Elecraft KAT2 - Manual (Page 23)

23
Circuit Details, KAT2 L-C Board
The L-C board provides eight series inductors and eight parallel capacitors, configured as an L-network. The
capacitance can be placed at the transmitter or antenna end of the network via a relay on the Control board (see next
page). Each inductor and capacitor has its own DPDT relay, with the individual sections of each relay placed in parallel
for reliability. The relays are selected under control of the ATU's microcontroller. Latching relays are used so that they
will not consume any power except when the operator is actually tuning. The relays are switched one at a time to keep
switching current low and to provide acoustically and electrically quiet operation. This results in somewhat longer tune
times.
For additional reliability, the connectors used between the L-C and control boards have gold-plated contacts, and
redundant pins are used for RF signals. Bypass capacitors are used on relay control lines to prevent RF signals from
reaching the microcontroller.
L-C Board Schematic
L8 is wound on T50-1 core (blue). All others are wound on T50-2 core (red).
= On bottom of PC board. All relays on the L-C board are on the bottom.
RELAY COMMON
W. Burdick
E. Swartz
L-NET OUT
Elecraft
L-NET IN
10.4 µH .64 µH 1.3 µH 2.6 µH 5.2 µH
Rev. Sht.
.08µH .16µH .32µH
Date
1200
.001 .001 .001 .001
.001
C1_2 C3_4 C5_6 C7_8
C
7_8 C
3_4
C
5_6 C
1_2
K12 K15 K16 K13 K14 K10 K11
K10 K11 K12 K13 K14 K15 K16
150 300 620
C20
C23
C22
C21
C24
C25
C26
C27
C31
C32
C33
C34
C35
C36
C37
C38
C42
K5 K6 K7 K8
P4 P5
By
10
K1
10 10
K2
10
K4
10 10
K9
10
K3
10 10 10 10 10 10 10 10 10
10 11 12 13 14 15 16 10 11 12 13 14 15 16
L1 L2
K2
L3 L4
K4
L5 L6
K6
L7 L8
K8
K9
C1 C2 C3 C4 C5 C6 C7 C8
10 22 39 82
K1 K3 K5 K7
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1
2 4
3
9 7
8
2 4
3
9 7
8
2 4
3
9 7
8
2 4
3
9 7
8
2 4
3
9 7
8
2 4
3
9 7
8
2 4
3
9 7
8
2 4
3
9 7
8
2 4
3
9 7
8
2 4
3
9 7
8
2 4
3
9 7
8
2 4
3
9 7
8
1 2 3 4 5 6 7 8 9 1 2 3 4 5 6 7 8 9
2 4
3
9 7
8
2 4
3
9 7
8
2 4
3
9 7
8
2 4
3
9 7
8
*
*
X Y
X Y
1 of 2
KAT2 ATU L-C Board
Pins 5 and 6 of each relay are used as tie points but are not internally connected.
NOTE: K1-K18 are single-coil latching relays, shown in the RESET position.
F 11/27/00