I wanna connect two gsm antenna ; one in internal PCB and the other is external GSM antenna. This is needed for places where signal quality is poor, so when 3 meter coax. external gsm antenna is connected the device continues to get connected.
so the RF signal source is 50 ohm and also antennas are 50 ohm. But direct connection to these antennas to the same source I think needs some matching circuitry. How to handle this?
The simplest way is to use a 50-Ohm power splitter. If you can afford to lose some RF power, you can make such power splitter with resistors, a triangle of 25-Ohm resistors can offer a good match but ~ 6 dB loss.
If you use the two antennas with a low-noise receiver, use the power splitter, or, add low-noise amplifier to each antenna before the splitter.
If you connect a pair of 1/2 wavelength lines to your feeder, putting a 50ohms on one will reflect 50 ohms to the source as the open circuit line will reflect an open circuit to the junction point. or use 1/4 wavelength lines with a short on the unused one.
Frank