Peter Chadwick <Peter_Chadwick@mitel.com> wrote:
>Chuck said:
>
>>In a high-power radar that I once used, "SWR" sensing was able to shut off
>>the PA within one microsecond.
>
>I worked on a satellite ground station tx some 35 years ago. (10kW CW at
>6GHz).
>That had a fibre optic cable looking down the waveguide towards the
>antenna; if
>an arc started because of excessive VSWR, the light was detected in a 931A
>photomultiplier and used to shut the RF down in under 1 microsecond. The arc
>would run along the guide until it hit the TWT output window. As the TWT's
>price
>in today's money was about $500K, it was worth protecting......
>
>73
>
>Peter G3RZP
The radar that I mentioned also had a photomultiplier looking down the
waveguide. This was Haystack Observatory's planetary radar, which (at the
time) put out several hundred kW at 8 GHz, _CW_, by means of two Varian
klystrons. In addition to sensing RF faults, the radar had DC fault
sensing that could discharge the large roomful of filter cap's of the 1-MW
DC power-supply into a spark gap. The sound of that crowbar firing was
enough to stop your heart. I've forgotten the numbers now, but I recall
that the energy stored in that capacitor bank was comparable to that of a
stick of dynamite. The EMP would stop every computer in the building, too.
73 de Chuck W1HIS
--
FAQ on WWW: http://www.contesting.com/FAQ/amps
Submissions: amps@contesting.com
Administrative requests: amps-REQUEST@contesting.com
Problems: owner-amps@contesting.com
|