Sonar Phone T Box by Vexilar

Hi All,

I recently acquired (through Navionics) a T box made by vexilar. This, along with their transducer allows you to convert any smart phone into a fish finder using WiFi. You can also share your signal with other users nearby just as you would a WiFi signal at home. It also works with the Navionics mobile app so you not only have a fish finder but a GPS with full navionics charts. It sounded impressive.

Sonar Phone Fishfinder and Marine Charts

With the Vexilar T Box and transducer you can use any smart phone or tablet as a fish finder. Combine with Navionics and you also have marine charts.

The transducer is a dual-beam transducer with a built in temperature sensor and can go down to 240ft. It states that in hull mounts are fine. I’ve gone through the set up process and my initial impressions are really good.

All you need is to add the T box fairly close to your battery. The T box needs a 12v power supply and once switched on, emits a WiFi signal that you can connect to via your phone. In my case, I then open my navionics app and it detects the T Box and offers both charts and fish finder. You can fully configure the fish finder just as you would any stand alone unit (i.e units, fish alarms, depth alarms).

I intend to use this unit when away on holidays when you might hire a kayak to fish from (or boat for that matter) and also to use on my father in laws sailing boat that I often go out on in the summer. We use this mostly for sailing but normally find time to wet a line. I will be using a temporary method to have the transducer on a form of transducer arm straight into the water. However, my initial impressions make me think that you don’t have to just view this as a temporary device. It could easily replace a number of standard fish finder models if you are happy to use your smart phone on the water (with a waterproof case!).

I stuck the T Box to my battery box using velcro so that it can be easily removed. A lot of cable is provided so I have just use some electric cable ties to wind up that which isn’t needed. You can see from the picture below I have also built a temporary transducer arm mount to fit to the outside of the kayak using dual lock (much stronger than velcro).

T Box Sonar Phone Vexilar

T Box mounted to battery box using velcro. Cables tidies with cable ties. A temporary transducer arm made to hold the transducer.

Whilst I know an in hull transducer mount is normally the way forward, I want this to be removable and used in a number of different applications. I don’t like the look of the ram mount transducer arm due to the cost and the bulky size and saw this idea on the Australian forum “yakshed”. This mount seemed popular as it is much more streamlined that manufactured transducer arms and requires no drilling and can be easily removed during launch and landings.

External transducer arm mount DIY

External Transducer Arm mount using velcro – Taken from the forum “YakShed”

Second picture taken from "YakShed"

Second picture taken from “YakShed”

Once the T Box had a 12v supply I turned it on by pressing the red button on the side. I then went into my smart phones WiFi settings and saw a “T Box” WiFi signal. You can connect to this without any password. Once connected I launched my Navionics mobile chart app (link:

Navionics Mobile App

Launching Navionics Mobile App

When loading, Navioncs detects the T Box and prompt you to choose between marine or lake.

Navionics Mobile Sonar Chart

On loading, Navionics detects the T Box and asks if you are going inland or into the sea.

You then get the choice to configure the fish finder just as you would a standalone variety.

Configuring Vexilar Sonar Phone

Configuring Vexilar Sonar app just as you would a stand alone fish finder.

I was beginning to get really impressed with the ease at which this all gets set up. It really is simple. Once configured you get something similar to the below. A split screen showing the Navionics charts along with the sonar results. This screenshot was taken inside my house hence the lack of reading on the transducer!

Vexilar Sonar Phone with Navionics

A screenshot showing the Vexilar Sonar Phone app with Navionics charts.

When you tilt the phone it toggles between full fish finder view (i.e. no chart) and split screen with chart and sonar. Below shows the full sonar view:

Full sonar view

Full sonar view

Over the coming weeks I should have a chance to test the sonar out and will report back on how I find it if anyone is interested.



Kayak Fishing Navionics Charts

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