Yaesu FT-901DM Instruction Manual page 16

improvement in sign al-to-noise rati o .
selec tivity of the APF circui t may be varied
by adjusting VR501 under the top cover.
(7) For ex tremely strong sign als, the ATT (RF
attenuator) switch may be pressed to activate
a 20 dB attenuation of the incoming signal .
This should preven t any chance of overload
of the receiver front end .
TRANSMITTER TUNE-UP
The following tune-up p rocedure must be per­
formed p rior to c ommencing operation on the
desired mode : LSB , U S B , CW, F S K , AM , or FM .
See the. paragraphs relating to the spe cific mode
after b asic tran smitter tune-up is describ ed.
Connect a dummy load or matched antenna to
the coaxial fit ting on the re ar apron. Preset the
controls as foll ows :
POWE R . . . . . . . . OFF
HEATER . . . . . . . OFF
CARR . . . . . . . . . Fully c ounter-clockwise position
MIC GAIN . . . . . . Fully c ounter-clockwise p osition
AMGC . . . . . . . . . OFF
METER switch . .IC
SELECT . . . . . . . VFO (Depre sse d)
BAN D . . . . . . . . . Desired b an d segment
MODE . . . . . . . . . USB or LSB
PLATE . . . . . . . . Desired b an d segment
PRESELECT . . . . Desire d b an d segment
LOADING . . . . . . To p osition shown in table
P ROC . . . . . . . . . OFF (Not d epressed )
TUNE . . . . . . . . . OFF (Not depresse d )
C LAR TX . . . . . . OFF (Not depresse d )
VOX GAIN . . . . . PTT position
Turn the POWE R and HEATER switches to ON .
From a cold start , allow 6 0 seconds after the
HEATER swi tch is turned on for warm-up of the
transmitter tubes. Be certain that the accessory
plug is inserted in the accessory plug is inserted
in the accessory socket ; without this plug being
so c onnected , there will be no power applied to
the tube heaters. Heater vol tage is supplied through
pins I and 2 of the accessory socke t .
LOADING POSITIONS
The
BAND
1 6 0
8 0
40
2 0
1 5
IOA
I OB
I OC
I OD
Note : LOADING positions are nominal. Minor
variations from position s shown are to
be expecte d .
Set t h e V O X GAIN control t o MOX. The meter
will n ow read final amplifier resting cathode
curren t . This sh ould re ad . 0 5 (5 0 mA). * If it is
not, adjust the bias control located under the top
cover near the rear of the se t . Set the METER
switch to ALC and adjust the ALC control under
the top c over for full scale deflection of the me ter.
Return the meter swi tch to I C and the VOX GAIN
control to PTT .
*No te : On
current should b e . 0 2 5 ( 2 5 mA).
PRE-TUNING
(IMPORT ANT
tuning utilizes the TUNE button inste ad of MOX
for actuating the transmitter. When p resse d , the
TUNE button causes the transmitter to be acti­
vated for ten second s, after which tim e the FT-
90 I DM returns to the receive condition . This is
a protective feature that should n o t be nullified
by u se of the MOX con trol . )
( I ) Adj ust the PRESELECT control for m axi­
mum receiver n oise level .
( 2 ) Depress the TUNE button . R otate the CARR
control un til the meter re ading rises just
ab ove the n ormal idling curren t of . 0 5 ( 5 0
mA) .
(3 ) Adjust the PRES ELECT c on trol for a maxi­
mum m e ter indication .
Caution : if t
mA) reduce the setting of the CARR control.
-14-
POSITION
5
4
3 . 5
3
2 . 5
3
3
3
3
t h e FT-90 1 S D , resting
NOTE : Subsequent
�
e m e ter reading exceeds . 1 ( 1 00
cathode
transmitter