Specifications

INSTALLATION
NOTE: The radio’s tuned circuits may need realignment after
installation of the EXPANDER 160. Much depends upon
the desired center operating frequency of the expanded
radio. Therefore a schematic diagram of the radio is
essential, as well as an accurate Frequency Counter.
Although specific installation points are described for some
popular models, the work should be done by a qualified
electronic technician. The supplier assumes no liability for
damage to any equipment resulting from improper
installation.
GENERAL INSTALLATION BY CHASSIS TYPE
Radios to be expanded can be classified into four general categories.
TYPE 1: All 23-channel AM or AM/SSB having crystal synthesizers.
TYPE 2: All AM or AM/SSB PLL types having a crystal oscillator
loop mixing stage which is doubled or tripled by subsequent
tuned circuits.
TYPE 3: All AM or AM/SSB PLL types having a fixed crystal
oscillator loop mixing stage operating directly at the crystal
frequency.
TYPE 4: All AM or AM/SSB PLL types with a loop mixing signal
generated indirectly from some other crystal-based circuit.
Instead it comes from another area of the PLL circuit. An
example would be the very common 15.36 MHz mixer
signal generated from a tripled 5.12 MHz PLL IC pin.
For the TYPE 1 and TYPE 2 radios, the EXPANDER 160 will be
used only in its SWITCH mode. For the TYPE 3 and TYPE 4 radios,
the OSCILLATOR mode will be used. Each mode is determined by
specific jumper wires on the PC board; install the correct jumper wires
for the desired mode.
Remember that any 40-channel radio modified by crystal mixing will
still have exactly the same channel skips as the standard 40 channels.
Examples include the five in-between “A” channels, and the
non-continuous frequencies between Ch. 22 and Ch. 26. These skips
are physically built into the sealed binary or BCD Channel Selector
switch, and can’t be changed.
Page 5 shows the general connection points for each type. Remember,
you must check the radio’s schematic for the exact location.
IMPORTANT: Regardless of the installation type, the YELLOW
“RF” output wire (or “A” and “B” hole wires if
used) must be as short as possible. The YELLOW
kit wires have purposely been left at 6" lengths for
this reason. Find a mounting location where these
wires can be connected into the radio’s PC board
without needing any longer lengths. Stray
capacitance from long wires can detune the circuit,
or even keep the crystals from oscillating. The
switch wires can be any length, and a 1-foot ribbon
cable is provided for this purpose.
TYPE 1 INSTALLATION — All 23-Channel AM or AM/SSB
Crystal-Synthesized Radios
See Figure 1. These radios all use banks of crystals that mix together,
most often in the 6-4-4 or 6-4-2 configurations. For SSB types there
are a few extra crystals in the Carrier Oscillator and synthesizer stages
to provide the SSB frequency offsets; these have no effect on the
location of the EXPANDER 160. The crystals to be added will go in
the bank containing the six mixing crystals, regardless of whether the
radio is AM or AM/SSB. These six crystals always mix to control the
following six continuous channel groups:
Channels 1, 2, 3, 4
Channels 5, 6, 7, 8
Channels 9, 10, 11, 12
Channels 13, 14, 15, 16
Channels 17, 18, 19, 20
Channels 21, 22, 23
For example, the most common AM schemes use a 37 MHz master
oscillator plus separate 10 MHz oscillators for RX and TX
(Figure 1A), or banks of 23 MHz, 14 MHz, and 11 MHz RX and TX
oscillators (Figure 1B). Most older SSB radios generally use crystals
in the 7.8 MHz or 11 MHz range, in the 6-crystal mixing bank.
Remove one of the six crystals from the radio and place it in the
#1 crystal position of the EXPANDER 160 instead. To make it easy
remembering which Channel Selector positions provide which new
channels, you should remove either the lowest or the highest
frequency mixing crystal, depending upon whether you are expanding
the radio below Ch. 1 or above Ch. 23. Install your new crystals in the
remaining three positions of the EXPANDER 160. Put them in the
correct position order (#2, #3, #4) so that your chosen switch makes
the frequency bands continuous. Since you’re adding an extra three
crystals, and each one will be mixed in the radio with four others, this
means you will get a total of twelve additional new channels.
Cut a 12" piece of hookup wire (provided in our kits) in half. Place
the two pieces in the “A” and “B” holes of the EXPANDER 160.
Install wire jumpers to put the EXPANDER 160 in the SWITCH
mode; i.e., remove J8, J4, J5, J6 and J7 and install jumpers in the J1,
J2, and J3 positions as shown on the X-Ray View and the PC board
legend. Install the two loose wire ends from holes “A” and “B” in the
two empty holes where you removed the mixing crystal, being sure to
put the “A” wire in the low or ground side hole, and the “B” wire in
the hot or oscillator side hole of the radio.
EXAMPLE A: Cobra 29 AM chassis. This uses the standard 23 MHz
and 14 MHz mixers, with the 11.730 MHz RX and 11.275 MHz TX
oscillators. There are six 23 MHz crystals, and these are the ones to
change. (Figure 1B.) Note that they change in 50 KHz steps: 23.290,
23.340, 23.390. 23.440, 23.490, 23.540. The next three for
continuous lower frequencies would be 23.240, 23.190, and
23.140 KHz.. This gives twelve continuous lower channels from
26.955 MHz downward in the Ch. 1-4 positions, four channels for
each of the three new crystals plus the original 23.290 MHz.
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EXPANDER 160 PAGE 4