File: P.D. Hall, Ferranti Ltd

Scope and Content

Re parametric amplifiers, Hanbury Brown to Hall: 'I have always been a bit lukewarm about the three level maser with paramagnetic salts, largely because of the sheer complication of the physics and of the apparatus; but I have followed the work on the parametric amplifier with great joy. It really does look as though the problem of good noise factors with reasonable bandwidths can be solved with something relatively simple'.