Having decent antennas does not compensate for being -10 to -13 db from the QRO of many (most?) stations on 80 and 160 meters. I also have to contend with the fact that the vast majority of stations do have local QRN that raises their noise floor, making it difficult to impossible to hear similarly equipped stations. In severe cases they can copy no one. A good recent example was the 6O6O DXpedition from Somalia who often had such strong QRN in Mogadishu that they simply shut down for hours at a time.
Unfortunately QRN from many sources in our modern civilization has become unavoidable. For the majority in urban and suburban locales it must simply be dealt with. It is no surprise that many stations, and not just on the low bands, cannot hear many of the stations that call them. QRO helps them to be heard with the small antennas they can fit within their properties, but that helps not at all on receive. Nulling loops and other compact directive receiving antennas cannot perform miracles.
As a result they have difficulty working the DX or contest QSO they are chasing. It is perhaps no surprise that some will take shortcuts to achieve their goals. By this I do not mean the cheaters using remote receivers that are easily accessible over the internet -- that's an entirely separate discussion. What I mean are those who complete their QSOs with a wish or a prayer. Let me give you a few examples.
- In the 160 meter Stew Perry Top Band Challenge there was one European station I called that managed at first to successfully copy my VE3 prefix and nothing else. This QSO would be a challenge regardless since I entered as QRP (5 watts). After a few more tries he started guessing. I attempted to correct his guesses, which he also couldn't copy. Eventually he settled on a particular call and stuck with it, going so far as to imagine the exchange and log it despite my repeated attempts to correct him. I didn't log the QSO.
- Several times while tuning 160 and 80 meters CW I would come across a QSO between a North American station and a DX station where one or both has difficulty copying. Whether it's QRN, local QRM, a power difference or an antenna difference I couldn't know. I can copy both perfectly well which gives me a front row seat to what follows. One station sends the incorrect call and other can't tell it's incorrect. They proceed to complete the QSO after numerous turn overs, with one or both call signs incorrect! I've heard the same with contest exchanges.
- In a DX pile up there will occasionally appear a caller who obviously does not hear the DX station very well for whatever reason. I hear a lot of this on split operations since I have dual receive, with one receiver to each side of the headphones. That operator proceeds to imagine that the DX has responded to him, despite (obvious to me) that it is another station that the DX is responding to. Usually there is some similarity between the call signs, which creates hope for our intrepid DXer. The phantom QSO is completed and logged without the DX operator's awareness.