Midland 70-1526A User manual

441 DLAN D
LAND MOBILE RADIO
SERVICE MANUAL
MOBILE TRANSCEIVER
UHF BAND
[406 - 430 MHz, 450 - 470 MHz)
15-25 WATT
MANUAL NO.: 70-152600
09-1526-SM-4/91-2M

This manual section is designed to facilitate the set-up and service of the Midland 70-1526
transceivers. As necessary, service maual supplements will be published and distributed on the
following forms:
Manual Addition (MA) .For supplemental information useful in product service or
improvement. Printed on BLUE paper.
Change Notice (CN).For details about changes made during production by
model and serial number. Printed on YELLOW paper.
Manual Correction (MC).For correcting literature errors not related to production
changes. Printed on GREEN paper.
Technical Bulletin (TB) ....... For solutions to field problems and tips for performance
improvement. Printed on PINK paper.
Comments or suggestions concerning areas of manual improvement are welcome.
ii

TABLE OF CONTENTS
Manual Supplement Information....... .11
Table of Contents ...... lil
SECTION 1 GENERAL INFORMATION
Description...1-3
Specifications.....1-3
SECTION 2 PREPARATION
Pre-Installation Check.2-3
Complete Realignment. 2 - 3
SECTION 3 INSTALLATION
Installation ..3-3
SECTION 4 SERVICING
Component Replacement.......4-3
Eliminating Radio Interference ..... 4 - 7
Voltage Charts. . 4 - 1 1
Troubleshooting Charts ........ 4 -14
SECTION 5 CIRCUIT DESCRIPTIONS
RF Section .5-3
25-Watt PA Section...5-5
Logic Section.5-5
SECTION 6 DIAGRAMS
Block Diagram...6-3
Wiring Diagram .6-4
CX-103 Layout.....6-4
CX-104 Layout.... 6 - 4
TR-423 Layout — Bottom View ...6-5
TR-423 Layout — Top View .6-6
TR-423 Schematic...6-7
Component Layout. , 6 - 8
Diode Pinouts...... 6 - 9
Transistor Pinouts.......6-9
Exploded View. 6 - 1 0
SECTION 7 PARTS
Parts List....7-3
Replacement Parts Ordering ... 7 - 1 0

SECTION 1 — General Information
SECTION 2 — Preparation
SECTION 3 — installation
SECTION 4 — Servicing
SECTION 5 — Circuit Descriptions
SECTION 6 — Diagrams
SECTION 7 — Parts

GENERAL INFORMATION
70-1526
NOTES

_ GENERAL INFORMATION
70-1526
DESCRIPTION
The 70-1526 Midland 8-Channel Wide Band transceivers are programmable frequency-synthesized two-
way FM mobile radios that operate in the UHF frequency range. They are programmable for up to eight
channels.
The 70-1526 is designed to operate within either of two frequency ranges: 406—430 MHz (A-Band), or
450—470 MHz (B-Band). Transmit RF power is adjustable for 15—25 Watts.
SPECIFICATIONS
Refer to EIA-152-C, EIA/TIA-204-D, EIA-220-B, and DOC RSS-119 for standard of performance and method
of measurement.
GENERAL
OPERATING FREQUENCY RANGE:
A-Band: 406^430 MHz
B-Band: 450—470 MHz
CHANNEL SEPARATION: 24 MHz
CHANNEL SPACING: 25 kHz
CHANNEL STEPPING: 12.5 kHz/5 kHz optional
CHANNEL CAPACITY: Programmable for up to eight channels
POWER SUPPLY: 13.6 V DC negative to ground
CURRENT DRAIN:
Transmit (at 25 W): 10.0 A
Receive (@ rated audio): 2.0 A
Standby (std, varies with options): 400 mA
OPERATING TEMPERATURE: -30° C + 60° C
DIMENSIONS (H xWxD): 2x7x87/ 8 i n (50x 178x225mm)
WEIGHT: 2.5 kg

GENERAL INFORMATION
70-1526
TRANSMITTER
RF POWER OUTPUT (adjustable):
FREQUENCY STABILITY:
MODULATION (FOR 100% AT 1000 Hz):
BANDWIDTH:
SPURIOUS AND HARMONICS:
FM HUM AND NOISE:
AUDIO RESPONSE:
AUDIO DISTORTION (±3 kHz deviation):
OUTPUT IMPEDANCE:
15—25 W
±0.0005% (—30°C + 60° C)
16K0F3E ±5.0 kHz @ 25 kHz
24/20 MHz without retuning
-60 dB
-50 dB
per EIA and DOC specifications
Less than 3% @ 1 kHz
50 Q
RECEIVER
FREQUENCY STABILITY:
SENSITIVITY:
12 dB SINAD:
20 dB Quieting:
SELECTIVITY:
BANDWIDTH:
ACCEPTABLE RADIO FREQUENCY
DISPLACEMENT:
SPURIOUS REJECTION:
INTERMODULATION:
SQUELCH SENSITIVITY:
AUDIO OUTPUT:
Internal Speaker:
External Speaker:
±0.0005% (-30° C + 60° C)
0.30 fiV
0.5/fV
-75 dB @ ±25 kHz
24/20 MHz without retuning
±3.0 kHz @ 25 kHz
-80 dB
-75 dB
0.2/A/ maximum
2 W @ less than 3% distortion @ 8 Q
5W@ less than 3% distortion @ 3.2 Q
INPUT IMPEDANCE: 50 Q

GENERAL INFORMATION
70-1526
CTCSS/DCS
OPERATING TEMPERATURE RANGE: -30° C — +60° C
CTCSS TONES: All EIA tones from 67.0 Hz to 250.3 Hz, plus 97.4 Hz
DCS CODES: All codes from 000 to 777, normal and invert
ENCODE TONE/DCS MODULATION LEVEL: 500 Hz —1000 Hz deviation
ENCODER RESPONSE TIME: CTCSS/DCS 50 ms max
ENCODER TONE DISTORTION (67 Hz—250.3): 3% max
TONE/SQUELCH OPENING SINAD: 8 dB max
HUM AND NOISE: 32 dB
DECODER RESPONSE TIME:
CTCSS: 200 ms max (for tones above 100 Hz)
DCS: 324 ms max
— Specifications subject to change without notice —
—H
-5

GENERAL INFORMATION
70-1526
NOTES

PREPARATION
70-1526
NOTES

PREPARATION
70-1526
PRE-INSTALLATION CHECK
The 70-1526 TX/RX Units are capable of operating across a20/24 MHz frequency spread and do not require
optimizing alignment, even when reprogrammed with new customer frequencies. Only genera!
transmitter/receiver performance should be checked. Complete realignment may be necessary after a
component that affects transceiver tuning has been replaced. Either the 70-1080A Programmer or 70-1489
PC Programming software (with 70-1308A programming interface) may be used.
SET-UP
1. Remove the PWR/VOL knob. Using a flat
blade screwdriver, carefully pry the unit cover
outward at the slots marked "RELEASE" near
the rear of each side. Lift the cover from the
chasis, starting at the back.
2. Connect a resistive, 50-Q RF load (with a
wattmeter) to Antenna Connector J501. Con¬
nect 13.6 V DC power to J415. Turn the radio
on, turn MON on, and turn selective signaling
options off.
CARRIER FREQUENCY
1. Initiate transmit on any channel. Measure
transmitted RF carrier frequency without
modulation and, if needed, set carrier fre¬
quency to within ±400 Hz of channel fre¬
quency using the programmer (either the
70-1080A programmer or 70-1489 software).
2. Initiate transmit on any channel. Measure
power of RF output at 50-Q Antenna Connec¬
tor J501. Adjust RV402 to obtain 25 W RF
output power.
MAXIMUM DEVIATION
1. Select a channel with a transmit frequency of
406 MHz for A-Band, or 450 MHz for B-Band.
If CTCSS or DCS is used, be sure this channel
is programmed to send the same.
2. Disconnect the hand microphone from its
front panel receptacle J301. Apply 3 Vrms of
1000 Hz signal to pin 1 of Mic Jack J301, then
initiate transmit by grounding pin 4. Make sure
total carrier deviation is below ±5 kHz (includ¬
ing CTCSS/DCS signal), if adjustment is
needed, see MODULATOR ALIGNMENT on
page 2 - 4.
COMPLETE REALIGNMENT
Complete realignment is needed only if a component that affects alignment has been replaced RADIO
REPROGRAMMING WITH TEST FREQUENCIES IS REQUIRED.
SET-UP
1. Remove the PWR/VOL knob. Using a flat
blade screwdriver, carefully pry the unit cover
outward at the slots marked "RELEASE* near
the rear of each side. Lift the cover from the
chasis, starting at the back.
2. Connect a resistive 50-Q RF load and watt¬
meter to Antenna Connector J501. Connect
13.6 V DC power to transceiver J415.
3. Connect a 3.2-Q, 20-W resistor to pins 4 and 6
of the Accessory Plug. The jumper between
pins 5 and 6 must be temporarily removed to
make this connection. The resistor serves as
a constant load to replace the speaker’s in¬
consistencies.
CAUTION: Both speaker terminals are LIVE. Never
ground either one. Connect grounded receive-
audio measuring equipment to only one side of the
speaker, and chassis ground. Normally, voltage
measurement will be half of true values.
4. Turn the radio on, set the VOLUME control to
a mid-position.
5. Connect the programmer (the 70-1080A or
70-1308A interface) to Programming Port
J402. Upload the radio programming Data-
Packet into the Programmer and initiate its
Remote Control Mode. Refer to the appropri¬
ate manual for details.

PREPARATION
70-1526
SYNTHESIZER ALIGNMENT
• VCO Resonance
1. Select the Remote-Control mode of the pro¬
grammer. For A-Band models, enter a test
frequencies of 406.00 MHz for both RX and
TX. For B-Band models, enter a test frequency
of 450.00 MHz.
2. Adjust Channel RX Tank L713 for 1.5 V DC at
CM701 pin 2 (VCO steering).
3. Activate transmit mode (using the program¬
mer) and adjust transmitter VCO L733 for
1.5 V DC at CM701 pin 2.
• Reference Oscillator
4. I n i tiate transmit on any channel. Measure
transmitted RF carrier frequency without
modulation and, if needed, adjust the carrier
frequency and bring the radio to within
±400 Hz of operating frequency.
25 W PA SECTION AUGNMENT
1. Change the TX test frequency to the desired
frequency.
2. Activate transmit mode, then adjust CV501 to
obtain maximum RF power at Antenna Con¬
nector J501.
3. Set RF output power to 25 W using RV402.
MODULATOR AUGNMENT
• Modulation Limiting
1. Disconnect the hand microphone from its
front panel receptacle J301. Apply 3 Vrms of
1000 Hz signal to pin 1 of Mic Jack J301, then
initiate transmit (if not using a programmer,
ground J301 pin 4).
2. Measure total carrier deviation and, if needed
adjust modulation limiting to obtain ±5 kHz
using RV403.
• Microphone Gain
3. No alignment for Microphone gain is required.
• CTCSS/DCS
4. Remove the 1 kHz audio signal from external
mic jack.
5. Add DCS code +023 to the transmit test mode
testing frequency in the programmer.
6. Adjust RV1 for 750 Hz ± 10 Hz deviation.
7. Adjust RV401 so that modulation waveform
from modulation analyzer matches the correct
waveform shown in Figure 2-1.
8. Change the transmit test code in the program¬
mer to 250.3 Hz CTCSS tone. Carefully adjust
RV401 for 750 Hz ±10 Hz deviation.
9. Change the transmit test code in the program¬
mer to 67.0 Hz CTCSS tone. Carefully adjust
RV1 for 750 Hz ±10 Hz deviation.
n
u
INCORRECT
Figure 2-1 — Modulation Waveforms

PREPARATION
RECEIVER
1. Change the RX test frequency to 418 MHz for
A-Band radios, or 460 MHz for B-Band.
• First injection
2. No adjustment for the first injection is needed.
• Preselector Alignment
3. No adjustment for the preselector (L201,
L202, L203, L204, L205, L206 and L207) is
required.
• Quadrature Detector
4. Apply 1 mV of modulated (by 1 kHz tone at
±3 kHz deviation) on-channel RF signal to
Antenna Jack J501. Adjust Detector L250 for
maximum audio output.
70-1526
• First i.F.
5. Apply enough modulated (by 1 kHz tone at
±3 kHz deviation) on-channel carrier to main¬
tain 12 to 15 dB SINAD. Adjust L245—L247 for
best SINAD.
• Squelch
6. Set the left side Squelch switch on. Set
Squelch Range RV241 fully clockwise.
7. Apply 0.2 [N of unmodulated on-channel RF
signal to the 50 Q antenna connector. Adjust
Squelch range RV241 counter-clockwise just
until squelch opens (audio on).
Table 2-1 — Required Test Equipment
TEST INSTRUMENT
INSTRUMENT CAPABILITIES USE
Regulated DC Power
Supply
13.6 V DC, 10 A
adjustable voltage
Radio power source
RF Wattmeter
for 70-1526
50 W, 406—470 MHz
50-Q circuit
Transmitter power
measurements
RF Load Resistor 50-Q; 50 W
Antenna dummy load
Frequency
Modulation Meter
406—470 MHz; peak -
responding, ±5 kHz range
Modulation level
measurements
Frequency Meter or
Frequency Counter
406—470 MHz
1.0 ppm accuracy
Carrier frequency
measurements
Audio Generator
1000 kHz sine-wave;
0—4 Vmis output
Modulation level
measurements
RF Signal
Generator
406—470 MHz range;
0.1—1 lyrV output; ±3 kHz
FM mod. with 1 kHz tone
All receiver
measurements
Distortion Analyzer
1 kHz notch;
1% measuring range
Receiver performance
test and IF alignment
Load Resistor
(audio)
3.2-Q, 20 W
Speaker load for ail
receiver measurements
AC Voltmeter
10 rnVtolOVrms
Audio level adjustments
Oscilloscope
DC to 500 kHz bandwidth
Digital Multimeter
0.1 to 20 V DC
Test point measurements
and powe.r p.piy. .set-up
70-1080A Programmer, or
70-1489 PC Programming software and
70-1308A PC Programming interface
Manual radio control

PREPARATION
CV501
L247 L246 L245
□ □ □
□ o
L248 M
RV401
RV241
RV403
RV402

INSTALLATION
70-1526
NOTES