Any non-symmetrical antenna will use feed line for it's balance.
It means that your feed line will be a part of the antenna.
And it means that it will suck in all noises from your home.
So, it is very important to use RF chokes and baloon on the feed line for non-symmetrical antennas (such as long wire).
RF-choke is needed to reduce parasitic RF currents on the outer side of coax cable braid.
But long wire is very unbalanced antenna, so it will be hard to eliminate parasitic currents on feed line.
That's why long wire is very sensitive to noises.
If you're want to reduce noise, it is better to use balanced antennas, such as half wavelength dipole.
And use RF-choke filters (from both side - near feed point and near receiver) and baloon on the feed line to avoid using feed line as a part of antenna.
Here is example on how to make RF choke with ferrite core:
Another important thing here is antenna near field region.
You can calculate near field region radius with the following formula:
D is the size of your antenna (in meters)
λ is wavelength (in meters)
Antenna is very-very sensitive to any noise source which falls into antenna near field region.
The most sensitive part of near field region is reactive near field region.
For 2 MHz (150 meters wavelength) and half-wave length dipole (75 meters length), reactive near field region can be calculated in the following way:
R = 0.62 * sqrt( 75^3 / 150 ) = 33 meters
It means that you're need to place your antenna at least for 33 meters away from any noise sources, mains, wires, any metal things, ground or other things.
The near field region (include radiating part) can be calculated in the following way:
R = 2 * 75^2 / 150 = 75 meters
It means that ideally, you're need to place your antenna 75 meters away from any noise source or other things. Unfortunately it is hard to implement for low frequency antennas due to large dimensions of antenna and long near field distance.
Sensitivity in the near field region falls by not linear law. It depends on r^2 and even r^3 at close distance to antenna. So, if you're not able to keep your antenna 33 meters away from any things, then try to keep that distance as big as possible. It will reduce noise and will improve your antenna efficiency
For receiver antenna there is a nice trick. You can use small size antenna + RF amplifier (placed near antenna).
Since antenna has a small size, it has small near field region. But also it has small efficiency.
The amplifier will compensate small efficiency. Such kind of antenna is named active antenna.
But there is a low limit of reactive near field region for very small antennas. For a very short dipole, or equivalent radiator, the outer boundary is commonly taken to exist at a distance R = λ / (2 * pi) from the antenna surface.
In your case, for 2 MHz band, it means that you're need to place small active antenna at least R = 150 / (2*pi) = 24 meters away from any noise source or other things.
Does it is possible to have an Wideband Antenna for Shortwave?
Bandwidth and noise level are related things.
Wide bandwidth antenna will suck in a lot of noises, so it will have higher noise level.
Narrow bandwidth antenna is sensitive to a narrow spectrum of frequencies and as result it has low noise level.