[Milsurplus] Re: Milsurplus Digest, LO radiation - Tempest

[Brooke Clarke]

Hi:

I've seen three different issues discussed under the subject of "LO radiation".

The first is LO radiation as a DF beacon, and most everyone has agreed that it's not practical and may have been promoted as a cover story.  

But some know that there are receivers with specs on LO radiation and shielding.  This is the case, but it's not done because of a possible DF threat.

Second is the case where there's multiple receivers all fed from a multicoupler and the LO radiation shows up as a bogus signal on another receiver.

Third is TEMPEST.  This is a very real situation and has nothing to do with DF.  In the highly recommended book "Wilderness of Mirrors" one of the stories is about the U.S. digging a tunnel under the East-West German border and tapping a telephone trunk line carrying encrypted teletype traffic (major tunneling opertion, pressurized underground room, SCUBA gear, many Ampex tape recorders, etc.).  We were able to read clear text messages directly without any crypto equipment by using the voltage spikes leaking through their crypto box.  

If an enemy set up a listening post adjacent to one of our listening posts and we were using non TEMPEST receivers, then it's very possible that they could determine what frequencies we were listening to.  In a similar way the Neilson TV rating company can, using a set top box that's not wired internally to your TV set, determine what channel you are tuned to, or can drive by in a van and pick up your LO to see what channel you are watching.

The newest TEMPEST threats are LED power on indicators and cell phones.  The old RF receiver method of remote viewing of a TV or computer monitor has been replaced with the use of a telescope and a wide bandwidth photo diode.  Just aim the scope at some spot on the ceiling or wall and the output is the video signal, use three scopes if you want a color display.

For more on TEMPEST and TEMPEST testing see my web page: http://www.pacificsites.com/~brooke/CEI.shtml

73,

Brooke Clarke, N6GCE

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