Model No: 3390 Drawring No:
Customer :
Title
M-490 Plus
Rev,Date:
2. BASIC SYNTHESIZER SCHEME
The crystal frequency (4.500 MHz) is divided by 1800 times to make 2.5 KHz which is fed to one side of
the phase detector. The VCO output is divided by a programmable divider, and fed to other side of the
phase detector Pin 75 of IC101. The feedback loop is closed by passing the phase detector output
through an active low pass filter and using the output to control the VCO frequency through varicap
diode D402
Under locked conditions, both of phase detector input signal must be indential at 2.5 KHz. The VCO
frequency is then given by:
FVCO / N = 0.0025 MHz or FVCO = 0.0025 x N MHz
Since “N” is an integer, the VCO frequency can be stepped up with 2.5 KHz increments. By suitable
choice of “N” the desired output frequency can be obtained.
Channel 1 Channel 40
N FVCO N FVCO
Function
Transmit 5393 13.4825 5481 13.7025
Receive 6508 16.2700 6684 16.7100
EU
Transmit 5520.25 13.800625 5598.25 13.995625
Receive 6762.50 16.90625 6918.5 17.29625
UK
(SEE TABLE FOR OTHER CHANNELS)
Created by: Approved by: Rev.No:
For Stage: Release Date: Page: 18 / 61
To Next Page
Loading...
