On Dec 4, 2007, at 11:07 PM, Kevin O'Dell wrote:
As far as Spread Spectrum systems. From purely an engineering
point of view, the Futaba system is by far more reliable.. Sure
the JR system might work just fine. Although we have already heard
reports of problems with satellite receivers... But true Spread
Spectrum is the only way to go and I would not buy any 2.4 system
that doesn't have it....
JR's Direct Sequence Spread Spectrum is true spread spectrum, as is
frequency hopping that Futaba uses.....the only reports I have seen
are problems that can't be traced to the radio......in a very
hostile RF environment (some major metro areas) Frequency Hopping
Spread Spectrum (FHSS) can have latency issues......you won't loose
any packets because the data is error correcting but, you might
have a delay in the data packet getting there.......this will slow
the response time of the system, but not break it....The DSSS
system can have an issue with signal fading depending on the number
of and orientation of antennas in the aircraft.....as well as the
construction of the aircraft......all carbon birds might not
present a great environment......but this also can happen in FHSS
systems.......under most circumstances, both systems provide a
solid, interference free link. At this point, most SS applications
outside the RC world have dropped the FHSS and gone with the
DSSS.......in IEEE 802.11 both FHSS and DSSS were standardized for
1 and 2 Mbit/s data rates.....with 802.11b and beyond FHSS was left
behind and DSSS was standardized for 5.5 Mbit/s and 11 Mbit/s data
rates......so if the data rates increase, they may have to shift to
DSSS.
Kevin O'Dell N0IRW
