FX 146
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132
However, DO NOT INSTALL L9, R32 or L10 UNTIL AFTER ALIGNMENT
HAS BEEN COMPLETED. Whether you test now or later depends on
how anxious you are to see (and hear) the results of all your hard work.
If you are still awaiting your ham license, you can test the FM
modulation of buffer stage Q10 and also enjoy your receiver fully. Be
aware, however, that the buffer stage, even with no antenna connected
to it, has a transmitting range of about 100 feet, even through walls and
obstacles.
TRANSCEIVER PLL ALIGNMENT (May also be done before Step TX35)
Our goal in this test is to verify speech amplifier operation (U4), actual FM
modulation of a low-level RF signal (Q10), and correct operation of the PLL
Frequency Synthesizer in Transmit mode. If an antenna is connected for this
test, it will affect receiver operation only. The "antenna" for the 10 milliwatt
output consists of of the lead lengths and circuit-board traces associated
with C76 and C82.
TEST PROCEDURE:
1.
Make sure work area is cleaned up and that the PC board is checked for
wire scraps lodged between connections, etc.
2.
Set transceiver frequency to 146.52 MHz Simplex.
3.
Obtain or make a non-metallic alignment blade capable of turning the
slug in L7 and also turning trimmer C81.
4.
Connect speaker, microphone, antenna and 12-15 volts DC. (Antenna
will serve receive function only.)
5.
Connect a digital voltmeter (DVM) of known accuracy to TP1 (red + lead
to the test point, and black lead to ground). Set the meter to the lowest
DC range that will handle up to 7 or 8 volts. A digital voltmeter is used
for this procedure because it has the required high input impedance.
6.
With the transceiver power turned on, press the microphone button and
adjust L7 for a reading of 1.6 VDC at TP1.
7.
A precision adjustment of C81 requires either a frequency counter
connected to TP2 or a digitally accurate VHF receiver tuned to 146.52
MHz. With the microphone keyed (button pressed), C81 is adjusted for
exactly 146.52 MHz on your Ramsey frequency counter or a zero-beat
146.52 MHz signal on a digitally accurate monitoring receiver. If you
cannot tune C81 low enough, install C80, 39 pf (this places more
capacity across C81). An adequate initial adjustment of C81 can be
made by listening to your signal on any VHF FM receiver and carefully
adjusting C81 for the clearest-sounding signal. Or: adjust C81 for the
best reception of a transmitted signal of known accuracy. This might be
all that you'll ever need to do, but it is recommended that you make the
precise adjustment when possible.
FX-146
•
15
1. PRIMARY CONNECTIONS:
PWR (near L20): +12-15 volts DC from S1.
GROUND: - DC from battery or power supply.
SPEAKER: both connections near C37
MIKE: both connections (IN & GND) near notched end of U1.
SQUELCH: two connections marked CW and W near C18
VOLUME: three connections marked IN, OUT, GND.
ANTENNA: Center of SO-239 connected at "RF OUT" near C71.
CHANNEL SWITCH: Row of holes numbered 1 through 12. The switch
wiper (moving contact) is wired to +5V near "1."
EXT AUDIO: must be jumpered per options to enable pin 4 of J1.
2. TEST POINTS:
+12V, +8V, +5V, +8R, +8T permit checking for presence of those voltages.
+8R = Receive mode. +8T = Transmit.
TP1: For checking of VCO control voltage during alignment.
TP2: For checking VCO frequency with counter.
TP3: For checking U3 prescaler output with counter.
R103: +7VDC at top lead shows locked PLL. 0 volts = problem.
3. OPTIONS:
+12V, GND, +8V, +5V, +8T, +8R: provide supply voltage for accessories or
modifications designed by you. +5V is available both near L1 and near
C102. +8T and, +8R are near Q13, Q14.
Jumper Options for Packet Operation: SPKR to EXT AUDIO: Speaker level
audio for packet (J1). DISC to EXT AUDIO: FM discriminator output for
packet.
COR: "Carrier Operated Relay" output from U1.
PL: Input point for audio tones (DTMF, CTCSS, etc.)
Binary Programming Holes: The row of holes alongside the Binary
Programming labels permits installation of ribbon cable for external
programming devices designed by the innovative amateur radio community.
switches or interfaces, or a row of internal DIP switches.