Elecraft and Flex are my 2 favorite amateur radio
transceiver manufacturers. Both design and make Software
Defined Radios (SDRs). They have incredible receiver and
transmitter performances - are very sensitive - and with DSP
filtering, very selective.
Both companies support their offerings directly from their
USA Headquarters. Both have passionate cult like followings
of users. Email reflectors and web blogs hail the praises as
do wins in radio sport contests all over the world.
Elecraft and from the Flex Radio SDR FAQ...
Flex Radio