Presumably you mean 810 kHz. *What is the source of the noise? Noise
generated in the receiver is usually insignificant in the medium-wave band.
If the cause is other transmissions on the same and nearby frequencies you
may not gain much by changing the antenna, but a receiver with better
channel (IF) filtering may help if there is any contribution from adjacent
channels. *If the noise is coming from your car (does it improve when you
park in a rural area) then you may need to improve the RF suppression of its
circuitry (e.g. ignition if it's a petrol engined car).

I expect you can work out what tests would be needed to locate the principal
sources of the noise.

Chris

Yes, KHz, sorry.

The noise goes up several fold when I pass underneath bridges/pass big
trucks, etc. Does this suggest that the noise is from other
frequencies?