Hi All,
Tom Vales, a member of the list and the TCBA, helped with the
following very fine article:
HOW EWEN AND PURCELL DISCOVERED THE 21 cm INTERSTELLAR HYDROGEN LINE
BY Karl D. Stephan
in IEEE Antennas and Propagation, Volume 41, No. 1, February 1999,
pages 7 to 16
There is a picture of the 3C22 "lighthouse" tube. Would this work
for a HFTTC?