From the data sheet of the LFCN-490 radio filter, the chip is marked with RF in, RF out and GND, but what is defined as RF in/out? I have seen some circuits using the rfm-22b with pin 1 (RF in) directed towards the antenna and RF out towards the circuitry, but I can't find how to be certain.

EDIT: Datasheet: https://www.minicircuits.com/pdfs/LFCN-490.pdf Looking at the internal schematic, it looks like it's bidirectional, but then I don't see any reason for marking pin on and naming them in/out


I expect that RF IN is where the signal goes in, and it comes out RF OUT. In a receiver, the RF IN terminal should be closest to the antenna.

  • \$\begingroup\$ So you're saying it's the other way around in a transmitter? How about bidirectional, the receiver can also send data back to the transmitter but with your explanation it seems that this filter is not made for transceivers(?). I use it in an openlrsng module. \$\endgroup\$ – chwi Sep 13 '16 at 6:14
  • \$\begingroup\$ Since you did not provide links to the relevant datasheets, my answer is just a guess based on what you wrote in your question. \$\endgroup\$ – Peter Bennett Sep 13 '16 at 15:56
  • \$\begingroup\$ minicircuits.com/pdfs/LFCN-490.pdf \$\endgroup\$ – chwi Sep 13 '16 at 19:03
  • \$\begingroup\$ I would guess, based on the schematic on that datasheet, that the filter is symetrical, and either terminal can be used as input - but only Mini-Circuits would know for sure. \$\endgroup\$ – Peter Bennett Sep 13 '16 at 19:23
  • \$\begingroup\$ Yeh, I guess :\ \$\endgroup\$ – chwi Sep 13 '16 at 19:29

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