Tutorial About SuperDF:

Search and Rescue Direction Finding

Applications

There are various applications for Radio Direction Finders in Search and Rescue. Here are some:

1. Finding downed aircraft using the 121.5 or 243 MHz ELT frequencies. See the article on hunting AM signals with SuperDF.
   
2. Triangulating on boats at sea. In Santa Barbara California a SuperDF was one of a pair of shore stations used for triangulating. The other station was using a Polaris Automatic RDF. I was told that the SuperDF produced bearings that were on average about 3 times more accurate than the Polaris station.
   
3. Finding people lost or injured in the wilderness. These might be campers, surveyors, timber workers, or others. They could be government workers, such as forest service, police, wild fire fighters, or others. They could even be members of the SAR team! Whatever radio they may be carrying can be hunted with SuperDF.
   
4. Locating from the air people on the ground in order to air drop or helicopter delivery tools, equipment, or supplies, or to pick up the people. This can be a particular problem for firefighters, as smoke may obscure them, or the people may mistake where they are. A helicopter equipped with SuperDF can zero in very easily, and set down within yards of the transmitter, without any visual contact.

SAR RDF Problems

There are a number of rather significant problems which must be overcome for generally good DFing for Search and rescue.

Frequency Coverage

Virtually any frequency might be involved in an emergency situation. SuperDF has a frequency range of 100 to 1300 MHz, and therefore it can handle a very wide range of communications frequencies.

Sensitivity

The lay of the land can shield direct paths. Because of its extreme sensitivity, SuperDF can hunt the very weakest of signals that no other general coverage system can hunt. This will allow progress generally towards the transmitter until a direct signal is encountered.

Accuracy

When triangulation is needed, accuracy is an important consideration. Triangulating on boats at sea might cover distances of 50 miles or more (depending on the elevation above sea level of the DFing systems). At 50 miles, a 5 degree error is a miss distance of 22750 feet (4.3 miles). In poor visibility or at night this is enough to prevent sighting the boat, and a search pattern must still be executed. SuperDF can produce bearings with an accuracy of about 1 degree. This puts the searchers within 1 mile of target; a substantial improvement.

Versatility

One SuperDF can serve in all DFing situations, from Base station, on foot, mobile, and aircraft. (For convenience, more than one antenna unit per antenna frequency band might be called for.) SuperDF uses your preexisting radio receiver, therefore if you can hear the distress signal, you can hunt it by connecting the SuperDF to the radio that hears it (except for AM-only radios).

BMG Assistance

BMG Engineering can work with anyone in doing an installation on a helicopter or fixed wing aircraft. We have some write-ups already used. The ideal installation would be one which can be field-installed in a few tens of minutes. This then allows operation with whatever airship that is available; preferably a helicopter.

George R. Andrews President

Also see...Hunting AM Signals with SuperDF* - Hunting an ELT on the ground - Hunting an ELT in the Mountains - Setting up an ELT Hunting Team. - SuperDF Used in Helicopter Search and Rescue

Contact

George R. Andrews (Russ, K6BMG)
BMG Engineering, Inc.
9935 Garibaldi Avenue
Temple City, CA
91780, USA

Voice 1(626)285-6963
Fax 1(626)285-1684 (24 hour automatic)
America OnLine: Grandrews
Web: http://members.aol.com/bmgenginc

(5 Feb 1996)

Send E-mail to grandrews@aol.com. (A message window will open.)
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