QK-A034-B Manual
V 2.1
15 of 17
2020
4.4. Filtering
The A034-B features filtering of NMEA 0183 sentences. Each input has a flexible filter that can be
configured to pass or block specific sentences from entering the multiplexer.
NMEA sentences can be passed or blocked, specified by input. This frees up bandwidth, significantly
reducing the possibility of data overflow and resulting loss of data.
Blacklisted input data is filtered out and ignored by the A034-B multiplexer while the remaining desired
data is then transmitted to the outputs. As default, all filter lists are empty so all messages are passed
through the filters. Filters can be set through the Configuration software.
Figure 5: Input Filters Example
Filtering allows the A034-B to reduce the processing data load by disabling these unneeded input
sentences. GPS receivers for example often transmit an abundance of sentences every second and can
fill much of the available bandwidth of an NMEA 0183 port at 4800bps. By filtering out any unnecessary
data the bandwidth is saved for other more crucial device data.
Most chart plotters also have their own sentence filter, however many PC/mobile phone-based
applications do not. So, using the black list to filter unnecessary sentences can be helpful.
Filtering also removes potential conflict if two similar NMEA devices provide the same sentence type.
Users may choose to enable this data on one input only (filtering), and to transmit to the outputs.
4.4.1. Configuring filters
Each
input port’s black list can block up to 8 types of sentences. To
filter out an unwanted message types from a specific input, enter the
details in the corresponding
‘Black List’ in the Configuration software.
Simply, r
emove the ‘$’ or ‘!’ from the 5-digit NMEA talker and
sentence identifier and insert separated by commas. For example to
block ‘!AIVDM’ and ‘$GPAAM’ enter ‘AIVDM,GPAAM’. If blacklisting
SeaTalk data, use the corresponding NMEA message header. (See
SeaTalk section for a full list of converted messages).
4.4.2. Routing data away from chosen outputs
As a default, all inputs’ data (excluding any filtered data) is routed to
all outputs (NMEAx2, WiFi and USB). Data can be routed to limit the
data flow to only certain output/s.
Simply un-tick the corresponding boxes in the Configuration
software.
