At the instant a transmission is detected from the signal intercept the data is collected and stored for later analysis. All signal characteristics and direction-finding data on targeted signals are compared to previously monitored data.
By use of these techniques signals can be classified by their unique characteristics which will identify the transmitter and determine the direction and with two or more monitoring stations, triangulate the location of the interference source in seconds.
By using computer based monitor receivers coupled with Doppler Radio Direction Finding (RDF), digital Audio Recordings and Radio Frequency (RF) Finger Printing (RFP) techniques, any jammer can and will be documented and located.
This now relatively inexpensive technology that has become available over the last few years which when integrated into a concerted effort has numbered the days of a jammers anomynity and the freedom to interfer with Amateur Radio communications.
Even the simple act of kerchunking a repeater, which is in violation of FCC Part 97 will result in an automated database entry complete with digital recording for future analysis and matching.
This is achieved through the use of off the shelf wideband computer controlled surveillance receivers and software (now available to Amateur Radio at resonable prices) slaved and fed by multicouplers to a single antenna system per site for an automated spectrum surveillance capbility. By viture of target signal identification, classification, and Direction finding (DF) on preprogrammed or operator-specified signals with offsets for repeater station input/output monitoring by an automated network of just two monitoring nodes connected via the Internet with commonly used CATV Internet modems monitoring a specific frequency or group of frequencies for signal intercept provides for instantaneous digital recording, identification and triangulation of emitters.
With these systems in unattended operation 24/7 monitoring all the area repeater stations, to detect, identify, and log changes in the RF spectrum. Unknown, unauthorized, or new target emissions are identified and analyzed to determine signal origin characteristics with all data achieved to RW/CD-ROM for all communications intercepted for later manual retrieval and analysis. Any report of an act of deliberate interference can later be manually researched when received against the database for a hit. As required one or more monitoring nodes can be dedicated to a specific list of systems being interfered with or just to one system.
Radio Direction Finding is used to find sources of interference to any form of wireless electronic communications, including broadcast and two-way radio, television, and telephones. It is also used to track missing or stolen cars and other property. Search and rescue workers use it to find persons in distress. Emergency Locator Transmitters in downed aircraft are tracked with RDF techniques.
Every weekend, in cities and towns all across the country, Amateur Radio operators gather on hilltops for a very special kind of contest -the Fox Hunt. A small, low power transmitter is hidden and the rest of the crew tries to find it. Sound simple? It can be very challenging and a whole lot of fun.
The direction finding skills learned in Fix Hunt activities can be very valuable in locating a repeater jammer, or a lost hiker. In our Central New Jersey area a number of clubs have held fox hunts where equipments and skills have developed over the last few years that are now being used to track down sources of interference within our Amateur community.
Methods from simple body blocking techniques to home made or commercial Time-Of-Arrival (TDOA) equipments and the the latest Doppler RDF system kits and commercial units are beieng used.
In the hands of two people, non-Doppler based system can triangulate on an emitter in a matter of minutes for rapid transmitter location.
In the hands of two or three people a Doppler based system allow for almost instantaneous triangulation from just two sites, with four being optimum. In the hands of just one person the Doppler based systems allows for rapid transmitter location in a matter of minutes.
Click here for information on a commercial doppler RDF manufacturer of interest.
Technology once used by signal intelligence organizations to identify radios of potential military or political targets can now be used to stop malicious interference in the Amateur Radio service.
Every emitter has individual characteristics that are as unique to it as are fingerprints to human beings. RF Finger Printing takes into account that each individual radio has specific characteristics based on subtle defects in the manufacture of the VCO and AMP sections in the radio. You sample the waveform of the emitter and you can differenciate that emitter apart from another emitter.
Every electronic device, even units manufactured to be identical, emit a singular radio frequency (RF) signal. This characteristic is used to differentiate between individual radios as fingerprints serve as unique identifiers for humans. The intelligence community has capitalized on this individuality for nearly 20 years to verify the identity of, and thereby assign value to, discrete platforms such as radios. Transmitters exhibit a unique frequency versus time start-up characteristic before stabilizing on the operating frequency.
Audio recordings of intercepted transmissions provide an awful lot of evidence and not just the voice of the LID asleep at the PTT switch.
With inexpensive MS-Windows based shareware Fast Fourier transform (FFT) analysis software, which has been used in many pursuits within Amateur Radio, provides for advanced pattern analysis of waveform comparisons over a range of signal analysis parameters to perform voice printing that was previously only available to governments and corporations big budgets.
The day of the tape recorder has not completely gone as its use is still being made. However, the day of the Personal Computer and Sound Card has arrived, along with a variety of audio recording and spectral analysis software, a lot of which is FREE, such as ScanRec for recording.
For automated monitoring and Digital Recording of transmissions one of the best inexpensive commerical packages available for Amateur Radio budgets for use with today's computer controllable scanner radios and various Amateur transceivers is Scan Cat Gold SE (Surveillance Enhanced).
The addition of a high speed scanner such as a Bearcat BC-895XLT and the required outdoor antenna system, provides for a complete digital monitoring and recording capability when coupled to an MS-Windows PC with a huge hard drive, which many have just sitting around not being used these days the way PC technology has been advancing. A 100Mhz Pentium is more than enough !
Click here to play for a single key up from a kerchunker incident that was instantenously detected and recorded and logged by Scan Cat Gold SE on both the repeater output and input using syncronized slave receivers.
The Scancat Gold SE software has the special features of:
· Multiple receiver and slave receiver support
· Digital Recording using the PC sound card to store .WAV files
to hard drive.
· Preprogrammed or manually initiated archived by frequency/date/time.
· “Point-and-shoot” selective playback
· Each individual transmission is 'databased', so that you can
selectively play back a single recording
· Graphic-analysis module for examining long-term logging
· Scheduled receiver control
· Spectrum analyzer with 6 graphical methods (any 3 at a time)
· Waterfall display (Z-axis) over time with multicolor signal-spike
differentiation
· Mouse-cursor selection of signal spikes for instant access.
· Mouse-cursor skate tuning of the entire spectrum range.
· Time stamp recordings and frequencies.
· Logs signal strength, air time, CTCSS/DCS tones (if radio supported)
· Plot, activate, and analyze other databases up to three screens at a time.
· Analyze hits on a frequency by histograph of signals strength or number of hits.
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