[MLB-WIRELESS] FW: [BAWUG] A Geek Who Climbed a Tree to Take a Peek, was: Passive repeater net gain
drew at no6.com
drew at no6.com
Sat Feb 16 09:45:01 EST 2002
Unfortunately it seems the Cringely passive repeater bank shot (http://www.pbs.org/cringely/pulpit/pulpit20020207.html) was bogus. Lame.
-D
Original Message:
-----------------
From: Tom Farrow tjf at jetcafe.org
Date: Fri, 15 Feb 2002 13:10:51 -0800
To: wireless at lists.bawug.org, NANP at jetcafe.org, WIT at jetcafe.org, bob at cringely.com
Subject: [BAWUG] A Geek Who Climbed a Tree to Take a Peek, was: Passive repeater net gain
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On Wed, 13 Feb 2002 10:43:53 Mark Rosenau <markr at jutland.com> wrote:
>At 03:41 PM 2/12/02 -0600, Nate Carlson wrote:
>>On Tue, 12 Feb 2002, Walter Bruce wrote:
>> > So, why did it work for Cringely?
>>
>>My question is if it actually worked for him, or if he's BS'ing all of us.
>>
>>He has yet to provide anyone with any evidence of how he did it, etc.. I'd
>>love to see his antenna design.
>
>This wouldn't be the first time Mr. Cringley fudged the truth a little. See
>his "design and build an airplane in 30 days" story in PSB several years ago.
This appears to be a good assessment of the situation. I have had a couple of
email exchanges with Cringely, starting with the path analysis posted to this
list.
He has written that he did not do the math, but that he does not find any
fault with the calculations. He also insists that the story is accurate, "Oh,
it works as I described." However, he evades answering specific questions,
such as the how, when, and where of his throughput measurements, or even if it
was end-to-end through the passive repeater.
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
* Bob, if any of the following is factually or materially inaccurate, please *
* let me know how to correct it. *
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
This is my assessment:
The numbers do not lie, the link from "chez Cringely" to Sonic in downtown
Santa Rosa, through the passive repeater he described, on FCC Part 15
frequencies, is not possible. That was in the original analysis and he did
not dispute it.
So, a closer reading of the story reveals that what one might have originally
ascribed to all too common sloppy reporting, may be a knowing and clever
attempt to fudge the truth for dramatic effect by leading the reader to imply
something that is never explicitly stated.
Undaunted, I decided to try a bank shot. I'd simply bounce my signal off
another, even higher, mountain ... whatever repeater I used
I had in hand a pair of double-headed yagi passive repeating antennas tuned
for 2.4 GHz.
so I mounted the first yagi and pointed each end in the
/appropriate/[emphasis added] direction.
[in a paragraph describing the complete system:]
Using both double yagis at the same time did increase total signal strength
And it works! Right now, I am getting a solid two megabits-per-second
I have them -- two megabits-per-second straight to chez Cringely.
- From these statements one would probably conclude that there was a bank shot
from Cringely home -- passive repeater -- Sonic using 802.11b.
However, look at what he ACTUALLY CLAIMS in the story:
From the treetop, I could log-in to my home network and also into Sonic.net.
This did not involve an end-to-end passive repeater, but a link through his
notebook computer, an active repeater, up in the tree. If the antenna on the
card in his notebook was within, I believe, 15 wavelengths (approximately
2meters @ 2.4GHz) it would operate in close coupled mode with the passive
antennas, where free space signal losses do not apply.
In any case the 2Mbps was to his home from the tree, 1.5 miles away. No
mention of throughput to Sonic, just that a login was possible, and in the
private email, he has even been hedging on that point.
Welcome to Al Capone's vault.
There is nothing particularly novel or interesting about either a 1.5 mile or
a 5 mile wireless link, nor even accomplishing both at the same time. If this
assessment is correct ;) then the passive repeater was nothing more than a
gimmick and a clever red-herring, its EM purpose better served by a short
length of coax.
But the subject line of this mail just doesn't sound as sexy as overcoming a
mountainous obstacle with a 'bank shot'.
An assessment of this ethical indiscretion reveals Bob has little to lose and
much to gain, ie. a good Machiavellian risk to benefit ratio.
Perhaps he did not think anyone would do the math, he could maintain a
mysterious aura of one who had done what all others have failed to do. And as
he did not actually write anything that was false, he could maintain that the
story as written is true. Admit it, if you've gotten this far, it has taken
alot of words to explain that while the story is perhaps truthful in its
explicit claims, it was deliberately written to mislead. Bob's reluctance to
clarify issues lends credibility to this claim.
I sent the mathematical analysis with a short explanation to PBS.com, and have
not heard a word from them, while Bob's story remains on their web site. It
is disappointing that they care so little when questions are raised about the
accuracy of a technical story. This mail will also be sent to PBS, but it is
a long read, and somewhat technical in a different sense, ie 'what is truth?'.
Even assuming that this explanation is understood and appreciated, being
sanctioned or dismissed by the 'stuffed shirts' at Public Broadcasting for an
ethical indiscretion to spice up a story may actually be a credential to get a
higher paying job at say a supermarket tabloid or even, Fox ;)
No publicity is bad publicity. Geraldo has made a career on that motto.
Well, to conclude my rant, let me add a few things to the list of reasons
given by Bob as to why his setup might not be a good long term solution:
Sitting up in that old blue oak might get cold and lonely, not to mention
dangerous in the bad storm of which he speaks.
Carrying enough food, water, and batteries to keep the network up for any
length of time could prove troublesome.
It would probably be easier to drive to Santa Rosa to use the Sonic network,
and then use some software to coordinate the notebook to the home system.
You see, even his assessment of the experiment is deliberately written to
blind the reader to the truth by omitting problems that are orders of
magnitude more pressing.
- --
Tom Farrow tjf at jetcafe.org
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