Kenwood TR 851 E Service Manual

Page 2

TR-851A/E

CIRCUIT DESCRIPTION

MODEL NAME -
TR-SSIA (K. M) Tn-asI e (T, wl
UNIT NAME
FINAL UNIT X45-3030-l1 X45-3030-51
CAR UNlT xsoaowoo xso-aowoo
COMPOSITE UNIT (PLL, DRIVE, FRONT) XSO-BOSO-il xeo-aoso II
X5314w52lTl
NT u I xsa-Iaswz
CO "0'- T x53-14w621wl
COMPOSITE UNIT IRXI xso-iazo-m XGD-IBZDAOI
Table 1 TR-astA/E Pc board chm
D _ , Fr u. lMHzl VFO step lkHzl TX OFFSET Repeater Tone . .'
"""'°" N "W FM ssa DISPLAY shift (kill) mm
KTM 430,o~ 325:3; it: _ : :155 r7502): t
43939995 . - {a one we
w 12.5kHz 5kHz D-A o-e 1'5 I750 Tone

Table 2 Frequency configuration at destination

FREQUENCY CONFIGURATION

The TR-861A/E utilizes a PLL synthesizer system in-
corporating a digital VFO, which covers each band in
5,on steps. (See Fig. 1.)

Received signals are mixed with the first local oscillator
(388.585 to 398,585MH2) to produce the first intermediate
frequency of 41.415MH2. In 583 or CW, the receiver
operates as a double conversion system. The 10.695MHz
lF signal is mixed with the second local oscillator (30.72
MHz) to produce the second intermediate frequency of
10,695MH1. The 10,695MHZ IF signal is applied to crystal
filter XFI (L71-0249-05), and the signal is then applied

to the ring detector to obtain the audio output.
In FM, the receiver operates as a double conversion

system, The 10,695MHZ signal is mixed with the PLL re-
ference frequency of 10.24MH2 to produce the second
intermediate frequency of 455k H2.

The transmitter system operates as a double conversion
system. In 553 made, output from the carrier oscillator is
modulated by a balanced modulator to produce an inter-
mediate frequency signal, which is then mixed with the
first local oscillator signal to produce the two meter
transmit signal. The carrier oscillator circuit is controlled by
the microprocessor according to the selected mode.

During USB or CW receive, the carrier oscillator fre<
quency is 10.6935MH1. During LSB receive, it is 10.6965
MHzt During CW transmit, it is 10.6943MH1, ln FM. 3

10.695MHZ crystal oscillator frequency is Used that is
directly modulated and then mixed with the first local
oscillator signal.

To minimize internal heterodyne tones and spurs in the
frequency generator and analysis are controlled by a
microprocessor. The PLL-based frequency system consists
of two PLL synthesizer loops controlled by a 4vbit high-
speed microprocessor and a stable, analog RIT oscillator
circuit.

Flfin',

10.99sz

Within :20on at one
2.2kH2 or more at ads
Within 21 .5kHz at 20:15
Within :ZAkHz at 60dB
his or less

see or less

lurn
Nominal frequency
Allowable center trsq' deviation
Pass bandwidth and
attenuation handwldth
(based on minimum loss)
nipple
Minimum loss ,
Guaranteed attenuation was or more within mom:
I/o terminating impedance I.2kn:5%/50Ft5%

Table 3 Crystal filter 10F2.2$ (L71-0249-05) characteristic!
(Composit unit (RX) XF1)