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Re: FM Satellite Etiquette



>From: "Dennis Morris" <denmorr@bellsouth.net>
Does anyone know at what power level you should water cool the
>antenna?
>
>73,
>Dennis
>WA4ZJJ

Now I know this is been a humorous topic, but when I worked at NASA's
Goldstone Tracking Network, we silver soldered copper cooling tubing to the
outside of the transmitting waveguide to water-cool it.  We were running 10
to 20 kW at 2 GHz.  The Tx waveguide runs were painted flat-black to
improve heat radiation characteristics.  RX lines were painted white to
reflect heat [this is in the Mohave Desert].  Thus it was real easy to
locate TX vs Rx lines ;-) 

The preamps [LNA's] were cooled to 4.3K with liquid Helium [about
-450F]...real cool!  The maser magnets were also cryogenically cooled, so
they went super-conducting...you just applied power to them then turned off
the power supply.  At zero resistance they held their field within 99% for
an est. 300 years.

Now if you could get ahold of one of them and the 85-foot dishes we used,
boy would you hear AO-40 ;-)  Of course today cooled GasFets now equal the
masers for a fraction of the cost or complexity.

Ed

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