I don't have broadband, and don't have a large dome or array antenna. Big ships almost always show up (unless lost in a squall). But smaller fishing vessels, even some decent size ones, sometimes didn't show up. I motored all the way back from Roque Is to Bar Harbor in dense fog, 3 or 4 boat lengths visibility. Several times largish lobster boats passed by almost close enough to touch, never showed a return. Other times (in a seaway and some weather now) even 70 or 80 ft steel fishing boats didn't have a reliable return. Most of the time I can see the reflectors on top of navaids or fishing gear, but not always. I went by a couple of net buoys with reflectors on top in the night, only saw them because they appeared out of the dark 20 ft away - not on radar.

Maybe my 18" Raymarine dome isn't working right, but other people I talk to with similar equipment agree with the experience. Broadband might be the solution - do they have magnetron heaters too? That's one thing that keeps me from having the radar on standby all the time - uses a fair amount of power.