The OSCOR trace files are actually just data pair set into a simple
array. It is very simple to take a trace file, and import it as raw data
points into Excel, and by the same means to create a data set in Excel or
Access and then convert it to a trace file or signal file and copy them
into the appropriate OSCOR files or folders.
You can even take all of the traces you collect with the OSCOR (or
multiple OSCOR's) and import them to Excel or Access into separate
columns with a very simple Visual Basic Script.
If you use a calibrated comb oscillator you can inject the signal
directly into the OSCOR antenna and create a correction data set array,
and then convert between a quasi calibrated/corrected linear or
logarithmic display. This way you can take traces from 5 different
OSCOR's, taken at dozens of different locations and bring them all
together in one place for visualizing. Once you have these baseline
corrections you can compensate for amplifier noise, cable attention,
etc.
Then you bring in a spectrum allocation trace that give you the geometry
of what you might see on the airwaves (I set this at an RSSI of 60%). In
the case of a wider signal (wider then 50 kHz) I sculpt the trace to
match the geometry of the allocation. So in the case of a TV channel
allocation I set the trace so that the video luminance carrier is at 60%,
the chroma carrier is at 25%, and the audio carriers are set at 45%. Same
type of action for FM stations where you set the RSSI at 60% for a dead
on center, then drop down to 45%, and then to 25% as we move away from
the carrier. These allocation traces are used as a reference trace that
we can use to subtract from an actual trace collected by the
OSCOR.
If you consider that the OSCOR channels are 50 kHz apart on the main
band, you get 30,000 data points to cover 1.5 GHz, then another for 3
GHz, etc. This allows you to very quickly lay out a series of blank Excel
spreadsheets as a channel map, then create your correction traces with
the OSCOR, download to the computer, then import the correction trace
into the Excel spreadsheet. Next add the rough band allocations in one
column, and use the following column to lay out the channel allocations,
but limit it to broadcast allocations.
Column A, Gives you the frequency (as mapped into the OSCOR, at 50 kHz,
etc.)
Column B, Correction values of raw noise floor, from loaded
amplifier (quasi calibration) This is optional
Column C, Correction value obtained by using a calibrated comb oscillator
(use with column B to map out noise floor)
Column D, International Band allocation (ie: 88 to 108 is FM broadcast,
Amateur Radio Bands, GSM, PDC, etc). This shows upper and lower limits
only
Column E, Specific Channel Geometry, basic channel mask names to quickly
ID broadcast stations (TV Channel 5, FM 206, etc)
Column F, Actual Geometry of potential broadcast signals (sculpt signals
at 60%, 45%, and 25% on wide signals, but only 60% on narrow
signals)
Up to this point all you have done is define a generic structure, so lets
now populate it with location specific data.
Column G, Import of FCC data sets for everything within 5 miles of sweep
location, plus all AM/FM/TV Broadcast Stations within 75 miles. This
comes from an ACCESS database that included all the FCC data on a
transmitter, tower locations, power levels, and so on.
Column H, Bearing to transmitter location as imported from ACCESS
database
Column I, Estimated power level in RSSI computed from the ACCESS
database, and based on distance to the transmitter, and
frequency.
Now we know what we SHOULD see once we get on site, but until we get to
the area near the site and grab a few traces outside the building we can
only estimate
Column J, Trace taken from the OSCOR located roughly 1000-1500 feet away
from proposed sweep location, but from outside the building. This is
usually done from a parked vechile with the OSCOR collecting traces only
for at least 15 minutes. VERY important to do this is such as way so as
not to tip off the eavesdropper. It is also important to perform this in
an open area so that you have at lest 300 feet clean in every direction,
the higher the elevation the better. You are only interested in the
peak traces. Be sure to download your peak traces to the computer BEFORE
you leave this position, and then clear your peaks inside the OSCOR
before you move.
Column K, Same as J but taken roughly 120 degree off from the position
used to collect the traces in column J. Be sure to download your peak
traces to the computer BEFORE you leave this position, and then clear
your peaks inside the OSCOR before you move.
Column L, Same as J and K, but taken another 120 degrees off the other
two. Be sure to download your peak traces to the computer BEFORE you
leave this position, and then clear your peaks inside the OSCOR before
you move.
You now have THREE traces taken at distances roughly the same distance
from the targeted sweep site.
Column M, First sweep inside the building, but no closer then 30 to 50
feet from area or room in which you will the sweeping (this need to be
close to an outside window or wall. Collect for AT LEAST 15 minutes of
raw sweeps. Be sure to download your peak traces to the computer BEFORE
you leave this position, and then clear your peaks inside the OSCOR
before you move.
Column N, Second sweep inside the building, but just like Column M you
are 30 to 50 feet away from the room you will be sweeping. A good option
for this is an electrical closet, unused office, or storage area. This
needs to be between 45 and 90 degrees away from the position used for
Column M. Be sure to download your peak traces to the computer BEFORE you
leave this position, and then clear your peaks inside the OSCOR before
you move.
Column O, Third sweep inside the building, just like the others, position
is unimportant, but pick you position so that you are around 180 degrees
off from the site used for position M (with the room you will be sweep as
the center of all of this). Be sure to download your peak traces to the
computer BEFORE you leave this position, and then clear your peaks inside
the OSCOR before you move.
OK, now the spread sheet has a huge amount of data and we are ready to
move close to the sound stage, but not actually enter the sound
stage.
Column P, Any position where you can get really, really close to the
sweep room (less then 50 feet), but not so close that you would tip off
the eavesdropper.
No back off, review all of the traces in the spreadsheet.
Column Q, is a logical flag of any frequency bin where you have any
unexpected energy (based on peak traces versus FCC allocations), versus
the peaks of column J, K, L
Column R, same as Column Q, but we use columns M, N, O instead of J, K,
L
Column S, same as Column Q, except that we only look at Column
P.
Column T, Is the difference between Column Q versus Column R.
Column U, is the difference between Column Q versus Coulm S
Column V, as you might expect is the deference between columns R and
S
Now, move into the area to be inspects and let the OSCOR run for at least
a good solid hour at one fixed position, and then reloate to 3-4 other
position in the same room wher eyou get it continue to run for about 15
minutes in each location.
Import the resultant peak trace into column W.
Column X (of course), is a logical test so that any signal that is hotter
in the room or in the nearby area creates a flag in this column.
The next columns are notes typed in by the sweep tech for each signal
observed, and their notes on what they did to clear the fact of if it was
from an eavesdropping device of not.
-jma
At 09:29 AM 1/25/2007, Paul Mason wrote:
Jim,
I've never heard of anyone taking a signal list and creating a trace for
OSCOR or OPC.
How have you been able to accomplish this? Can you please that file
to me?
Paul
We won't tell. Get more on
shows you hate to love
(and love to hate):
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Received on Sat Mar 02 2024 - 00:57:15 CST