Dealing With Interference; Front End Selection; Wide Band & Tuned Amp Selection - Yaesu FT-1000MP Operating Manual

Operation
Dealing with Interference
The FT-I OOOMP includes a wide range of spe-
cial features to suppress the many types of inter-
ference that may be encountered on the HF
bands. However, real world interference condi-
tions are constantly changing, so optimum setting
of the controls is somewhat of an art, requiring
familiarity with the types of interference and the
subtle effects of some of the controls. Therefore,
the following information is provided as general
guidelines for typical situations, and a starting
point for your own experimentation.
Front End Selections:
Amp Selection, A TT, /PO, & RF GAIN
you tune or change bands; however, you can
disable the tuned amplifier pair and only use the
wide-band amp via menu selection 8-4.
/PO (ln tercept Point Optimization)
Normally, the front-end FET RF amplifiers pro-
vide maximum sensitivity for weak signals. During
QRM conditions on lower frequencies (such as
strong overloading from signals on adjacent fre-
quencies), the RF amplifiers can be bypassed by
pressing the !PO button so the green LED is on.
This improves the dynamic range and IMD (inter-
modulation distortion) characteristics of the re-
ceiver, at a slight reduction of sensitvity.
The best receiver front-end selection will de-
ATT (RF Attenuator)
pend on background noise at the time, the pres-
ence or absence of strong signals, and whether or
not you want to hear very weak signals. If the front
end is set for too much gain, background noise
will make listening difficult, and very strong sig-
nals on other frequencies may cause intermodu-
lation interference, masking weaker signals. On
the other hand, if the front end is set for too little
gain (or too much attenuation), very weak signals
will not be heard.
Wide-Band and Tuned Amp Selection
Three high-performance FET RF amplifiers
are utilized in the FT-IOOOMP receiver front end.
A flat wide-band amp (factory default) is provided
for good general all-around performance along
with dual tuned amplifiers: one optimized for
24-30 MHz, the other for 1.8-7 MHz (see illustra-
tion). Each amplifier is selected automatically as
Bandpass
Filter Section
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
:
E]
22-30 MHz
1
1
m]
15-22 MHz
1
/
~ I Z - 1 5 M t i z
- 1
m i
8.58 MHz
i
4-6.5hVi.
i
F 1 3 4 M H z
i
i
m]
1.8-3 MHz
1
RJ
0 . ~ 1 . 8 MHZ
i
1
F]
o.,-0.5 .HZ'
*
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
8
Even with the IPO function on, very strong
signals can still overload the mixer. So if you still
,
notice intermodulation, or if the signals you want
to listen to are very strong, you can use the ATT
selector to insert 6, 12, or 18-dB of RF attenu-
ation in front of the RF amplifier. If background
noise causes the S-meter to deflect on clear
channels, turn the
A'TT
selector clockwise until the
S-meter drops below S-1 (the white area at the left
end of the top meter scale). This setting optimizes
the trade-off between sensitivity and interference
immunity. Also, once you have tuned in a station
you want to work, you may want to reduce sensi-
tivity further (or add more attenuation) by turning
the
ATT
control to a more clockwise setting. This
reduces the strength of all signals (and noise) and
can make reception more comfortable, important
especially during long QSOs.
bypass
I
RF Amp
..........................
Section
wide
............................
,
I
I
Tuned RFAmp
I
I
Sactim
I
I I
Receiver Front End Configuration
for illustrative purposes
page
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