Specifications

originals, plus six to fit in the EXPANDER 240.
Obviously, you could choose anything from 20-43
channels, depending upon how much you’re willing
to spend on new crystals.
TYPE 2 INSTALLATION — All PLL AM or AM/SSB with
Oscillator Doubler or Tripler Stages
In these radios, the crystal oscillator is doubled or tripled in
frequency to get close to the output frequency of the VCO,
which is typically operating in the 33-38 MHz range. The
multiplier stage can’t be bypassed for two reasons:
1. The SSB versions will have USB/LSB offset tuning
adjustments following the multiplier stage.
2. There is usually a Delta-Tune (AM-only rigs) or
Clarifier (AM/SSB rigs) circuit on the low side of the
crystal, which must be retained for proper operation.
See FIGURE 1, TYPE 2. Remove the radio’s loop mixing
crystal, and install it in the EXPANDER 240 along with your
new crystals. The signal at point “B” now depends upon which
external mixing crystal you select. Remember to use the
correct crystal positions that match your desired switching
order. Install two short hookup wires in the EXPANDER 240’s
“A” and “B” holes. Place the other wire ends in the
corresponding high side (“B”) and low side (“A”) holes where
you removed the radio’s crystal. The net effect is that you
now have several loop mixing crystals in series between the
Delta Tune/Clarifier (low crystal side) and the oscillator
(high crystal side) circuit points.
For the SSB radios in particular, it’s very important to adjust
all crystals for the proper frequency. Make all adjustments in
the “AM” mode. There should be enough range with the
trimmers for exact netting. You should then check the
USB/LSB offsets. These are usually ±1.5-2.5 KHz, as
measured at the output of the tuned circuit which does the
multiplication. Adjust the offsets according to the radio
service manual, using the standard FCC band, Clarifier at its
midrange. When switching to the new crystals, the existing
offset adjustments should shift them by about the same
amount. The Cybernet PLL02A SSB chassis uses trimmer
capacitors for the offsets, while the Uniden SSB chassis
types use coils to set the offsets.
EXAMPLE A: Cobra 140/142GTL Uniden chassis. This
uses an 11.1125 MHz tripler crystal. New crystals might be
10.9625 for the lower 40, 11.2625 for the high 40, and
11.4125 MHz for the high-high 40 channels. For 10 Meters,
use 11.5575 MHz (28.300 to 28.740 MHz) or 11.4575 MHz
(28.000 to 28.440 MHz) depending upon your need for the
USB or CW/USB parts of the band.
EXAMPLE B: Cobra 148/2000GTL, new Uniden GRANT
or MADISON chassis. The existing crystal is a tripler,
11.325 MHz. New crystals would be 11.175 for the lower
40, 11.475 for the high 40, and 11.625 MHz for the high-high
40 channels. For 10M, use 11.770 or 11.670 for USB or
CW/USB; same coverage as above.
NOTE: The 11.325 crystal used in some older Cobra chassis
is the oversize HC/33 type, not the standard
HC/18 case. For CB expansion you’ll also have to
replace that one, since the HC/33 type won’t fit in
the EXPANDER 240 PC board.
EXAMPLE C: Cybernet PLL02A U.S. SSB chassis
(Telsat SSB140, JC Penney 6247, etc.). The existing crystal
is 10.0525 MHz and is doubled. New crystals would be
9.94 MHz for the low 40, 10.165 MHz for the high 40, and
10.2775 MHz for the high-high 40. On 10M, you can use
10.38625 for USB, or 10.31125 MHz for CW/USB.
EXAMPLE D: Early generation Cybernet PLL02A AM
chassis with the 11.8066 MHz crystal. (Midland 13-857B,
13-882C, G.E. 3-5810B, Kraco KCB2320B, etc.) This
crystal is being tripled. New crystals could be 11.6567 MHz
for the low 40, and 11.9567 MHz for the high 40 channels.
EXAMPLE E: Cobra 138/139XLR Uniden SSB chassis.
These models use three separate 11 MHz tripler crystals for
loop mixing. Therefore you can’t use the EXPANDER 240 for
CB expansions because you’d need three of them. However
for 10-Meter Novice use you only need USB, and could
change just that mode’s crystal. Replacing the existing
11.2858 MHz USB crystal with one of 11.7308 MHz would
give you 28.300 MHz to 28.740 MHz.
There are many other American SSB chassis that use separate
AM/LSB/USB mode crystals, and the same principle would
apply. A few examples are the JC Penney 981-6246 and
981-6248, Realistic TRC448, Sears 934.3826, 934.3827,
and 934.3831, and Wards GEN719A.
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EXPANDER 240 PAGE 6