Sub-Mini Dunker Release Kit

Portable solution for commanding RT 6 acoustic releases from small boats
Works with all RT 6 acoustic releases deployed in depths to up to 1,000 m
Built with Wideband 2 inside delivering secure communications in all conditions
Rugged and reliable hardware engineered to withstand commercial operations
Internal re-chargeable battery provides over a month’s standby life

Everything you need to command and recover your RT 6 deployed moorings

Built tough and reliable to work where you work, the Sub-Mini Dunker Release kit is the perfect addition to your Sonardyne RT 6 acoustic release transponder inventory. Use it over-the-side of your vessel to securely command, range to, activate and retrieve units deployed within 1,000 m of your location.

The Sub-Mini Dunker Release kit is a rugged and cost-effective back deck instrument for securely commanding and controlling your Sonardyne medium frequency RT 6s - our latest and most capable family of acoustic release transponders. Its introduction means that along with any Ranger 2 USBL system, or our Android app (used with a surface deployed RT 6-1000), there’s now three ways to trigger the recovery your RT 6s from the seabed. So whatever your budget or operational requirement, with the RT 6 you have total flexibility when planning your next instrument deployment.

The kit consists of the Sub-Mini Release acoustic transceiver, dunker clamp with eyebolts for attaching to a deployment rope or strop, 20 m of deck cable and a comms/charger interface box.

The Sub-Mini Dunker Release kit can be used with the RT 6-1000 as an alternative to using an RT 6-1000 and Sonardyne Android App as a surface release unit. It is also compatible with the RT 6-3000 when surface-to-transponder location slant ranges do not exceed 1,000 m.

In operation, the Sub-Mini is dunked over the side of a vessel to a depth of several metres below the water’s surface. The MF omni-directional transducer provides excellent acoustic performance, especially in shallow, noisy and reverberant environments and with over 500 unique addresses, you can be assured that only the RT 6 you wish to release will be activated via a secure command sequence.

On deck, the Sub-Mini’s 20 m cable is connected via an interface/charging box to either a Sonardyne iWand (supplied separately) or a PC running Sonardyne 6G Terminal Lite software. iWand is our popular handheld, splash proof test and configuration device for testing and configuring Sonardyne 6G series transponders prior to deployment. When used with Sub-Mini Dunker 6, it is able to releases RT 6s.

The Sub-Mini Dunker 6 is powered by a rechargeable battery, which can be disconnected via an external on/off switch to prolong its shelf life when not in use, but also to make shipping easier.

Why Sub-Mini Dunker Release Kit?


  • Medium Frequency (19-34kHz) band
  • Omni-directional transducer
  • Sonardyne Wideband 2 signal architecture supporting over 500 unique addresses. Perfect for very large surveys involving multiple moorings close to each other


  • Built around field-proven Sonardyne 6G hardware
  • Portable and rugged; ideal for commercial and scientific operations
  • 426 x 79 mm housing size, 1.3 kg weight in water
  • Plastic, super duplex stainless steel and anodised aluminium construction. ROHS compliant
  • External on/ off switch to extend battery life
  • Depth sensor


  • 1,000 m maximum operating range
  • Greater than 35 days quiescent battery life
  • Supports acoustic testing, release loading, ranging and releasing functions
  • Secure and robust two-way acoustic communications. Only release what you want to release


  • What’s in the box: Sub-mini Dunker transceiver, dunker clamp and eye bolts, 20m deck cable and charger/comms interface unit
  • Warranty: 1 year return to Sonardyne service centre
  • ITAR Controlled: No
  • UK Export License: Not required

More about this product

Sub-Mini Dunker Release Kit Specifications & DataSheet

Feature Type 8370-1111 (1,000 m)
Depth Rating 1,000 metres
Operating Frequency MF (19–34 kHz)
Transducer Beam shape Omni-directional
Power Supply Rechargeable NiMH battery
Operating Channels All Sonardyne Wideband
Depth Sensor ±0.5% Full Scale (100 Bar)
Quiescent Life (Battery) >35 Days
Connector (5-Way) Subconn MCBH5M
Operating Temperature -5 to 40ºC
Storage Temperature

-20 to 55ºC

Mechanical Construction Aluminium Alloy, Anodised
Housing Dimensions (Length x Diameter) 426 x 79 mm
Clamp Diameter 125 mm
Weight in Air/Water (without clamp) 3.2 kg/1.3 Kg
Cable Assembly  
20 m 5W Subconn to 9W 820-0426

Comms/Charger Assembly


*TEE – WBv2 signals are 2x the duration of Sonardyne tone signals, therefore the TEE figure is to give the user an idea of the operational performance when comparing Wideband and Tone systems.
**Estimated Weights.



The transponder is not replying to interrogation or commands

An incorrect transponder address is set in the Topside Control – check the address and repeat using the correct address.

Operating at long range – increase transmit power and receive gain to the surface transceiver (Ranger 2).

Surface thermocline refracting reply signals – lower transducer below thermocline.

Noise level at surface transceiver too high – lower the dunking transducer – reduce the surface transceiver gain settings (Ranger 2).

Transponder battery power low – check battery levels.

Other acoustic systems maybe operating in the same frequency band.

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