Version: 13. September 2004
49
The Low Pass Filters
The low pass filter was developed especially for the „Tramp-8“ and the
„Black Forest Transceiver“ of the DL-QRP-AG and is consequently used for
the SPEAKY too. The parts for the low pass filters are selected for an output
power up to 15 Watts.
The group contains 3 low pass filters and the switching logic for 8 bands:
Low pass 1
for 80 m band
Low pass 2
for 40 and 30 m bands
Low pass 3
for 20 and 17 m bands
For the 15, 12 and 10 m bands the signals passes though the group, as
above of 21 MHz the cascaded 36 MHz filter on the basic board is already
active.
All switching is done bei SIL-Relays making sure that the brilliant strong-
signal capability of the device does not degrades.
The early ideas where to use SMT capacitors but some values where not
available for sufficient high voltages. Therefore they were substituted by
ceramic- or multilayer capacitors of high quality with a 1/10" raster and are
soldered on the PC board directly.
Parts List
Part
Value
Material
C1
1000pF
NP0 (102)
C10
270pF
COG 1206
C11
120pF
COG 1206
C12
270pF
COG 1206
C13
270pF
COG 1206
C14
120pF
COG 1206
C15
22nF
0805
C16
22nF
0805
C17
22nF
0805
C18
22nF
0805
C19
22nF
0805
C2
1000pF
NP0 (102)
C20
22nF
0805
C21
22nF
0805
C22
22nF
0805
C23
22nF
0805
C24
22nF
0805
C25
22nF
0805
C26
22nF
0805
C27
22nF
0805
C28
22nF
0805
C29
22nF
0805
C3
680pF
NP0 (n68)
C4
1000pF
NP0 (102)
C5
680pF
NP0 (n68)
C6
1000pF
NP0 (102)
C7
270pF
COG 1206
C8
560pF
COG 1206
C9
560pF
COG 1206
Rel1-7
MEDER Typ SIL12-1A72-71L
D1-D11
LL4148
SOD80
Dr1
47µH
1210
Dr2
22µH
1210
Dr3
10µH
1210
Dr4
10µH
1210
L1=L3
30 turns 0,3 CuL (AWG 28) on AMIDON T37-6
L2
31 turns 0,3 CuL (AWG 28) on AMIDON T37-6
L4=L6
19 turns 0,3 CuL (AWG 28) on AMIDON T37-6
L5
20 turns 0,3 CuL (AWG 28) on AMIDON T37-6
L7=L9
15 turns 0,3 CuL (AWG 28) on AMIDON T37-6
L8
16 turns 0,3 CuL (AWG 28) on AMIDON T37-6
