Hi Jerome:
Some time ago a company called Opto Electronics made a frequency counter with a small antenna that would count the
frequency of a nearby signal. They call these Near Field Receivers.
Some modern scanner radios incorporate some of these ideas.
http://www.prc68.com/I/BC125AT.html
--
Have Fun,
Brooke Clarke
http://www.PRC68.com
http://www.end2partygovernment.com/2012Issues.html
The lesser of evils is still evil.
-------- Original Message --------
Thank you all who responded including Bob, Attila, Vlad, Brooke, and Chris for
some great suggestions.
This is a fun side project of mine to passively detect RF emitters based upon
strongest nearby signal using ToA pulses from cheap log power sensors or
perhaps the Watson-Watt method. The hope is to use it in a vehicle with
sufficient antenna spacing and time pulse accuracy to create a neighborhood
plot with strongest TX locations.
Yes, there are major issues to be overcome. The super wide band input has no
tuner and will pickup massive noise from many near-field sources, such as
wi-fi, Bluetooth, or phones, however some can be filtered as noise.
Additionally, very few omni antennas cover such a large input range and I don't
think CW signals will be detected properly, as they don't use a distinct
rising-edge pulse.
I'm leaning toward what Bob suggested with a single shot Ghz counter possibly with some type of pulse start/stop timer or a double input A/D with GS/s buffers that can be stopped and momentarily read off whenever a new strong signal is detected or after a set time each second. Vlad mentioned a phase comparator AD8302, which would also be interesting and allow for analog or possibly digital wideband multi-frequency comparison using phase. The AD8302 apparently comes with its own internal double log power RF input, which could save on purchasing additional power sensor ICs as well.
Best Regards,
-Jerome
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