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Opposite sideband suppression
Figure 127. Adjustment points for nulling out the opposite sideband
The adjustment is very straight forward. First a strong, steady signal source is required. Some examples
of signal sources are:
-
A RF signal generator. For this purpose, a setting of –50 dbm is ideal.
-
A crystal oscillator loosely coupled into the front end (1 to 2 pf in series). QRP crystals are
available from a number of sources including Norcal.
-
A marker generator such as the one available from Norcal.
-
A QRP transmitter transmitting at minimum power into a dummy load produced a very strong
signal that can be readily picked up using a 1 inch "sniffer" stub of wire connected to the antenna
port of the NC2030.
RECEIVER!
-
Over the air signals can be used, but these are usually neither strong nor consistent.
Before the alignment is started, listen to the signal on both sidebands. The weaker sideband will be the
USB signal that we are going to suppress. When we first start, it will not be weaker by very much.
Tune the receiver back and forth and try to place the signal in the middle of the audio pass band. This
will be at about 550 to 600 Hz.
Next, adjust the phasing adjustment trim cap to null out this signal as much as possible.
DO NOT TRANSMIT DIRECTLY INTO THE FRONT END OF THE
Norcal NC2030 v5
Page 102 of 128
12-18-05
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