joseph at pfeifferfamily.net
Tue Sep 4 20:33:31 CEST 2007
Richi Plana writes:
>On Tue, 2007-09-04 at 10:27 -0700, John Seghers wrote:
>> Part of the process of receiving signals involves heterodyning--basically
>> mixing a received signal with lower intermediate frequencies (IFs) to
>> amplify the desired actual signal, while making the carrier signal something
>> easier to work with. See http://en.wikipedia.org/wiki/Heterodyne for a very
>> basic description.
>Fascinating. So "passive receivers" really aren't? Or are there classes
>of receivers which are (no amplification or very sensitive pickups)?
>Prolly off-topic, but I sure am curious. Are there no radar detectors
>which don't give off their presence?
There have been receiver technologies that are essentially passive
(good ol' crystal radios come to mind), but not many, and not that
That said, a GPS receiver isn't going to affect avionics. Neither is
a cell phone, a bluetooth, nor an 802.11 wi-fi. But since they
haven't been *proved* not to, they aren't allowed.
(there have been radar detectors that set off other detectors as
loudly as radar does! Haven't followed that market since US highway
speed limits in the West got reasonable)
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