According to the owner's manual, it is possible to address and compose a text message on the MHS 335 radio itself. The process is described in the manual as follows:
- push the BT SOFT KEY (BT= Bluetooth apparently);
- select TEXT MESSAGING; a new screen appears with a keyboard and text entry field with the entry cursor in the TO field;
- enter a stored MMSI number, a new MMSI number, or a stored name from the stored-name directory in the TO field;
- press NEXT softkey to move entry cursor to message field
- enter your message text;
- press NEXT when done;
- press SEND to send;
- press EXIT to return to prior mode
Because the Unidn MHS 335 has a Bluetooth interface, you can also use an iOS or Android mobile device, running a Uniden Marine App, to compose and send text message. Communication between the radio and the smartphone apparently occurs via the Bluetooth link.
The smartphone and Bluetooth link and Uniden Marine App can also be used to change settings on the radio to configure it.
This is quite a novel feature for a DSC radio. I infer that the link between radios must be via DSC as the address for the text message is the MMSI of the other "text message capable" radio.
I have not looked at other features of the Uniden MHS 335, but certainly the ability to send text message to other compatible DSC radios and to be able to connect an iOS or Android smartphone via Bluetooth are very distinctive new features in VHF Marine Band Class-D DSC radios.
For more about the radio, visit
https://www.uniden.com/shop/communication/marine-radios/6-watt-class-d-floating-handheld-vhf-marine-radio/
The Uniden MHS335 radio carries the FCCID AMDW70001. The same radio is also sold under the model names VHF470B and VHF470G, which are identical in the internal printed circuit boards, electrical circuits, and structure, and differ only in packaging, backlight color, owner's manual, and accessories. The FCC granted approval for sale of this radio in the USA on December 4, 2017.