Vertex Standard VX-520U Service Manual
UHF Hand-Held Portable
Land Mobile Transceiver
VX-520U
Service Manual
©2003 VERTEX STANDARD CO., LTD.
VERTEX STANDARD CO., LTD.
4-8-8 Nakameguro, Meguro-Ku, Tokyo 153-8644, Japan
VERTEX STANDARD
US Headquarters
10900 Walker Street, Cypress, CA 90630, U.S.A.
International Division
8350 N.W. 52nd Terrace, Suite 201, Miami, FL 33166, U.S.A.
YAESU EUROPE B.V.
P.O. Box 75525, 1118 ZN Schiphol, The Netherlands
YAESU UK LTD.
Unit 12, Sun Valley Business Park, Winnall Close
Winchester, Hampshire, SO23 0LB, U.K.
VERTEX STANDARD HK LTD.
Unit 5, 20/F., Seaview Centre, 139-141 Hoi Bun Road,
Kwun Tong, Kowloon, Hong Kong
Introduction
The VX-520U is a compact hand portable transceiver
for the UHF land mobile band that offers the convenience
of small size, light weight, and simple operation. The
VX-520U can be simply programmed by your
VERTEX STANDARD Dealer with up to 32 channels for
single and split frequency operation. The VX-520U pro-
vides up to 5 watts of RF output power and includes a
flexible quick-connect antenna.
The transceiver and Ni-Cd battery packs are construct-
ed of thick high impact polycarbonate plastic, with spe-
cial attention paid by the designers to tight sealing and
ruggedness, assuring years of reliable operation even in
harsh environments.
The following pages describe the operation, features
and accessories of the VX-520U. With proper care and op-
eration, the transceiver will provide many years of reli-
able communications.
Contents
Operating Manual Reprint .......................... 2
Specifications ................................................. 8
Exploded View & Miscellaneous Parts .... 9
Block Diagram ............................................. 11
Circuit Description.....................................13
Alignment ..................................................... 15
Interconnection Diagram ........................... 19
Board Unit (Schematics, Layouts & Parts)
CNTL Unit .............................................................. 21
LCD Unit ................................................................. 29
VR & PTT Unit........................................................ 31
Main Unit ................................................................ 33
APC Unit ................................................................. 39
PLL Unit .................................................................. 41
REG Unit ................................................................. 44
IF Unit ...................................................................... 46
VCO Unit ................................................................. 48
TCXO Unit .............................................................. 50
1
Operating Manual Reprint
The VX-520U is a frequency-synthesized, microprocessor-controlled FM hand-held portable transceiver providing up to five watts of power output on up to 32 channels in the UHF Land Mobile Band. Designed specifically
for commercial and professional applications, the VX520U is housed in high-strength die-cast aluminum alloy, sealed to MIL-810 C, D & E intrinsically safe (I/S) and
weather-tight specifications.
User selectable features include a four-mode display
with channel name or number, upright or inverted for
easy viewing when on your belt; selective channel scanning, adjustable-pause priority scanning, and variable
transmitter power output.
Other user-selectable features include push-button display illumination, 2-tone decoder enable/disable (with optional F2D-5 Unit installed), and manual squelch override. The VX-520U is easily programmed by your dealer
using a Vertex Standard Service Kit with an IBM PC-compatible computer.
Please read this manual carefully to become familiar
with the features of the VX-520U.
CONTROLS & CONNECTORS
requirements (See “PRE-PROGRAMMED FUNCTIONS”, page 6).
Pressing and holding this button more than 4 seconds inverts the LCD display to either frontward or backward
facing readout (the backward display is convenient for
viewing when wearing the transceiver on your belt).
(4)
A/B Toggle Switch
The 32 available channels in the VX-520 can be orga-
nized into 2 Groups with up to 16 channels in each. Toggle this switch to select a group “A” or “B” for operation.
(5)
BUSY/TX Indicator
This lamp blinks green when a signal is being received
(or the squelch is opened by pressing the MON RES button) and red when transmitting. To avoid interference,
do not transmit if the lamp is glowing green. When the
battery almost depleted, this lamp blinks red, indicating
that the battery needs recharging or replacement very
soon.
(6)
CH Rotary Selector
This rotary switch selects the operating channel. If a
channel is selected that is not available for operation,
“-- -- -- --” is displayed, accompanied by a rapid warning
beeper (2 beeps/sec.).
Top panel
(1)
VOL Control
This control adjusts the volume of the receiver, and
turns the radio off when rotated fully counterclockwise
to the click-stop
(
2) S/DW Button (Scan/Dual Watch)
Pressing and holding this button more than 2 seconds
(but less than 4 seconds) turns the channel scanner on and
off. Pressing and holding this button more than 4 seconds
activates the Dual Watch feature (explained later).
(7)
Antenna Jack
This threaded-type jack accepts the supplied flexible
antenna. Any other antenna types used here must be designed for the programmed operating frequencies.
(8)
Liquid Crystal Display
In addition the channel number name, the display includes some operating status symbols, indicated in the
diagram below.
(3)
DISP Button
Pressing and holding this button more than 2 seconds
(but less than 4 seconds) activates functions as programmed by your dealer and determined by your system
2
Operating Manual Reprint
Side Panel Buttons
(1)
MON RES (Monitor/Reset) Button
Pressing and holding this button more than 2 seconds
(but less than 4 seconds) disables the tone squelch, and
permits monitoring of stations transmitting on the selected channel while still keeping your receiver quiet from
noise (“MO” will appear at the top right of the LCD). Press
it again to only hear calls within your network.
Pressing and holding this button more than 4 seconds
toggles the tone and noise squelch override, allowing all
stations (and noise) on the channel to be heard. This may
be used to hear weak stations whose signals would not
normally open the squelch. Do this to pre-adjust the VOLume control before receiving calls.
(With Selective Calling Option)
When the two-tone sequential decoder unit (F2D-5) is
installed, and a selective call has been received (“CALL”
indicator on), pressing and holding this button more than
2 seconds (but less than 4 seconds) will reset the call function on the current channel and silence the receiver, otherwise pressing and holding this button more than 4 seconds resets the call function on ALL channels.
(4)
Battery Release button
Slide this button in the direction of the arrow (upward)
for battery removal.
(5)
EAR and MIC Jacks
These jacks primarily intended for use with the op-
tional MH-45E2B External Speaker/Microphone. An external earphone can be used in the larger jack, in which case
the internal speaker will be disabled. When these jacks
are not used, make sure the plastic cap and its two screws
are in place to protect the insides of the transceiver.
OPERATION
Preliminaries
If the transceiver has not been used since leaving the
factory, fully charge the battery using VAC-520 Rapid
Desktop Charger before using it.
Mount the battery on the transceiver as described and
shown in the illustration below. Also, install the antenna
on the jack on top of the transceiver by screwing the connector into the jack until it is finger-tight.
Battery Removal & Replacement
Make sure that the VOL control is set into the off
click-stop, and remove the protective soft or hard
case, if used.
Grasp the transceiver with your left hand, so your
palm is over the speaker and your thumb is on the
Battery Release Button.
Move the button in the direction indicated by the
arrowhead, while using your right hand to slide
the battery pack toward the side with the button.
The battery pack should slide smoothly out of its
track.
To replace the Ni-Cd pack, repeat the second and
third steps above, simply sliding the battery case
in the other direction after aligning the shorter side
of the battery pack with the track below the Battery Release Button.
(2)
PTT (Push-To-Talk) button
Hold this button to transmit (the “BUSY/TX” indica-
tor glows red).
(3)
LAMP/LOCK button
Press this button momentarily to illuminate the dis-
play for five seconds. Pressing and holding this button
locks top-panel push-buttons (S/DW, DISP, and the optional DTMF keypad); this can be enabled to prevent radio settings from being disturbed.
3
Operating Manual Reprint
Preliminary Steps
Before operating the transceiver for the first time:
Charge the battery pack and connect the supplied
helical rubber flex antenna to the antenna jack on
the top of the transceiver. Never operate the trans-
ceiver without an antenna connected.
If you have a Speaker/Mic, we suggest you do not
connect it until you are familiar with basic operation.
Before proceeding, please review the “Top & Side
Panel Controls” outline, if you have not already,
to familiarize yourself with the functions of the controls.
Basic Operation
Switch on the transceiver by rotating the VOL con-
trol clockwise out of the click-stop (a momentary
beep will sound). For now, adjust the control to
about mid-position (12-o’clock), later you can adjust the level to suit the operating environment.
Switch the A/B toggle switch to select the channel
group "A" or "B" for operation, then rotate the CH
knob to select a channel for operation, the LCD will
show the currently selected channel. If “-- -- -- --” is
displayed, along with a rapid (2 beeps/sec.) beeping tone, the selected channel position is not available for operation.
To transmit, wait until the channel is clear (“BUSY/
TX” LED off), then press in the PTT switch on the
side of the transceiver while speaking across the
face of the radio. A clear normal voice will provide
the best quality transmission. For maximum battery life, select low power output (covered later)
whenever possible. During transmission the
“BUSY/TX” indicator glows red. Release the PTT
switch to receive.
To receive weak stations better, try positioning the
radio as high and far away from your body as possible, or disable the squelch momentarily by holding the MON RES button on the side of the radio
for > 4 sec. (until the second low/high beep sounds).
With the squelch disabled, the “BUSY/TX” indicator will blinks green and channel noise and weak
stations can be heard. To quiet the radio again, press
the MON RES button again momentarily.
When you are done operating, be certain to turn
the VOL control to the off position to conserve battery life.
An important note about your radio !
Some of the radio/button functions discussed next
will only operate in your radio if so programmed by
your dealer, or after the installation of certain internal optional units. In this way, the radio’s operation
can be simplified and customized specifically for the
user according to network requirements. If pressing
a button on your radio does not result in the same
function described in this manual, or if you are uncertain of the functions your particular radio is configured with, contact your dealer. See “PRE-PRO -
GRAMMED FUNCTIONS” on page 6.
Scanning
Scanning allows you to sequentially check for calls on
all or only those channels you select. To start scanning,
pressing annd holding the S/DW button more than 2 seconds (but less than 4 seconds). A beep then sounds and
the display will clear and show “SCAN”. Scanning will
pause when a signal is received, at which time the channel number (or alphanumeric tag) will be displayed. A
small “S” will be displayed above the channel, indicating
the scanner is still active, but paused.
During this pause, you can press the PTT switch and
talk to the station. Otherwise, scanning will resume a few
seconds after the signal is no longer present. While scanning, if you momentarily press the PTT switch, operation
automatically shifts to a default channel. This default channel can be set to the priority channel (both “P” and “S/
DW” are displayed), last-busy channel, or home channel,
depending on how your radio was programmed.
To stop scanning, simply press S/DW momentarily
again. Operation will return to the channel that was last
selected when scanning was activated.
If enabled by dealer programming, you may select only
the channels you want to scan, and have others skippedover by performing the following routine.
Turn the radio OFF, then depress the S/DW button
while turning the radio back ON again. “PROG” will momentarily appear on the display, after which it will revert
to the currently selected channel (this indicates you are in
the programming mode). If user-access is disabled “INH”
will appear briefly.
Use the CH knob to select a channel, then press the S/
DW button to enable the channel for scanning (“E” will
appear in the upper left corner of the LCD). Repeat this
process for each channel you want the scanner to check.
To remove a channel from those to be scanned, press
S/DW again, so that “E” no longer appears in the display.
After you have enabled all the channels you want to
scan, turn the radio off, then on again to return to normal
operation.
4
Operating Manual Reprint
Priority Scanning
Priority scanning allows you to scan and monitor channels while the receiver periodically checks for calls on a
pre-selected (“priority”) channel. You may want to use
this feature if you want to scan different channels, but
don’t want to miss a call for you on a primary dispatch,
emergency or tactical frequency. After a call has been
received on the priority channel, operation returns to the
programmed default channel scheme, as mentioned before. Only one channel at a time can be selected as the priority channel.
To assign the priority channel;
Turn the radio OFF, then depress the S/DW button
while turning the radio back ON again. “PROG” will
momentarily appear on the display, after which it
will revert to the currently selected channel (this
indicates you are in the programming mode). If
user-access is disabled “INH” will appear briefly.
Use the CH knob to select a channel which you wish
to assign the priority status, then press and hold in
the S/DW button more than 1 second. A small “P ”
will now appear at the top left corner of the display whenever this channel is selected, along with
an accompanying “beep”.
If you wish to change the priority status;
1. Delete the priority status by pressing and hold-
ing the S/DW button more than 1 second.
2. Rotate the CH knob to select the new priority
channel, then assign the priority status by pressing and holding the S/DW button for more than
1 second.
After you have assigned the priority channel, turn
the radio off, then on again to return to normal operation.
When a priority channel has been selected, the scanner will check the priority channel regularly as you scan
the other channels. If a signal appears on the priority channel, the scanner will pause and operation will jump to the
priority channel. Otherwise, the scanner will pause on
active non-priority signals as previously described.
If a call comes in on a non-priority channel that you
need to respond to, just press the PTT switch while the
scanner is paused on that channel. As long as no call comes
in on the priority channel, you can send and receive on
the other channel: scanning will resume when you finish
and the channel clears.
Dual Watch
If you need to operate on a non-priority channel while
still checking for calls on the priority channel, the Dual
Watch feature let’s you to do this without using the scanner. When enabled, operation on any selected non-priority remains normal as before, however, when a signal is
received on the priority channel or when you press the
PTT switch, operation immediately shifts to the priority
channel. The rate at which the Dual Watch feature samples the priority channel can be set by the user.
To begin Dual Watch operation, first assign a pri-
ority channel as described before, then select the
non-priority channel you wish to operate on.
Press and hold the S/DW button until the second
beep sounds, “DW” (but not “S”) will appear at
the top of the display.
To manually shift to the priority channel, press the
PTT switch. At this time you make transmit, otherwise, if no signal is received within 2 seconds, operation will revert back to the other selected Dual
Watch channel.
To turn off the Dual Watch Feature, press and hold
the S/DW button again (“DW” will disappear in the
display).
Low Battery Power Indication
When the rechargeable Ni-Cd battery pack voltage
reaches a low level, the “ ” indicator appears at the
lower right corner of the LCD, and the “BUSY/TX” indicator will blinks red. Immediately remove the Ni-Cd pack
and install a freshly charged battery pack, or insert the radio
into the charging stand for a complete recharge cycle. If you
plan to operate your radio for extended periods of time,
you may want to keep a spare, fully-charged pack
handy.
5
Operating Manual Reprint
PRE-PROGRAMMED FUNCTIONS
The function selected by pressing and holding the DISP
button more than 2 seconds (but less than 4 seconds) can
be customized by dealer programming and your network
requirements. A brief explanation of available functions
is provided below. However, contact your dealer for details on their use and operation.
Low Transmit Power
This reduces the power output of your radio to approximately one watt to conserve battery life, and when
full power is not needed to maintain reliable communications. “LO ” will be displayed at the upper right corner
when enabled.
Alpha Tag
This displays an alpha-numeric channel name, usually describing the channel, rather than merely displaying
a channel number. These may be programmed to assist
you in recognizing channels by name, rather than by memorizing channel numbers and their assignments.
Talk Around
This feature enables simplex operation on semi-duplex
channels: the transmit frequency becomes the same as the
receive frequency (regardless of any programmed offset
for the channel).
Note: This feature has no effect on simplex channels.
Optional Accessory
Voice Encryption (FVP-22):
When installed, pressing and holding this button more
than 2 seconds (but less than 4 seconds) will turn on the
optional voice encryption unit for privacy during communications.
ENI (Emergency Numbering Identification)
Unit (FTE-19):
When installed, pressing and holding this button more
than 2 seconds (but less than 4 seconds) will turn on the
optional ENI Unit, then within 1/2 second, press this button again to transmit the ENI signal.
BUTTON FUNCTIONS
As mentioned before, button functions can be customized by programming from your Vertex Standard dealer
to meet your communications/network requirements.
Some features may require the purchase and installation
of optional internal accessories for operation. The table
below illustrates the possible Top-panel button programming combinations. Functions are explained on the previous page “PRE-PROGRAMMED FUNCTIONS.” For further details contact your nearest Vertex Standard dealer. For future reference, check the box next to the function that has
been assigned to the button on your particular radio, and
keep it handy.
DISP
Butto n
S/DW
Button
Press and Hol d
(< 2 s e co nds )
HI/LOW TX Power
Alpha Tag
Ta lk A ro und
Accessory (Voice Encryption)
Accessory (ENI)
Press and H old
(< 2 second)
Starts/St ops
Channel Scanning
Pre ss a n d H ol d
(> 4 second)
Starts/Stops
Dua l-Watch
Feature
Pre ss a n d H ol d
(> 4 se co nds)
To gg l es t he To p Pa n e l L CD
display between normal and
inverted readout
Press and H old
while Power-o n
1) User-selectable
channel scanning
programming (if enabled)
2) Priority channel
assigning (if enabled)
CUSTOM SETTINGS
Below is a table of radio features that can be customized by dealer programming. To change a feature as your
requirements change, contact your Vertex Standard dealer. For future reference, check the box next to the option
that has been programmed in your particular radio, and
keep it handy.
Fe at ure Options Explanation
Channel
Scan
Scan-Stop
Resume
User-Scan
Program
Dual
Watch
Channel
after PTT
Monitor
DISP
Button
Enabled
Disabled
5-s eco nd s
Carrier
Enabled
Disabled
Enabled
Disabled
Priority Ch.
Home Ch.
Las t- Busy
Enabled
Disabled
See Table
Channel scanning can be disabled
completely for systems not requiring this
feature.
In the 5-seconds mode, scanning pauses
on a busy channel for 5 seconds, then
resumes.
In the Carrier mode, scanning pauses and
remains on a busy channel until the
station stops transmitting.
If enabled, the user can program which
channels are to be scanned; otherwise,
dealer-programmable only.
Dual-Watch can be disabled completely for
systems not requir ing this feature.
If the PT T is pressed during scanning,
de ter mine s whic h d e fa ul t cha n ne l th e rad io
returns to : the selected Priority Channel,
a de s ignated " Home" Ch a nn el, or t he
channel that was last-busy.
Enable/Disable the side-panel MON RES
button (See pages 6 & 9).
Flexible dealer-programming as outlined in
the table on the previous page.
6
INSTALLING CHANNEL-STOPS
To simplify operation and prevent selection of unprogrammed/unused channels or channel groups, tiny metal inserts or “stops” can be inserted into the top panel
beneath the CH selector knob. A tiny tab protruding from
beneath the skirt of the CH knob engages the stop(s) as it
is turned, preventing further rotation.
To insert a stop, rotate the CH knob to the channel “1”
position and use the Allen wrench to loosen the setscrew
locate the CH knob, then pull off the CH knob. Insert the
stops firmly into the appropriate slot(s) for the desired
channels, using a pair of tweezers or fine needle-nose pliers, according to the drawing below. For example, to limit CH selection to channels 1 - 4, insert one metal stop at
the slot 16 (channel 1 minus “one position”), and the other
at the slot 3 (channel 4 minus “one position”). When done,
press the CH selector knob back on the shaft, align the
indicator of the CH knob to channel “1,” then tighten the
setscrew.
Note: The use of mechanical stops should not be used
or relied upon as the sole means to prevent selection or
transmission on an invalid or unauthorized channel.
Channels should be locked-out or TX-inhibited via programming by your Vertex Standard dealer, and stops inserted as a operating convenience to you and your network users.
Operating Manual Reprint
7
Specifications
General
Number of Channels:
Frequency Range:
Channel Spacing:
Power Supply Voltage:
Current Consmption:
Battery Life:
Ambient Temperature Range:
Frequency Stability:
Dimensions:
Weight:
32
450-488 MHz
12.5/25 kHz
7.2 VDC
Standby (Saver On) 19 mA
Standby (Saver Off) 50 mA
Receive 200 mA
Transmit 2/1 A
11 hrs. (13.3 hrs. w/saver)
–22° F to +140° F (–30° C to +60° C)
±2.5 ppm
2.3" (W) x 5.9" (H) x 1.5" (D) inch w/FNB-29A
59 (W) x 149 (H) x 39 (D) mm w/FNB-29A
2.3" (W) x 6.7" (H) x 1.5" (D) inch w/FNB-29AL
59 (W) x 171 (H) x 39 (D) mm w/FNB-29A
1.21 lbs (547 g) w/o ANT w/FNB-29A
1.24 lbs (564 g) w/o ANT w/FNB-29AL
Receive
Circuit type:
Sensitivity:
Adjacent Channel Selectivity:
Intermodulation:
Spurious and Image Rejection:
Conducted Spurious:
Hum & Noise:
Audio Output:
Double-conversion Sperheterodyne
0.25 µV (EIA 12 dB SINAD)
0.35 µV (20 dB Quieting)
75 dB/65 dB
72 dB
75 dB
–57 dBm
40/45 dB
0.5 W @16 Ohms, 5 % THD
Transmit
Power Output:
Modulation:
Conducted Spurious Emmisions:
FM Hum & Noise:
Audio Distortion (@1 kHz):
Specifications may be subject to change without notice or obligation.
5.0/1.0 W
11K0F3E, 16K0F3E
60 dB Below Carrier
45/50 dB
<2.5 %
8
RA0277900
CONNECTOR
COVER
RA0278400
PACKING SHEET
R8141000
NAME PLATE
R7145910A
RUBBER
Exploded View & Miscellaneous Parts
R3518770
SUB PANEL
CP7023000
PANEL SUB ASS'Y
(w/ NYLON NET (2pcs))
RA0071100
RELEASE KNOB
R0117370
COIL SPRING
No.
VXSTD P/N
U20204027
U07240101
U07270127
U07430127
U32450001
U33104001
U43105001
U44204001
U32230127
U32430127
M4090103
SPEAKER
T9206264A
WIRE ASS'Y
Description
BINDING HEAD SCREW M2.6×4B SUS
PAN HEAD SCREW M2×4 #1
PAN HEAD SCREW M2×7B SUS
PAN HEAD SCREW M2.6×3B SUS #1
FLAT HEAD SCREW M2.6×5
TAPTITE SCREW M2×4
TAPTITE SCREW M2×5
TAPTITE SCREW M2.6×4
FLAT HEAD SCREW M2×3B SUS #1
FLAT HEAD SCREW M2.6×3B SUS #1
N0190177
ROTARY SWITCH
MAIN Unit
IF Unit
PLL Unit
VCO Unit
REG Unit
APC Unit
PA Unit
Qty.
2
4
4
2
2
4
2
10
2
4
R7124630A
NYLON NET
R3130400A
HOLDER
M3290019
MIC ELEMENT
VR Unit
K22174809
CHIP CAP. 0.001µF
CNTL Unit
PTT UNIT
R0518720A
HOLDER
RA0409100
HOLDERPTT (Lot. 10~)
R3146900
INSULATOR ASS'Y
T51005012
WIRE ASS'Y
T95102171
JUMPER ASS'Y
RA0278500
RUBBER KNOB
U76004001
PLAIN WASHER AW4
S2000054
O RING
RA0277700
TOP PANEL ASS'Y
R6054387B
SPECIAL NUT (2pcs)
RA0278000
KNOB
RA0278100
VOLUME KNOB
LCD Unit
S2000052
O RING
RA0277800
RUBBER KNOB
R6149640
SPECIAL NUT
R3149660A
WASHER (2pcs)
R4900691
REAR PANEL
R0149670B
CONNECTOR ASS'Y
Non-designated parts are available
only as part of a designated assembly.
9
Note:
10
Block Diagram
11
Block Diagram
Note:
12
Circuit Description
Refer to the block diagram when reading this descrip-
tion. For finer details, refer to the schematic diagram.
Receiver
In coming signals at the antenna are passed through a
low pass filter and T/R switching diode on the ANT SW
Unit before delivery to the front-end circuitry on the mother board. Here the signal is band-pass filtered again by a
2-stage resonator, amplified by Q3201 (2SC3356-R24),
and then further filtered by a 2-stage band-pass resonator befor application first mixer FET Q3202 (SGM2016M)
along with the first local signal from Local Amplifier
Q2406 (2SC4226-R24) on the VCO Unit.
The 47.9 MHz product from the first mixer is delivered through 4-pole monolithic crystal filter XF3201 (± 6.0
kHz BW) to strip away all but the desired signal, which is
amplified by Q3203 (2SC2620QB) on the Main Unit. FM
receiver sub-system IC Q2302 (BA4116FV) on the IF Unit
includes local oscillator, mixer, IF limiter amplifier and
FM detector circuits. The amplified first IF signal is applied to mixer section, along with the second local signal
generated via 48.355 MHz crystal X2301, which produces
the 455 kHz 2nd IF when mixed with the 1st IF signal
within Q2302. The 2nd IF passes through ceramic filter
CF2301 (4.5 kHz BW) or CF2302 (7.5 kHz BW) to strip
away unwanted mixer products, and is then applied to
the limiter amp in Q2302, which remove amplitude variations in the 455 kHz IF before detection of the speech by
Q2302 via quadrature resonator CD2301.
Detected audio is delivered to the CTCSS IC Q1001
(FX165CLH) and then passes through the de-emphasis
circuitry consisting of R1033 & C1015, via muting gate
Q1011 (2SK160-K6) and volume control to audio power
amplifier Q2206 (TDA2822D) and Q2211 (2SC4116GR)
on the regulator unit, providing up to 0.5 W to the external speaker jack or 16-Ω loudspeaker.
Squelch Control
The squelch control circuit consists of noise amplifier
Q2304 (2SC4116GR) and band-pass filter and squelch trigger within Q2302 on the IF Unit, and control circuitry within
microprocessor Q1017 (M38067MC) on the control unit.
When no carrier is received, noise at the output of the
detector in Q2302 is amplified by Q2304, and band-pass
filtered by the noise amplifier section of Q2302 and then
rectified by D2302 to provide a DC control voltage for the
squelch switching transistor Q2306 (2SA1586Y). With no
carrier, the emitter of Q2306 is high. The signal is buffered by Q1013. This SCAN STOP signal is delivered to
the microprocessor on the Control Unit, and microprocessor controlled through Q1003 (FMG5) to the BUSY indicator on the top panel, which remains off until a carrier
is received. The microprocessor causes audio mute gate
Q2207 (DTC144EU) & Q2202 (2SB1132Q) to open the audio power amplifier power source, thus disabling the au-
dio amplifier and silencing the receiver when no signal is
being received, and during transmission.
When a carrier appears at the discriminator, noise is
removed from the output, causing the emitter of Q2306
to go low, then Q1017 controls the signal high, which in
turn causes Q1003 to turn on the BUSY indicator. The
microprocessor then checks for CTCSS tone information
from Q1001, plus Digital Code Squelch information form
Q1006 (TA75S393F). If not transmitting and no tone
squelch is programmed for the channel, or if the received
tone matches that programmed for the channel, the microprocessor switches Q2207 to allow operation of the
audio power amplifier.
Transmitter
When the PTT switch is depressed, audio from the microphone is delivered to the Control Unit, where it is highpass filtered by Q1018 (2SC4116GR), and by one section
of microphone audio processing dual opamp IC Q1008
(NJM2904V). After pre-emphasis by C1074 and R1030,
another section of Q1008 serves as an IDC (Instantaneous
Deviation Control) amplifier to prevent over-deviation
from excessive microphone levels, and the two remaining states provide low-pass filtering to suppress out-ofband modulation, and buffering.
Processed audio from the IDC Unit is delivered to VCO
Unit where it is applied, along with carefully filtered DC
from Q2407 (2SC4116), to varactor diode D2403 (1SV230)
to modulate (via the TX Line) VCO FET Q2404 (2SK508-
K52, on the VCO Unit), which oscillates at the transmit
frequency. VCO output is buffered and amplified by
Q2406 on the VCO Amplifier Unit before returning to the
Main Unit. Buffered, modulated VCO output is applied
via T/R switch D3202 to driver Q3205 (2SC3356), Q3214
(2SC3357), and the transmit signal is delivered to RF Power Module Q3206 (M68732H).
The transmit signal is passed through T/R switching
diode D2001 on the APC Unit, and then low-pass filtered
by L2003~2005, and C2007, C2011 to suppress spurious
harmonics before application to the antenna.
Transmitter output is controlled by Q2001 (2SA1586Y)
and Q2002 (FMW1) on the APC Unit. When the TX 5V
line (from the regulator Unit) is active, bias voltage and
driver collector voltage is applied to the RF Power Module via Q2003 and Q2004 , turning it on. A sample of the
final transistor collector current in the RF Power Module
is taken via R3224 on the mother board, detected by Q3207
(IMZ2), passed through RF Power potentiometer VR3201
on the main unit back to APC switch Q2001 (2SA1586Y)
via one half of Q2002 (FMW1) on the APC Unit. Q2002
passes the Automatic Power Control voltage when enabled by the other (transmit sequencer) half of Q2002. This
circuit is also used by the PLL to disable the transmitter
when the PLL is unlocked, and by the microprocessor to
select low power output.
13
Circuit Description
PLL
The first local signal for the receiver, and the carrier
for the transmitter (at the transmitter frequency) are generated by the PLL. This circuit consists two voltage controlled oscillator (VCOs), prescalar, programmable divider, reference oscillator, phase detector, charge pump and
low pass filter.
The VCO (on the VCO Unit) consists of Q2401, Q2404
and varactor diodes D2401, D2402 and D2403 (mentioned
above). The oscillating frequency is controlled primarily
by the level of DC voltage fed from the loop filter (lowpass filter) to the varactor diodes. The VCO output is buffered by Q2406 (2SC4226), and then to prescalar within
Q2105 (MB1505) on the PLL Unit, which divides the VCO
frequency by 64 or 65, according to a control signal from
the prescalar control logic section of PLL IC Q2105.
The divided signal from the prescalar is fed to the programmable divider section of Q2105, where it is further
divided down to 10/12.5 kHz according to data from microprocessor Q1017 on the Control Unit. Meanwhile, the
reference oscillator section of Q2105 generates the reference frequency with crystal X2101, which signal is divided by Q2105.
The reference and the divided VCO signal are applied
together to the phase detector section of Q2105, from
which any phase difference between the two signals results in a pulse train from the phase detector. The pulses
are applied to the charge pump Q2102 (IMD3) and then
through low-pass filter R2101, R2103 ~ R2106, R2122 and
C2102, C2104 ~ C2107, to produce a DC voltage at a level
corresponding to the difference in phase between the reference and the divided VCO signal. This DC voltage is
returned to the varactor diodes on the VCO Unit, locking
the frequency of the VCO to the crystal reference oscillator.
In the Tx mode, Tx 5 volts applied to inverter Q2106
pulls analog switch Q2101-1/2 off, removing R2106 and
R2122 from the PLL loop.
Also, the transmitter VCO is modulated by the filtered
speech audio applied to modulating varactor diode D2403,
as previously described. If Digital Coded Squelch is in
operation, the DCS signal modulation is applied to the
PLL reference, via varactor D2102 & D2103 (HVU350).
Control Unit & Supply Buses
Microprocessor Q1017 (M38067MC) on the control unit
contains programming in masked ROM to generate serial data to control the Liquid Crystal Display driver IC
Q5001 (LC75821E) on the LCD Unit, and the programmable divider in the PLL according to channel frequency
data stored in externally programmable EEPROM. Q1017
also includes programming for channel frequency scanning. DCS encode/decode, CTCSS IC Control, option unit
control, selectable channel steps and frequency range.
The microprocessor receives an indication of the condition of the noise squelch from the FM receiver subsystem
IC on the IF Unit, by which scanning is activated or deactivated.
Q1017 also controls the power saver function and transmit/receive switching by selecting the supply buses on
the regulator unit:Q2209 (DTB123EK), Q2205
(DTA143XK) and Q2210 (DTC144EU) disables the RX 5V
bus when the power saver is active.
When the PTT switch is pressed, the impedance change
on the microphone line is detected by Q1015 (2SA1586Y)
on the control unit, which signals the microprocessor that
the transmitter is active. The microprocessor then activates
LED indicator D5001 to glow red (TX).
Voltage comparator Q1012 (RH5VL45AA) controls
power-up resetting of the microprocessor.
14
Alignment
UHF Transceiver Required Test Equipment
H IBM PC compatible computer
H Vertex Standard VPL-1 Cable, or FRB-2 Service Kit, with
CE37 Channel Programming Diskette
H Vertex Standard CN-1 BNC Adapter plug
H RF Signal Generator with calibrated output level at 1 GHz
H Deviation Meter (Linear Detector)
H AC Voltmeter
H SINAD Meter
H In-Line wattmeter with 5% accuracy at 1 GHz
H Regulated DC Power Supply adjustable from 4 to
10 V, 3 A
H 50-Ω Non-reactive Dummy Load: 10 W at 1 GHz
H Frequency Counter: ±0.2 ppm accuracy at 1 GHz
H AF Signal Generator
H DC Voltmeter: high impedance
Before beginning alignment, connect the transceiver and
PC using the VPL-1 Cable or FRB-2 Set as described in
the EEPROM Programming chapter, and download the
EEPROM data from the transceiver to the computer.
Then store this data in a disk file so that it can be uploaded when alignment is finished.
You should find the corresponding data file on the computer disk for the transceiver version you are aligning, containing channel settings for the high edge, middle and low
edge of the transceiver’s frequency range in channels 1, 2
and 3, respectively. Up-load this file to the transceiver.
LOW BAND
EDGE CH. (1)
450.0 MHz
BAND CENTER
CH. (2)
460.0 MHz
HIGH BAND
EDGE CH. (3)
470.0 MHz
PLL & Transmitter
Set up the test equipment as shown for transmitter
alignment. Adjust the supply voltage to 7.2 V for all steps
where not specified otherwise.
Sampling
50-ohm
Dummy Load
Freq. Counter
Coupler
Inline
Wattmeter
Deviation
Meter
AC Voltmeter
ANT
MIC
AF Signal
Generator
AC Voltmeter
Regulated DC
7.2V PSU
PLL & TX Alignment Setup
PLL VCV (Varactor Control Voltage)
Ë Connect the DC voltmeter between C2105 on the PLL
Unit and chassis ground.
Ë Set the transceiver to CH 3 (high band edge), and ad-
just L2402 on the VCO Unit for 3.5 V ± 0.1 V on the
voltmeter.
Ë Transmit on the high band edge, and adjust L2406 for
3.5 V ± 0.1 V on the voltmeter.
Ë Set the transceiver to CH 1 (low band edge), and con-
firm the low-end VCV is more than 1.3 V while transmitting, and also while receiving.
PLL Reference Frequency
Ë With CH 2 (band center) selected, key the transmitter
and adjust TC2101 on the PLL Unit, if necessary, so the
frequency counter displays the band center frequency
±300 Hz (for the version being aligned) when transmitting.
L2402
L2406
C2105
VR3204
VR3201
VR3202
TC2101
PLL & Transmitter Alignment Points (I)
15
Alignment
Transmitter Output Power
Ë Set the transceiver to band center CH 2, and select high
power output.
Ë Ensure that the supply voltage is precisely 7.2 V, then
adjust VR3201 (while the PTT switch is pressed) for 5.0
W on the wattmeter, and confirm that supply current
remains below 2.2 A.
Ë Select low power output (“LO” displayed on the LCD),
and adjust VR3202 on the Main Unit for 1.1 W on the
wattmeter, and confirm that supply current remains
below 1.2 A.
Modulation Level
Ë With the transceiver set to band center CH 2, adjust the
AF generator for 77 mVrms output at 1 kHz to the MIC
jack.
Ë Press the PTT switch and adjust VR3204 on the Main
Unit for a deviation of ±4.3 kHz (for 25 kHz steps) or ±
2.1 kHz (for 12.5 kHz steps).
Ë Reduce the AF generator output to 7.7 mVrms.
Ë Press the PTT switch and adjust VR1002 on the Con-
trol Unit for a deviation of ± 3.0 kHz (for 25 kHz steps)
or ± 1.5 kHz (for 12.5 kHz steps).
CTCSS Tone Level
Ë With the transceiver set to band center CH 2, set the
CTCSS encoder on .
Ë Press the PTT switch and adjust VR1001 on the CNTL
Unit for a deviation of ±0.7 kHz (for 25 kHz steps) or ±
0.35 kHz (for 12.5 kHz steps).
DTMF Tone Level
Ë With the transceiver set to band center CH 2.
Ë Press [1] key on the DTMF keypad while press and
holding the PTT switch, adjust VR1003 on the CNTL
Unit for a deviation of ±2.5 kHz (for 25 kHz steps) or ±
1.25 kHz (for 12.5 kHz steps).
16
PLL & Transmitter Alignment Points (II)
VR1001
VR1003
VR1002
Note!
Because of the bridge audio amplifier circuit used in the
VX-520U, it is necessary to construct and use a simple
audio load test adapter as shown in the schematic diagram above, when conducting receiver alignment steps.
Do not connect either side of the speaker leads to chassis
“ground”.
φ
PLUG
3.5
Attenuated
8Ω 1W
470µF
8Ω 1W
AF Test Adapter Schematic
Test Output (1/2)
Ground
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