Linksys BEFDSR41W router useless for wifi?

Last year I bought a Linksys BEFDSR41W dslmodem/wireless router, and
then a WPC11 card which plugs into the unit to give it wireless
capabilities. Despite a technical support case lasting several months,
the unit keeps disconnecting on wireless, and frequently you can't
connect at all.

now I have a Netgear wireless router, which works perfectly.

Have other people tried the BEFDSR41W and what was your experience of
wireless connectivity with the unit? The problem seems to be its use
of the WPC11 card which has a small integrated antenna giving rise to
poor signal, as the Netgear router has an external antenna which
provides very good signal.