I want to change a 300mhz crystal to a 433.92 mhz crystal in a gate transmitter

 

So what type of crystal is it and what is it used in?

 

So what's stopping you?

 

I want to change a 300mhz crystal to a 433.92 mhz crystal in a gate transmitter

...and I want to own a submarine, what's your question?

 

... and I want to play tiny winey soca!

 

I want to change a 300mhz crystal to a 433.92 mhz crystal in a gate transmitter

It's funny but I've never seen a crystal work at those frequencies. Are you sure the equipment is not using a lower frequency crystal as a reference in a PLL to control a higher frequency VFO?