|BoatGear: Speed and Temp Units|
|Written by Tom Greenberg - Team Experience Outdoors|
|Wednesday, 30 May 2007 15:46|
There are a number of speed and temperature devices on the market today. Their purpose? To give you a sneak peek at what is really happening down where your lures are. Speed and Temp devices can give you feedback on temperature, speed, underwater currents and in one case, even light levels “at the ball”…in other words, down at the depth where you are fishing. Since those numbers can vary quite a bit from surface conditions, it is important information you need in order to be successful finding and catching more fish.
Most species of fish like certain temperature ranges and that’s where they tend to be found. Find the right temp…find the fish. And presenting your baits to them at the right speed is essential…to make sure the lures are running correctly, and to maximize the chances of triggering a strike.
Underwater currents, structure, wind and wave action and surface currents can all affect your “down speed” or speed “at the ball”. And knowing the speed differential between surface speed and down speed can help you properly orient your boat to the underwater currents. Not all currents occur over a large area or just near the surface. Some water currents occur in narrow areas far beneath the boat. By looking at the speed differential between up speed and down speed, you can determine the strength and direction of the currents. For example, if your surface speed is 2.0 mph and you are heading into a down current of 1.5 mph, your down speed is only .5 mph. This speed is way too slow if you are running a lure that was designed to work at 2-3 mph. On the other hand, if you are running at 2.0 mph, in the same direction as a down current of 1.5 mph, your down speed is 3.5 mph…this might be too fast for the species of fish you are targeting.
Some of the most well known speed and temp units are the Fish Hawk 840, the Moor Electronics Sub-Troll 900, the Depth Raider from Kell Laboratories and the Cannon Speed-n-Temp.
The ST-900 system consists of three parts. The display readout, the antenna, and the sending unit. The ST-900 is wireless in a similar fashion to the Fish Hawk, although it does not have a transducer mounted on the transom of the boat. The sending unit (probe) attaches to the downrigger cable and transmits a signal to the antenna which is mounted on the downrigger boom. From the antenna, the signal is sent to the display through a cable. There is no physical contact between the sending unit and the display readout. The readout may be installed up to 25 feet from the downrigger using the supplied cable. Because there is no transducer, the ST-900 can be installed even when the boat is already floating.
Because the ST-900 uses a radio signal for the transmission of information, you eliminate some of the problems associated with sonar type systems. The 9-volt battery will last up to a full season and, will not interfere with sonar or other electronics on the boat. This can be a problem with the Fish Hawk and certain brands of fishfinders. Because there is no transducer, you will get a constant reading on the display, even in choppy conditions.
The ST-900 underwater sending unit automatically turns its transmitter off when removed from the water. This insures that the 9-volt battery will remain ready for your next fishing trip. While trolling after dark, the ST-900 Illuminated display makes it easy to see speed and temperature data.
The Cannon's Speed-n-Temp Monitor has a 7 inch high-resolution screen, which provides an easy-to-read display of all the transmitted information. The monitor can be easily mounted at any location on the boat. The Cannon Speed-n-Temp Sensor attaches to the downrigger cable just above the weight, and provides true underwater conditions and lure depth.
In addition, the Cannon Speed-n-Temp probe can be integrated with the Humminbird 900, 700 & Matrix series Fishing Systems. In that case, the Speed-N-Temp unit data is displayed on the Humminbird fishfinder screen along with the rest of the fishfinder data, giving the angler a truly integrated multifunction display.
The Depth Raider system measures and displays this information with digital precision. The Depth Raider monitor tells you the exact speed and the exact temperature of your lure at it's running depth.
The Depth Raider requires the use of a coated downrigger cable. When placed into the water, the underwater transmitter probe unit continuously measures speed and temperature, then periodically transmits a digitally encoded RF (radio) signal via the coated downrigger cable. Like the SubTroll ST-900, the signal is received by a receiving antenna mounted on the downrigger boom. This signal is then routed to the receiver/display unit via a coaxial cable.
The display unit continuously monitors transmissions from the underwater probe unit. Once a transmission is received, the RF signal is decoded and the data is converted into speed and temperature info which is then displayed on the LCD display.
Coated downrigger cable is necessary to prevent the water from absorbing (and diminishing) the signal transmitted from the probe. The coating on the cable provides electrical isolation, since water is a very good conductor of electricity. Without the coated cable, as the depth of the probe continues to increase, the signal level at the antenna would diminish until it is no longer able to be deciphered by the display unit.
While the Depth Raider system will operate without the coated cable; installation of a coated cable is highly recommended to provide proper operation to 200 feet.
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