Some weeks ago I alluded to a new development over here by Racal aimed
at producing a low cost portable transponder.
Those that have the opportunity to visit the PFA rally at Cranfield this
weekend should take a look at the CAA Safety Regulation Group's stand
where dummy models are on display. Not that these represent the final
packaging but from the limited amount of information available the
following picture emerges.
The units will be handheld and about as large as a Garmin 195 with a
detachable whip antenna permitting fixed antenna installation. The units
will most likely also contain a GPS engine, the cost of which have
fallen like stones over the past twelve months. This makes a lot of
sense as the transponder market moves toward Mode S applications where
"GPS squittering" will become a preferred means of position
determination. An external power socket is available for 10-33V DC
sources.
Presently the unit will integate an inbuilt altitude encoder with an
operator keypad for 4096 conspicuity codes, mode select, ident select
and will respond to normal ground based or air derived Mode A and 3C
interrogations.
---From examination of the prototype internals it is obvious that much of
the unit is based on state of the art cellphone type technology and
looks to have a maximum power output of about 5-10W peak. This will
provide adequate portable battery operated time of the region of three
to four hours but will require the CAA to file an exemption with ICAO to
permit low power operations for operation in the UK. Present
requirements for Mode A/C and S transponders calls for 250W peak power.
I did a few quick signal budget calcs which showed even at that power
level it would mean that most of the UK interrogators would still
receive enough reply to function within the major part of the country.
Racal claim that the unit is functionaly upgradeable to Mode S which if
so is a major braekthrough at the proposed cost level. Whether this
means all Mode S functionality is another question. I would settle for
GPS squitter.
Cost is expected to be L500 (Circa $825) with units available in the
Winter of '97
--
Graham E Laucht
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