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RFID Radio Frequency Identification

RFID is the wireless use of electromagnetic fields to transfer data, for the purpose of identifying and tracking tags attached to objects.

These RFID tags can be powered by battery or electromagnetic induction fields produced by the reader.  The tag does not have to be within the line of sight of the reader and may be embedded into the object.

RFID can be used to track production, pharmaceuticals, and animals outside. It can also be used to unlock doors and track employee productivity and access to secure facilities. I have an indoor cat that removes his break away collar and gets outside.  The cat has a microchip number that can be read at any vet or the humane society and checked at a data base with a cross reference to the owner.

RFID in 2014 has a world market worth of $8.89 billion which includes readers, tags, software and services.  The reading of personal information has raised privacy concerns.  Toll collection is very rapid with RFID transponders such as Sun Pass.  Remember the traffic backups at the toll booth in Jacksonville?

Every country in principle can set their own rules for RFID frequency allocation.  These frequencies are known as the ISM (industrial, scientific, and industrial bands).  The return signal may cause interference with other users.  Toll collections systems I have seen have extended sides around the antenna at the toll lane to isolate the signals from reading the transponders in adjacent lanes.

There is a possibility unique RFID smart tags could be put on every product and replace universal product codes UPC codes and talk to a networked system to track everything that is put into a shopping cart so a shopper could just walk to front station to pay for purchases without waiting for a cashier to scan each item in the shopping cart one item at a time.  RFID signals can be blocked so that would have to be worked out to prevent inventory shrinkage.

Frequencies for RFID:
Low frequency 125-134.2 kHz and 140-148.5 kHz (Proposed amateur LF band 135.7 to 137.8 kHz).

High frequency 13.56 MHz.

Ultra high frequency 865-928 MHz (cannot be used globally because there is no single standard)   However, in North America UHF can be used unlicensed with restrictions for transmission power.  The North American standard is not allowed in France as it interferes with military bands.

Reference:  Wikipedia:  RFID
            How Stuff Works, Bonsor and Fenlon:  How RFID Works

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SCADA: Telecommand and Telemetry

On the extra class license exam you may see a question on telecommand and telemetry.  The process of transmitting communications to a satellite to initiate, modify, or terminate the various functions of a space station is called telecommand operation.

When information is transmitted back to earth, this is called telemetry. 1

Telemetry and telecommand can also be applied to non-satellite communications.  Telemetry and telecommand are used to control power generation, power grids, water treatment, wastewater collection and treatment, oil and gas pipelines, civil defense siren systems, and smart meters.

SCADA (supervisory control and data acquisition) is a system of sending and receiving coded signals over communication channels to provide remote control of equipment. SCADA systems usually control large scale processes and multiple sites.   SCADA systems can be used also to control HVAC and energy usage.  There is a saving of manpower using a system of SCADA since it would be very costly to have personnel be on each site to monitor and control a localized system.

There are usually five sub systems to make up a SCADA system.  

A. a sensor.

B. Logic controller to take sensor data to digital data.  

C. Programmable logic controller send telemetry to connect to control centers.  These can be wired, wireless using satellite, radio, cellular and microwave.

D. a remote terminal unit (RTU) data concentrator that opens and closes breakers and valves.

E.  Human –machine interface. (Most control functions are performed automatically)  

F. a historian software service to store data.

Early SCADA systems were not very secure, but that has improved with advanced encryption, virus protection and anti-malware programs. SCADA is a great tool where there needs to be a centralized monitoring and control of operational duties at many sites. 2

Looking around you will see these systems being widely employed in our area at lift stations, electrical substations, and water pumping stations, and with smart meters.  On some bridges you will see a circular polarized beam pointing upward to a satellite to provide water information. You can approximate the frequency ranges that these stations are using by looking at the antenna length and type as well as where the data is being sent by examining antenna direction.

References:
The ARRL Extra Class License Manual, 2012, Page 3-13
Wikipedia:  SCADA

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DISTRESS RADIO BEACONS

There are several types of Emergency radio beacons:  

PLB (personal locator beacon) ,

ELT (emergency locator transmitter)

and EPIRB (emergency position indication radio beacon).  

These aid in the detection and location of boats, aircraft and people in distress.  These beacons use the Cospas-Sarsat international satellite system.  These may be manually or automatically activated upon immersion.

The basic purpose is to help rescues find survivors within the first 24 hours known as the “golden day”.  Since 1982 these radio beacons have assisted in the rescue of over 28,000 people in more than 7000 situations.  Beacons should be registered.   EPIRBs are locally available for $420 and PLBs for $254 at marine stores.

There are 16 digital channels used between 406.022 and 406.076 MHz. In the past VHF channels 15 and 16, 1646 MHz, 121.5 MHz, and 243.0 MHz were used but are obsolete. 

Search and response to registered beacons is swift.  Unregistered beacons can be responded to more slowly.  False alerts from registered units are resolved by phone or radio call which saves search and rescue resources and makes them available for real distress calls.  

These modern beacons transmit a unique hex code of up to a 30 digit serial number and may also be combined with GPS data to give an accuracy within 49 feet. There is no charge to register 406 MHz beacons and registration is mandatory in most countries.

Transmitter power is 5 watts pulse mode.  GEOSAR provides nearly instantaneous coverage 70 degrees north and south of the equator. LEOSAR provides worldwide coverage with 6 satellites.  1

Back about 1990, I remember a presentation that was done on a false EPIRB alert that come from the rural area of Hastings, FL.  A plane flying over picked up a distress signal and a group went to locate the signal.  They had problems tracking its exact location because the EPIRB was in someone’s metal roof barn.  

What happened was that the boat owner used the boat that he stored in the barn and tossed the PFDs (personal flotation devices) into the boat unknowingly striking and setting off the EPIRB.  The EPIRB in use in this instance was the old type and not registered.  If it was the new type in wide use today a phone call could be made and it would have saved much time.

Most general aviation aircraft in the U.S. are required to carry an ELT.  In commercial aircraft a cockpit voice recorder must contain and underwater locator beacon.  Most commercial off-shore working vessels are required to carry a self-deploying EPIRB.  

Personal locator beacons must be registered and should not be used where normal emergency response exists. 1
Reference
1 Wikipedia:  Distress Radio Beacon

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