On 6/29/2010 2:17 AM, ursus wrote:
On Jun 22, 6:42 am, Mike
wrote:

There is no inherent reason that ADS-B UAT transceivers using consumer
grade GPS and RF components can't be built for the same general price
point as FLARM units. The only difference in the hardware is frequency
and transmit power.

The FLARM RF transceiver costs about $5 in parts. The ADS-B UAT
transceiver is how much ???
Most glider pilots are in complete denial about the commercial
realities of the gliding business:
Selling and supporting an *empty* box, with no production costs, to
glider pilots could not be done below USD 600 per unit.
It is not pretty, but that's the reality if your business intends to
still be around in a few years, while supporting and innovating for
the customers...

The MITRE unit
transmits "unknown" for integrity, as that information is not available
from a consumer grade GPS chipset.

The 'consumer grade' GPS chipset in FLARM provides all the information
you ever need:
DOP, accuracy estimates, pseudorange errors, satellite health and
whatever comes in through WAAS / EGNOS...
Some of that information is also transmitted in the FLARM signal and
used for alarm evaluation.
Just because a device is FAA certified does not mean it is better, it
just means it is outdated ;-)

Another note: FLARM and ADS-B units are not a cure alls for collision
avoidance in competition flying. The accuracy of the GPS fixes and the
update rates (even for units meeting the FAA's latest approved specs)
are not high enough to provide collision warnings for gliders that are
sharing a thermal in a gagle.

The update rate and relative (!) precision of the GPS used in FLARM is
by far sufficient to do collision avoidance in glider competitions.
Other factors are more limiting.
However, if you stick various FAA approved GPS's into gliders your
relative position and velocity information will not be nearly as
good...

My dear US friends; we do agree that 'classic' FLARM is not the best
solution for the US. This is why we never launched it there.
Stay tuned for PowerFLARM; it will deliver all you need, soon.
www.powerflarm.com

Urs - FLARM


You are obviously much more knowledgeable about FLARM and the associated
engineering than most of us. Please educate us on how much the price of
a FLARM unit would increase if it were re-engineered to meet the ADS-B
standards, assuming that the FAA would permit the utilization of
consumer grade components, eliminate the need for antenna diversity, and
reduce the transmit power levels somewhat to reflect the lower closing
rates of GA aircraft.

The other key consideration is that such a unit would not just be of
interest to the soaring community, but would also be sold into the VFR
GA market, dramatically increasing the potential sales volumes compared
to FLARM in Europe.


--
Mike Schumann