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For the ST7580, it uses PSK or FSK to send a signal over power lines. In the design guide the example is designed for an FSK or PSK signal to be transmitted at 80 kHz see page 23 for reference to the RX filter calculations below.

RX filter calculations

For my design I would like to send and receive signals across multiple bands. As this is industry related, I will have to stay away from CENELEC Band A. So I would like to make use of CENELEC Band B (102.5 kHz and 117.5 kHz), C (132.5 kHz), D and a part of the FCC Band (147.5 kHz); As the ST7580 can modulate up to 250 kHz but the RX filter need select these frequencies.

I would like to find out if the following sketch is a viable option:

enter image description here This is just a crude drawing, the final design will only use one inductor and the capacitor will be selected with transistors rather than all the filter components.

The two main components of the filter is C3 and L2. I would like to know if I "take" GND away from the filter via a NPN transistor, will this lead to the effect that I am going for? (Which is to have four RX filters on the same board and simply flick between them with a few pins on my microchip). Only one transistor will be on at one time.

EDIT: To clarify I am just focusing on the reception filter, as shown in the figure below boxed in red, for now. This does not have the R5 resistor included, but it is a part of the circuit.

enter image description here

I eventually wish to make this a selectable BPF with a few transistors. Is this a valid method of performing this by changing L2 and C3?

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    \$\begingroup\$ Your circuit makes no sense and it doesn't contain any information about the net at the top nor the base signals. \$\endgroup\$ – Andy aka Oct 12 '18 at 17:43
  • \$\begingroup\$ @Andyaka I am not sure what you are referring to, but I have added an image to explain a bit better what I would like to do. Is this method valid for changing the center Frequency of the BPF? See page 24 of the design guide for the filter response centered at 80Khz. I would like to change that to the aforementioned frequencies \$\endgroup\$ – Gareth T. Oct 15 '18 at 6:12