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Page: 16 Of 57
Model No: 3420
Drawing No:
Customer :
Model No:
H 520 PLUS
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PLL CIRCUIT BLOCK DIAGRAM
1. INTRODUCTION
The frequencies for transmitter and receiver first local frequencies are all derived from a single 10.240 MHz
crystal by means of a phase locked loop. The first local oscillator frequencies are 16.270 MHz (CH 1) to 16.710
MHz (CH 40) for EU and 16.90625 MHz (CH 1) to 17.29625 MHz (CH 40) for UK. The second local frequency is
fixed at 10.240 MHz to generate second IF 455 KHz. During transmit, The VCO of the PLL operates 13.4825 MHz
(CH 1) to 13.7025 MHz (CH 40) for EU, 13.800625 MHz (CH 1) to 13.995625 MHz (CH 40) for UK the VCO
frequency goes to the double circuit Q201, T203, T204 which doubles the frequency to generate 26.965 MHz (CH
1) to 27.405 MHz (CH 40) for EU and 27.60125 MHz (CH 1) to 27.99125 MHz (CH 40) for UK
13.4825 MHz
(CH 1) EU
26.965 MHz (CH 1)
13.7025 MHz
(CH 40) EU
27.405 MHz (CH 40)
13.800625
MHz (CH 1) UK
27.60125 MHz (CH 1)
13.995625 MHz (CH 40) UK 27.99125 MHz (CH 40)
The VCO operating frequency for the receiver is 16.270, 16.90625 MHz (CH 1) to 16.710, 17.29625 MHz (CH 40)
as the first local oscillator, injected through the buffer AMP Q302 into the first fed balanced mixer Q102, Q103.
Q 201
VCO
T203,T204
Doubler
To Transmitter
