The ONWA KP-25A is a competitively priced GPS chartplotter with a built-in SOTDMA AIS transponder. It is marketed as a GPS chartplotter and, due to its size, is an ideal solution for vessels with limited space above deck .
But aren't we doing this little powerhouse a disservice?
Doesn't the KP-25A - in its function as an AIS transponder with display - also deserve a place below deck , i.e. instead of a black-box AIS transponder?
The need for such an "AIS transponder with a display" is evident from the existence of the Icom MA510TR and Em-Trak B400. I also used to have an AIS transponder with a display on board, the Vesper Marine WatchMate 850 with a 5" monochrome display (320x240). I found it a very practical instrument. After it broke, I had to look for a replacement. That became the ONWA KP-25A.
The advantages of the KP-25A below deck
Installing a KP-25A as an AIS transponder below deck and a 'regular' chartplotter on deck has several advantages:
- The crew below deck also has a view of the movements of other vessels equipped with AIS transponders. These movements are displayed on a detailed nautical chart.
- The crew can hear collision and anchor alarms below deck, useful if the cabin hatch is closed or it is noisy on deck.
- Less wiring is required for the chartplotter on deck. Instruments can be connected below deck, and the signal is then transmitted to the chartplotter on deck via a single NMEA cable.
- Backup of the chartplotter on deck in case of failure.
Four products compared
The table below lists the features of the KS-200A+, KP-25A, Icom MA510TR, and Em-Trak B400.
|
ONWA KS-200A+ |
ONWA KP-25A |
Icom MA510TR |
Em-Trak B-400 |
|
| Device type | AIS transponder |
AIS transponder with built-in chartplotter |
AIS transponder with display | AIS transponder with display |
| AIS Class | B+ (SOTDMA) |
B+ (SOTDMA) |
B (CSTDMA) |
B+ (SOTDMA) |
| Transmit power | 5W | 5W | 2W | 5W |
| Display | no (black box) |
5" color TFT (800x480) (1,000 NITS) |
4.3" color TFT (resolution and brightness not specified) |
5" color (800x480) (500 NITS) |
| AIS screens | n/a | AIS, nautical chart with AIS overlay | AIS; AIS with navigation | AIS, nautical chart with AIS overlay |
| Sea charts | n/a | K-Chart, Navionics, C-MAP |
n/a | C-MAP |
| GNSS | internal; GPS, Beidou, GLONASS and Galileo | internal; 50 channels; GPS and Beidou |
internal; 72 channels; GPS and GLONASS |
internal; 75 channels; GPS, Beidou, GLONASS and Galileo |
| MOB button | no | Yes | Yes | no |
| Alarms | no | (T)CPA, anchor watch; battery voltage; and plotter-related alarms | (T)CPA, anchor watch | (T)CPA, |
| Power consumption | 0.2A | 0.9A | TX: 1.5A, RX: 0.7A | 0.9A |
| Connectivity | NMEA0183, NMEA2000, WiFi (output) | NMEA0183, NMEA2000 |
NMEA0183, NMEA2000, USB (output) |
NMEA0183, NMEA2000, WiFi |
| Supported NMEA sentences / PGNs | NMEA0183: 6 NMEA2000: 22 |
NMEA0183: 34 NMEA2000: 46 |
NMEA0183: 16 NMEA2000: 34 |
NMEA0183: 13 NMEA2000: 30 |
| Water resistance | IP66 | IPX6 | IPx7 (except connectors) | IPx6/IPx7 |
| Market | €325,- | €429,- | €949,- | €1,399.00 |
| Comments | also variant with SART button |
Free external indoor GNSS antenna; free K-Chart; full chartplotter functionality; also available with a 7" or 9" display and with connectors for sonar |
Free outdoor GNSS antenna; DSC call possible based on AIS target (requires compatible Icom marine radio); 100 waypoints | Free outdoor GNSS antenna; three bidirectional NMEA data ports; three sensor input ports |
Conclusions
The ONWA KP-25A's capabilities significantly surpass those of the Icom MA-510TR and Em-Trak B400 AIS transponders with integrated displays. And all at a much lower price.
A key feature of the Icom is the ability to select an AIS target from the AIS screen and then directly initiate a DSC call. The MA-510TR must be paired with a compatible Icom marine radio.
The Em-Trek's strong point is the presence of multiple bi-directional NMEA0183 ports and input sensor ports.
Both Icom and Em-Trak include an outdoor GPS antenna as standard. This is similar to the ONWA KA-09.