That's expensive because it's a full GPS receiver and not only a TMC Box.I also wondered why this could not be used. But the GNS support explained to me that all GNS TrafficBoxes which are fitted with a mUSB plug only looks like USB. They all have a serial interface with TTL level built in. That is because all PNA (Navigation) units are using their mini USB plug for power supply, for USB-Storage device function and additional for serial data transfer on TTL level. It's a tripple function combined in one plug. To connect a TrafficBox to the QL-RAV977 we need a regular USB data interface. Now there are 2 options:
1) Combining a GNS TrafficBox Universal GNS GmbH - Onlineshop - GNS TrafficBox Universal with MD6 plug 4037735101807 (that has real RS232 interface) with FTDI adapter USB-RS232-WE-1800-BT_5.0.
2) Using a GNS TrafficBox 5860 GNS GmbH - Onlineshop - GNS 5860 GPS RDS TMC Receiver Bluetooth USB (32-channel GPS) 4037735103924
Advantage of this unit: It has already built in Serial / USB Converter and so it is plug&play for the USB of QL-RAV977. Disadvantage is its price of 89,- Euro plus shipping.
I decided option 1) because of less cost. FTDI adaptor about 35.- Euro incl. tax and shipping from GB and GNS TRafficBox Universal about 15,- Euro off eBay.
I think that this should be the right choise at a much more cheaper price:
GNS GmbH - Onlineshop - GNS TrafficBox FM9 USB2USB (mio A201, Transonic 3040) 4037735101845