Yaesu FT-7900R, Technical Supplement

Page: 10 / 50

FT-7900R/E Technical Supplement
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 20 °C and 30 °C. When the transceiver
is brought into the shop from hot or cold air it should be
allowed some time for thermal equalization with the en-
vironment before alignment. If possible, alignments
should be made with oscillator shields and circuit boards
firmly affixed in place. Also, the test equipment 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-7900R/E 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 while turning
the radio on.
2. Rotate the
DIAL
konb so select menu “
F-8 NOR / CH
.”
3. Press and hold in the [ BAND
(
SET
)] key for 1/2 sec-
ond. The radio is turned off automatically, and then
switched on again afterwards.
4. Press and hold in the [ PWR
( )] switch for 1/2 sec-
ond to turn the radio off.
5. Press and hold in the [
V/M
(
MW
)] key while turning
the radio on. The display
will be show in the illus-
tration at the right.
6. Press and hold in the [ PWR
( )] switch for 1/2 sec-
ond to turn the radio off.
7. Press and hold in the [
MHz
(
PRI
)] key and the Hyper
Memory [ 5
] key while turning the radio on.
8. 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
)]
9. Press and hold in the [
(
L
)] key to cause “
A-0 REF.xxH
”
to appear on the display, this signifies that the trans-
ceiver is now in the “Alignment mode.”
PLL Reference Frequency
1. Rotate the DIAL knob to set the display to “
B4006
”,
then set the Transmit Power Level to “LOW” by press-
ing the [
LOW
(
ACC
)] key repeatedly.
2. Press the [ BAND
(
SET
)] key while pressing and hold-
ing in the [
(
L
)] 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
[ (
L
)] key, if needed, so that the counter frequency
reading 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. Rotate the DIAL knob to set the display to “ B4906 ”.
3. Press the [ BAND
(
SET
)] key while pressing and hold-
ing the [
(
L
)] key to set the Alignment parameter to
“
A-1 TUN.xxH
”.
4. Adjust the DIAL knob while pressing and holding in
the [
(
L
)] key, if needed, so that the DC voltmeter
reaches maximum deflection. The FT-7900R/E ’s RF
Front-end has a broad bandwidth.
5. Press the [ BAND
(
SET
)] key, then rotate the
DIAL knob
to set the display to “
B0106
”.
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 [
(
L
)] 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