i designed bandpassfiletr with central frequency 120MHz and band width 5MHz .i got circuit simulations .i finished board. i am getting signals nearly at 400MHz how to supress that one.
May be you can put a simple RC network after the Bandpass filter with a cut off frequency of about 125 -130 MHz. It will not help very much,but it can reduce the spur at 400 MHz.Can you send in the architecture of the filter so that we can look at any tweaks.......