Yaesu FT DX 9000D - COMPUTER AIDED TRANSCEIVER, Руководство по эксплуатации

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Page 61 FT
DX
9000D 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 frequencies (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 charac-
teristics 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
9000D’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.
Main (VFO-A) IPO Setup
Press the Main (VFO-A) side’s -IPO switch key
(# ) to engage the IPO on the Main (VFO-A) band.
A Red LED imbedded in the switch will light up, and the
preamplifier for the Main (VFO-A) receiver will be by-
passed. 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.
SUB(VFO-B) IPO Setup
Press the Sub (VFO-B) side’s -IPO switch key
(# ) to engage the IPO on the Sub (VFO-B) band.
An Orange LED imbedded in the switch will light up, and
the preamplifier for the Sub (VFO-B) receiver will be by-
passed. 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.
SUB(VFO-B)
-IPO switch
MAIN(VFO-A)
-IPO switch
C
ONVENIENT
F
EATURES