I have an old 2008 version of a Becker BXP6403 Mode S transponder. It is a Class 2 level 2ES device. As it is an early version it says it does not support ADS-B out.
Becker have told me that it has "Mode”S” functionality with extended squitter. There is an interface for an Avionics Data Link processor and a data transfer interface protocol document available. It does not accept GPS NMEA data (so they say it does not transmit GPS position).
The data interface is fairly basic but it does has a command to be able to set GICB (Ground initiated Comm-B) registers. I have assumed that these are the equivalent to the 1090ES BDS registers.
I can successfully establish a connection to the transponder and send messages to the GICB registers - I get a reply back from the transponder with an updated message counter so I´m assuming they have been correctly received however there is no way to check.
I know the transponder is "squitting" as I attached a neon to the antenna and I see it regularly flashing. I don´t know what is being sent though.
I have a FlightAware PiAware system running and I see aircraft that are near to me but I don´t see any messages from my transponder. I know the transponder can be seen by ATC as I checked with them whilst I was flying and they could see me and my altitude (although this could have been from Mode-C I guess). I didn´t confirm if they could see my ICAO code (maybe I should re-check).
I´ve also set up a (separate) ModeSDeco2 installation but this doesn´t see messages from me either.
So my question(s) are:
- If the transponder is Mode-S and is squitting data then why can't my PiAware or ModeSDeco systems see me?
- Is there more of a difference between Mode-S and ADS-B than there appears to be?
- Is my assumption correct about the GICB and BDS registers?
It seems I´m missing something but everything I seem to find about Mode-S refers to it as squitting ADS-B messages.
