C
C
C
CIIIIRCU
RCU
RCU
RCUIIIIT
T
T
T D
D
D
DES
ES
ES
ESCR
CR
CR
CRIIIIP
P
P
PTIO
TIO
TIO
TION
N
N
N
1
1
1
1.... F
F
F
Frrrre
e
e
equ
qu
qu
que
e
e
en
n
n
nc
c
c
cy
y
y
y c
c
c
con
on
on
onffffigur
igur
igur
igura
a
a
attttion
ion
ion
ion
The receiver utilizes double conversion. The first IF is 26.450MHz and the second IF is
450kHz. The first local oscillator signal is supplied from the PLL circuit. The PLL circuit in
the transmitter generates the ecessary frequencies. Fig. 1 shows the frequencies.
2
2
2
2.... R
R
R
Rece
ece
ece
eceiiiiv
v
v
ve
e
e
errrr
The freauency configuration of the receiver is shown in Fig.2.
1)
1)
1)
1) F
F
F
Frrrron
on
on
ontttt ---- e
e
e
en
n
n
nd
d
d
d R
R
R
RF
F
F
F am
am
am
amp
p
p
plifi
lifi
lifi
lifier
er
er
er
An incoming signal from the antenna is applied to an RF amplifier (Q1) after passing
through a transmit/receive switch circuit (D2,D3) and a 3-pole LC filter(L8,L11).After
the signal is amplified (Q1), the signal is filtered by a band pass filter to eliminate
unwanted signals before it is passed to the first mixer. The voltage of these diodes
are controlled by to track the MPU(U10) center frequency of the band pass filter. (See
Fig. 2)
