User Manual

LX Series Power Am plifier Assem bly Chapt er 5, Detailed Alignm ent Procedures
LX Series, Rev. 0 5- 6
adjustments. The Trap Filter is
com prised of four trap sections
connected to the m ain transm ission line.
The Trap Sections are Reflective Notches,
adjustable across the entire UHF
Frequency Band. The electrical length of
the Outer Sleeve and the Center Rod of
the Notch can be adj usted to Tune the
Notch Frequency. The Depth of the
Notch is set by the gap between the
Center Conductor of the Trap Section and
the Center Conductor of the Main Line.
Tight Coupling makes a Deep Notch,
while Loose Coupling m akes a Shallow
Notch.
FI N E TUN I N G of the Notches Center
Frequency can be accomplished with the
Tuning Bolts located on the side of the
Filter Section. Loosen the nut locking the
Bolt in place and adjust the Bolt to
change the Frequency of the Notch.
Monitor the output of the Transm itter
with a Spectrum Analyzer and Null the
Distortion Product with the Bolt. Red
Field is a good Video Test Signal to use to
see the + 8.08 MHz Product. Tighten the
nut when the tuning is com pleted. Hold
the bolt in place with a screwdriver as
the nut is tightened to prevent it from
slipping.
MAJOR TUN I NG, such as changing the
Notch Depth or m oving the Notch
Frequency more than 1 MHz, the Outer
Conductor and the Center Conductor of
the Trap Section m ust both be m oved.
This requires a RF Sweep Generator to
accom plish. Apply the Sweep signal to
the Input of the Trap Filter and monitor
the Output. Loosen the Clam p holding
the Outer Conductor in place and make
the length longer to Lower the frequency
of the Notch or shorter to Raise the
frequency of the Notch. Loosen the
Center Conductor with an Allen Wrench
and move it Deeper for a Lower
Frequency Notch or out for a Higher
Frequency Notch. These adj ustm ents
must both be m ade to change the Notch
Frequency. Moving only the Center
Conductor or the Outer Conductor will
effect the Notch Depth in addition to the
Center Frequency. The variable that is
being adjusted with this procedure is the
length of the Center Conductor inside the
Trap Filter. The gap between the Trap
and the Main Line should not be changed.
Moving only the I nner or the Outer
Conductors by itself will effect the Gap
and the Notch depth.
To effect the Notch Depth Only, both
sections will have to be m oved. The
Notch Depth is controlled by the Gap
between the Center Conductor and the
Trap Section. This Gap also has an effect
on the Center Frequency. To Deepen the
Notch, Short en the Outer Conductor and
pull the Center Conductor Out until the
Notch is back in the sam e place. Move
the Sections in the opposite direction to
make a Shallow Notch. NOTE: THE
TRAP FILTER I S TYPI CALLY ADJUSTED
FOR A NOTCH DEPTH OF 10 dB.
5 .4 .1 The Effect s of Tuning the
Out put Tra p Filt er
Lengthening Outer Conductor Only -
Notch Frequency Up, Shallower Notch.
Shortening Outer Conductor Only - Notch
Frequency Down, Deeper Notch.
Inserting Inner Conductor Deeper - Notch
Frequency Down, Deeper Notch.
Inserting Less Inner Conductor - Notch
Frequency Up, Shallower Notch.
Tuning Bolt I n - Notch Frequency Down.
Tuning Bolt Out - Notch Frequency Up.
Moving both Inner and Outer Conductors
to keep the Sam e Gap inside - Center
Frequency Moves, Notch Stays t he Sam e.
After tuning has been completed, tighten
the Clam p and the Allen Screws that hold
the Conductors. Use the Fine Tuning
Bolts to bring the Frequency In. The
Final Tuning Adjustm ents should be
com pleted with the Transm itter driving