Vertex Standard FT-817, User Manual

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Circuit Description
The FT-817 internal assembly consists of the MAIN Unit,
Control ( PANEL) Unit, and the PA Unit. The MAIN Unit
contains the receiver front end, PLL IC, and switching cir-
cuits, as well as the VCO Unit (local oscillator for trans-
mission and reception). The PANEL Unit contains the
CPU and reset circuits, as well as the power circuitry for
the LCD.
Receive Signal Circuitry
High-Frequency Circuit
The receive signal enters from the Front (J1001) or Rear
(J1002) ANT connector , as selected by relay RL3016 on
the PA Unit.
Signals between 0.1 and 154 MHz received at the an-
tenna terminal pass through an input low-pass filter com-
posed of L3081, L3082, C3264, and C3265.
Received 430 MHz signals, after passing through a high-
pass filter composed of L3071, L3076, C3245, and C3254
are passed through low-pass filter composed of L3028,
L3032, L3035, C076, C3082, C3088, and C3093, and then
are fed through the directional coupler to the UHF T/R
switch circuit composed of diode switch D3004/D3035
(both HSU277). The signal then is fed to MAIN Unit via
J3002.
Received 145 MHz signals, after passing through a high-
pass filter composed of L3071, L3075, L3079, C3234, C3245,
C3252, and C3260 are passed through low-pass filter com-
posed of L3027, L3031, L3034, C3075, C3081, and C3092,
and then are fed through the directional coupler to the
VHF T/R switch circuit, composed of diode switch D3003/
D3005 (both HSU277) . The signal then is fed to MAIN
Unit via J3002.
Received 0.1-54 MHz signals, after passing through the
first low-pass filter, are passed through another low-pass
filter composed of L3069, L3070, L3074, L3077, C3239,
C3242, and C3248, plus LPFs 1-7 (5th or 7th-order
Chebyschev type filter) and HPFs 1-7, utilizing seven dif-
ferent sections to create optimized bandpass responses for
the various amateur bands at 0.1-54 MHz. The signal then
is fed to the 50MHz pre-amplifier (when engaged) and on
to the MAIN Unit via J3002.
The receive signal then passes through the input attenua-
tor (-10dB) which consists of resistors R1001, R1014, and
R1015 plus diodes D1003/D1011 (both DAP236U) on the
MAIN Unit .
Incoming wideband FM (76-108 MHz) signals, after pass-
ing through a high-pass filter composed of L3071, L3075,
L3079, C3234, C3245, C3252, and C3260 are passed
through a low-pass filter composed of L3027, L3031,
L3034, C3075, C3081, and C3092 , and through a direc-
tional coupler, to the VHF T/R switch circuit, composed
of diode switch D3003/D3005 (both HSU277) . Then it is
fed to the MAIN Unit via J3002. The signal is delivered to
IC Q1025 (CXA1611N) which contains the front-end and
discriminator circuits for Wide-FM demodulation. Then
the audio signal is passed to analog switch IC Q1049
(BU4066BF).
The FT-817 includes four receiver front ends, each opti-
mized for a particular frequency range and mode combi-
nation.
1st Mixer Circuit/1st IF Circuit
The 1st mixer on the MAIN Unit consists of a quad MES
FET, D1047 (GN2011). The 1st local signal (68.430-538.330
MHz) from the PLL Unit is applied to the gates of each
FET in the 1st mixer.
The resulting output signal (the difference between the
local signal and receive signal) passes through a mono-
lithic crystal filter (MCF) XF1001 (MF68R, BW:±7.5 kHz)
to obtain the 1st IF signal having a center frequency of
68.33 MHz. The signal is then fed to the 2nd mixer circuit
on the MAIN Unit after it is amplified by FET Q1051
(BB304C).
2nd Mixer Circuit/2nd IF Circuit
The 2nd mixer consists of FETs Q1060 and Q1062 (both
2SK302Y) on the MAIN Unit. The 2nd local signal (67.875
MHz) is amplified by Q1047 (2SC4154E) and is applied
to each FET's gate in the 2nd mixer.
The signal output from the 2nd mixer passes through a
ceramic filter, or optional mechanical filter (U1003), to
become the 455-kHz 3rd IF signal.
Noise Blanker Circuit
A sample of the 2nd IF circuit is amplified by FETs Q1052
and Q1061 (both BB301C) on the MAIN Unit, and then
is rectified by D1068 (1SS372). The resulting DC voltage
passes through R1343 and R1345, C1360 and C1362, and
Q1076 (2SC4154E) to yield an average AGC voltage for