[NSRCA-discussion] 2.4ghz

[John Konneker]

Fred,
Thanks for the thoughtful response.
I really am ignorant in these matters plus...I'm OLD!
;-)
The .4 second "sharing" would seem to be noticeable.
I remember in my F3C days back in the mid '80s I flew JR PCM 9's.
In certain environments, especially in Austin, Texas, I would get noticeable 
lockouts.
They would be short duration...
Just long enough to put that doubt in the back of you mind "do I still have 
it" and for the hair to start to stand up on the back of your neck.
I guess I should write the AMA but wonder if JR, Futaba, Spektrum, Nomadio, 
etc have gone to Muncie and stood shoulder to shoulder with each other with 
several of each radio turned on?
The systems that have data loggers could supply some interesting 
information.
JLK



>From: "Fred Huber" <fhhuber at clearwire.net>
>Reply-To: NSRCA Mailing List <nsrca-discussion at lists.nsrca.org>
>To: "NSRCA Mailing List" <nsrca-discussion at lists.nsrca.org>
>Subject: Re: [NSRCA-discussion] 2.4ghz
>Date: Mon, 26 Feb 2007 10:16:59 -0600
>
>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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