1442-50
2057-05
2447-15
2464-52
2464-55
3477-45
3601-50
3601-04
PARTS LIST
Squelch control
Volume control
R.F. filter assembly
Weather switch
Transmitter Power Switch
_ Speaker
Lamp, 24 volt
Knob, 1/2" with insert
Knob, pointer with insert
Channel marker labels
Microphone
Microphone hanger
B. Receiver P.C. Board, Assembly #4241
eis ss iss ss St PO Ss is ss
0425-25
0425-25
0425-25
0931-07
0931-18
1014-05
1014-06
1015-08
1016-12
1016-16
1611-07
2186-05
7025
0931-09
Trimpot, AFC adjust
Trimpot, Squelch A
Trimpot, Squelch B
R.F. coils & Mult. coil
Oscillator coil
Crystal filter coupling coil
LE com 5216.9:
Crystal filter, 16.9 MC
Ficoll. a5 MC
Discriminator coil
Zener Diode, 10 volt (1N4740)
Crystal, 15.15 MC
Receiver P.C. board
Antenna coil
C. Transmitter P.C. Board, Assembly #4242
SHWee ee ee ee ee ee
0425-25
0801-50
1012-04
1035-04
1035-05
1036-03
1055-02
1130-03
1511-05
2435-08
2431-04
7019
Deviation control
Antenna tuning capacitor
Audio filter choke
Multiplier coil, 39 MC
Multiplier coil, 78 MC
Driver coil, 156 NC
Final amplifier coil
Microphone transformer,
Relay 4PDT, 12 volt coil
Tube socket, 8156
Tube socket, 9 pin
Transmitter P.C. board
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Channel Crystal Switch, Assembly #4243
hp —— Po | — no —
ine)
0801-50
1463-08
1463-09
1496-75
2396
7027
7029
5599
Frequency Adj. capacitors
Switch wafer, 12 position
Switch wafer, shorting
Switch index, 12 position
Crystal socket assembly
Transmitter Crystal P.C. board
Receiver crystal P.C. board
Crystal hold-down bracket
Power Supply, 13.6 volt Rear Panel
— ee ee ee |
0737-10
0915
1249-26
1510-04
Electrolytic filter, 4 x 4/450 volt
Hash choke
Power transformer
Relay, SPST ,12 Volt con]
K-25/34 Regulated Power Supply
Sepp Ss SP
1106-12
1249-28
1510-04
2447-15
0425-05
7068
3621-10
Choke
Power transformer
Relay, SPST, 12 volt coil
Lamp, 24 volt
Trimpot, 5K
Regulator P.C. board
Cable Assembly, 10 wire & plug
K-25/115 Regulated Power Supply
]
]
2
2
]
]
]
128]
1510-04
1511-05
0411-03
1281-10
7064
3621-10
Power transformer
Retay, SPST, #Z-volt col
Revayeeteoneelc VOlt cOmiseheG euboand
Trimpot, 250 ohm
Voltage sensing transformer
Regulator P.C. board
Cable assembly, 10 wire & plug
35
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