If you have a Volkslogger, it is working fine and it does the job for
you, keep using it. It uses a Garmin 25 module for the GPS receiver
running at 5 volts. The backup battery in the Garmin 25 module is
INSIDE the metal rf shielding and I'm not sure if you replace the
battery that you don't need a special factory firmware file to get
the thing going again. Even if you buy a discontinued Garmin 25
module from a stockist it will have been in storage for a long time
and the battery will likely be near the end of life.
There are only 3 wires connecting it to the guts of the VL and it
would be very simple to put a uBlox module in it running at 3.0 volts
by using a small linear regulator EXCEPT that this would invalidate
the IGC approval and the VL would require re-sealing for security.
This would also cost about half what a new FR would. Do yourselves a
favour. If your VL goes wrong, buy a new flight recorder.
We currently sell EW MicroRecorders. The only known issue with the
current production standard is that the Ni-MH battery is good for 3
to 4 years but replacement DOES NOT require re-sealing of the
recorder and we generally keep a spare battery or two in stock.
There are many other similar ones on the market and like the EW, all
have GPS modules newer than the Garmin 25 in the VL (incidently is
also the one in the CAI 302 vario according to some igc files I just
looked at.) and have features like data storage on a SD card. The
SirfStar II module in the EW is a particularly good one for GPS
altitude. I've seen others that aren't as good for GPS altitude. Some
GPS modules seem to be designed for surface vehicle use. Better ones
like the uBlox and SirfStar can be user configured for the expected
use. We set uBlox modules for aviation dynamics, no dead reckoning.
You can see what GPS module and pressure sensor your FR uses by
opening the *.IGC file in Notepad. The relevant stuff is in the top few lines.
Consider any glider avionics as about a 10 year thing, currently.
Gliders haven't improved much in 35 years(1979 original Ventus
A with full carbon wing and custom designed airfoil, neither have
motorgliders - the PIK guys got the two stroke retractable engine
about right in 1975) but avionics have improved greatly.
From flow sensor type varios relying on thermistors or hot wires to
silicon pressure transducers, sunlight visible colour LCDs for moving
maps, GPS, Flight recorders, inertial MEMS sensors and now our soon
to be released Dynamis system there has been huge development in
glider instruments. By the time a modern instrument breaks it is
likely obsolete.
A little GPS history:
Early GPS receivers were of the sequential type, looking at each
satellite in turn.
Later receivers used the parallel method but most of the early
receivers had a problem with getting an initial fix if they didn't
know the time or, roughly, the position.
Hence the solution of using a real time clock on board which was
maintained by battery backup. That way the receiver knows the time
and can acquire satellites quickly. The time gets updated and
corrected as soon as the first satellite is acquired.
Modern GPS receivers do not need this. The ones we use from uBlox
will, from a cold start (no backup battery, no time etc) get a time
in about 25 seconds or slightly less and a full 3D position fix in 45
seconds. Adequate for gliding. Faster if they have a time to begin
with but as we aren't firing them from guns in artillery shells or
dropping them from the bomb bays of B-52s or B-1s(JDAM, GPS guided
bombs) it doesn't seem necessary to use a backup battery to keep the
time alive for ultra fast starts.
Mike
Borgelt Instruments - design & manufacture of quality soaring
instrumentation since 1978
www.borgeltinstruments.com
tel: 07 4635 5784 overseas: int+61-7-4635 5784
mob: 042835 5784 : int+61-42835 5784
P O Box 4607, Toowoomba East, QLD 4350, Australia
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