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Reason for heating caused due to PH2931-135S microwave amplifier ?

Started by Sanoj Singh March 5, 2014
     I am working on development of RF driver input for Klystron amplifier.
As usual, pulsed output of PH2931-135S microwave amplifier (input to amplif=
ier provided after successive amplifications) on spectrum analyzer with 40 =
dB external attenuation produces normal output of around 13dBm on the Spect=
rum analyzer without any heating on the attenuator.

But, today I am not getting the reason behind excessive heating produced by=
 the PH2931-135S microwave amplifier (M/A Com) on the external attenuator w=
ithin 2-3 minutes. After 40 dB attenuation using external attenuator, I get=
 the same 13dBm output display on the spectrum analyzer but the attenuator =
is heated. Also, there is loading on the Vcc applied to the amplifier (42V =
Vcc becomes around 33V).
Also i have provided Fuse of 1A at the input side of Vcc.

What is the reason behind heating and how to eliminate?