Loran receiver envelope-cycle discrepancy compensation

Claim 2

For use with Loran receiver, apparatus for limiting the effect of the envelope-cycle discrepancy of received Loran transmissions comprising: means for receiving Loran signals corresponding to Loran pulse transmissions: means responsive to received Loran signals for identifying a point on the pulse envelope; means operative in response to a control for adjusting the identified point on the envelope for received signals from at least one Loran slave stations; means responsive to the identified point and responsive to carrier cycles in the received Loran signals for identifying a predetermined carrier cycle point which bears a predetermined relationship to the identified envelope points; and means for indicating an adjustment in the control for the identified envelope point in response to known position with respect to the location of the Loran stations whose transmissions are being received.

Claim 3

The apparatus for limiting envelope-cycle discrepancy of claim 1 wherein the identified cycle point having said predetermined relationship is the cycle zero crossing point closest to the identified envelope point.

Claim 4

The apparatus for limiting envelope-cycle discrepancy of claim 1 wherein: said means for indicating an adjustment includes a map having generally hyperbolic lines of constant envelope-cycle discrepancy for at least a master and slave station thereon; said control being operator adjustable in accordance with the envelope-cycle discrepancy for a selected location on said map.

Claim 5

The apparatus for limiting envelope-cycle discrepancy of claim 1 wherein said Loran receiver has an output indication of at least a line of position with respect to two Loran stations and further wherein: said means for indicating an adjustment includes means responsive to said output indication for providing a corresponding control signal; and means are provided for automatically responding to said control signal to provide the corresponding control of said means for adjusting the identified point.

Claim 6

The apparatus for limiting envelope-cycle discrepancy of claim 1 wherein said means for identifying a point on the pulse envelope includes means for identifying that point generally independent of received signal amplitude.

Claim 7

The apparatus for limiting envelope-cycle discrepancy of claim 5 wherein said means for identifying said point further includes: means for generating a signal representative of the difference between the envelope and the time derivative of the envelope of said received signal to provide a difference signal; and means for detecting a predetermined amplitude of said difference signal to identify said point.

Claim 8

The apparatus for limiting envelope-cycle discrepancy of claim 6 wherein said adjusting means includes means for varying said difference signal in response to said control.

Claim 9

The apparatus for limiting envelope-cycle discrepancy of claim 6 wherein said control has a front panel setting for said receiver and data is provided to correlate control setting with geographic position.

Claim 10

The apparatus for limiting envelope-cycle discrepancy of claim 6 further including means for varying said difference signal to produce time coincidence in the identification of said predetermined carrier cycle point and the detected amplitude of said difference signal.

Claim 11

The apparatus for limiting envelope-cycle discrepancy of claim 9 wherein: said varying means includes means for varying said difference signal for a master station received signal; and said control includes means for producing a further variation in said difference signal for a slave station received signal in addition to the variation for said master station received signal.

Claim 12

The apparatus for limiting envelope-cycle discrepancy of claIm 10 wherein said means for producing a further variation includes means for combining said variation with said further variation.

Claim 13

The apparatus for limiting envelope-cycle discrepancy of claim 10 wherein said receiver provides an output indication of at least a line of position and means are provided automatically operative in response to said output indication to activate said means for producing a further variation for producing a corresponding further variation.

Claim 14

For use in a Loran receiver which provides output position data, apparatus for limiting the effect of the envelope-cycle discrepancy of received Loran transmissions comprising: means for receiving Loran signals corresponding to Loran pulse transmissions from a master and one or more slave stations; means responsive to the received signals for providing a carrier representing signal; means responsive to the received signals for providing an envelope signal; m means for detecting a point on said envelope signal as a function of the time of reception of said pulse transmissions and generally independent of received amplitude; means for tracking a point on the cycles of said carrier signal which corresponds by a set time relationship to the detected point on said envelope signal for signals received from said master and one or more slave stations; means for adjusting the detected envelope point for master and slave envelope signals to produce a futher predetermined relationship between the detected point and the tracked point for received signals from one of said master and slave stations; means for adjusting the detected envelope point for the other of said master and slave stations in response to an adjustable control; and means for providing an indication of the adjustment of said control as a function of said output position data.

Claim 15

For use in a Loran receiver which provides output position data, apparatus for limiting the effect of the envelope-cycle discrepancy of received Loran transmissions comprising: means for receiving Loran signals corresponding to Loran pulse transmissions from a master and one or more slave stations; means responsive to the received signals for providing a carrier representing signal; means responsive to the received signals for providing an envelope signal; m means for detecting a point on said envelope signal as a function of the time of reception of said pulse transmissions and generally independent of received amplitude; means for tracking a point on the cycles of said carrier signal which corresponds by a set time relationship to the detected point on said envelope signal for signals received from said master and one or more slave stations; means for adjusting the detected envelope point for master and slave envelope signals to produce a futher predetermined relationship between the detected point and the tracked point for received signals from one of said master and slave stations; means for adjusting the detected envelope point for the other of said master and slave stations in response to an adjustable control; and means for providing an indication of the adjustment of said control as a function of said output position data.

Claim 16

The apparatus for limiting envelope-cycle discrepancy of claim 13 wherein said indicating means includes a map marked to show an adjustment in said control as a function of geographic position specified by said output position data.

Claim 17

The apparatus for limiting envelope-cycle discrepancy of claim 13 wherein said indicating means includes a feedback control for adjusting said adjustable control in response to said output position data whereby said detected and tracked points for each master and slave stations generally maintain said further predetermined relationship.

Claim 18

For use in a Loran receiver which provides output position data, a method for limiting the envelope-cycle discrepancy of received Loran transmissions comprising the steps of: receiving Loran signals corresponding to Loran pulse transmissions from a master and one or more slave stations; providing a carrier representing signal in response to the received signals; providing an envelope signal in response to the received signals; detecting a point on said envelope signal as a function of the time of reception of said pulse transmissions and generally independent of received amplitude; tracking a point on the cycles of said carrier signal which corresponds by a set time relationship to the detected point on said envelope signal for signals received from said master and one or more slave stations; adjusting the detected envelope point for master and slave envelope signals to produce a further predetermined relationship between the detected point and the tracked point for received signals from one of said master and slave stations; adjusting the detected envelope point for the other of said master and slave stations in response to an adjustable control; and providing an indication of the adjustment of said control as a function of said output position data.

Claim 19

For use in a Loran receiver which provides output position data, a method for limiting the envelope-cycle discrepancy of received Loran transmissions comprising the steps of: receiving Loran signals corresponding to Loran pulse transmissions from a master and one or more slave stations; providing a carrier representing signal in response to the received signals; providing an envelope signal in response to the received signals; detecting a point on said envelope signal as a function of the time of reception of said pulse transmissions and generally independent of received amplitude; tracking a point on the cycles of said carrier signal which corresponds by a set time relationship to the detected point on said envelope signal for signals received from said master and one or more slave stations; adjusting the detected envelope point for master and slave envelope signals to produce a further predetermined relationship between the detected point and the tracked point for received signals from one of said master and slave stations; adjusting the detected envelope point for the other of said master and slave stations in response to an adjustable control; and providing an indication of the adjustment of said control as a function of said output position data.