Understanding how wireless communications work is important to the success of a good experience communicating. It’s important to know there are factors that can alter the performance of wireless communications.
There are also easy tips that can be applied for optimum performance. Using the example of cell phone reception to a land line telephone, while both of these devices achieve the same goal, external factors can sometimes affect the quality of cell phone usage due to dropped calls or static interference that land lines do not experience. The below sections will explain how wireless underwater communications work, what can affect the communications, and some tips to make you the most successful at using them.
In most cases when the diver wants to talk, he simply depresses the push-to-talk (PTT ) button located on the full face mask (FFM) and talks. The diver’s speech is picked up via the microphone installed in the FFM and sent to the communication unit. The speech is then converted into 33 kHz and sent into the water via the transducer. The 33 kHz signals out omnidirectional and can bounce off the bottom and surface. When another transceiver’s transducer picks up the sonic signal, the 33 kHz is converted back to intelligible speech, amplified and sent up to the earphone. The diver has the freedom of free swimming without carrying a long wire to the surface.
It’s important to recognize there is a learning curve while working toward becoming proficient in wirelessly communicating underwater. It took the U.S. Navy 3 days to master this skill. What we learned from that experience is there are a lot of factors that can make communicating underwater challenging. For starters, the underwater environment is a lot noisier than a lot of people realize. Bubbles blowing by your ear with every exhale, water affecting your ears, and general critter noise add to the experience of listening. As with any piece of technology practice and understanding how it works will help you to achieve success.
Identifying what kind of diving environment you will be in is key to assessing the reliability and clarity of your communications. Below are situations that create less than ideal communications and tips to navigate them.
The Affect: The change in water temperature with thermoclines can create a potential barrier with transmission depending on where the divers are located relative to the thermocline. For example, if one diver is above the thermocline and another is below the thermocline, intermittent communications may occur due to the transmissions bouncing off the thermocline and not fully reaching from one transducer to another.
Tip: Ensure you and your buddy are diving either above or below the thermocline together so that there is not one diver above the thermocline and one below. This will ensure you are communicating in the same space. This concept should also be applied to surface station placement of the transducer. If there is a thermocline ensure the transducer is above or below the thermocline where the divers are.
The Affect: Some biological noise such as popping shrimp emit noise at the same frequency as the wireless communications. This means that anything emitting at the same frequency as your wireless communications can be heard on your communication device and often be interpreted as loud static. One thing to note is that a single dive site can be peaceful and quiet at one time of the day and with a tidal change the same dive site can become more noisy.
Tip: If you are experience loud static noise, knowing your dive site and understanding that what you are hearing is due to biological noise is half the battle. This will help ease the frustration in trying to understand why you are listening to what’s transmitting. For products that have adjustable squelch, adjusting the squelch can assist in cutting out some of the noise. Consequently, it’s important to know that by closing the squelch you are limiting your range. Reference your user manual for tips on squelch usage.
Tip: If you are diving in an area where you know there is a lot of biological noise at risk, choose your dive with tidal patterns in mind to minimize diving at a noisier time.
The Affect: Mechanical noise such as boats or motors can alter the ability to transmit or hear communications well.
Tip: If you have the ability to turn off the mechanical noise temporarily for your dive this is the best option.
The Affect: The diver’s body is in between two transmitting transducers or units can lower volume / distance / intelligibility of communications.
Tip: Position the unit’s transducer in a way that offers the best line of sight to another unit’s transducer. For any higher powered diver unit, we typically recommend placing it at the 6 o’ clock position of the diver’s tank on the tank strap. If using a Buddy Phone, a diver may need to turn their head to better their communications.
The Affect: In using wireless underwater communications air kills the signal. This means wireless communications will not work on the surface. This also means that air in the water will greatly diminish or affect transmission of your communications.
Tip: Ensure there is no aerated pumps in a pool or confined area as this will negatively effect your communications. If you can shut off the aeration an hour before diving, this will warrant the best results.
Tip: Assess the water in which you are diving. If you are diving in surf or areas where a lot of air bubbles, such as kelp, consider this when communicating and adjust your approach as necessary.
