Abstract:
An electronic apparatus for measuring water speed and water temperature then periodically transmitting said data during controlled depth fishing wherein an underwater probe is secured to and insulated conductive downrigger cable and gathers and relays data though the cable to a remote receiver/display unit disposed on the watercraft.

Description:
RELATED APPLICATIONS 
   This application is subject to now expired U.S. provisional application Ser. No. 60/648,876 filed 1 Feb. 2005. Please incorporate by reference all information in said provisional application into this instant application. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   Controlled depth fishing has been a popular sport for many years. Controlled depth fishing methods allow fishermen to troll a lure such as a spoon, crankbait, dodger-fly combination, etc. at depths much greater that the lure would dive on its own. 
   Controlled depth fishing is accomplished by means of a downrigger mounted to a watercraft. The downrigger is comprised of a frame which mounts to a boat, a reel with an electric motor or hand crank mechanism, a boom extending from the boat over the water, a pulley at the end of the boom, stainless steel cable that is spooled onto the reel and threaded through the pulley at the end of the boom, and a cannonball attached to the end of the cable. The cannonball is usually constructed of lead and typically weighs between 10 pounds to 18 pounds. The downrigger may also include a counter connected to the reel and calibrated in feet to indicate to the user how far below the water surface the cannonball is tracking.  FIG. 1  illustrates a typical downrigger. 
   To use a downrigger in controlled depth fishing, the fisherman would first allow a lure attached to a standard fishing reel and pole to troll out behind the watercraft. Typically the lure is let out about 10 to 30 feet. The fisherman would then attach the line from the rod and reel to the cannonball with a rubber band or pincher type release mechanism. The fisherman would then slowly allow the cannonball to descend into the water to a predetermined depth. The depth can be read from the counter on downriggers so equipped. In this scenario, the lure is now running at the depth of the cannonball. This depth would also be shown on the downrigger&#39;s counter.  FIG. 2  illustrates the details controlled depth fishing. Note that the lure attached to the rod and reel is now being trolled at the depth of the cannonball. 
   When a fish strikes the lure, the strike either breaks the rubber band attaching the line to the cannonball or pulls the line out of the pincher release and allows the fisherman to fight the fish with just the rod and reel. Once the line is released from the cannonball, the downrigger no longer plays a part in the fighting and retrieval of the fish.  FIG. 3  illustrates a scenario right after the rubber band has broken or pincher has released. 
   Controlled depth fishing has been proven to be a very effective method for catching fish species such as Salmon and Trout in the Great Lakes. It has also proved to be an effective method for catching a wide variety of fish in the ocean. 
   Additionally, it is well known that fish such as Salmon and Trout prefer waters of certain temperature ranges and will seek out the waters that provide these temperatures. Additionally, it has been found that fish are most likely to strike a lure traveling or trolled at a specific range of speed. Therefore, fisherman will seek a particular temperature of water and a troll at a specific speed when targeting a specific species of fish. 
   Most watercraft used for fishing usually includes a means for measuring water surface temperature and surface speed. However, this information usually has no bearing as to what water temperature and water speed are well below the surface at the cannonball and lure. 
   2. Description of the Prior Art 
   Over the past decade or so, there have been several electronic apparatus sold to fisherman who practice controlled depth fishing to measure the water temperature and water speed at the cannonball and lure. These systems are comprised of an underwater sensor/transmitter probe, a special downrigger cable with a plastic coating, a receiving antenna, a receiver/display unit, and a shield cable that connects the receiving antenna to the receiver/display unit, and a power cable that provides 12V boat power to the receiver/display unit. 
   The theory of operation of such a system is as follows: 
   The underwater probe unit is mechanically and electrically attached to the special coated downrigger cable as to provide a strong mechanical connection to suspend the probe, as well as provide an electrical connection such that the downrigger wire is used as a signal path to the watercraft. This connection must be wrapped in a special rubberized electrical tape or apply liquid sealant to electrically isolate the connection from the water. The probe transmits its sensed data over this cable via a low frequency RF signal—typically anywhere between 100 KHz and 500 KHz. 
   A drop leader of 18″-24″ typical is attached to the bottom tab of the underwater probe, and the cannonball is then attached to this leader to provide the weight necessary to hold the probe and fishing lure at a predetermined depth. 
   A pick-up antenna in the form of a spring with multiple turns of wire is used to receive the signal sent on the downrigger cable from the underwater probe. The downrigger cable passes through the center of the spring. The spring is also attached to a cable (usually shielded cable or coax). This antenna cable then connects to another cable (usually shielded cable or coax) which carries the signal received from the underwater probe to the receiver/display module. 
   The underwater probe periodically measures water temperature and speed with respect to the surrounding water; and periodically reports this information to the receiver/display unit by transmitting the sensed data via an RF signal over the coated downrigger cable. 
   The receiver/display module monitors the received signal, decodes the data and displays the speed and temperature as reported by the probe on the LCD display for viewing by the operator.  FIG. 4  illustrates the major components of the system as well as their connectivity. 
   The installer replaces the ordinary downrigger cable with the special coated cable. This coated cable is then attached to the underwater sensor/transmitter probe. To make the attachment to the probe, the coating on the cable must be stripped away such that there is an electrical connection between the cable and the metal tab on the probe unit. The user would then install a thimble and barrel crimps to secure the cable to the tab. Once the barrel crimps are installed, the user would then insolate this connection with a special rubberized electrical tape to isolate the electrical connection from the water.  FIG. 5  illustrates this interconnection method between the coated downrigger cable and the underwater probe.  FIG. 6  illustrates this connection after rubberized electrical tape has been applied. 
   The spring antenna is mounted to the downrigger boom as illustrated in  FIG. 7 . The coated downrigger cable passes through the center of the spring antenna. The shielded cable connecting to the spring antenna is mounted to the downrigger boom—typically with nylon tie straps. The tie straps are usually positioned at least 6-10″ from the spring antenna to allow the antenna to flex and move with the downrigger cable. This is necessary so that the shielded cable is not damaged from the constant movement of the spring antenna/downrigger cable. 
   The antenna cable includes a connector on the end opposite the spring antenna. This connector is plugged into a second shielded cable with connectors on both ends. This cable is then routed throughout the watercraft up to the display/receiver unit, where it plugs into a connector on the receiver/display. 
   The receiver/display unit is mounted on the watercraft in a convenient viewing location. A third cable, the power cable, is plugged into the receiver/display unit. The opposite end of the power cable is wired directly into the 12VDC power of the watercraft. 
   Further, another system readily available to fisherman operates in a similar fashion to the system described above, but additionally includes a means for the underwater sensor/transmitter unit to measure ambient light intensity, water pressure, and probe battery voltage. This information is transmitted up the coated downrigger cable in addition to the speed and temperature information. The receiver/display in this system also includes provisions to decode this information and display it on the LCD screen. The receiver/display unit converts measured pressure into depth. In this system, water temperature, water speed, probe battery voltage, ambient light intensity (in percentage) and probe depth are displayed on the LCD. 
   Shortcomings of Prior Art: 
   Many fishermen have expressed great disappointment in being required to use the special coated downrigger cable to carry the underwater probe transmitted signal to the spring antenna mounted on the downrigger boom. After weeks and months of use, the coating on the cable may become damaged or frayed, thereby exposing the inner conductor to the water. When water contacts the conductor in the coated cable, the signal becomes attenuated, and at a certain depth, the system no longer operates. As an example, with new coated cable the system may operate to 200′ of water. However, when the insulating coating becomes damaged and frayed thereby exposing the inner conductor to water, system operation may be limited to 40′ or less—depending on the extent of damage to the insulating coating—again, this is due to the attenuation effects of the water on the transmitted signal. Further, this special coated cable is much more expensive than ordinary downrigger cable, and therefore it costs the user time and money to replace the coated cable. Still further, the cable is of larger diameter than ordinary cable due to the insulating coating, and this additional diameter increases the cables drag in water causing the cannonball to run much father behind the boat at normal trolling speeds as compared to a cable without the coating. 
   Another shortcoming is that of an underwater probe of the prior art that is large and bulky. Large probes cause additional drag in the water, and therefore cause the downrigger cannonball to track much farther behind the boat than the cannonball would track without the probe attached to the downrigger cable. Ideally, the fisherman would like the cannonball to track directly beneath the watercraft. The more drag on the system, the farther behind the watercraft the cannonball will track. 
   Still another shortcoming of the underwater probe of the prior art is that many times they do not track true with respect to the line of motion of the watercraft. This is due to the ferromagnetic rotor or ‘paddle wheel’ that is mounted on the side of the probe unit—causing the probe to ‘dog track’ or track at somewhat of an angle to the line of motion of the watercraft. 
   Yet another shortcoming of the underwater probe of the prior art is that of the wire and snap-clip attachment means of the 9V battery. This snap-clip attachment means can become damaged over time, and the wires can fatigue and break—requiring the probe to be sent in for repair. 
   Yet another shortcoming of the underwater probe of the prior art is that the electronics are not sealed against water damage should the O-rings that seal the battery cover fail. Once water enters the unit, the electronics become submerged in water and potential permanent failure of the electronics could occur. 
   Yet another shortcoming of the underwater probe of the prior art is that the housing only includes one O-ring seal to seal the battery cover to the housing. Many times the single O-ring seal becomes damaged and allows water to enter the probe. 
   Yet another shortcoming of the underwater probe of the prior art is that the electronics consume a fair amount of power, requiring the user to replace the 9V battery at regular intervals during use. 
   Yet another shortcoming of the underwater probe of the prior art is that the design is not such that it can be easily injection molded and has to be machined from tubular plastic piping such as PVC. 
   Yet another shortcoming of the underwater probe of the prior art is that it is not easily manufactured and requires a large amount of labor. 
   Yet another shortcoming of the underwater probe of the prior art is that the housing has a geometry which does not easily lend itself to applying rubberized electrical tape to create an adequate seal against water intrusion. 
   A shortcoming of the spring antenna of the prior art is that it does not provide adequate means to recover maximum amount of received signal due to its construction of only a few turns of wire and short length. 
   Yet another shortcoming of the antenna of prior art is that the spring-to-cable connection is covered with heat shrink tubing and is mechanically weak and prone to breakage. 
   A shortcoming of the receiver/display unit of the prior art is that while it displays the underwater probe&#39;s battery voltage, the average user does not possess the detailed knowledge required to determine at what voltage should the probe battery be replaced. 
   Another shortcoming of the receiver/display unit of the prior art is that there is no backlight for the LCD to be viewed at night, and if a backlight is provided, it is not user adjustable. 
   Another shortcoming of the receiver/display unit of the prior art is that there is no backlight for the user controls to be viewed at night, and if a backlight is provided, it is not user adjustable. 
   Another shortcoming of the receiver of the prior art is that the input signal receiving circuitry does not provide adequate selectivity to the specific received signal frequency. 
   Yet another shortcoming of the receiver/display unit of the prior art is that it does not provide a means for easy software updates such as new speed and temperature calibration tables, new software features, and the like. 
   Yet another shortcoming of the receiver/display unit of the prior art is that it does not provide a means for the user to calibrate the speed and temperature as reported by the probe to a separate system on the watercraft that measures surface speed and temperature. 
   Yet another shortcoming of the receiver/display unit of the prior art is that it requires the user to manually shut if off after use. If a user forgets to shut it off, it continues to consume boat battery power—which could lead to a dead boat battery over a period of time. 
   Yet another shortcoming of the receiver/display unit of the prior art is that it does not allow the user to variably adjust the averaging of displayed data to compensate for calm or wavy water conditions. 
   Yet another shortcoming of the receiver/display unit of prior art is that it is large and bulky thereby limiting mounting locations on the watercraft. 
   While the methods described above for measuring water temperature and water speed at the underwater probe as well as optionally measuring probe battery voltage, water pressure and water clarity at the probe may be suitable for the purposes for which they were designed, they would not be suitable for the purposes of the present invention, as hereinafter described. 
   SUMMARY OF PRESENT INVENTION 
   A primary object of the present invention is to pro vide a measurement and reporting system that overcomes the shortcomings of the prior art. 
   Another object of the present invention is to eliminate the coated downrigger cable. Prior art systems must use the coated downrigger cable to prevent the lake water from attenuating the transmitted signal from the underwater probe. If the center conductor of the coated wire is exposed to the lake water, the signal level is reduced and the maximum depth of system operation is degraded. 
   However, it has been discovered that even if the insulating coating was completely eliminated from the downrigger cable, all the signal is not attenuated. There still exists a very small signal at the antenna or pick-up coil mounted on the downrigger boom. The problem is that the signal level is so small, prior art systems are not able to discern the information the signal contains. Hence, the system stops operating. 
   There are several improvements needed in the system to solve this technical issue. The first area discussed will be that of the antenna or pick-up coil. 
   Yet another object of the present invention is to provide an improved antenna. Those skilled in the art of electronics understand that as a varying current passes through a first wire it generates a small varying magnetic field about the first wire. This varying magnetic field will induce a small varying current into a second wire if the second wire is in close proximity to the first wire. This induced varying current in the second wire will create a varying voltage as measured at the second wire based on the impedance of the second wire and the impedance of the circuitry attached to the second wire. However, if the second wire were to completely surround the first wire in the form of multiple turns, the varying voltage induced in the second wire is larger that if the second wire had no turns at all. 
   This concept is used on existing systems by means of an air wound spring that is used as a receiving antenna or ‘pick-up coil’ antenna. The coated downrigger cable is routed through the center of the pick-up coil for best reception. Existing systems use springs or pick-up coils of only 10-35 turns. 
   Due to the pick-up coil being wound from bare wire, each turn has to be spaced apart from the previous turn to prevent electrical contact between the turns or windings. With existing systems, the spring length is usually limited to approximately 3″. 
   Method #1: 
   By simply manufacturing the pick-up coil to a longer length, say 4″ or more, and maintaining the same turn-to-turn spacing, it is easy to understand that new pick-up coil would have more turns. More turns equate to more recovered signal. Using this analogy, a pick-up coil of 15″ in length would of course recover more signal than a pick-up coil of 2″. Therefore, simply increasing the number of turns and hence the length of the pick-up coil will recover more signal than that of a shorter pick-up coil. 
   Method #2: 
   Unfortunately method #1 has practical limits since the available space on a downrigger boom is limited and mounting would become a problem. 
   An alternate method to increase the winding count is to use smaller gauge wire with an electrical isolation on its exterior. This isolation is typically an enamel or lacquer coating (i.e. magnet wire) or it could be a plastic coating such as PVC. Now the pick-up coil can be wound with each turn touching the previous turn while each turn is still electrically isolated from the adjacent turns. With this approach, it is easy to see that a pick-up coil of 3″ of length could have 4 or more times the turns of an air wound coil constructed of bare wire. Now, because the wire is of smaller diameter, it usually won&#39;t keep its form properly and its thin electrical coating is easily damaged. However, winding this type of pick-up coil on a plastic bobbin with a hole through the center such that the downrigger cable could pass through solves the problem. The bobbin is used to maintain the form of the coil as well as protect the coil windings and thin insulation from the downrigger cable that is passing through the center of the coil. Additionally, because this type of wire is more fragile, the complete assembly of turns of wire on the bobbin would need to be enclosed or encapsulated in a material such as plastic or epoxy to prevent damage and corrosion to the wires. 
   Method #3: 
   While method #2 allows many more turns in the same length required for an air would coil, the turn count may not be adequate for the task at hand. Therefore, the insulated wire could be wound onto the bobbin in multiple layers, the second layer of windings directly on top of the first layer, the third layer wound directly on top of the second layer, and so on. With this approach, a much larger turn count pick-up coil can be constructed in a similar space as required for present air wound bare wire coils. With this layered winding approach, a much higher signal level would be recovered from the downrigger cable as compared to the air wound bare wire coil as used in existing systems. Of course this assembly would also require protection from mechanical damage and corrosion so the same type of enclosure or potting method would be employed. 
   Method #4: 
   While methods #2 &amp; #3 are practical to recover larger amounts of signal from the downrigger cable, another alternative exists to increase the effectiveness of the antenna. This is referred to as an active antenna. Essentially, the pick-up coil as described in method #2 &amp; #3 would be mounted in conjunction with a small circuit board that includes the receiving circuitry. With the receiving circuitry in very close proximity to the pick-up antenna, maximum signal is recovered from the downrigger cable and cabling signal loss from the antenna to receiver/display unit is overcome. Active antennas usually include a preamplifier, and can also contain front-end tuned circuits as well as inter-stage ceramic filters or crystal filters to greatly increase the selectivity of the circuit while increase the rejection of unwanted signals. Power for the active antenna module would be provided in the cable connected to the receiver/display module or by means of direct wired connection to boat DC power. 
   Still another object of the present invention to provide improved receiver sensitivity. We have learned how to recover a stronger signal by means of antenna improvements. By improving the receiver circuitry the receiver sensitivity can also be improved. Increasing the receiver sensitivity allows the receiver to receive and recover data from signals that are too low in level to be recovered by prior art systems. 
   The first method to increase the receiver sensitivity is to increase the receiver&#39;s selectivity. Selectivity is a measure of how well a receiver receives a specific frequency while rejecting unwanted frequencies. This equates to narrowing the bandwidth of the receiver and providing much steeper roll-off of frequencies outside the desired bandwidth. Since the underwater probe modulates its data onto a single frequency carrier or about a single frequency carrier as in the case of frequency shift key (FSK) modulation, it is possible to narrow the bandwidth of the receiver such that it only receives signals of a specific frequency. The probe may employ amplitude shift key (ASK) modulation, frequency shift key (FSK) modulation or both amplitude shift key and frequency shift key modulation. Prior art systems employ bandwidth limiting circuitry in the form of a tuned LC circuit. Unfortunately, tuned LC circuits do not provide the selectivity or narrow bandwidths needed to recover the low level signals that are present when a downrigger cable has no insulation or coating. Additionally, LC tuned circuits do not have a steep roll-off or attenuation of frequencies outside the desired bandwidth. While a tuned LC circuit may still be employed as a first stage of the receiver, a better method to improve the receiver&#39;s selectivity is to employ a ceramic filter or crystal filter network. These types of inter-stage filters are employed in many communication systems such as two-way radios, AM and FM receivers and the like as they provide a much narrower bandwidth than can be, obtained by a simple LC filter. Narrower bandwidth equals improved receiver sensitivity. Additionally, the out-of-band rejection of these types of filters is much greater than that of a LC tuned circuit thereby eliminating interference noise from sources such as two-way radios, radar, livewell pump motors, fan motors and the like wherein said noise signals reside in close proximity to said carrier frequency of received probe transmissions. 
   The second method to increasing the effective sensitivity of the receiver is to employ automatic gain control (AGC) circuitry or automatic level control (ALC) circuitry. This circuitry is constantly monitoring the output of the amplifier or amplifiers in the receive circuitry and dynamically adjusts the gain of the amplifier(s) to maintain a relatively constant output signal level. If a strong signal is received from the antenna, the AGC or ALC circuit will dynamically reduce the gain of the amplifier to maintain a relatively constant amplitude which prevents overdriving the next stage in the receiver. Conversely, if a very weak signal is received from the antenna, the AGC or ALC circuit will dynamically increase the amplifier gain until the amplifier&#39;s output is at a desirable level. This type of circuitry is very important in the recovery of digitally modulated signals that have a wide range of signal levels. As an example, when a system as described does not use a coated downrigger cable, when the underwater probe is at 200 feet depths of water the signal level recovered at the pick-up coil antenna might be measured in microvolts. 
   Conversely, when the underwater probe is only at 10 foot depths, the voltage level recovered at the pick-up coil antenna might be measured in a volt or more. To handle this wide range of signal levels, a receiver must employ AGC or ALC circuits. 
   Underwater Sensor/Transmitter Probe Operational Description 
   The probe circuitry is in an ultra-low current sleep mode when out of the water to conserve battery power. When the probe is placed in water, the probe water sensing circuitry senses or measures current flow across two water sensing elements, or across one sensing element and the second connection tab, if that tab is tied electrically to ground. When current flow is detected, the internal circuitry enters run mode. The probe circuitry may include at least one electrically conductive element penetrating the housing forming means for sensing the presence or absence of water. The means may measure resistance between an electrically conductive element and another electrically conductive circuit element. The means may measure resistance between and electrically conductive element and circuit ground. The means may measure current between an electrically conductive element and another electrically conductive circuit element. The means may measure current between an electrically conductive element and circuit ground. When in ultra-low current sleep mode less than 200 uA of current is consumed. The average current consumption is less than 1.75 mA. 
   As the probe moves in the water, the ferromagnetic rotor starts to rotate. This rotational speed is correlatable to MPH through software algorithms. As the ferromagnetic rotor rotates, each of its teeth pass by a magnetic field sensor such as a hall-effect sensor. The hall-effect sensor has internal chopper circuitry thereby greatly reducing its average current consumption. As each tooth passes by the magnetic sensor, the magnetic sensor creates a digital pulse. The microcontroller counts these pulses over a specific period of time and stores this data until it is time to transmit an RF message up the downrigger cable. Alternately; the microcontroller may measure the time between each pulse, then average this data over multiple measured durations, and store the averaged data until it is time to transmit an RF message up the downrigger cable. 
   Additionally, the microcontroller is periodically communicating with the temperature sensor to extract temperature data. This temperature data is extracted then stored until it is time to transmit an RF message up the downrigger cable. The microcontroller may average several samples of data and store the average data. 
   Additionally, the microcontroller is periodically measuring the probe&#39;s battery voltage and storing this data until it is time to transmit an RF message up the downrigger cable. 
   Periodically, the microcontroller collects the stored data, formulates a message and transmits this message up the downrigger cable by means of an RF driver circuit that is electrically connected to the first connection tab. 
   Optionally, the probe electronics may include a means to measure ambient light intensity and water pressure. Ambient light intensity is used by fisherman to help choose appropriate colors for lures as it is well known that light intensity continues to decrease as the depth of the lure is increased. Water pressure as measured at the probe can be converted into actual depth via software algorithms. 
   The process of periodically collecting data, optionally averaging data, and periodically transmitting said data via an RF message transmission continues until the probe is removed from the water. When the water sensing circuitry in conjunction with the water sensing elements detects that the probe has been removed from the water, the probe electronics is placed in an ultra-low current sleep state to conserve battery power. 
   Underwater Sensor/Transmitter Probe Improvements 
   The various figures illustrate an under water sensor/transmitter probe design with many new features not available on prior art systems. 
   First, the probe housing is constructed of three pieces. The main body, the nose piece, and the battery access cover. The overall probe enclosure features a reverse taper i.e. the probe housing is physically larger at the front toward the nose than it is toward the back. The reverse taper aids in reducing hydrodynamic drag as well as greatly improves the produce-ability of the enclosure. The nose is fabricated in a separate piece to aid in assembly of the electronics internal to the unit. After the electronic assembly is installed, the nose piece is installed to complete the assembly. 
   The battery access cover installs to the main body by means of threads. The battery access cover features internal threads and the mating threads on the main body are external threads. This approach helps reduce overall size while greatly improving produce-ability. The battery access cover has provisions for an O-ring seal on the inside bottom of the cover. The O-ring seal mates with the bottom edge of the main body. The battery access cover also includes a spring and back-up washer fastened to the inside bottom of the cover by means of a screw, bolt or rivet. This spring presses against the battery and this pressure maintains the contact between the battery terminals and the fixed position power terminals (i.e. fixed position battery contacts) within the probe unit. The battery contacts are constructed from a material that resists corrosion, such as stainless steel or nickel plated brass. A second O-ring seal is located on the main body and this seal mates with the inside surface of the battery access cover. The main body is a housing that contains a gland for placement of the second O-ring seal, where the gland is located prior to the start of the external screw threads but after the end of the housing&#39;s outer surface is The battery access cover features aggressive knurled surface to aid users in removing and installing the cover when their hands may be wet and slippery. 
   The main body of the unit includes the rotor housing detail as well as provisions for the rotor axle. A rotor mounting detail is constructed at the same time as the main body. 
   The main housing contains slots or channels on its interior for alignment of the circuit board assembly. 
   The main housing and nose piece, when assembled, also include a raised boss that surrounds the upper connection tab. This boss aids in creating a good seal between the housing and applied rubberized electrical tape, necessary if used with coated downrigger cable. 
   The nose cap features an elliptical contour on the front to aid in reducing hydrodynamic drag. 
   Additionally, the main body of the probe may include stabilization fins to aid in the proper tracking of the probe unit with respect to the direction of the boat. Due to the ferromagnetic wheel protruding on one side of the probe, the probe may track at an angle (or dog track) to the boats direction of movement. 
   Circuit Board Assembly for Underwater Sensor/Transmitter Probe Unit. 
   The circuit board assembly is designed such that all electrical components, connecting tabs, and power contact terminals can be assembled prior to installation into the housing, then slideably installed into the slots or channels within the main body. Prior to installing the circuit board assembly, a battery alignment housing is slide-ably installed into the slots or channels. The battery alignment housing aids in positioning the battery to make proper contact with the power contact terminals on the circuit board assembly. Optionally, this battery alignment housing may be attached to the circuit board assembly, then the completed circuit board assembly including the battery alignment housing is slideably installed into the slots or channels within the main body. 
   Each connection tab (i.e. mounting tab) is fabricated with identical geometry to reduce tooling costs, piece part costs, and to reduce errors in assembly. They are installed with a series of shims and washers to sandwich the circuit board thus creating an electrical connection between the RF signal drive circuitry on the circuit board while electrically isolating the lower tab from the upper tab. The lower tab may include a terminal and wire that connects the lower tab to ground potential of the circuit board. 
   All the sensor devices such as the magnetic sensor device and the temperature sensing device are mounted directly to the circuit board. The sensors are located directly below the axis of rotation of the ferromagnetic rotor. The circuitry has provisions to protect itself from damage should the power be installed in a reverse-polarity manner. 
   Receiver/Display Functional Overview: 
   The receiver/display unit is comprised of the following major components: 
   An enclosure, a multiple button keypad with integral seal for the enclosure, a keypad backlight, a circuit board assembly consisting of a regulator circuit, microcontroller, an LCD, a LCD backlight, circuitry to receive the signal from the antenna and convert said signal into digital data, a DC power connector, and a signal input connector. It should be noted that the two connectors could be combined into a single connector without varying from the theme of the disclosed invention. 
   To turn on the receiver/display unit, the user presses the ON button for a short period of time. Once the unit is operating, it continues to monitor the signal input line for data coming from the underwater sensor/transmitter probe unit. When a signal is detected, the signal receive circuitry converts this signal into digital data for processing by the microcontroller. The microcontroller then decodes this data and displays the data on the LCD. 
   The signal receive circuitry includes a ceramic filter or crystal filter to provide a high degree of selectivity and thus improve sensitivity to low-level input signals. Additionally, this signal receive circuitry also includes an automatic gain control circuit (sometimes referred to as automatic level control) that dynamically adjusts the gain of an amplifier or amplifiers such that the output signal level is maintained at a desired level. 
   The receiver/display unit also includes features to allow users to calibrate various parameters and displayed data. As an example, a user may notice that receiver/display unit&#39;s data does not match that of his other instrument for measuring surface speed and temperature. The user can enter a wide variety of calibration modes by pressing a specific button, a specific series of buttons or a specific combination of buttons. 
   Once a specific calibration mode is entered, the CAL icon will illuminate on the display to indicate the receiver/display system is in the calibration mode. If the user had chosen to calibrate the speed function, he would have pressed the appropriate buttons to enter the speed calibration mode. To adjust the reading on the display, the user would simply press another button such as the up or down arrow button to adjust the display in specific increments per button press. Say 0.1 MPH per button press as an example. This same process could be followed to calibrate the temperature display function as well. 
   Additionally, the user can calibrate the low battery indicator threshold. This threshold determines when the low battery warning icon would be activated. Remember, the low battery icon indicates the battery in the underwater sensor/transmitter probe is low. Again, the user would press a specific button, a specific series of buttons or a specific combination of buttons to enter the ‘low battery warning threshold’ calibration mode. Once in calibration mode, the CAL icon would be activated. Now the current low battery warning threshold would be displayed on the LCD. The user would simply press a button such as the up or down arrow to adjust this threshold to a new value. 
   Yet another calibratable feature is available to the user. This calibration is for the data averaging setting. Data averaging is used to smooth out dynamic changes in data from one received transmission to the next. To explain a bit further, let&#39;s think about what happens to an underwater probe when it is connected to a watercraft via a rigid downrigger cable. Now let&#39;s also assume the boat is bouncing around in 4 or 6 foot waves. As the boat bounces up and down, the downrigger cable will also pull the probe up and down in the water column the same distance as the boat is bouncing. This action can adversely affect the readings of speed from one moment to the next. If the readings were taken every second for example, one reading might show 2 MPH, the next might show 4 MPH, and the next might show 0 MPH. These quick changes in speed are due to the effects of wave action on the ferromagnetic rotor&#39;s RPM. If the data averaging setting was only set to 1 second, the user may think something is wrong with the system when its being used in wavy water conditions. The user may notice the readings for speed jumping all over the place. To eliminate this problem, the receiver uses data averaging to smooth out these varying readings. If the data averaging was set a 5, the receiver/display unit would average the data over 5 consecutive received sensed data, then display the average of this data. The disclosed invention allows the user to calibrate the data averaging by means of entering a calibration mode. 
   Again, the user would press a specific button, a specific series of buttons or a specific combination of buttons to enter the ‘data averaging’ calibration mode. Once in calibration mode, the CAL icon would be activated. Now the current data averaging is displayed on the LCD. The user would simply press a button such as the up or down arrow to adjust this averaging to a new value. As an example, each press of the up or down button may change the data averaging setting by 1 sample. 
   The receiver/display unit also provides a means to exit the calibration mode. To exit any of the calibration modes, the user would press a specific button, a specific series of buttons or a specific combination of buttons. Once the calibration mode is exited, the CAL icon is turned off. 

   
     BRIEF DESCRIPTION OF THE DRAWING FIGURES 
       FIG. 1  is a side view of a typical downrigger; 
       FIG. 2  is a side view of a controlled depth fishing set-up; 
       FIG. 3  is a side view of a controlled depth fishing set-up immediately after a fish strikes; 
       FIG. 4  illustrates the main components of a controlled depth speed and temperature monitoring system; 
       FIG. 4A  illustrates a controlled depth fishing set-up when a speed and temperature monitoring system is installed; 
       FIG. 5  is a side view illustration of the downrigger cable-to-underwater probe interconnect method; 
       FIG. 6  is a side view illustration of the downrigger cable-to-underwater probe interconnect after applying rubberized electrical tape to isolate and seal the connection; 
       FIG. 7  is a side view of a downrigger illustrating the pick-up coil antenna installation; 
       FIG. 8  is a side view of the underwater sensor/transmitter probe unit; 
       FIG. 9  is an exploded view of the underwater sensor/transmitter probe unit; 
       FIG. 10  is a cross-sectional view of the underwater sensor/transmitter probe unit; 
       FIG. 11  is an end view of the underwater sensor/transmitter probe unit with battery access cover removed—looking into the battery compartment; 
       FIG. 12  is an angle view of the underwater sensor/transmitter probe unit with nose cap removed so as to see the circuit board assembly; 
       FIG. 13  is an angle view of the underwater sensor/transmitter probe unit; 
       FIG. 14  is a back side view of the underwater sensor/transmitter probe unit; 
       FIG. 14A  is an angle view of the underwater sensor/transmitter probe unit with optional stabilization wings 
       FIG. 15  is an angle view of the circuit board assembly of the underwater sensor/transmitter probe unit; 
       FIG. 16  is an exploded view of the circuit board assembly of the underwater sensor/transmitter probe unit; 
       FIG. 17  is an internal view of the main housing of the underwater sensor/transmitter probe unit; 
       FIG. 18  is an angled internal view of the main housing of the underwater sensor/transmitter probe unit; 
       FIG. 19  is a view of the battery access cover assembly; 
       FIG. 20  is an exploded view of the battery access cover assembly; 
       FIG. 21  illustrates a hollow bobbin form in on which the pick-up coil windings are wound; 
       FIG. 22  illustrates a pick-up coil assembly with a single or multiple layers of windings wound onto the bobbin form; 
       FIG. 23  illustrates an active antenna assembly; 
       FIG. 24  illustrates a complete antenna module; 
       FIG. 25  illustrates a complete active antenna module; 
       FIG. 26  illustrates a flexible mounting method to mount the antenna module or active antenna module to a downrigger boom; 
       FIG. 27  illustrates a front view of the receiver/display unit; 
       FIG. 27A  illustrates a one-piece molded silicone keypad and sealing member; 
       FIG. 28  is an electrical block diagram of the underwater sensor/transmitter probe unit; 
       FIG. 29  is an electrical block diagram of the receiver/display unit when used in conjunction with a standard pick-up coil antenna; 
       FIG. 30  is an electrical block diagram of the receiver/display unit when used in conjunction with an active antenna module where the signal output of the active antenna module is digital data; and 
       FIG. 31  is an electrical block diagram of an active antenna module where the signal output of the active antenna module is digital data. 
   

   DESCRIPTION OF REFERENCED NUMERALS 
   
       
       
         
             10  Downrigger 
             12  Reel 
             14  Boom 
             16  Cannonball Weight 
             18  Downrigger Cable 
             20  Pulley 
             22  Crank Handle 
             24  Downrigger Frame 
             26  Fishing Line Release 
             28  Water Surface 
             30  Watercraft 
             32  Rod Holder 
             34  Fishing Rod &amp; Reel 
             36  Fishing Line 
             38  Fishing Lure 
             40  Trolling Direction 
             42  Fish 
             44  Coated Downrigger Cable 
             46  Underwater Sensor/Transmitter Probe Unit 
             48  Receiver/Display Unit 
             50  Antenna Assembly 
             52  Signal Pick-Up Coil 
             54  Antenna Cable 
             56  DC Power Cable with In-Line Fuse 
             58  Antenna-to-Receiver Interface Cable 
             60  Coated Downrigger Cable with Coating Removed 
             62  Barrel Crimp 
             64  Thimble 
             66  Rubberized Electrical Tape 
             68  Plastic Tie Wraps 
             70  Cable Connector 
             76  Drop Leader 
             78  Nose Cap 
             80  First Connection Tab 
             82  Second Connection Tab 
             84  Main Body 
             86  Battery Access Cover 
             88  Ferromagnetic Rotor 
             90  Rotor Axle 
             92  Raised Flange 
             94  Circuit Board Assembly 
             96  Battery Alignment Housing 
             98  External Threads 
             100  Internal Threads 
             102  Back-up Washer 
             104  Battery Retention Spring 
             106  First O-Ring Gland 
             108  Second O-Ring Gland 
             110  First Power Contact 
             112  Second Power Contact 
             114  Water Sensing Element 
             116  First Isolator 
             118  Second Isolator 
             120  Circuit Board 
             122  Shim Washer 
             124  Circuit Board Alignment Channel 
             126  Battery Access Cover Assembly 
             128  Fastening Screw 
             130  Bobbin 
             132  Through-hole 
             134  Bobbin Assembly 
             136  Insulated Wire 
             138  Active Antenna Module Assembly 
             140  Antenna Module Circuit Board 
             142  Multi-Conductor Cable 
             144  Antenna Module Complete Assembly 
             146  Antenna Enclosure 
             148  Mounting Provisions 
             150  Active Antenna Module Complete Assembly 
             152  Active Antenna Module Enclosure 
             154  Mounting Springs 
             156  Mounting Adapter 
             158  LCD Display 
             160  7-Segment Digits 
             162  LO BAT icon 
             164  calibration mode icon 
             166  Temperature icon 
             168  Speed icon 
             170  First Pushbutton 
             172  Second Pushbutton 
             174  Third Pushbutton 
             176  Fourth Pushbutton 
             178  Receiver/Display enclosure 
             180  Separator icon 
             182  Optional Stabilization Fins 
             184  Temperature Sensor 
             186  Magnetic Field Sensor 
             188  Signal Conditioning Circuit 
             190  Micro-Controller 
             192  Regulator 
             194  Auxiliary Power Switch 
             196  Diode 
             198  RF Final Drive Amp 
             200  Power Jack 
             202  Micro-Controller of  48   
             204  Test Points 
             206  Diode Clipper 
             208  Signal Jack 
             210  LC Tuned Circuit 
             212  First Amp of  48   
             214  Second Amp of  48   
             216  Ceramic or Crystal Filter 
             218  Data Slicer Circuit 
             220  Keypad 
             222  Connector to Active Antenna Module 
         
       
     
  
   The foregoing and other objects and advantages will appear from the description to follow. In the description reference is made to the accompanying drawings, which forms a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. These embodiments will be described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural changes may be made without departing from the scope of the invention. In the accompanying drawings, like reference characters designate the same or similar parts throughout the several views. 
   The following detailed description is, therefore, not to be taken in a limiting sense, and the scope of the present invention is best defined by the appended claims. 
   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   The following discussion describes in detail one embodiment of the invention (and several variations of that embodiment). This discussion should not be construed, however, as limiting the invention to those particular embodiments, practitioners skilled in the art will recognize numerous other embodiments as well. For definition of the complete scope of the invention, the reader is directed to appended claims. 
     FIG. 1  is a side view of a typical downrigger  10  having a frame  24  for housing a reel  12  and its associated crank handle  22 . A boom  14  extends from the frame  22  and a pulley  20  is disposed on the distal end of the boom  14  for guiding the downrigger cable  18  that is wound around the reel  12  and has a cannonball weight  16  fastened to the distal end thereof. A fishing line release  26  is secured to the cannonball  16 . 
     FIG. 2  is a side view of a typical controlled depth fishing set-up using a downrigger  10 . Shown is a fishing rod and reel  34  inserted in a rod holder  32  attached to the watercraft  30  and its fishing line  36  is connected to the fishing line release  26  of the cannonball weight  16  and has a fishing lure  38  secured to the end thereof. The cannonball weight  16  has been lowered to a predetermined depth below the water surface  28  by the downrigger cable  18 . The trolling direction  40  of the watercraft  30  will be moving away from the cannonball  16 . 
     FIG. 3  is a side view of a typical controlled depth fishing set-up immediately after a fish  42  strikes. The fish  42  has been hooked by the lure  38  and the fishing line  36  has been freed from the cannonball weight  16  by the fishing line release  26 . The fishing line  36  is now exclusively controlled by the rod and reel  34 . 
     FIG. 4  illustrates the main components of the controlled depth speed and temperature monitoring system of the present invention. Shown is the underwater sensor and transmission probe  46  secured on top to a coated downrigger cable  44  and on the bottom to a drop leader  76  that is secured to the cannonball weight  16 . The downrigger cable  44  passes through a signal pick-up coil  52  which is integral with an antenna assembly  50  that includes an antenna cable  54  and cable connectors  70  attached to an antenna to receiver interface cable  58  which terminates at the receiver/display unit  48 . The receiver/display unit  48  is connected to a 12 VDC battery with a DC power cable with in line fuse  56 . 
     FIG. 4A  illustrates a controlled depth fishing set-up with the present invention installed. Shown is a fishing rod and reel  34  inserted in a rod holder  32  attached to the watercraft  30  and its fishing line  36  is connected to the fishing line release  26  of the cannonball weight  16  and has a fishing lure  38  secured to the end thereof. The cannonball weight  16  has been lowered to a predetermined depth below the water surface  28  by the downrigger cable  18 , 44  working in concert with a downrigger  10 . The trolling direction  40  of the watercraft  30  will be moving away from the cannonball  16 . 
     FIG. 5  is a side view illustration of the downrigger cable  44  to underwater probe  46  interconnect method. Shown is the coated downrigger cable  44  with a section  60  having the coating removed. A thimble  64  forms a loop secured by a pair of barrel crimps  62 . 
     FIG. 6  is a side view illustration of the downrigger cable  44  to underwater probe  46  interconnect after applying rubberized electrical tape  66  to isolate and seal the connection; 
     FIG. 7  is a side view of a downrigger  10  illustrating the pick-up coil  52  antenna installation. Shown is the downrigger cable  44  and extending through the center of the signal pick-up coil  52  leading to an antenna cable  54  and secured by a pair of plastic tie-wraps  68 . A cable-connector  70  is disposed on the distal end of the antenna cable  54 . 
     FIG. 8  is a side view of the underwater sensor/transmitter probe unit  46  demonstrating the physical relationship of the various components. The substantially cylindrical main body  84  has a nose cap  78  on the front end and a battery access cover  86  on the rear. A first connection tab  80  extends from a raised flange  92  on the top portion of the main body  84  proximal the nose cap  78  and an opposing second connection tab  82  is disposed on the bottom portion thereof. A ferromagnetic rotor  88  is interiorly disposed within the main body  84  and rotatively secured therein by a rotor axle  90 . 
     FIG. 9  is an exploded view of the underwater sensor/transmitter probe unit  46 . The circuit board assembly  94  attaches to the battery alignment assembly  96  which in turn slides into the main body  84  and then covered by the nose cap  78 . The ferromagnetic motor  88  extends beyond the main body  84  on one side and is retained therein by the rotor axle  90 . A battery retention spring  104 , back-up washer  102  and fastening screw  128  are positioned within the battery access cover  86 . Internal threads  100  within the battery access cover  86  and mating external threads  98  on the main body  84  provide securing means therebetween. 
     FIG. 10  is a sectional view of the underwater sensor/transmitter probe unit  46  showing the position of the first o-ring gland  106  and the second o-ring gland  108 . 
     FIG. 11  is an end view of the underwater sensor/transmitter probe unit  46  with battery access cover removed to show the inside of the battery compartment to demonstrate the relationship between the first power contact  110 , the second power contact  112  and the battery alignment housing  96 . 
     FIG. 12  is an angle view of the underwater sensor/transmitter probe unit  46  with nose cap removed so as to see the circuit board assembly  94 . 
     FIG. 13  is an angle view of the underwater sensor/transmitter probe unit  46  with the nose cap  78  installed. 
     FIG. 14  is a back side view of the underwater sensor/transmitter probe unit  46  showing the water sensing elements  114 . 
     FIG. 14A  is an angle view of the underwater sensor/transmitter probe unit  46  with optional stabilization wings  182 . 
     FIG. 15  is an angle view of the circuit board assembly  94  of the underwater sensor/transmitter probe unit. 
     FIG. 16  is an exploded view of the circuit board assembly  94  of the underwater sensor/transmitter probe unit comprising a circuit board  120  sandwiched between a second isolator  118 , a first connection tab  80  and shim washer  122  and a first isolator  116  and second connection tab  82 . a first power contact  110  and a second power contact  112  extend perpendicularly from the edge of the circuit board  120 . 
     FIG. 17  is an internal view of the main housing  84  of the underwater sensor/transmitter probe unit showing the circuit board alignment channels  124  into which the circuit board and it&#39;s related assembly is inserted. 
     FIG. 18  is an angled internal view of the main housing  84  of the underwater sensor/transmitter probe unit showing a circuit board alignment channel  124  into which the circuit board and it&#39;s related assembly are to be inserted. 
     FIG. 19  is a view of the battery access cove assembly  126 . 
     FIG. 20  is an exploded view of the battery access cover assembly  126  showing the battery access cover  86 , the back-up washer  102 , the battery retention spring  104 , the fastener screw  128  and the second o-ring gland  108 . 
     FIG. 21  illustrates a hollow bobbin  130  form in which the pick-up coil windings are wound and the through-hole  132  extending longitudinally therethrough. 
     FIG. 22  illustrates a pick-up coil bobbin assembly  134  with a single or multiple layers of windings of insulated wire  136  wound onto the bobbin  130  form and a through-hole  132  extending longitudinally therethrough. 
     FIG. 23  illustrates an active antenna assembly  138  comprising the insulated wire  136  would around the bobbin  130  in communication with the circuit board  140  and the associated multi-conductor cable  142 . 
     FIG. 24  illustrates a complete antenna module assembly  144  comprising an antenna enclosure  146  with a through-bore  132  and a pair of mounting provisions  148  and in direct communication with the antennae cable  54   
     FIG. 25  illustrates a complete active antenna module  150  comprising an active antenna module enclosure  152  with a through-hole  132 , a pair of mounting provisions  148  and is in direct communication with the multi-conductor cable  142 . 
     FIG. 26  illustrates a flexible mounting method to mount the complete active antenna module assembly  138  or the complete antenna module assembly  144  to a downrigger boom  14 . The downrigger cable  18 , 44  passes through the pulley  20  and the though-bore of either the complete active antenna module assembly  138  or the complete antenna module assembly  144  which is suspended by mounting springs  154  engaged with its mounting provisions  148 . The mounting springs  154  are fastened to mounting adapters  156  that are secured to the boom  14  by plastic tie-wraps  68 . the antenna cable  54  or multi-conductor cable  142  is also secured to the boom  14  with plastic tie-wraps  68  but with enough play to prevent exposure to stress due to the movement of the complete active antenna module assembly  138  or the complete antenna module assembly  144 . 
     FIG. 27  illustrates a front view of the receiver/display unit  48  comprising a receiver/display enclosure  178 , a first pushbutton  170 , a second pushbutton  172 , a third pushbutton,  174 , a fourth pushbutton  176  and an LCD display  158 . The LCD display provides indicators for a LO BAT icon  162 , a CALIBRATION mode icon  164 , seven segment digits  160 , a temperature icon  166 , a separator icon  180  and a speed icon  168 . 
     FIG. 27A  illustrates a one-piece molded silicone keypad and sealing member of the receiver/display enclosure  178  with 4 push button  170 ,  172 ,  174  and  176 . 
     FIG. 28  is an electrical block diagram of the underwater sensor/transmitter probe unit  46 . The path includes fixed battery contacts  110 , 112  through a diode  196  and a regulator  192  providing regulated power to the circuitry including the microcontroller  190 . The micro-controller  190  receives input from the temperature sensor  184 , the magnetic field sensor  186  with affiliated ferromagnetic rotor  88  and from the water sensing elements  114  through the signal conditioning circuit  188 . The collected data is then transmitted from the micro-controller  190  to the downrigger cable via the RF final drive amp  198  and the first connection tab  80 . The optional grounding of the second connection tab  82  is also shown. The temperature sensor includes a digital interface that preferably has at least 13 bit resolution. 
     FIG. 29  is an electrical block diagram of the receiver/display unit  48  when used in conjunction with a standard pick-up coil antenna. The circuitry includes a power jack  200 , a diode  196 , a regulator  192 , an auxiliary power control  194 , a micro-controller  202 , a keypad  220 , an LCD display  158  and test points  204 . The signal receive circuitry contained therein comprises a signal jack  208 , a diode clipper  206 , an LC tuned circuit  210 , a first amp  212 , a ceramic or crystal filter  216 , a second amp  214 , and a data slicer circuit  218 . 
     FIG. 30  is an electrical block diagram of the receiver/display unit  48  when used in conjunction with an active antenna module  150  wherein the signal output of the active antenna module  150  is digital data. 
     FIG. 31  is an electrical block diagram of an active antenna module wherein the signal output of the active antenna module is digital data. 
   It will be understood that each of the elements described above, or two or more together may also find a useful application in other types of methods differing from the type described above. 
   While certain novel features of this invention have been shown and described and are pointed out in the annexed claims, it is not intended to be limited to the details above, since it will be understood that various omissions, modifications, substitutions and changes in the forms and details of the device illustrated and in its operation can be made by those skilled in the art without departing in any way from the spirit of the present invention. 
   Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention