432 MHz Cavity PA with Triode GS35b
The amplifier is build as split compartments, HV source and RF deck - which is 19" 4HE.
I bought it 2014.02.09 from DF0MU as they sell a number of their tube backup amplifiers.
It has a circulator (Narda?) in the input and a directional coupler in the output port,
two panel meters: one for bias/anode current, the other to read output and reflected power.
the HV is supplied via an RG-141 PTFE coax with a professional safety plug.
Due to the relatively low anode voltage of 2.8 kV gain is about 11.5 dB (only). Maybe a little more when
running "QRP" power, like from 25 watts of drive to at least 450 watts+ out, see testing data in table below.
Inside the PA compartment: a beautiful cavity (designed by DJ6JJ, make: DJ3FI), all silver plated brass and PTFE,
note the brown plastic stub on left - which is used for fine tuning the input cavity. The outputs plug socket is 7/16.
A few minutes of polishing with a soft piece of cloth brings back the glory of the high times of pre LDMOS age cavity amps
Some data for higher anode voltage that show the ability of that cavity design
Data N2DX/DJ3FI My Test Va 3200 V 2800 V Ia 850 mA 490 mA Ia idle 75 mA 95 mA Vg bias 34 V - Ig 170 mA - Pin 100 W 25 W Pout 1500 W 580 W - - - - - - - - - - - - - - - - - - - Gain 11.8 dB 13.7 dB Source http://www.nd2x.net/DJ3FI-70-1.html
a ... TURBINE ... or what? Air outlet on right side
This HV Sources weight is 40 kg or 88 lbs
On startup HV is brought up in two steps, 1100 V and to 2800 V after 60 secs
Capactor 32 uF (by SEL) / 3.75 kV, Pabst Blower, solid state relais for soft start.
73, Hartmut, DG7YBN