How much is pass band of machined circulator?

i have 10gig mixer with machined circulator. the problem is when i feed LO with original oscillator it works, but when i feed it with another 10 gig oscillator it does not work, even no noise level. oscilattor works. Original oscillator can work even if not directly fixed on machined LO port. frequency difference is about 200MHz. Is it possible, that circulator is narrow band somehow? Construction is very simple, some machined circular area with some magnetic or other material glued in center. I thought such simple construction cant be so narrowband, i must se something on IF port, but it is silent. Transistors are ATF similar in both oscillators, with almost similar biasing and i guess power...

yeah it is possible, but even if out of band, will probably not have too much loss. more likely your oscillator stops oscillating with the load u have. Try a short length of straight waveguide between the two to see if it works then.