Three-axis pedestal having motion platform and piggy back assemblies

Abstract

An antenna system includes a first drive assembly configured to rotate a vertical support assembly relative to a base assembly about a first axis, a second drive assembly configured to pivot a level frame assembly relative to the vertical support assembly about a second axis, and a third drive assembly configured to pivot an elevation frame assembly relative to the level frame assembly about a third axis. The antenna system additionally includes a primary antenna and a secondary antenna affixed relative to the level frame assembly and a control unit configured for: selecting operation of a selected one of the primary and secondary antennas, determining a position of the elevation frame assembly based upon sensed motion about said the first, second, and third axes, and controlling one or more of the first, second, and third drive assemblies to alter the position the selected one of the primary and secondary antennas.

Claims

1. A rotationally-stabilizing tracking antenna system suitable for mounting on a moving structure, the antenna system comprising: a first drive assembly configured to rotate a vertical support assembly relative to a base assembly about a first axis; a second drive assembly configured to pivot a level frame assembly relative to the vertical support assembly about a second axis; and a third drive assembly configured to pivot an elevation frame assembly relative to the level frame assembly about a third axis; a primary antenna affixed relative to the level frame assembly; a secondary antenna affixed relative to the level frame assembly; wherein the primary antenna is mounted at a fixed offset angle relative to the secondary antenna and configured such that in use: the first drive assembly rotates the primary antenna and the secondary antenna about the first axis, the second drive assembly pivots the primary antenna and the secondary antenna with the level frame assembly about the second axis, and the third drive assembly pivots the primary antenna and the secondary antenna about the third axis; and a control unit configured for: selecting operation of a selected one of the primary and secondary antennas, determining a position of the elevation frame assembly based upon sensed motion about said the first, second, and third axes, and controlling one or more of the first, second, and third drive assemblies to alter the position the selected one of the primary and secondary antennas.

2. The antenna system of claim 1, wherein the fixed offset angle of the primary antenna relative to the secondary antenna is approximately 70-120?.

3. The antenna system of claim 1, wherein the fixed offset angle of the primary antenna relative to the secondary antenna is approximately 85-105?.

4. The antenna system of claim 1, wherein the fixed offset angle of the primary antenna relative to the secondary antenna is approximately 70-85 or 105-120?.

5. The antenna system of claim 1, wherein the primary antenna is an offset antenna.

6. The antenna system of claim 5, wherein the primary antenna has a look angle that is approximately 5-20? below the horizontal when the cross-level frame is positioned at 0? relative to the horizontal.

7. The antenna system of claim 1, wherein one of the primary and secondary antennas includes a feed assembly including a remotely adjustable polarizer.

8. The antenna system of claim 7, wherein the remotely adjustable polarizer is rotated by an electric motor disposed on the feed assembly.

9. The antenna system of claim 1, wherein both of the primary and secondary antennas are operably connected to the control unit via a single coax cable.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a perspective view of a known level platform of a three-axis pedestal of the type described in U.S. Pat. No. 5,419,521 to Matthews.

(2) FIG. 2 is a perspective view of an exemplary tracking antenna having a three-axis pedestal with motion platform assembly in accordance with the present invention

(3) FIG. 3 is a right isometric view of the tracking antenna of FIG. 2 without the radome and radome base.

(4) FIG. 4 is a left isometric view of the tracking antenna of FIG. 2 without the radome and radome base.

(5) FIG. 5 is an enlarged perspective view of a motion platform subassembly of the tracking antenna of FIG. 2.

(6) FIG. 6 is an isometric view of the motion platform subassembly being installed within a Pedestal Control Unit (PCU) of the tracking antenna of FIG. 2.

(7) FIG. 7 is an enlarged perspective view of the motion platform subassembly mounted within the PCU of the tracking antenna of FIG. 2.

(8) FIG. 8 is an isometric view of another exemplary tracking antenna similar to that shown in FIG. 2.

(9) FIG. 9 is a perspective view of another exemplary tracking antenna similar to that shown in FIG. 2.

(10) FIG. 10 is an enlarged perspective view of the motion platform mounted within the PCU of the tracking antenna of FIG. 9.

(11) FIG. 11 is an elevational view of another exemplary tracking antenna similar to that shown in FIG. 2 having a piggy back configuration.

(12) FIG. 12 is an elevational view of the tracking antenna of FIG. 11 showing the antennas positioned at a first extent of motion.

(13) FIG. 13 is an elevational view of the tracking antenna of FIG. 11 showing the antennas positioned at a second extent of motion.

(14) FIG. 14 is an elevational view of another exemplary tracking antenna similar to that shown in FIG. 11 having a piggy back configuration.

(15) FIG. 15 is an isometric view of another exemplary tracking antenna similar to that shown in FIG. 11 having a piggy back configuration.

(16) FIG. 16 is an elevational view of the exemplary tracking antenna of FIG. 15.

(17) FIG. 17 is an enlarged isometric view of an exemplary OMT assembly of the exemplary tracking antenna of FIG. 15.

(18) FIG. 18 is another enlarged isometric view of the exemplary OMT assembly of the OMT of FIG. 17.

(19) FIG. 19 is an enlarged isometric view of an exemplary secondary antenna assembly of the exemplary tracking antenna of FIG. 15.

(20) FIG. 20 is an elevational view of another exemplary tracking antenna similar to that shown in FIG. 11 having a piggy back configuration.

(21) FIG. 21 is an elevational view of the exemplary tracking antenna of FIG. 20 positioned at a second extent of motion.

(22) FIG. 22 is an elevational view of the exemplary tracking antenna of FIG. 20 positioned at a second extent of motion.

DETAILED DESCRIPTION OF THE INVENTION

(23) Reference will now be made in detail to various embodiments of the present invention(s), examples of which are illustrated in the accompanying drawings and described below. While the invention(s) will be described in conjunction with exemplary embodiments, it will be understood that present description is not intended to limit the invention(s) to those exemplary embodiments. On the contrary, the invention(s) is/are intended to cover not only the exemplary embodiments, but also various alternatives, modifications, equivalents and other embodiments, which may be included within the spirit and scope of the invention as defined by the appended claims.

(24) In its simplest form the present invention includes supporting structural members, bearings, and drive means for positioning various rotating and pivoting structural members which are configured to align a tracking antenna about three axis, an azimuth axis, a cross-level axis, and an elevation axis. Antenna stabilization is achieved by activating drive means for each respective axis responsive to external stabilizing control signals. In some aspects, the pedestal of the present invention is similar to that disclosed by U.S. Pat. No. 5,419,521 to Matthews, U.S. Patent Application Publication No. 2010/0149059 to Patel, the entire content of which patent and publication is incorporated herein for all purposes by this reference, as well as those used in the Sea Tel? 4009, Sea Tel? 5009 and Sea Tel? 6009, and other satellite communications antennas sold by Sea Tel, Inc. of Concord, Calif.

(25) Generally, when a ship is not in motion, for example, when it is in port, antenna pointing in train and elevation coordinates is relatively simple. But when underway, the ship rolls and/or pitches thus causing the antenna to point in an undesired direction. As such, corrections of the train and elevation pointing angles of the antenna are required. Each of the new pointing commands requires solution of a three-dimensional vector problem involving angles of ship's heading, roll, pitch, yaw, train, and elevation.

(26) A pedestal in accordance with the present invention provides support means for tilt sensors, accelerometers, angular rate sensors, Earth's magnetic field sensors, and other instruments useful for generating pedestal stabilizing control signals.

(27) Turning now to the drawings, wherein like components are designated by like reference numerals throughout the various figures, attention is directed to FIG. 2 which shows an exemplary satellite communications antenna system 30 in accordance with the present invention generally including a three-axis pedestal 32 supporting an antenna 33 within a protective radome 35 (shown cutaway and transparent to facilitate viewing) and a radome base 37. The antenna system is adapted to be mounted on a mast or other suitable portion of a vessel having a satellite communication terminal. The terminal contains communications equipment and otherwise conventional equipment for commanding the antenna to point toward the satellite in elevation and azimuth coordinates. Operating on the pedestal in addition to those antenna pointing commands is a servo-type stabilization control system which is integrated with the pedestal.

(28) With reference to FIG. 3, the servo-control system utilizes sensors, electronic signal processors and motor controllers to automatically align the antenna about an azimuth axis 39, a cross-level axis 40, and an elevation axis 42 to appropriate elevation and azimuth angles for accurate tracking of a satellite or other communications device.

(29) The pedestal generally includes a base assembly 44, a vertical support assembly 46 rotationally supported on the base assembly about azimuth axis 39. Preferably the vertical support assembly may rotate 360? with respect to the base assembly. A cross-level frame assembly (or level frame assembly) 47 is supported by the vertical support assembly such that the antenna may pivot about cross-level axis 40. Preferably the cross-level frame assembly may pivot at least +/?20 to 30? relative to the vertical support assembly. And an elevation frame assembly 49 is supported by the cross-level frame assembly such that antenna 33 may pivot about elevation axis 42 in an otherwise conventional manner. Preferably, the elevation frame assembly may pivot at least 90?, and more preferably at least 120? (e.g., 90? pointing+2?roll range) relative to the cross-level frame assembly.

(30) A three-axis drive assembly is provided that includes an azimuth driver 51 for rotating the vertical support assembly relative to the base assembly, a cross-level driver 53 for pivoting the cross-level frame assembly relative to the vertical support assembly, and an elevation driver 54 for pivoting the elevation frame assembly relative to the cross-level frame assembly. One will appreciate that each of the drivers may be an electric motor or other suitable drive means configured to impart rotational or pivotal motion upon their respective components in an otherwise conventional manner. One should also appreciate that the order of the three axes may be changed without affecting the scope of this invention. For example, the order may be azimuth, elevation and then cross level. The end result will be the same pointing angle.

(31) Motion Platform

(32) In contrast to prior systems, tracking antenna system 30 includes a motion platform assembly 56 including an enclosure 58 affixed to and movable with the elevation frame assembly 49.

(33) With reference to FIG. 5, the motion platform assembly includes three orthogonally mounted angular rate sensors 60, 60 and 60 disposed within the enclosure for sensing motion about orthogonal X, Y and Z axis of the elevation frame assembly. In the illustrated embodiment, the sensors are CRS03 angular sensors provided by Silicon Sensing Systems Limited of Hyogo, Japan. One will appreciate, however, that other suitable sensors may be utilized.

(34) In various embodiments, the rate sensors are disposed in close proximity with one another on a motion platform subassembly 61. As shown in FIG. 5, the motion platform subassembly may take the form of orthogonally disposed circuit boards orthogonally secured to one another by an assembly bracket 63. Such an arrangement facilitates fabrication and assembly as it allows the sensors circuitry to be preassembled and simultaneously installed within the closure, as shown in FIG. 6. One will appreciate, however, that the sensors may also be indirectly mounted to the motion platform subassembly or elsewhere within the enclosure.

(35) With continued reference to FIG. 5, a three-axis gravity accelerometer is also mounted on motion platform subassembly 61 within enclosure 58. The three-axis gravity accelerometer is in the form of first and second gravity accelerometers 65, 65 are also mounted on motion platform subassembly 61 within enclosure 58. In the illustrated embodiment, the gravity accelerometers are ADIS16209 accelerometers provided by Analog Devices of Norwood, Mass. One will appreciate, however, that other micro-electro-mechanical system (MEMS) accelerometer and/or other suitable accelerometers may be utilized, preferably ones that meet various desired operational parameters discussed in further detail below.

(36) In various embodiments, one dual axis gravity accelerometer 65 is mounted on a base circuit board while the second dual axis gravity accelerometer 65 is mounted on a rear wall circuit board, however one will appreciate that the second gravity accelerometer may be instead mounted on the illustrated side wall circuit board. Mounting the gravity accelerometers directly to circuit board facilitates assembly and reduces the number of electrical connections needed, however, one will appreciate that the gravity accelerometers may also be indirectly mounted to the motion platform subassembly. Moreover, mounting the gravity accelerometers on the motion platform assembly within the Control Unit enclosure obviates the need for a braided and shielded wiring harness because the gravity accelerometers are operably connected to the control circuitry within the enclosure and without exposure to the harsh outdoor environment. To this end, one will appreciate that the gravity accelerometers may be located elsewhere within the motion platform assembly or the Control Unit enclosure. For example, as shown in FIG. 10, one gravity accelerometer 65b may be located on motion platform subassembly 61b while another gravity accelerometer 65b may be mounted on a wall of enclosure 58b.

(37) In the illustrated embodiment, both gravity accelerometers 65, 65 are two-axis accelerometers, the first being disposed along X and Y axes, and the second being disposed along X and Z axis. While such configuration creates some redundancy, it may lead to manufacturing efficiencies in that it reduces the number of unique parts required to keep in inventory. Nonetheless, one accelerometer may be replaced with a single-axis device, provided that the single axis is arranged orthogonal to both axis of the other two-axis device (e.g., the two-axis accelerometer arranged along the X and Y axis while the single-axis accelerometer is arranged along the Z axis). Moreover, the accelerometers may be replaced with three single-axis devices, provided that each axis is arranged mutually orthogonal to the other single-axis devices (e.g., the two-axis accelerometer arranged along the X and Y axis while the single-axis accelerometer is arranged along the Z axis).

(38) Two-axis gravity accelerometers are particularly well suited for use in the present invention as they may be rotated completely around and provide acceptable accuracy. For example, the two-axis ADIS16209 accelerometers used with the present invention are accurate to within 1? regardless of the angle of the elevation frame assembly, and more preferably less than 0.1?.

(39) Moreover, the ADIS16209 accelerometers are particularly well suited as they have a maximum error less than 1? within an operating temperature range, and presently within approximately of 0.2? within an operating temperature range of ?40? C. to +125? C. The accelerometers incorporate a microprocessor, calibration capabilities, temperature sensing capabilities, temperature correction capabilities, and other processing capabilities. Accordingly, such accelerometers are particularly well suited for use of ocean-going vessels operating in a wide range of climates and temperatures, anywhere from the equator to the North Sea and beyond.

(40) The tracking antenna system of the present invention further includes a pedestal control unit (PCU) 67 for determining the actual position of elevation frame assembly based upon signals output from the angular rate sensors 60, 60 and 60 and the gravity accelerometers 65, 65.

(41) In contrast to prior devices in which gyroscopic rate sensors were mounted in a level platform structure (e.g., level platform structure 20 in FIG. 1), the gyroscopic rate sensors were always kept substantially aligned with the three stabilized axes, namely longitudinal, lateral and vertical axes. Such prior designs allowed for very simple control loops: a cross level sensor exclusively drove the cross level axis; an elevation sensor drove elevation axis; and an azimuth sensor drove the azimuth axis.

(42) In the motion platform configuration of the present invention, angular rate sensors 60, 60 and 60 move with antenna 33 and elevation frame assembly 49 as the antenna rotates between 0? and 90?, and thus the sensors change their relationship with respect to the elevation, cross level and azimuth axes. Thus the angular sensors sense motion about orthogonal X, Y and Z axes fixed with respect to the elevation frame assembly.

(43) To correct for this, gravity accelerometers 65, 65 sense a true-gravity zero reference (i.e., the earth's gravity vector). In particular, the gravity accelerometers sense gravitational acceleration along the X, Y and Z axes and, utilizing analytic geometry, control unit 67 determines the true-gravity zero reference. Armed with the zero reference, the control unit can determine the actual location of the X, Y and Z axes relative to the zero reference, and using otherwise conventional coordinate rotation mathematics, for example, rotational transformation matrices, to determine the desired position of the X, Y and Z axis and control azimuth, cross-level and elevation drivers 51, 53 and 54, respectively, to position the elevation frame assembly in a desired position.

(44) While it is preferred that the gravity accelerometer(s) are arranged along orthogonal X, Y and Z axis, one will appreciate that the accelerometers may be placed in other known orientations to one another. For example, if one or more axis is non-orthogonal to the others, provided that at least three axes are non-parallel to one another, and their orientations are known with respect to one another, the control unit can be modified to account for the alternate orientations of the axes, for example, by modifying the rotational transformation matrices to account for the oblique angle(s).

(45) Tracking antenna systems in accordance with various aspects of the present invention to provide an improved maritime satellite tracking antenna pedestal apparatus which provides accurate pointing, is reliable in operation, is easily maintained, uncomplicated, and economical to fabricate.

(46) In other exemplary embodiments of the present invention, tracking antenna systems 30a and 30b are similar to tracking antenna system 30 described above but includes different pedestals 32a and 32b as shown in FIG. 8 and FIG. 9, respectively. In particular, motion platform assemblies 56a and 56b are affixed to elevation frame assemblies 49a and 49b, and thus move with antenna 33a and 33b, respectively. Like reference numerals have been used to describe like components of these systems. In operation and use, tracking antenna systems 30a and 30b are used in substantially the same manner as tracking antenna system 30 discussed above.

(47) Piggy Back

(48) In various embodiments of the present invention, the antenna assembly may be provided with multiple antennas on a single three-axes pedestal for providing additional functionality within a specified footprint. For the purposes of the present invention, piggyback refers to such a dual-antenna/single pedestal configuration, along with all other usual denotations and connotations of the term.

(49) With reference to FIG. 11, antenna assembly 30c has a three-axes pedestal 32c that is, in many aspects, similar to that of the Sea Tel? 6009 3-Axis marine stabilized antenna system but having a secondary antenna 33c mounted on the same pedestal. In the illustrated embodiment, the primary antenna has a primary reflector 71 that is compatible with C-band satellites, while the secondary antenna has a reflector 71 that is compatible with Ku-band satellites. One will appreciate that various configurations may be utilized. The primary antenna may be compatible with one or more bands including, but not limited to, C-band, X-band, Ku-band, K-band, and Ka-band, while the secondary antenna is compatible with one or more other bands. In various embodiments, the larger primary antenna is preferably compatible with C-band transmissions, and the smaller secondary antenna is preferably compatible with Ku-band or Ka-band transmissions.

(50) As shown in FIG. 11, FIG. 12, and FIG. 13, secondary antenna 33c is mounted for movement along with primary antenna 33c. In particular, reflector 71 of the secondary antenna is affixed relative to reflector 71 of the primary antenna. In the illustrated embodiment, the secondary reflector is mounted on cross-level frame assembly 47c along with the primary reflector but offset approximately 90?

(51) In FIG. 11, primary reflector is shown at 45? with respect to the horizontal, while the secondary reflector is shown at 135?. In FIG. 12, the primary reflector is shown at its lower extent of ?15?, while the secondary is at 75?. And in FIG. 13, the primary is shown at its higher elevational extent 115?, while the primary is shown at 205?. In the illustrated embodiment, the working elevational range of the primary antenna is approximately ?15? to 115? (25? past zenith) which accommodates ship motions of up to +/?20? roll and +/?10? pitch, assuming preferred communications with satellites are from approximately 5? above the horizon to zenith. This allows for a working elevational range of the secondary antenna of approximately ?30 to +100?. One will appreciate, however, that the actual range of motion may vary.

(52) The above-described piggyback antenna assembly is particularly well suited for VSAT communications. One will appreciate that piggyback antenna assemblies are well suited for other applications such as Tx/Rx, TVRO (TV-receive-only), INTELSAT (International Telecommunications Satellite Organization) and DSCS (Defense Satellite Communications System). For example, the antenna assembly shown in FIG. 14 is particularly well suited for TVRO applications, while the antenna assembly shown in FIG. 15 is particularly well suited for applications that are INTELSAT and DSCS compliant applications.

(53) Turning now to FIG. 16, one will appreciate that the primary and secondary antennas need not be precisely orthogonal to one another, and may instead be oriented at various angles with respect to one another. In the illustrated embodiment, primary antenna 33e and elevation frame assembly 49e is approximately level with the horizontal. The primary antenna, however, is an offset antenna in which the look angle ?.sub.L is approximately ?17?, that is, approximately 17? below horizon H. In this case, the secondary antenna is approximately 197? beyond zenith. In this embodiment, the primary and antenna are positioned approximately 87-88? relative to one another. However, one will appreciate that the cant of the secondary antenna relative to the primary antenna may vary, for example, 90? or more, or 80? or less. Preferably, the cant is in the range of approximately 70-120?, more preferably in the range of approximately 85-105?.

(54) In various embodiments, such as shown in FIG. 11 the smaller secondary antenna is canted more than 90? relative to the primary antenna order to provide sufficient clearance to stay within the radome. The actual amount of cant may vary depending upon the overall configuration of the antenna assembly, with a primarily purpose being the use of otherwise unused space for a secondary antenna located behind the primary antenna.

(55) Preferably, the piggyback antenna assembly is remotely switchable. To this end, the assembly may be provided with hardware and software that is configured to remotely and readily switch bands and/or polarizations.

(56) For example, the antenna assembly may not only include otherwise-known capabilities for switching between dual bands on one reflector, but may also, or instead, include capabilities for switching between different bands on different reflectors. For example, in the embodiment illustrated in FIG. 11, the antenna assembly may be configured to switch between C-band and X-band on the large primary reflector 71, and be figured to switch between the band(s) of the primary reflector and the Ku-band on the small secondary reflector.

(57) The antenna assembly may also provide for an electronically switchable to accommodate for circular and linear polarizations on the same reflector without having to manually change the feed. For example, FIG. 17 and FIG. 18 depict a remotely adjustable polarization feed 73, in which a motor 74 drives a polarizer 76 to vary the signal received by orthomode transducer (OMT) 78. In the illustrated embodiment, the polarizer is generally a length of tube inside of which is a quarter-wave plate or quarter-wavelength plate. The quarter-wavelength plate changes a linearly polarized signal to a circular polarized signal before it is received by the OMT. Rotating the polarizer tube to 45? counterclockwise (ccw) or 45? clockwise (cw) determines whether horizontal or vertical components of the signal wave get converted into right hand or left hand.

(58) In accordance with the present invention, motor 74 is remotely operable to rotate polarizer tube 76 and the quarter plate therein. Such remote operation avoids the present necessity of climbing up to the antenna assembly, accessing the assembly with the radome, disassembly of the feed and polarizer tube, rotating the polarizer, reassembly, etc. The remote control of the present invention reduces the conventional couple-hour job of manual adjustment of the polarizer to a process that may be accomplished within minutes, or less

(59) Preferably, the hardware and software of the present antenna assemblies are configured to reduce the cabling from multiple antennas. Generally, a coaxial cable is necessary for each antenna. However, the present invention allows for reducing the number of coax cables to a single coax cable 80 by frequency shifting the transmit, receive, Ethernet control channel and 10 MHz TX reference clock all onto a single coax cable.

(60) The control unit may be provided with relay board switches to control two sets of control signals from the control unit to the primary and secondary antennas. For example, a bank of relays may be configured for designed switching between conventional 25 pin connectors and 10 pin connectors in order to selectively route communications between the control unit and the desired one of the primary and secondary antennas.

(61) In accordance with the present invention, when multiple antennas are used in a piggy-back configuration, control unit 67 is integrated with various programming and algorithms to accomplish the search, track, targeting and stabilization. A primary purpose of the piggy back antenna pedestal is to communicate via two separate reflectors on the same pedestal. Typically, these reflectors would be tuned and equipped with different transmit and receive equipment for different radio frequency segments.

(62) For example, one C-band radio frequency reflector and one Ku-band radio frequency reflector. Since Ku-band requires a much smaller reflector, it is possible to use the empty space in the radome enclosure on the backside of the C-band reflector to mount the Ku reflector. In doing so, the same mechanical equipment can be used to point both reflectors. However, the control system for accurately pointing each reflect toward its desired target must be adjusted.

(63) One difference between the traditional pointing control system and the dual antenna system of the present invention is to know which antenna is currently being used to communicate and how driving the pedestal in one direction or another will influence the point angle of the operating reflector.

(64) In the case described above the C and Ku reflectors have different pointing angles. For example, and as discussed above, a three-axis pedestal generally moves about an azimuth axis 39, an elevation axis 42, and a cross-level axis 40. When a pedestal is equipped with multiple reflectors, there are various implications to be considered. A clockwise increase in azimuth (i.e., rotation about the azimuth axis) is a clockwise increase on both reflectors. However, since the reflectors are generally pointing toward opposing horizons, an increase in elevation (i.e., rotation about elevation axis) on the primary reflector (e.g., 71, 71d, 71e) is a decrease in pointing elevation on the secondary reflector (e.g., 71, 71d, 71e), and vice versa. Also, a clockwise increase in cross level (i.e., rotation about the cross level axis) on the primary reflector is a counter-clockwise motion on the secondary reflector. accordingly, movement in azimuth is offset by 180?, movement in elevation is inverted, and movement in cross level is reversed.

(65) In accordance with the present invention, the software of the control unit is specifically configured to compensate for various other factors, such as trim for mechanical alignments, polarity angle offset, scale and type, tracking, and system type.

(66) In various embodiments, the control system is configured with azimuth trim and elevation trim to help compensate for mechanical variations from pedestal to pedestal. One will appreciate that, due to various manufacturing processes and despite manufacturing tolerances, there will be certain dimensional variances from pedestal to pedestal. In addition, various reflectors configured for different bands will have varying structure and dimensions. Accordingly, the control system may be provided with adjustable trim settings to compensate for such variations.

(67) In various embodiments, the control system accommodates for Polang (Polarity Angle) Offset, Scale and Type. Polang Offset is similar to the azimuth and elevation trims above and works to align the feed Polarity Angle for each antenna to a nominal offset. Polang Scale will vary the amount of motor drive which is used to move the feed. Polang Type will also change from antenna to antenna as this parameter is used to store information about the motor and feedback used.

(68) In various embodiments, the control system accommodates for varying tracking processes including dish scan and step size. These parameters are used to increase or decrease the corresponding amount of movement when while the antenna is tracking a satellite, that is, attempting to find the strongest pointing angle which can be used to receive and transmit signals. These values usually change dependant on the size of reflector and frequency spectrum which is currently being tracked. When a smaller secondary antenna is used to receive a different frequency spectrum, this parameter will have to change.

(69) In various embodiments, the control system accommodates system types. This parameter is used to store several different settings which may change when a different antenna is used to transmit and/or receive signal. One example is modem lock and blockage signal polarity. If two separate modems are used for the two separate antennas, the polarity of the modems may be different from antenna to antenna. The same logic can be used for signaling a blockage for the modem. Another example is external modem lock. This may be used to indicate that an external source is receiving the correct signal. Since separate modems may be used for each antenna, this may also change from antenna to antenna. One more example is LNB (low noise block-downconverter) voltage. Since the two antennas will likely utilize two different LNBs, there may be two different methods of using those LNBs.

(70) Accordingly, control system 67 will be provided with one or more stored sets of parameters which account for the variations between the primary and secondary and antennas. These stored sets of parameters may be in the form of lookup tables or other suitable stored information.

(71) In many respects various modified features of the various figures resemble those of preceding features and the same reference numerals followed by subscripts a, b, c, d, and e designate corresponding parts.

(72) The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teachings. The exemplary embodiments were chosen and described in order to explain certain principles of the invention and their practical application, to thereby enable others skilled in the art to make and utilize various exemplary embodiments of the present invention, as well as various alternatives and modifications thereof. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents. It is also intended that the terms comprising, including, and having are open terminology, allowing the inclusion of other components in addition to those recited.