Ramsey Electronics FX-440 Manual page 108

matrix. In practice, this proposition need NOT be pursued, because it
would require 16 wire jumpers to connect the A inputs of the adders to
the summing outputs. Also, the programming formula would involve
subtraction of the receiver IF frequency. For example, to receive 446. O
MHz, we would have to determine N as ( 446000-21400)
+
12.S.
Consquently, we can see that it will actually EASIER to install the 4 IC's,
install diodes in the RECEIVE line of the second matrix and proceed to
find "N" simply by dividing our desired frequency by 12.S KHz.
CONSTRUCTION PROCEDURE NOTE:
The suggested order of assembly for the PLL Frequency Synthesizer
portion of your transceiver is exactly that: a suggestion. This stage
involves some repetitive work that may seem extra easy, but it also can
become easier to make mistakes: skipping connections, causing solder
bridges, etc. Some builders may prefer to push ahead and do all of the
repetitive soldering as a single operation, while others do better work with
frequent breaks in the phases that involve repetition of steps. The
suggested order of assembly is for the benefit of the latter group. If you
wish to proceed differently, feel free to do so. Just be sure to check off
the respective assembly steps as you finish or review your work
[ ] [ ] G1 a Insert the 28-pin DIP socket for U6 into its PC board
position and slightly bend the 4 outermost pins to hold it in place.
[ ] [ ] G1 b. Examine the solder side and verify that ALL 28 pins extend
through their respective holes. Solder the 4 outermost pins and
then solder all the remaining pins.
[ ) [ ] G2. Install oscillator crystal Y2, 12.80 MHz. Be sure it is firmly
seated on the board before soldering.
[ I [ I
G3. Install C87, 39 pf.
[ I [
J
G4. Install C80, 1
s
pf.
[ ) [ ) GS. Install R38, 1 OK (brown-black-orange).
[ ] [ ] G6a Identify C81, a 35 pf. trimmer capacitor. (C81 has a black
body and orange top). Press it in place flat on the PC board.
[ ] [ ] G6b. Solder C81 's two leads.
[ ] [ ] G7. Identify and install US, the LM358 dual op amp IC. Be
certain to orient the notched end as pictured on the PC board.
OBSERVE CORRECT POLARITY FOR THESE 5 CAPACITORS:
[ ] [ ] G8. Install C70, 2.2 uf electrolytic.
[ ) [ ] G9.
lnst~I
C67, 2.2 uf electrolytic.
[ ] [ ] G10. Install C96, 4. 7 or 1 O uf electrolytic.
Assm. 48 FX-440