[Milsurplus] L.O. radiation

[mikea]

On Tue, Mar 22, 2005 at 12:23:41PM -0500, Radioman390 at cs.com wrote:

> Another indication that LO signals get out a ways is that a TV
> ratings outfit in the 60s was able to determine what TV channel you
> were watching by driving a van down the street with a big loop on the
> front, which would pickup the TV set's LO signal, and identify the
> channel. Similarly another ratings outfit had receivers by the side
> of the road to pickup LOs from passing cars and calculate the channel
> tuned to.

More recently, there has been at least one billboard in the Bay Area with
receiver that detects radiation from car radios and adjusts the message on
the display to suit what (the majority of) the drivers in the covered area
are listening to. That's an interesting use of interception technology, 
though I have to wonder exactly what they're listening to: LO, images, or
something else. 

In Peter Wright's _Spycatcher_, we get to see sensitive monitors (TRF, I 
suspect) used to detect LO radiation from clandestine receivers and maybe 
from transmitters as well. 

-- 
Mike Andrews, W5EGO
mikea at mikea.ath.cx
Tired old sysadmin