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
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