Chosen Solution
I was losing airport signal - as if signal strength dropped to zero. It took several weeks for me to track down the correlation. It has to do with temperature. If I put the Mac to sleep for a while it works again - if I put the Mac on a bedspread with poor airflow the signal drops out sooner. I can move the Mac much closer to the AP and it works OK. Its probably the airport card, but it could be the antenna connector. The card is cheap enough so I’ll change it - but that won’t prove that the card was bad - perhaps just re-plugging in the antenna would work. Anyone else seen that behavior?
With WIFI there is a correlation between chip temperature and signal strength. This not only holds true with the “wireless card” on a computer/laptop but is also the case with the router. The issue is discussed on many wireless forums
