Ramsey Electronics FX-440 Manual page 100

[ ) [ ) F13. Install R106, 1 OK (brown-black-orange).
[ ) [ ] F14. Install R105, 100 ohms (brown-black-brown).
[ ] [ ] F15. Install L21, . 04 uh. L21 is a small 4 turn pre-wound coil.
[ ] [ ] F16. Install C35, 100 pf. C35 couples the VCO buffer to T1.
[ I [ I
F17. Install C21, 27 pf.
[ ) [ ) F18. Solder 1 /4 • lengths of scrap component lead wire in the two
test point holes marked TP2 and TP3. See the following optional
test before installing a similar test point at TP1 .
[ ) [ ) F19: TEMPORARY RECEIVER PTT/T-R CONNECTION
OMIT this step if you prefer to install ALL transceiver parts before
any testing or use of the Receiver alone. If you wish to conduct
further tests or put the receiver to work, it is necessary to solder a
5" length of hookup wire from the hole marked •
+
8R" (near 013,
R112) to the hole marked
·+av·
near C29. In lieu of the
switching done by the PTT circuit (Stage M), this temporary
jumper applies
+
8V to all
+
8R points on the board. (You also
have, of course, the option of wiring the microphone input and
PTT circuitry before testing the receiver).
Even
if
you do not perform the following test, be aware that there is one
more step following this discussion (F20) - please don't forget to do it.
OPTIONAL VCO RECEIVER TEST OR DEMONSTRATION
At this point in building your transceiver, the VCO is functional but is
lacking any control voltage to varactor diodes 03 and 023 that would
permit tuning. Supplying this precision controlled voltage is, of course,
the function of the PLL Frequency Synthesizer that will be constructed
next. However, for those who would benefit from such a test or
demonstration, it IS fairly easy at this point to set up temporary manual
or "analog" tuning with an ordinary potentiometer.
Notice on the schematic diagram that the control voltage to the tuning
diodes comes from USA through R47 and R25. Notice that a Test Point
(TP1) is conveniently located at R25. The purpose of TP1 is to permit
measurement of the precision voltage to the varactor diodes generated
by the frequency synthesizer's phase detector. Since no such voltage is
yet reaching TP1, we can put it there ourselves! If we connect a
potentiometer as illustrated below, the wire soldered to TP1 can be
trimmed down later to serve as the intended test point. The potentiometer
will vary the voltage to 03 and 023, thereby varying the VCO frequency
and tuning your receiver.
Assm. 40
FX-440