If the 681XXB contains an Option 16
high-stability time base, connect the coax-
ial cable between the 681XXB rear panel
10 MHz REF OUT
connector and the 360B
rear panel
10 MHz REF IN
connector.
Step 3
Connect one end of a GPIB cable, 1 meter
in length, to the 681XXB rear panel
IEEE-
488 GPIB
connector. Connect the other
end of the cable to the 360B rear panel
SOURCE CONTROL SYSTEM BUS
con-
nector.
Step 4
Turn on the 681XXB and configure it as
described in the following paragraphs.
Modes of
Operation
There are two 360B VNA receiver modes of opera-
tion that are used with the 681XXB—the 360B
source lock mode and the 360B tracking mode. The
configuration and operation of the 681XXB for both
modes of operation are described in the following
paragraphs.
Source Lock
Mode
When operating in source lock mode, the 360B
phase locks the frequency output of the 681XXB.
This is accomplished by sending a dc control voltage
to the FM input on the 681XXB. Due to the inher-
ent resolution of the 360B’s synthesized local oscilla-
tors, frequency resolution is limited to 100 kHz
intervals.
Source Lock Mode Configuration
In order for the 681XXB to operate with a 360B in
source lock mode, the sweep generator must be
placed in the SS Mode of operation.
To place the sweep generator in SS Mode, first press
the main menu key
SYSTEM
. At the System Menu
display, press
Config
. The System Configuration
Menu (below) is displayed.
USE WITH
USE WITH A 360B VECTOR
OTHER INSTRUMENTS
NETWORK ANALYZER
681XXB OM
7-13
