The problem is solved, and I'm feeling quite stupid about the solution.
It turns out that setting a reserved DHCP address for the wireless client MAC address un-isolates hosts on WiFi. Ssh and ping work now. Interestingly, setting a static address at the client end, by itself, does not lift the isolation. An old iMac with a static IP connected to the LAN via a WiFi- Ethernet bridge still can't be pinged but connects outbound just fine.
On reflection it makes perfect sense.....
I've played with the idea of getting an open-wrt-compatible router in the past, but dropped the idea after finding nothing suitable at the local thrift store. Perhaps I should look again.
Thanks to everyone for all your help!
bob prohaska