Yaesu FT DX 9000 CONTEST - 2, Руководство по эксплуатации

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Page 51 FT
DX
9000 C
ONTEST
O
PERATION
M
ANUAL
IPO
(
I
NTERCEPT
P
OINT
O
PTIMIZATION
)
Normally, the front-end FET RF amplifiers provide maximum sensitivity for weak signals. During typical conditions on lower frequen-
cies (where strong signals and high noise are common), the RF amplifiers can be bypassed by pressing the IPO button so that the
button’s illumination is lit. This improves the IMD (intermodulation distortion) rejection characteristics of the receiver, with only a
slight reduction of sensitivity. On frequencies below about 10 MHz, you generally will want to keep the IPO button engaged at all times,
as the preamplifiers are usually not needed at these frequencies unless you are using a Beverage or other lossy receive antenna.
Quick Note
The FT
DX
9000 Contest’s first mixer is an active type, using four SST310 Junction FETs. This mixer design provides gain to the
receiver chain, so the noise figure of the receiver is fundamentally lower than with some other designs. Therefore, it frequently
is not necessary to utilize the RF preamplifier, and the receiver Intercept Point will be substantially increased by engaging IPO,
so as to feed the incoming signals directly to the first (active) mixer. We recommend that IPO be switched on whenever possible.
VFO-A IPO Setup
Press the VFO-A side’s -IPO switch key (# ) to
engage the IPO on the VFO-A.
A Red LED imbedded in the switch will light up, and the
preamplifier for the VFO-A will be bypassed. The system
gain and sensitivity will be reduced.
To cancel IPO operation and restore full system gain and
sensitivity, press the
-IPO switch key once more.
VFO-B IPO Setup
Press the VFO-B side’s -IPO switch key (# ) to
engage the IPO on the VFO-B.
An Orange LED imbedded in the switch will light up, and
the preamplifier for the VFO-B will be bypassed. The sys-
tem gain and sensitivity will be reduced.
To cancel IPO operation and restore full system gain and
sensitivity, press the
-IPO switch key once more.
VFO-B
-IPO switch
VFO-A
-IPO switch
C
ONVENIENT
F
EATURES