Several tests have been performed at JBO to investigate the problem of representative FM BEM
compression. Evidence of some compression happening inside the BEM is given by the high noise
temperatures measured during the December test campaign, firstly on FEM 4F2 and then on FEM 4F3 when
coupled to representative BEMs. JBO has four representative BEMs, two (B3 and B4) provided with diodes
and then having a DC output, two (B1 and B2) without any diode and having an RF output. During last 2005
JBO tests, DC BEMs have shown to be compressed while RF BEMs have shown only a weak compression.
Dedicated tests have been performed during the last test campaign to investigate the degree of compression,
common features between the two BEMs, the noise temperature reachable in compressed conditions.
Comparison tests have been also performed to check the repeatability of procedures used
