A dream come true - seeing the original Penzias - Wilson radiometer:

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- a memo of my first, very memorable encounter with the Penzias - Wilson radiometer at the Deutsche Museum in Munich, in Finnish

- this fantastic piece of radio astonomy history has been arranged to the museum by Dr. Arno Penzias, the horn still exists too in New Jersey

- here is the block diagram of the radiometer, drawn based on the layout of the equipment at the museum

- an overall photo of the front-end microwave arrangement (left to right: horn input, cold noise reference, polariser/switch, hot reference, MASER amplifier, IF amplifier

- the back-end rack containing power supplies, the IF amplifier and envelope detector, the adjustable attenuation pad, the audio amplifier and the paper plotter

- the feedhorn square-circular transition and rotary joint (antenna pointing) and a closeup photo

- the orthomode transducer port for the cryogenically cooled reference waveguide "cold" termination

- photo (bit out of focus) of the motor driven rotary switch with ball bearing rotary waveguide joints and fine tuning matching screws

- motor driven rotary vane, a different view

- the orthomode transducer that feeds the receiver (right hand side), circular wavguide section termination missing

- the 24 dB crossed waveguide coupler (note termination) at the front lefthand side (the coupled to OMT via a short tapered section)

- the receiver port waveguide twist is at the extreme left and the receive port waveguide bend, between the Dewar and twist section, feeding the Ruby MASER

- the Argon tube hot noise source (note termination) at the left rear and in this photo, at the top rear (noise tube diagonally through waveguide wide side)

- the service meter in front of the horn rotary joint and taper

- a photo without flash to show the cross polarisation rejection attenuator vane (terminating adjustable short missing)

- a photo with flash to show the waveguide vanes (termination missing), showing the amplifier port fixed vane in the front and the motorized rotary vane (switch) further down

- the MASER K band pump source (a reflection Klystron ?) waveguide flange on top of the Dewar, in front of the amplifier output N connector

- the MASER amplifier output N connector and short coax section to another N connector and coax to waveguide adapter for the mixer isolator (center right)

- the waveguide isolator section (fed at input and output via waveguide tapered sections) with the four valve IF preamplifier mounted on top (slightly different view)

- the balanced Magic T mixer is at the left and the DC bias ports at the extreme left (going to the diode mixer current meters)

- clearly there had been some local VHF interference breaking through into the receiver IF at the mixer end - hence the ad hoc copper foil shielding ;-)

- the Magic T balanced mixer Local Oscillator port for the Local Oscillator (Reflex Klystron Oscillator ?) port is at the bottom left (light blue waveguide/coax apapter)

- photo of balanced mixer with adjustable shorts, bias box, LO waveguide matching, LO coax to waveguide adapter (LO missing, possibly a Reflex Klystron ?), also this photo

- a view of the cold reference source termination Dewar, showing also service meter and Argon hot noise source

- the Magic T mixer diode current indicators (these must have been most useful)

- the MASER DC magnetizing field controls were in the Dewar rack, on the opposite side of the cryogenices control panel

- some of the cryogenic plumbing

- the molecular amplifier cryogenics control panel, bearing the MASER type number M4901 and serial number 1 (!)

- here you may find an illuminating (no pun intended) description of the Holmdel Horn

- link to the Nobel laureates of 1978 website

- and finally, here is a youtube video of the Holmdel Horn in action !

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Created 11.11.2007
Published 19.12.2008
Updated 11.11.2014