i have a 80 foot longwire, attached to the center conductor of a coax
which then leads into my house and to my reveiver (NRD 545). The coax
shield is grounded at the entry point into my house..

I have no balun between the longwire and my coax. So my question is
would a 9:1 balun give me any SIGNIFICANT improvement in signal level
or in noise reduction?