This can be used to connect to the input coming from the arrow antenna and a single output to your rig for convenient bird watching.
The band splitter is just a 250 MHz High Pass Filter and a 250 MHz Low Pass Filter connected together. This doesn't have to be very complex, or even very accurate. As long as the filters cut off somewhere between 200 and 400 MHz, they will work fine. So if the coils get squished, just bend them kind of back in shape, and go for it. This one is built cheap, just out in the air on a piece of PC Board. You can build the splitter into a box if you like, with connectors and all, but it's not going to change their performance. And this Band Splitter even makes a good project if you want to use two other 145/435 MHz antennas.
Remember, we are not trying to filter off harmonics, just make the 2 Meter energy go to the 2 Meter antenna, and the 435 MHz signals go to the 435 MHz antenna.
The Circuit Diagram
Coils Wire & Turns
435 MHz High Pass
2 x 4.7 pF Caps
1 Coil 1-1/2 turns #18 or #20 wire on a Pencil
145 MHz Low Pass
1 x 10 pF Cap
2 Coils 3 turns #18 or #20 wire on a Pencil
For the inductors of 1-1/2 turns and 3 turns, i used a shielded copper wire of and wound it on the regular pencils available in the shops (the grading may not matter HB or 2HB, it can be any; either case we are using it only to get the coil shape).
Photographs of the Band Splitter
Original Design courtesy
Kent Britain -- WA5VJB