T855 Circuit Operation
B2.11
Copyright TEL
2.11
VCO
(Refer to the VCO circuit diagram in Part E.)
The VCO transistor (Q1) operates in a common emitter, and uses a transmission line res-
onator (TL1). The transmission line is used in a two port configuration with varicaps
positioned at one end. The VCO control voltage from the loop filter (IC750) is applied to
the varicaps (D1 & D2) to facilitate tuning. The VCO output is coupled into a cascode
amplifier stage (Q2 & Q3) which su10dBm (nominal) output. Further amplifica-
tion in Q5 brings the output drive level to +20dBm to drive the mixer.
A low level "sniff" is taken from the input to Q5 to drive the divider buffer to the synthe-
siser (IC740).
The VCO operates at the actual frequency required by the first mixer, i.e. there are no
multiplier stages.
The VCO frequency spans from either 355-395MHz, 395-435MHz or 435-485MHz
according to product type (refer to Section 1.4). The VCO is tuned to 45MHz below the
desired receive frequency (low side injection) to produce a 45MHz IF signal at the out-
put of the mixer.
Summary of Contents for T850 II Series
Page 12: ...12 M850 00 31 09 98 Copyright TEL...
Page 14: ...AII M850 00 31 09 98 Copyright TEL...
Page 20: ...A2 4 Mechanical M850 00 31 09 98 Copyright TEL...
Page 26: ...BII M850 00 31 09 98 Copyright TEL...
Page 28: ...B1 2 T855 General Information M850 00 31 09 98 Copyright TEL...
Page 40: ...B1 14 T855 General Information M850 00 31 09 98 Copyright TEL...
Page 42: ...B2 2 T855 Circuit Operation M850 00 31 09 98 Copyright TEL...
Page 68: ...B4 2 T855 Functional Testing M850 00 31 09 98 Copyright TEL...
Page 74: ...B4 8 T855 Functional Testing M850 00 31 09 98 Copyright TEL...
Page 94: ...B5 20 T855 Fault Finding M850 00 31 09 98 Copyright TEL...
Page 96: ...B6 1 2 T855 PCB Information M850 00 31 09 98 Copyright TEL...
Page 102: ...B6 2 2 T800 04 0000 RSSI PCB Information M850 00 31 09 98 Copyright TEL...
Page 108: ...B6 3 2 T855 PCB Information M850 00 31 09 98 Copyright TEL...
Page 115: ...IPN 220 01396 02 M850 00 T855 PCB Information B6 3 9 Copyright TEL 31 09 98...
Page 122: ...IPN 220 01396 02 B6 3 16 T855 PCB Information M850 00 31 09 98 Copyright TEL...
Page 124: ...CII M850 00 31 09 98 Copyright TEL...
Page 126: ...C1 2 T856 857 General Information M850 00 31 09 98 Copyright TEL...
Page 140: ...C1 16 T856 857 General Information M850 00 31 09 98 Copyright TEL...
Page 154: ...C2 14 T856 857 Circuit Operation M850 00 31 09 98 Copyright TEL...
Page 170: ...C4 2 T856 857 Functional Testing M850 00 31 09 98 Copyright TEL...
Page 176: ...C4 8 T856 857 Functional Testing M850 00 31 09 98 Copyright TEL...
Page 198: ...C6 1 2 T856 857 PCB Information M850 00 31 09 98 Copyright TEL...
Page 204: ...C6 2 2 T856 PCB Information M850 00 31 09 98 Copyright TEL...
Page 220: ...C6 3 2 T857 PCB Information M850 00 31 09 98 Copyright TEL...
Page 232: ...IPN 220 01398 02 C6 3 14 T857 PCB Information M850 00 31 09 98 Copyright TEL...
Page 234: ...DII M850 00 31 09 98 Copyright TEL...
Page 236: ...D1 2 T858 859 General Information M850 00 31 09 98 Copyright TEL...
Page 248: ...D2 2 T858 859 Circuit Operation M850 00 31 09 98 Copyright TEL...
Page 256: ...D3 2 T858 859 Initial Adjustment M850 00 31 09 98 Copyright TEL...
Page 264: ...D3 10 T858 859 Initial Adjustment M850 00 31 09 98 Copyright TEL...
Page 266: ...D4 2 T858 859 Fault Finding M850 00 31 09 98 Copyright TEL...
Page 282: ...D5 1 2 T858 859 PCB Information M850 00 31 09 98 Copyright TEL...
Page 288: ...D5 2 2 T858 PCB Information M850 00 31 09 98 Copyright TEL...
Page 293: ...IPN 220 01141 01 M850 00 T858 PCB Information D5 2 7 Copyright TEL 31 09 98...
Page 298: ...IPN 220 01141 01 D5 2 12 T858 PCB Information M850 00 31 09 98 Copyright TEL...
Page 300: ...D5 3 2 T859 PCB Information M850 00 31 09 98 Copyright TEL...
Page 305: ...IPN 220 01159 01 M850 00 T859 PCB Information D5 3 7 Copyright TEL 31 09 98...
Page 312: ...EII M850 00 31 09 98 Copyright TEL...
Page 316: ...E2 2 T850 VCO PCB Information M850 00 31 09 98 Copyright TEL...
Page 328: ...G1 4 T855 Link Selectable Features M850 00 31 09 98 Copyright TEL...
Page 332: ...G2 4 T856 857 Optional Features M850 00 31 09 98 Copyright TEL...
Page 334: ...G3 2 Talk Through Repeater M850 00 31 09 98 Copyright TEL...
Page 340: ...HII M850 00 31 09 98 Copyright TEL...
Page 356: ...I II M850 00 31 09 98 Copyright TEL...
Page 358: ...I1 2 Tools Required M850 00 31 09 98 Copyright TEL...
Page 366: ...I2 8 T855 856 857 SII SI Conversion M850 00 31 09 98 Copyright TEL...
Page 370: ...I3 4 T858 859 SII SI Conversion M850 00 31 09 98 Copyright TEL...