Topband: Define "near"

[Ray, W Marty]

I am new to low band dxing (been a ham for 22 years and just figured out that this might actually be fun!) and I am trying to figure out rx antennas. I have a 20 acre field behind my house, but the land owner is a little hard to deal with. So, if I can't get permission for winter beverages, I need to come up with an alternative (need it for summer anyway). I have been looking at the K9AY as a possibility, but I have noticed several commments about making sure it isn't near my transmitting antenna. The various sources, however,  have neglected to comment on what, exactly, 'near' means. How close is too close?

Thanks for any advice!

Regards,

Marty Ray, N9SE
Sharpsville, IN