FMA5-F Sound Subcarrier Generator
The front panel 10K Line audio and 50K Mic audio pots vary the audio gain. The switch on the line audio pot turns on power to this board.
The 10K deviation pot on the board is roughly set to just start soft limiting at 25 kHz deviation and hard limit around 40 kHz deviation. The
500 Ohm subcarrier injection pot is set to no less than 15 dB down from peak sync by us with a spectrum analyzer. If set any higher, the
4.5 MHz subcarrier will give increased sync buzz from limiting during white video periods and sync time as well as crosshatch intermod
beat with color video. If set too low, the sound will drop out with increasingly snowy pictures or not give best sound when the downconverter
is tuned for best picture at the other end. Sound will normally drop out when color does in snowy conditions. The 18 uH inductor is set to
within 2 kHz of 4.500 MHz with a frequency counter connected to the subcarrier output pad.
6
6
6
6
6
(c) 1999 P. C.
Electronics
TVC-2G Downconverter
No adjustments. The 10K pot on the front panel varies the varicap voltage between 0 (lowest frequency) and 8 Vdc to change the
frequency. C1, 2 and 3 are bandpass filters peaked for the 420-444 MHz ATV frequencies. C4 sets the local oscillator frequency. C4 is
factory set to roughly 434 MHz into CH3 with the knob between 3 and 5. No adjustments are necessary if CH2 or 4 is used as there is
plenty of excess tuning range. If you believe the GaAsfets have popped from lightning, etc., check with a Voltmeter at the Source and Gate
2 leads. G2
≤
S voltage. Gennerally they may be popped if the source or gate 2 is above 2 Vdc.
DMTR-10 Relay and Monitor Board
Transmit monitor video level out is adjusted with the 5K pot on the bottom of the board. Reset to 1 Vp-p if you reset the RF power output.
It may work in your monitor if a linear amp is added. The 100K resistor test point can be used with a DC voltmeter for final RF peaking and
pedestal setting if a RF Watt meter is not available. The Trimmer cap C is peaked and need not be touched, do not detune this cap to
reduce power, it could blow the power module - use the RF power pot on the TXA5-70 board - see next page. The extra R and
+T pads can be used for controlling external devices by jumpering to the open power connector pins 3 or 4 (1/2 Amp max).
PA5 Power Module
board - no adjustments
DO NOT ADJUST ANY OF THESE BOARDS WITHOUT PROPER TEST EQUIPMENT AND EXPERIENCE
M57716 Power Module
To TXA5
PTL
T
R
Monitor video out
To Power on Switch
To TVC-2G +
To FMA5 +
To TXA5 T+
TX Lamp
To Video gain pot CCW
To TVC-2G In
Antenna N
Connector
RF Power out test
point >-10Vdc
33K
33 pF
Antenna
C
100K
+T
10 pF
+
+
+
+
10 mF
10 mF
10 mF
10 mF
5K
Video
Level
adjust
22K
33K
1K
2 2 0
.5 W
2N2222A
1N5711
Monitor
Video
out
+13.8
PTL
To PA5
To
TVC-2G
+R
4.5 MHz
Trap
To PA5
To FMA5
To TXA5
r e l a y
r e l a y
r e l a y
video
power
1 2 0
RF
Test
Point
-Vdc
+
10 mF
DMTR70-10
(c) 1998
video in
Band
Spread
. 0 0 1
C1
+
+
+
75 Ohm
50 Ohm
( 2 )
C3
C2
+8V
+8V
+11 to
14 Vdc
10mF
1mF
.3V
.8V
1V
1V
. 0 1
NE253
Preamp
NE253
M i x e r
1 0 0
1N914
1 0 0
. 0 1
1 5
2 2
Ch3 out
. 4 7
. 0 1
2 2 0
1K
L1
L3
4 7 0
6.5V
70 CM
Antenna
Input
2 2 0
. 0 1
10K
3.3K
10K
MV2105
C4
1
5
1K
MPSH81
OSC
353 - 394 MHz
10K
Varicap
Tuning
+8V
6V
2 2 0
0 to 8 V
1mF
1K
4 7
4 7
AGC
2N2222
. 0 0 1
1 0 0
3.3K
2.2K
1 0 0
10K
e x t
1N4745
. 1
1 0 0
TVC-2G rev F 70 CM
ATV Downconverter
(c) PC Electronics 1998
G1
G2
L2
G1
G2
78L08
8V reg
16Vz
4 7 0
Lo Z
Mic
input
+
+
+
+
Line
Audio
input
10K
10K
10K
1K
1K
470 pF
1 0
1 0
10Kt
5.6K
50K
Mic Gain
22K
15K
.01
100K
4.7K
1N914 (2)
1
2
3
4
5
6
7
8
10K
10K
10K
10K
1 0
+
1
1
4 7 0
pF
4 7 0
pF
MV
2 1 1 5
18uH
Tune
4 5 0 0
kHz
4 7 0
pF
4 7 0
pF
1 2 0
pF
10uH
2N2222
Inj.
Level
.01
1 0
+
Dev.
adj.
TLO82CP
Mic Amp
Audio Amp
VCO
Buffer
+11 to
15 Vdc
+ 1 1 6
Vz
+8 Vreg
4.6Vdc
75uS
Pre-emphasis
4.5 MHz
Output
470 pf
MPF102
1K
5 0 0
1 0 0
4 7 0
4 7 0
pF
C1
FMA5-F2 ©1998
P.C. Electronics
78L08
8V reg
RG-174
pin 1
+13.8
pin 2
5 A
16 Vz
1N5353B 5W
To +
DMTR