Sencore CB42 User Manual

SSB TRANSMITTER
lIooIanc.
Control
-
-
"
Input
Fill. 19-5impli(ied SSB buklllced moduwlor.
The heart of an SSB transmitter i. a "Balanced Modu.
lator". The balanced modulator is a bridge ci~uit
with an audio input and an RF input. A simplified
balanced
modulator i$ sbown in Fig. 19 • The function
of the balanced modulatO!" is to produce both the
upper and lower sidebands when the audio modula.
ting signal and RF signal are inje<;wd at their ~spee·
tive inputs. The balance control is adjusted until the
RF carrier is completely canceled in the bridge.
Fig.
20 shows how the balanced modulator is used in
a typical
SSB tranamitter. This example typifies mOllt
SSB transmitters which use a frequency lower than
the carrier frequency to operate the balanced modu.
lawr. This simplifies the design of the balanced mod·
ulawr since it operates at a lower frequency.
upper and lower sidebands p~sent. To seled the pro-
per sideband, the output of the balanced modulator
is fed to a filter that removes the unwanted .ideband.
At this point. we have an SSB signal with a sup.
pressed carrier of 7.8 MHt. This signal is applied to
the input of the transmit mixer which opera/.e$ the
Jame as a receiver mixer except we are raising the
frequency instead of lowering it. The output of this
mixer
is the desired RF frequency.
The output of the transmit mixer is fed to several
stages
of linear amplification, Bnd finally to a low·
pass filter to eliminate any harmonic content that has
boon
created in the mixing processes. The output of
the filwr is fed to the anwnna for transmission.
The output of the balanced modulator has both the
t
"
Mcasu,e PEP F,.q.
Us. Scope Converte,
Mea.",e
F,equency
J
RF Volt.ge .. ~
RF TVI
Amp Filte'
I
••
USB AM LSB
....
Inject
Audio
24

Sencore CB42 Specifications

General

Brand	Sencore
Model	CB42
Category	Measuring Instruments
Language	English