Disclaimer:All mods given in good faith
and will not be held responsible for any
loss,damage or any other act incurred
User carry out mods at OWN risk and must have some
Technical know how and experiance.Test equipment will be required will
to align radio correctly.

Refer to schematics web link http://www.cbtricks.com/radios/crt/ss_3900/index.htm

Narrow Narrow FM Detector
TX FM Modulator

*IF REQUIRED
V2.2 F 1 F
-Less Bass response
Do not use anything lower
than 1uF,as circuit will not
have enough drive level to
function correctly
as a Audio Clipper.

FM Deviation set @2.00khz max (26.965mhz)
Mic Gain on radio MAX
Input 50mV RMS 1Khz test tone Input at microphone socket

check speech peaks should not exceed 2.5khz!!

C28 1nF (102) change to 10nF (103)

TX Side
Improves FM Audio punch and drive
to give you clear punchy FM Transmit Audio
Value changes help with improving the FM Waveform
to more a square wave and adds so Pre-Emph on wave form transmitted.
NOTE:Not shown on digarms R174-10K MUST BE CHANGED TO 1K resistor

T
R55 47K

RX Side

Improves FM-Narrow quieting-Less backgound hiss
Using the 12K resistor across L5 helps to reduce audio level to drive AF pre-amp stage correctly.
R24 reistance value prodvided a better drive level and reduced hiss
Values selected will also give better compatability with Multi-Norm CB sets using Super Narrow FM mod.

DET.IN(+)

DET.IN( )

+8V D

How to improve your SS-3900\Galaxy Super Narrow FM Mode

R65
68K

1

From IC4 A Pin 1
SEE NOTE R174

3

R2
6K8

22

68 F

F L4/21

3

1

Version:SS3900/GALAXY DX SERIES

6

2

5 5

4

**ADD-12K decrease and dampen audio

CHOOSE which one best suits operation needs in locality
Narrow Fm deviation System 12K ohms is DEFAULT Value

7

0R L

126

R160

1 F 10V

R34-1M5 change to 220K

30 V R S 1.2 D
50mV RMS Audio@2.00khz Deviation
50uV PD AT ANTENNA SOCKET

2

R34

Change Value-6K8 to 10K wire link
-Improve clipping Waveform symmetrically

R123
10

D 10
*OPTION
LTGW +/
LTHT FL1F

10 F

27
103/

4.7 F

28

7
OUTPUT

+
26
47 F 10V

R32
100R

R33
1K

25
15P/ H

Peak L5 coil @60% dev

I 1
UP 1028
SIL

V

3

4

GND

INPUT

2

BY PSS

1

maxium AF Audio of 5.0V RMS or greater at 60% Mod level
at speaker terminals into 8ohm resistive load.
5khz max deviation input on headroom
Audio Distortion 5% or better (typ 1%-2%)
@50uV pd input to radio antenna socket

RV5
10K

D :3001 2018
Remove 22K value wromg on text

Square clipped Audio @30-50mV RMS
input
at microphone socket 1Khz test tone
Set RV-5 2.00khz MAX
D 15KHZ LPF
MIC Gain on Radio MAX

NOTE A:
Multi-Norms FM CB
12K Resistor chosen for 1.2khz dev=60%
10K Resistor chosen for 1.5khz dev=60%Ham NFM

+8V In FM Mode

220K

1

1

6

**
See Text Note A

5

Change Value-15K to 0R wire link
I