Looking inside a 144 - 432 - 1296 triplexer

It has recently come into my hands a 144 - 432 - 1296 MHz triplexer. A Comet CFX-4310. I was curious, so I opened it:

The construction is quite classic, without fancy components. It is interesting that the 23cm arm is build using trimmers, and every other capacitor is made from two capacitors in parallel. It was so clear that I drew the schematic, just to keep it:

CFX-4310 schematic

Component values are:

C1: Trimmer	C9: 3pF	C17: 8pF	L4: 2 turns
C2: Trimmer	C10: 3pF	C18: 15pF	L5: 1 turn
C3: Trimmer	C11: 2pF	C19: 11pF	L6: 2 turns
C4: Trimmer	C12: 3pF	C20: 3pF	L7: 2 turns
C5: Trimmer	C13: 3pF	C21: 3pF	L8: 2 turns
C6: 2pF	C14: 10pF	L1: See text	L9: 5 turns
C7: 2pF	C15: 5pF	L2: 2 turns	L10: 4 turns
C8: 2pF	C16: 8pF	L3: 2 turns	-

Some quick notes:

• All capacitors seems to be 500 volts rated.

• All coils are 5mm internal diameter with 1mm diameter enamelled wire.

• All coils seem to be "tuned" by adjusting turn separation.

• L4 and L5 are placed together, so I suspect they are coupled.

• L1 is made with a small piece of cooper sheet in "M" shape.

• C1-C5 are small ceramic trimmers, maybe 10-15pF maximum.

• L2-C5 is a tuned trap I suspect is tuned to 435 MHz.

And that's all. So in the case you burn one capacitor you can replace it using the above table.

Miguel A. Vallejo, EA4EOZ