Model Forum / Radio Controlled / Air Models / February 2004

Not quite Vance.  I don't claim to be an expert but I see you don't
understand the way it works.  It doesn't change channels because of
interference.  It changes channels constantly, regardless of the situation.
Many times a second.  It's a form of encryption.  It uses 25 channels
essentially all at the same time.  It shifts between these channels in a
pattern determined by some algorithm built into the radio.  So it doesn't
hit each channel in numerical order but in some pattern known by the Tx and
Rx.

Read the four levels of protection at the bottom of this page:
http://www.auav.net/spread_spectrum_radio.htm

The Tx and Rx are in sync with each other.  What this means is the Rx also
knows the pattern and is expecting to "hear" from the Tx at the prescribed
time on the prescribed channel.  Correct channel at wrong time is ignored as
is correct time on wrong channel.  Even another R/C Tx using the same
pattern would not cause interference unless it was in the same exact spot of
the pattern at the same exact instant in time.  And instant is the key here
because to our perception it is only an instant that it is on any given
channel.  If fact, I suspect it hits each channel several times each second.
And if I remember my math correctly, with 25 channels we end up with well
over 13,000 possible patterns (probably more but hey, do we need more?:)
which would equate to the possibility of 13,000 models in the air at once.

Likewise, any phones or wireless computers would have to be on the same set
of channels and the same pattern to cause any problems.  As would the Line
of Site microwave shots and Satellite links that used this band.  This is a
proven technology that has been in use for years.  It is simply, finally
being implemented in R/C.  About time too!

Chuck