Vertex Standard VXA-200, Service Manual

Page: 9 / 28

9
Alignment
Introduction
The
VXA-220
is carefully aligned at the factory for the
specified performance across the Aircraft and Weather
bands. Realignment should therefore not be necessary
except in the event of a component failure.
The following procedures cover the adjustments that are
not normally required once the transceiver has left the
factory. However, if damage occurs and some parts sub-
sequently are replaced, realignment may be required. If a
sudden problem occurs during normal operation, it is like-
ly due to component failure; realignment should not be
done until after the faulty component has been replaced.
We recommend that servicing be performed only by au-
thorized Vertex Standard service technicians who are ex-
perienced with the circuitry and fully equipped for re-
pair and alignment. If a fault is suspected, contact the
dealer from whom the transceiver was purchased for in-
structions regarding repair. Under no circumstances
should any alignment be attempted unless the normal
function and operation of the transceiver are clearly un-
derstood, the cause of the malfunction has been clearly
pinpointed and any faulty components replaced, and re-
alignment determined to be absolutely necessary. Prob-
lems caused by unauthorized attempts at realignment are
not covered by the warranty policy
Vertex Standard reserves the right to change circuits and
alignment procedures, in the interest of improved perfor-
mance, without notifying owners.
The following test equipment (and familiarity with its use)
is necessary for complete realignment. While most steps
do not require all of the equipment listed, the interactions
of some adjustments may require that more complex ad-
justments be performed afterwards. Do not attempt to
perform only a signal step unless it is clearly isolated elec-
trically from all other steps. Have all test equipment ready
before beginning, and follow all of the steps in a section
in the order presented.
Correction of problems caused by misalignment result-
ing from use of improper test equipment is not covered
under the warranty policy.
Required Test Equipment
ˆ
Radio Tester with calibrated output level at 200 MHz
ˆ
In-line Wattmeter with 5 % accuracy at 200 MHz
ˆ
50 Ohm, 10 W RF Dummy Load
ˆ
Regulated DC Power Supply adjustable from 3 to 15
VDC, 2 A
ˆ
Frequency Counter: ±0.2 ppm accuracy at 200 MHz
ˆ
AF Signal Generator
ˆ
AC Voltmeter
ˆ
DC Voltmeter: high impedance
ˆ
VHF Sampling Coupler
Alignment Preparation & Precautions
A 50 Ohm RF load and in-line wattmeter must be con-
nected to the main antenna jack in all procedures that call
for transmission, except where specified otherwise. Cor-
rect alignment is not possible with an antenna. After com-
pleting one step, read the next step to see if the same test
equipment is required. If not, remove the test equipment
(except dummy load and wattmeter, if connected) before
proceeding.
Correct alignment requires that the ambient temperature
be the same as that of the transceiver and test equipment,
and that this temperature be held constant between 20 -
30 °C (68 - 86 °F). When the transceiver is brought into the
shop from hot or cold air, it should be allowed some time
to come to room temperature before alignment. Whenev-
er possible, alignments should be made with oscillator
shields and circuit boards firmly affixed in place. Also,
the test equipment must be thoroughly warmed up be-
fore beginning.
Set up the test equipment as shown below for transceiver
alignment, apply 7.2 VDC power to the transceiver.
Notes : signal levels in dB referred to in alignment are
based on 0 dB μ = 0.5 μ V (closed circuit).
F