[NSRCA-discussion] 2.4ghz

[Fred Huber]

In theory, the hoppers would change frequencies so fast that just one bad 
packet should result for both systems that happen to be on the same 
frequency momentarilly.  As with PCM, a single bad packet should just give a 
virtually unnoticeable delay in control response due to using the last good 
packet. while waiting for the next one.

Theory to practice does not always work....


The FASST would expect to see some instances of the radios hopping to the 
same frequency, but the randomization should be based on the TX's unique ID 
code and thus prevent there being significant chance of any 2 TX's hopping 
through the same frequency series at the same time, thus causing several bad 
packets in a row.
(If they used the TX ID as the random number "seed")

Computer random numbers aren't really random.  If no "seed" is given, they 
may base off of the "timer" or 0 depending on the programming.  The timer 
gives a very good semblance of randomness.  If you give the random number 
generator the same seed number and then ask it to randomize the same way 
you'll get the same result every time.

----- Original Message ----- 
From: "John Konneker" <jlkonn at hotmail.com>
To: <nsrca-discussion at lists.nsrca.org>
Sent: Monday, February 26, 2007 9:59 AM
Subject: [NSRCA-discussion] 2.4ghz


>I have been teetering back and forth over buying one of the new DX7's.
> There has been a lot said about the "can't" be interfered with in the 
> 2.4ghz
> band.
> Someone posted this link on one of the RCU threads.
> http://www.fcc.gov/Bureaus/Engineering_Technology/Documents/cfr/1998/47cfr15.pdf
> Specifically section 15.247 looks as though it says a channel hoping 
> system
> can occupy any channel for up to .4 seconds.
> Although the data to the rx may be unique wouldn't this still cause a
> lockout due to the bad "packet" being received?
> Does this mean it would be possible for several FASST channel hoping 
> systems
> to cause a noticeable problem on a system such as Specktrum's that locks 
> on
> to a single channel when turned on and stays there?
> And I guess to some extent to other channel hoping systems?
> I am no expert...
> Just trying to understand this sea change about to occur with our radios.
> Thanks!
> JLK
>
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