19
Pressurization and Startup
Step 2. Transmission
Line TDR Reading
With the transmission line still terminated in 50 ohms, make a time
domain reflectometer (TDR) plot. Label and file the plot with this man-
ual.
Step 3. System VSWR
Reading
You tested the VSWR of the transmission line alone. Now test the
VSWR of the system as a whole.
a. Remove the load and connect the transmission line to the trans-
former input, with an O-ring to seal the connection.
b. Repeat the purge process after sealing the line, in accordance with
Purging the System
on page 16.
c. Measure VSWR. VSWR at this point should be below 1.2 : 1.
d. Record the reading and file it with this manual.
If VSWR is not satisfactory, check to be sure all the radiators are func-
tioning (see below). If they are, call Shively Labs to help identify the
problem.
Step 4. Checking
Radiator Function
Again using the low-power test equipment to provide a signal to the
antenna and read VSWR, have the rigger detune each radiator in turn.
The simplest way to detune a radiator is to short across the "wings" or
dipole arms, for instance with a screwdriver or wrench.
Each time, a deflection in VSWR should be apparent. The deflection for
various bays should be similar, but not necessarily identical.
If the VSWR of the array does not change when a radiator is detuned,
that bay is not functioning. Check to be sure the radiator was installed
properly, including the inner conductor connector.
If you cannot find the problem, please call Shively Labs before pro-
ceeding.
Checkout
Before beginning checkout of the antenna system, be sure the follow-
ing items have been done:
• The antenna system has been installed in accordance with this man-
ual and the installation drawing.
• All radiators are operating and VSWR is within specification.
• The initial characterization data have been recorded.
• The system is gas-tight and purged.
Check the system out as follows:
a. Bring up RF power slowly and observe transmitter readings, stability,
and general operation.
b. Run at about half power for at least an hour, reading forward and
reflected power, stability, etc.
