It is not that clear what you are trying to do. If I assume you are trying to transmit 4.803 ghz, by upconverting a 10 mhz bspk if signal with a 4.793 ghz lo, then yes, the LO leakage is huge. It is big enough that the receiver will have trouble ingnoring it. Also, you have an equal power other modulated signal (at 4.783 MHz), that will jam other users.
What type of mixer do you have? If you have access, try varying the LO power up/down to get best rejection. Make sure you have a "balanced" mixer that serves to null out the LO leakage. Bump up the IF power ot the mixer to get bigger sidebands out.
The signal is too close to the LO to easily bandpass filter it. But there are other tricks to reduce the LO leakage if you don't mind more complexity.