TYPE 3 INSTALLATION — All PLL AM or AM/SSB with
Direct Frequency Mixing
See FIGURE 1, TYPE 3. The oscillator output is coupled
through a small disc capacitor or tuning coil to the Mixer
stage. Remove the oscillator crystal, and place the “A” and
“B” wires of the EXPANDER 240 in those empty holes.
EXAMPLE A: Any AM Courier model with the REC86345
PLL chip.
The mixer crystal is 36.380 MHz. New crystals might be
35.930 MHz for the lower 40, and 36.830 MHz for the
upper 40 channels. These are tripler cut (Third Overtone)
type crystals.
NOTE: Many other AM-only PLL radios also use the
36 MHz circuit. Included are those models with the
SM5104, TC5080, µPD858, and µPD861 chips, and
the Royce “sardine can” modular AM models. The
same method works in all these as well.
EXAMPLE B: Cobra 29/89XLR Uniden chassis with
µPD858 PLL chip.
Replace the existing 36.57 MHz crystal. New crystals would
be 36.12 MHz for the lower 40, and 37.02 MHz for the upper
40. These are also Third Overtone cuts.
EXAMPLE C: Realistic TRC459/TRC480
Because the LC7113 PLL chip is now extinct and this chassis
was very expensive, it’s worth saving and expanding. The loop
crystal is 17.8875 MHz. New crystals might be
17.4375 MHz for the lower 40, and 18.3375 MHz for the
upper 40 channels. For 10M, use 18.4825 MHz CW/USB or
18.7825 MHz USB only.
IN CASE OF DIFFICULTY
Recheck soldering and parts placements. Use a strong
backlight against the PC board to look for solder bridges and
shorts. Check for proper diode polarity mounting. Use a
’scope, RF voltmeter or Frequency Counter to see if radio
oscillator is running with EXPANDER 240 installed. Verify
that the EXPANDER 240 is in fact being powered by DC; the
common “GND” hole in the PC board must be tied to the
radio’s common foil via the BLACK wire, and the RED wire
to your switch common pole. If it’s getting power, the
cathode of the diode that’s currently being switched will
measure about 0.6 VDC less than its anode supply.
If you expect your kit to work properly, try very hard to
install the parts neatly and correctly, as shown in the
X-Ray View and the photograph on Page 8 and Page 10.
Press all parts down tight against the PC board; rock the
diode or resistor leads back and forth while pressing,
until they fit flush against the PC board.
For specific information about models not included here,
send a large self-addressed stamped envelope or an email, and
the exact radio make and model. We do not sell schematics
or SAMS Fotofacts, so please don’t ask. If you don’t have a
schematic or don’t understand exactly what to do,
don’t touch! Leave it to professionals.
Telephone to order SAMS CB Fotofacts:
(800) 428-7267, (317) 298-5400
Internet:
www.samswebsite.com/photofacts.html
___________________________________________________________________________________________________
EXPANDER 240 PAGE 7
(16 pages)
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