vicmiller1
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Classic AM Band (MW) Long Range Line-of-Bearing and Triangulation Position Fix / Location Techniques
The traditional / classic method of Line-of-Bearings (LOB's) for Triangulation and Positional Fix / Location uses known transmitters sources / sites such as Non-Directional Beacons (NDB's) ... A large widespread series of NDB's was established to support this capability and technique.
However, the use of the biggest, strongest full power (50 KiloWatt) AM Band (MW) / Long Range Standard Broadcast Stations can , and are used for this technique as well. It provides a long range / long reaching (using night sky wave skip propagation) set of transmit sources / transmit sites which can also be used for good line-of-bearing (LOB) measurements to perform classic triangulation for ownship positional fix / location fix.
These stations reach way out from USA East and West Seaboards / Coastal Cities like helping hands and reassuring well-known familiar friends over 1000 miles (at night) into both Atlantic and Pacific oceans - even 1000 miles out in a feature-less ocean and even in bad weather conditions with RF radio penetrating through weather, and with no visibility / no star navigation available ...
The method of lines-of-bearing (LOB's) for triangulation and postion fixing is a traditional well-understood technique. The traveling craft measures the lines-of-bearing (LOB's) to two , three , or more receivable transmitting stations / sites with known transmit locations. The receive operator must listen for these strong AM Band / Long Range Standard Broadcast stations for their identification which typically also includes their location such as WABC - New York , WBZ - Boston, etc. Selected stations should be (preferrably) widely separated to establish large spatial baselegs and angular differences for good crossing intersections and best triangulation geometry.
These measured lines-of-bearing - (the traveling craft / ownship must be able to make these measurements on it's own when a position fix is needed) - are then plotted / graphed on an appropriate large scale map (adding or subtracting a 180 degree factor to properly reflect the reversal for transmit site - to - receiver line of bearing). The straight line from transmit sites towards the receiver are plotted. The intersection of these lines of bearing are known as triangulation and yields the ownship position fix / ownship location . The more accurate the transmitting site locations are known and the more accurate the received lines-of-bearing are measured , the more accurate the determined ownship position fix will be.
The general triangulation technique / method is illustrated here:
http://freepages.misc.rootsweb.ancestry.com/~taylorydna/images/triangulation1.jpg
In order to accomplish this method, the traveling craft / ownship must be able to make line-of-bearing measurements on it's own ... So how do classic rotating top "Ray Jeff / Marine" style RDF Radios achieve these measurements. By using a directional loop / loopstick antenna that is rotatable (in Azimuth). A typical loopstick antenna pattern is illustrated here:
http://www.aa5tb.com/loop07.gif
Note that the loop pattern has sharp / narrow nulls (in azimuth / angle) ... As the loop is slowly rotated, the tuned-in received radio station is heard to rapidly and distinctly drop in strength allowing the operator to place the pattern null directly on the transmit source's line-of-bearing and accomplishing the needed measurement. In this way the measured line-of-bearing (from North) on the ownship craft to the transmitter site is established.
Also note the loop pattern actually has two nulls , and to determine which of the two nulls is producing the real / proper line of bearing the RDF Radio has a circuit to tell the two nulls apart and determine the correct one. In many practical situations the receive operator can eliminate one of the two nulls by knowing the approximate position of the transmit source relative to compass north, such as by knowing that ownship is in the Atlantic and east coast radio stations would be in a general westerly direction, however the RDF radio is equipped with a null distinguishing circuit - just to make sure !
Once the measured lines-of-bearing (LOB's) are established the operator plots these from the known transmitting stations / transmit site postions and completes the triangulation to establish ownship postional fix / ownship location fix ... even 1000 miles out in a feature-less ocean and even in bad weather conditions with no visibility / no star navigation available ...
So Strong AM Band (MW) / Long Range Standard Broadcast Stations provide a set of friendly helping hands
reaching way out for reassurance and passive line-of-bearing (LOB) transmit sources for triangulaton and positional fixing ... what a great idea / what a great classic technology ... (of course now people just look at their GPS readout ! )
Here are some pictures of the many RDF Radios that were produced and used on these (above) principles:
A true benchmark navigation technique / principle and supporting technology from the past to be appreciated:
RDF - RADIO DIRECTION FINDER RADIOS
Many Thanks,
Victor L. Miller - Electrical Engineer
E-Mail: vicmiller1@aol.com
The traditional / classic method of Line-of-Bearings (LOB's) for Triangulation and Positional Fix / Location uses known transmitters sources / sites such as Non-Directional Beacons (NDB's) ... A large widespread series of NDB's was established to support this capability and technique.
However, the use of the biggest, strongest full power (50 KiloWatt) AM Band (MW) / Long Range Standard Broadcast Stations can , and are used for this technique as well. It provides a long range / long reaching (using night sky wave skip propagation) set of transmit sources / transmit sites which can also be used for good line-of-bearing (LOB) measurements to perform classic triangulation for ownship positional fix / location fix.
These stations reach way out from USA East and West Seaboards / Coastal Cities like helping hands and reassuring well-known familiar friends over 1000 miles (at night) into both Atlantic and Pacific oceans - even 1000 miles out in a feature-less ocean and even in bad weather conditions with RF radio penetrating through weather, and with no visibility / no star navigation available ...
The method of lines-of-bearing (LOB's) for triangulation and postion fixing is a traditional well-understood technique. The traveling craft measures the lines-of-bearing (LOB's) to two , three , or more receivable transmitting stations / sites with known transmit locations. The receive operator must listen for these strong AM Band / Long Range Standard Broadcast stations for their identification which typically also includes their location such as WABC - New York , WBZ - Boston, etc. Selected stations should be (preferrably) widely separated to establish large spatial baselegs and angular differences for good crossing intersections and best triangulation geometry.
These measured lines-of-bearing - (the traveling craft / ownship must be able to make these measurements on it's own when a position fix is needed) - are then plotted / graphed on an appropriate large scale map (adding or subtracting a 180 degree factor to properly reflect the reversal for transmit site - to - receiver line of bearing). The straight line from transmit sites towards the receiver are plotted. The intersection of these lines of bearing are known as triangulation and yields the ownship position fix / ownship location . The more accurate the transmitting site locations are known and the more accurate the received lines-of-bearing are measured , the more accurate the determined ownship position fix will be.
The general triangulation technique / method is illustrated here:
http://freepages.misc.rootsweb.ancestry.com/~taylorydna/images/triangulation1.jpg
In order to accomplish this method, the traveling craft / ownship must be able to make line-of-bearing measurements on it's own ... So how do classic rotating top "Ray Jeff / Marine" style RDF Radios achieve these measurements. By using a directional loop / loopstick antenna that is rotatable (in Azimuth). A typical loopstick antenna pattern is illustrated here:
http://www.aa5tb.com/loop07.gif
Note that the loop pattern has sharp / narrow nulls (in azimuth / angle) ... As the loop is slowly rotated, the tuned-in received radio station is heard to rapidly and distinctly drop in strength allowing the operator to place the pattern null directly on the transmit source's line-of-bearing and accomplishing the needed measurement. In this way the measured line-of-bearing (from North) on the ownship craft to the transmitter site is established.
Also note the loop pattern actually has two nulls , and to determine which of the two nulls is producing the real / proper line of bearing the RDF Radio has a circuit to tell the two nulls apart and determine the correct one. In many practical situations the receive operator can eliminate one of the two nulls by knowing the approximate position of the transmit source relative to compass north, such as by knowing that ownship is in the Atlantic and east coast radio stations would be in a general westerly direction, however the RDF radio is equipped with a null distinguishing circuit - just to make sure !
Once the measured lines-of-bearing (LOB's) are established the operator plots these from the known transmitting stations / transmit site postions and completes the triangulation to establish ownship postional fix / ownship location fix ... even 1000 miles out in a feature-less ocean and even in bad weather conditions with no visibility / no star navigation available ...
So Strong AM Band (MW) / Long Range Standard Broadcast Stations provide a set of friendly helping hands
reaching way out for reassurance and passive line-of-bearing (LOB) transmit sources for triangulaton and positional fixing ... what a great idea / what a great classic technology ... (of course now people just look at their GPS readout ! )
Here are some pictures of the many RDF Radios that were produced and used on these (above) principles:
A true benchmark navigation technique / principle and supporting technology from the past to be appreciated:
RDF - RADIO DIRECTION FINDER RADIOS
Many Thanks,
Victor L. Miller - Electrical Engineer
E-Mail: vicmiller1@aol.com
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