Automatie Tuning - JRC JRL-2000F Service Manual

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(3)SWR Detector Circuit
Vf and Vr detected by the outputpower detectorcircuit of CFG-111 are compared by
comparator IC15. ·
When the VSWR value which is a ratio of Vf to Vr, exceeds 3.5, No.4 pin of IC15
becomes Low Ievei to inform CPU of the SW_R alarm (A8).
On the other hand, Vf and Vr are applied to the SWR operating circuit made up of
IC14, IC17 and peripheral parts. The calculated SWR is indicated in the voltmeter on
the front panel.
The circuit made up of IC15, CD6, R54, R55 and C67 holds the peak of Vf.
Data selector IC of IC1 0 selects signals which are connected to the front panel meter.
Camparator IC16 which has an outputterminal (No.8 pin) compares Vf with the refer-
ence voltage adjusted by the variable resistor RV1. lf Vf exceeds the reference volt-
age, an ALC voltage is generated.
The ALC voltage moves the pointer of the voltmeter via diode CD5 and it is inversely
amplified to a negative voltage by IC17 oparational amplyfier and then sent to the
exciter.
(4)Frequency Measurement Circuit
The RF signal from the exciter, which is detected by the CSC-433 antenna switch
circuit, is applied to J41 0, and is then amplified by transistor TR2.
The signal is wave-shaped to the reetangular Wave by the IC23 two-stage buffer
amplifier.
After the divider of IC11 divides this signal ten times, it is applied to the timer IC of
IC4.
IC4 is controlled by CPU and measures frequency of the exciter output signal by
counting this signal.
2. 7 Automatie Tuning
The CDJ-1143 control CPU of the JRL-2000F automatically tunes the antenna by
controlling relays of the CFG-111 matehing circuit according to the program written to
ROM1. ,
SET and TUNE operations will be described here.
(1 )SET
When the SET switch is pressed, No.11 pin (SELBK) of the CDJ-1143 control J3
changes to Low Ievei and requires power from the exciter.
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