Yaesu FT-7800R, Техническое дополнение

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Alignment
Alignment Preparation & Precautions
A dummy load and inline wattmeter must be connected
to the main antenna jack in all procedures that call for
transmission, except where specified otherwise. Correct
alignment is not possible with an antenna. After complet-
ing one step, read the following step to determine wheth-
er the same test equipment will be required. If not, re-
move the test equipment (except dummy load and watt-
meter, if connected) before proceeding.
Correct alignment requires that the ambient temperature
in the repair shop be the same as that of the transceiver
and test equipment, and that this temperature be held
constant between 68 °C and 86 °F (20 °C ~ 30 °C). When
the transceiver is brought into the shop from hot or cold
air it should be allowed some time for thermal equaliza-
tion with the environment before alignment. If possible,
alignments should be made with oscillator shields and
circuit boards firmly affixed in place. Also, the test equip-
ment must be thoroughly warmed up before beginning.
Notes : Signal levels in dB referred to in alignment are
based on 0 dBµ = 0.5 µV (closed circuit).
Entering the Alignment mode
Alignment of the FT-7800R is performed using a front-
panel software-based procedure. To perform alignment
of the transceiver, it must first be placed in the “Align-
ment Mode,” in which the adjustments will be made and
then stored into memory.
To enter the Alignment mode:
1. Press and hold in the [ MHz
(
PRI
)] key and the Hyper
Memory [ 5
] key while turning the radio on. Once the
radio is on, release these two keys.
2. Press the front panel keys in the following sequence.
[
MHz
(
PRI
)]
[ TONE
(
HM/RV
)] [
LOW
(
ACC
)]
[
BAND
(
SET
)]
[ V/M
(
MW
)]
[
SCAN
(
SEL
)]
[ S.SCH
(
ARTS
)]
3. Press and hold in the [
] key to cause “
A-0
REF.xxH ” to appear on the display, this signifies that
the transceiver is now in the “Alignment mode.”
PLL Reference Frequency
1. Tune the frequency to 435.050 MHz, then set the Trans-
mit Power Level to “LOW.”
2. Press the [ BAND
(
SET
)] key while pressing and hold-
ing in the [
] key, if needed, to set the Alignment
parameter to “
A-0 REF.xxH
.”
3. Press the PTT switch to activate the transmitter, and
adjust the DIAL knob while pressing and holding the
[ ] key, if needed, so that the counter frequency read-
ing is 435.050 MHz (±100 Hz).
RF Front-end Tuning
1. Connect the DC voltmeter to TP1010 on the MAIN
Unit, then inject a 439.050 MHz signal at a level of +10
dBµ (with 1 kHz modulation @±3.5 kHz deviation)
from the RF Signal Generator.
2. Tune the frequency to 439.050 MHz.
3. Press the [
BAND
(
SET
)] key while pressing and hold-
ing the [
] key to set the Alignment parameter to
“
A-1 TUN.xxH
.”
4. Adjust the DIAL knob while pressing and holding in
the [
] key, if needed, so that the DC voltmeter
reaches maximum deflection. The FT-7800R’s RF
Front-end has a broad bandwidth. Therefore, prior to
adjustment you must adjust the
DIAL knob to set the
frequency to the middle of the band, in step 2, so you
can set peak in the DC voltmeter's deflection in the
center of the RF passband.
5. Tune the frequency to 145.050 MHz.
6. Inject a 145.050 MHz signal at a level of +10 dBµ (with
1 kHz modulation @±3.5 kHz deviation) from the RF
Signal Generator.
7. Adjust the DIAL knob while pressing and holding in
the [
] key, if needed, so that the DC voltmeter
reaches maximum deflection. As in the previous sec-
tion, be sure to set the
DIAL knob for the center of the
band prior to making this adjustment.
MAIN UNIT T
EST
P
OINTS
E-2
TP1010