On Thu, Apr 07, 2005 at 08:01:59PM -0400, [EMAIL PROTECTED] wrote:
| Doug McLauren wrote:
Hmm ...
| >Still, it's time for the thread to die.
What is it with people taking private emails and replying to them to
the list? Guys, it's rude to reply to a private email and CC a
mailing list like this. If I reply to you directly, it's because I
don't think something is worth sending to the list, or shouldn't be
sent to the list. (And this topic is not really very soaring related,
so I didn't want to perpetuate it.)
| Guess again. Now that we've established that with 50 channels, only
| eight people can show up before there's a better than 50:50 chance
| of a frequency conflict, let's imagine how it would be if we got
| awarded 50 more R/C aircraft channels for a total of 100.
If we are magically awarded 50 more R/C channels, I would hope that
they would be allocated ONLY for spread spectrum R/C use. And we
don't really need 50 more channels under the current system anyways --
how often do you see 50+ airplanes in the air _at once_? (Perhaps
once in a while at a slope or something.) More channels would reduce
the odds of conflicts, but wouldn't make the problem of frequnecy
control go away. (And don't forget that there are a few more channels
available -- 27 mHz, 50 mHz, 53 mHz, 49 mHz if you're really
deseperate, 900 mHz, 2.4 gHz, 5.8 gHz if you don't mind violating AMA
rules and using non-standard equipment ...) [ I'm talking US here, of
course. ]
Of course, it _would_ require magic to get these channels allocated.
Or a lot of money -- the FCC does seem willing to sell spectrum for
money.
| Of course there would be a bias at the beginning, but once usage came to be
| spread out evenly and randomly among those 100 channels, how many people
| could then show up at a field before probability favored a conflict?
|
| Before working it out, take a guess at what the new answer will be. You might
| be surprised.
... or might not. It's still the birthday paradox, it's just that the
numbers have changed. In fact, since the birthday paradox is based on
365 `channels', the answer has gotten even closer to what people are
used to seeing.
Also, note that what you're figuring out is the odds for _anybody_ to
have a conflict. Assuming that everybody only has one channel, the
odds of _you_ having a conflict with somebody else are approximately
(the number of other people) / (50 {the number of channels
available}.) (It's approximately because we ignore the possibility of
multiple other people sharing a frequency. This approximation starts
to fall apart as the number of people grows and approaches 50.)
The odds of you personally having a conflict are a lot smaller. And
even having a conflict isn't the end of the world. Quite often,
people have different planes on different channels, or can change
modules and crystals. (I certainly never go out to the flying field
with only one plane. What if I break it?) And if it does turn out
that you're sharing a frequency with somebody else, it just means that
you get to watch half the time. I learn as much by watching other
people fly as I do by flying myself ...
The local soaring club's leadership doesn't really like me because I
pointed out that their idea of `owned frequencies' really wasn't fair
(leadership got first dibs), and limited the club's size to 50
members. But fair or not, it does bring the odds of a conflict down
to almost zero. And even at the power club that I'm a member of,
while there are no `owned' frequencies, there is a frequency list. I
almost never have conflicts when I fly at that field, even if there's
30+ people out there for a contest. Frequencies are *not* random.
--
Doug McLaren, [EMAIL PROTECTED]
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