FX 146
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130
IMPORTANT:
DO NOT install any parts near Q8 until after Q8 has been installed in accord
with the explicit directions in Step TX2. If you fail to observe this caution, it
will be virtually impossible to perform the installation of Q8 correctly.
DO NOT INSTALL L9, R32 or L10 UNTIL AFTER ALIGNMENT HAS BEEN
COMPLETED.
C75 is a SMT (surface-mount-technology) "chip" capacitor and is the only
part installed on the SOLDER SIDE (bottom) of the board.
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TX1. Install Q9, RF NPN type 2N3866. Let it rest flush on the round
bare area of the board. The holes match the pins, so the tab will point
exactly as illustrated.
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TX2a. RF Final transistor Q8 (MRF237 or SD1127) is also installed
completely flush on the board, with the tab oriented toward L9. The
case of Q8 is common to the emitter. Be sure the case stays completely
flat against the top ground plane when soldering the 3 points.
READ CAREFULLY: The following procedure lets the top groundplane serve
as the heatsink for the RF final output transistor. Do not be hesitant in
making a smooth solder bond between Q8's case and the board. An ordinary
soldering pencil tip applied to both the case and the groundplane at the
same time will NOT damage Q8. On the other hand, the lack of a good
heatsink bond WILL destroy Q8 when transmitting. This procedure is
INTENDED by the manufacturer.
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TX2b. Now, using only your regular soldering pen and NOT a soldering
"gun," solder the rim of Q8 directly to the top ground plane, starting at
the square tab. Use enough solder for thorough bonding.
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TX3
A. Prepare the following tools for installing SMT chip capacitor C75:
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Tweezers
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Magnifier (if needed)
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Low wattage, clean soldering tip.
C75
Location of C75
FX-146
•
17
VHF PACKET DATA OPERATION
Your FM transceiver was planned and designed to accommodate easy and
reliable VHF packet radio operation.
The J1 Packet I/O port can be quickly connected to many modern TNC's and
the Ramsey P-IBM or P64 Packet Modems with Radio Shack's shielded DIN
cable (42-2151). Otherwise, your first step is to prepare a reliable 5-
conductor cable with a 5-pin DIN plug (RS 274-003) at one end, and the
correct connector needed by your packet TNC at the other end. If you
salvage a "ready made" 5-pin DIN cable from something like a discarded
computer joystick, be sure that there are indeed 5 wires, or at least the ones
that are required by your TNC!
Consult your Packet TNC or Packet Modem documentation for ALL details
on hookup and operation. Pin 4 of J1 offers a choice of amplified and
squelched (speaker level) audio output or low-level (discriminator) output.
This choice is set up by the jumper wire positions clearly visible on the PC
board.
Packet RX Audio Jumper: Some TNC's require low-level audio from the
discriminator output of the FM detector, while others will accept speaker
output. Either is available in the FX transceivers. Simply install a jumper in
the appropriate location near VR1, to connect "EXT AUDIO" to either
"SPKR" for speaker audio or "DATA" for discriminator audio. Use scrap
resistor wire to make the jumper. You also can choose to wire these three
points to a miniature SPDT switch which you can mount on the rear panel
near the packet connector. OR, use a PC mount switch in the jumper area
itself.
Use this space to diagram your TNC cable connection:
DRAW YOUR TNC CONNECTIONS