Uniden AX 144 Specifications download pdf

CONSTRUCTION, INSTALLATION, & OPERATION

EXPANDER 160 CRYSTAL OSCILLATOR & SWITCH

The EXPANDER 160 is a compact crystal oscillator unit which allows

remote controlled selection of up to four different crystals. This

provides new injection signals for loop mixing in PLL synthesizer

circuits, or additional synthesizer frequencies in 23-channel CB

transceivers. The RF output is approximately 5 V peak-peak when

supplied at +8 VDC, and is buffered to minimize loading at its

connection. Each crystal position includes a series trimmer capacitor

for exact frequency adjustment. Crystal selection is made by diodes,

which eliminates the problem of stray wire capacitance often found in

mechanical switches.

A unique system of wire jumpers allows the EXPANDER 160 to be

used solely as a crystal switch, with the oscillator circuit disconnected.

This configuration is needed for all 23-channel crystal-synthesized

radios, and all 40-channel PLL radios whose crystal frequency is

doubled or tripled before mixing with the VCO signal. In such radios,

the existing crystal is removed from the radio’s chassis, and two

EXPANDER 160 wires are installed at the empty crystal location.

The removed crystal is soldered into the EXPANDER 160 PC board,

along with up to three new crystals. The module is now in series with

the radio’s crystal circuit. This allows up to four crystals (the original

plus your three) to be chosen instead of just the original. The radio’s

total operating range and bandwidth will depend upon the specific

chassis type.

CIRCUIT DESCRIPTION

See the Schematic Diagram on Page 9. The EXPANDER 160 consists

of a Colpitts oscillator, bipolar buffer stage, a diode switching array,

and various jumper wire options.

One of four crystals is chosen when a DC voltage is applied through

your hard switch (toggle, rotary, slide, CB/PA, etc.) to one of the PC

board holes numbered “1” through “4.” The “5” hole is the

common hot side for the hard switch, and connects directly to the

radio’s regulated +DC supply bus. With voltage applied, the

appropriate diode (D1-D4) is turned on by the current flowing

through it and R1/L5 to ground. R1 limits the current to a safe

value. L5 keeps all crystals above RF ground, since the crystal’s hot

side is being switched. RF is decoupled from the DC power supply by

L1-L4 and C1-C4.

OSCILLATOR MODE

The Colpitts oscillator common to CB radios has a relatively high

shunt or parallel input capacitance. This can pull the crystal off

frequency, so series trimmers CT1–CT4 are provided for exact

adjustment after installation. The trimmers have a range of 9-50 pF,

which is more than enough if proper crystals are specified when

ordering.

Jumpers J4-J7 are installed for the OSCILLATOR Mode, and are used

to ground one side of the crystals. Sometimes a particular crystal can

be difficult to trim to the correct frequency. In such cases, you can

often replace the bare jumper wire with a small capacitor (5-68 pF)

or RF choke (1-10 µH) to get the oscillator within the range of the

trimmers.

Q1 is the oscillator. R2, R3, and R4 provide the DC operating biases,

and are chosen to oscillate with any crystal between 10-20 MHz at DC

supply voltages of about +5-12 VDC. C6 is the feedback capacitor

which causes oscillation. The values of C6 and C7 are chosen to

oscillate with any fundamental crystal from approximately 8 MHz to

20 MHz, or any Third Overtone crystal type. (Typically these are in

the 36 MHz range, and are actually cut near 12 MHz.) Q2 is a buffer

stage which isolates the oscillator from possible loading effects in the

radio. C8 has purposely been kept small (22 pF) for this same reason.

DC operating power comes from the radio. The source must be

well regulated for maximum frequency stability. Most CB transceivers

all have at least one such source, usually +5-8 VDC, and this is used to

power the EXPANDER 160. The DC source you choose must be

present for both RX and TX. Connect the RED wire to that, and the

BLACK wire to chassis common.

SWITCH MODE

The EXPANDER 160 is connected as a straight electronic switch in

many PLL radios, and always in the older crystal-synthesized radios.

In this mode J8 is left out, which disconnects the active transistor

stage. J4, J5, J6, and J7 are also removed, and J1, J2, and J3 are

used instead. This ties the low side of all crystals together at hole “A,”

and all the high sides together at hole “B.” In most radios the crystals

are not directly grounded, grounding instead through a Delta Tune

or Clarifier VXO circuit on the crystal’s low side. Thus the jumpers

allow the EXPANDER 160 to be used as a multiple series crystal

switch. Wires from holes “A” and “B” are installed in the appropriate

holes formerly occupied by the original mixing crystal. Crystals are

chosen by diodes D1-D4, in exactly the same way as the

OSCILLATOR Mode.

Published by:

CBC INTERNATIONAL • P.O. BOX 30655 • TUCSON AZ 85751 U.S.A.

TEL/FAX: 888-I-FIX-CBs (1-888-434-9227), (520) 298-7980

Internet: www.cbcintl.com • Email: [email protected]

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Summary of Contents

Page 1 - CIRCUIT DESCRIPTION

CONSTRUCTION, INSTALLATION, & OPERATION EXPANDER 160 CRYSTAL OSCILLATOR & SWITCH © The EXPANDER 160 is a compact crystal oscillator unit wh

Page 2 - EXPANDER 160 PAGE 2

C1, C2, C3, C4, C9 = .01 mF C5 = .001 mF R1, R5, R7 = lKΩ C6 = 150 pF R2, R3 = 10KΩ C7 = 68 pF R4 =

Page 3

_________________________________________________________________________________ EXPANDER 160 PAGE 11

Page 4 - INSTALLATION

ASSEMBLY INSTRUCTIONS PLEASE READ CAREFULLY BEFORE PROCEEDING! NOTICE This device will operate as advertised when properly constructed, installed,

Page 5

CRYSTAL ORDERING The following specifications should be observed when ordering crystals. FREQUENCY: As desired. ACCURACY: .005% or better. HOLDE

Page 6

INSTALLATION NOTE: The radio’s tuned circuits may need realignment after installation of the EXPANDER 160. Much depends upon the desired center op

Page 7

EXAMPLE B: Cobra 134/138/139/Midland 13-895 AM/SSB chassis. This uses 8 MHz and 11 MHz mixing banks, with a 7.8 MHz Carrier Oscillator. The 8 MHz

Page 8

Delta Tune or Clarifier (low crystal side) and the oscillator (high crystal side) circuit points. For the SSB radios in particular, it’s very importa

Page 9 - EXPANDER 160 PAGE 9

EXAMPLE B: All late generation Cybernet PLL02A AM chassis with 10.24 MHz and 10.695 MHz crystals. (HyGain 2702, Midland 77-857, G.E. 3-5804D, etc.) I

Page 10

2. Reinstall the crystal directly across the base of the oscillator “K” and ground. The simplest way is to first splice some short bare wires to its

Page 11 - EXPANDER 160 PAGE 11

_________________________________________________________________________________________ EXPANDER 160 PAGE 9

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Uniden AX 144 Specifications

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