Okay, let me restate, since I seem to be mis-understood,

The I.F. is stagger tuned, with swamping resistors to kill the Q. It is
running at 60mhz with a 6db bandwidth of 8mhz. It is part of a 'short pulse'
marine radar unit. The pulses were like maybe .06microseconds at about 1khz
rep rate.

The transmitter now squirts out 'long pulses' of about .8microseconds. I
want to raise the value of the swamp resistors, and 'un-stagger' the tuning
to get a 1.5mhz bandwidth at the 6db point.

So the original question was "If I reduce the bandwidth from 8mhz to 1.5mhz,
and everything else remains the same, what will happen to the signal to
noise ratio in terms of db snr?

I have done similar mods before, and the units work better than ever. Just
getting the swamp resistors up in value helps receiver gain more than the
numbers would apparently indicate, as I can see small craft at 24 miles, when
I could hardly see them at 12 miles before mods.