I was thinking about this a few weeks ago.

Doppler shift would substantially change the wavelength, and frequency too.

Perhaps the number of light years a wave has traveled moving in the same direction that Earth is moving in, would be less distance than the side facing the direction that we are moving away from.

The Earth, and Solar System are always moving in motion; I would imagine doppler shift would also have a significant impact on the success of receiving such transmissions.