GSM and 433MHz radio antenna interference

Hi All

does any one can help me with this doubt

I have a GSM anenna and a 433MHz Radio antenna in my system, how far i need to put the antennas to avoid interference between them or not matter the distance this signals do not interfere with each

The interference is happened between two RF systems, where the antennas are only part of them.
To avoid interference in a professional matter, you have to do an RF system analysis (intermods, spurs, blocking, wideband noise power, etc.) and also an RF link budget calculation including antennas.

Legal 433 MHz applications are low power compared to GSM, also standard GSM equipment can be expected to implement a high EMC standard. In so far, a possible problem is most likely in the GSM -> 433 MHz direction. The main factor is receiver preselection, to prevent e.g. overload of the input stage. Simple 433 MHz circuits don't neccessarily provide it, although low-pass filters would be an appropriate means for antenna impedance matching and transmitter harmonics filtering. But you have to analyze the actual circuit and possibly need to measure the 433 MHz antenna gain at GSM frequencies.