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Re: Monkey Brains
On Tuesday, August 21, 2018 at 2:34:21 PM UTC+10, John Larkin wrote:
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Until everybody does it, and the spill-over from everybody else's links turns into an impossibly high noise level on your link.

Our WiFi from one end of the flat to the other works fine, until all our neighbours get busy. So my wife's computer is now linked to our router by data over the mains wiring.

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But everybody using the same microwave frequencies in free space will be even more barbaric.  

Cellular networks minimise the problem, but you don't seem to have that.

--  
Bill Sloman, Sydney



Re: Monkey Brains
On Mon, 20 Aug 2018 21:34:13 -0700, John Larkin

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That would create the ultimate single point of failure.  For example,
if the favored monopoly of the day built such a network on 60GHz, and
San Francisco had an earthquake, most of the dish antennas involved
would go out of alignment and out of service until a mythical army of
technicians could be deployed to put things back together, assuming
there are no aftershocks.  Of course, motorized mounts that compensate
for building or ground movement would fix the problem, but at this
time, only cellular providers use them, primarily to avoid paying for
expensive truck rolls and tower climbers.

Another problem is if you try to build a mesh network at 60GHz.  Mesh
requires omnidirectional or sector antennas.  However, to get any kind
of range out of such antennas, one would need to trade antenna gain
for a wide horizontal radiation angle.  That can be done, but the
resultant vertical radiation angle will end up very narrow, probably
on the order of a small fraction of a degree.  Something like this
2.4GHz sector antenna:
<http://www.learnbydestroying.com/jeffl/antennas/AMOS-7/slides/3D.html>
That means all the neighboring mesh nodes, with identical equipment,
will need to be located at exactly the same altitude as your antenna.
In my disorganized talk on the topic, I presented this drawing of a
mesh network, and asked the audience "what is wrong with this
picture"?
<
http://www.learnbydestroying.com/jeffl/FLUG-talk-2015-02-28/rooftop-mesh.jpg

The answer is that with a narrow vertical radiation angle antenna
system, rooftops of different heights cannot "see" each other.

So, let's pretend that all this and related problems are solved by
flying an aerostat balloon antenna over every building so that
everyone's antenna is at the same altitude.  That would probably work
for a 60GHz mesh network.  However, such a network needs to connect to
the internet at some point.  Let's pretend that your new offices are
located fairly close to a major network wireless hub for the 60GHz
wireless network.  You would have great latency because you're only
one hop away from the internet, but you also need to pass all the
traffic originating from all the other outlying users.  Your corner of
the mesh would suffer from major congestion problems.  (I'll spare you
my rant on the futility of exotic routing algorithms and bandwidth
management).

Think about what might happen if something fails.  Is there a
fall-back available?  With the current tangled mess of different ways
to connect to the internet, there are alternatives that can be made to
work temporarily.  When my home DSL fails, I point my wireless antenna
to the neighbors Comcast router.  Some people use their cell phone as
a wi-fi hot spot.  Others drive to the nearest coffee shop or library
with a working internet.

I can rant on forever on the topic, but that should suffice for now. I
suggest that you be careful of what you ask for.  Just because one
particular technology is superior in one application, doesn't make it
superior or even suitable for all other related applications.


--  
Jeff Liebermann     snipped-for-privacy@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
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Re: Monkey Brains
wrote:

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The power would be out too. Unless our building collapsed, I suspect
our dish would still be aimed OK. A dinky little dish like that isn't
super directive, and we have 170 dB to spare.

I'm thinking that the super-net backbone would be fiber, run to
micro-towers every few blocks. Microwave could be used when fiber is
hard to run. Some sort of Ricochet mesh could work a couple of hops in
places where the aggregate bandwidth is moderate; upgrade as needed.

It's just that I have noticed that things keep changing, and most
people assume that nothing will change.







  Of course, motorized mounts that compensate
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If a micro-tower can reach its customers, it can be arranged to hit
adjacent towers. Beats trenching streets.

Cell phones work pretty well.





  That can be done, but the
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Or maybe nothing will ever change.


--  

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement  

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Re: Monkey Brains
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Actually those MikroTik dishes are "self aligning".  The feed has a square
array of antennas and the optimal configuration is continuously
determined.  So there is no exact pointing required.

There also exists a bare feed version ("wireless wire") that is
usable on shorter distances and actually uses the antenna for
beamforming.  I think it can sweep the beam over a 100deg angle or so.
For the dish version, it is of course less.

Re: Monkey Brains
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Earthquake here (https://en.wikipedia.org/wiki/2011_Christchurch_earthquake )
didn't disturb the satellite dish enough to stop reception, but the power was
off here for several days. it also damaged the copper phone lines
disrupting service but the DSL kept working. (this was fairly close:
the epicenter was about 5km West and 5km down)

Antennas are light and need to be secured well to maintain alignment
during strong winds, even a large shake should not disturb their
alignment unless the whole building shifts

--  
     ?

Re: Monkey Brains
On Wed, 22 Aug 2018 06:44:17 -0000 (UTC), Jasen Betts

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We had something similar here in 1989.

https://en.wikipedia.org/wiki/1989_Loma_Prieta_earthquake

We lost power for a couple of days, so we had an all-block ice cream
party before it melted.

I don't know of any antenna alignment problems. It would take Gs of
horizontal acceleration to move an antenna, and a fraction of a G will
tear a building apart.

Brick chimneys (like ours) commonly crumbled, so an antenna strapped
to one of those would fall. The big killer in San Francisco was
bricks.





--  

John Larkin         Highland Technology, Inc

lunatic fringe electronics  


Re: Monkey Brains
onsdag den 22. august 2018 kl. 17.22.05 UTC+2 skrev John Larkin:
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the whole building might move  






Re: Monkey Brains
On Wed, 22 Aug 2018 09:32:01 -0700 (PDT), Lasse Langwadt Christensen

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I suppose that might mis-align a dish.


--  

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement  

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Re: Monkey Brains

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A few years ago, I read that the biggest earthquake risk to homes in
my area (mostly single-story wood-frame, built in 1960 or so) is
chimney failures.  The codes at that time did not require
reinforcement.  An unreinforced chimney falling over and crashing
through your roof would definitely spoil your whole day.  Even if it
doesn't hit somebody, it could easily be the difference between a
house which takes superficial damage, and a house that's red-tagged as
"uninhabitable, do not enter" for months.

The chimney at our house had taken some minor cracking damage during
Loma Prieta (several years before we bought the place) but was
evaluated as sound during the pre-purchase inspection.

About two years back, I got a Round Tuit and did something about
it... had a local mason disassemble the chimney, brick by brick, down
to the "shoulder", and then rebuild it to meet current code
standard... rebar up each corner, steel straps going through the wall
and tying it to the house beams, a larger-diameter flue, cement
"fill" in each corner around the flue and rebar, and a new cap and
spark arrestor.  Visually you really can't see any difference from
outside, but internally it's a very different beast.

Good, cheap investment.

And, I decided not to ever fasten an antenna of any sort to
it... turns out that the repeated bending stress from an antenna being
blown around by the wind is one of the things which tends to weaken
brick antennas over time.  I installed a separate mast at ground level
(goes through a hole in the eaves, bolted to the roof beams, and sunk
into concrete at ground level) for the TV antenna.







Re: Monkey Brains
On Wed, 22 Aug 2018 10:37:07 -0700, snipped-for-privacy@coop.radagast.org (Dave
Platt) wrote:

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Our old house was built in 1892, and the chimney was brick with,
probably, beach-sand mortar. You could scrape the mortar out with a
fingernail. In '89, the chimney sort of crumbled but didn't go through
the roof. I took it down a brick at a time and turned it into a
skylight.


--  

John Larkin         Highland Technology, Inc

lunatic fringe electronics  


Re: Monkey Brains
On Wed, 22 Aug 2018 06:44:17 -0000 (UTC), Jasen Betts

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My earthquake experience was mixed.  In 1989, we had the Loma Prieta
earthquake:
<https://en.wikipedia.org/wiki/1989_Loma_Prieta_earthquake
Most DBS dishes maintained alignment if the building wasn't damaged by
the quake.  Some buildings shifted on their foundations, which
certainly caused alignment problems.  Anything mounted on a chimney
went out of alignment.  In my area, every chimney had some kind of
damage (except one that was build around a large steel pipe).  On the
commercial side, I lost 2 out of 7 point to point microwave links to
alignment problems.  I lost 2 more when the tower respective owners
decided to adjust the tower so that it was properly plumb (vertical)
and everyone had to realign their dishes.  The heavy 1 meter
fiberglass satellite dishes (mostly paging downlink and broadcast
audio) were also mixed.  
<http://www.k6hju.com/pics/Outside/IMG_0710.JPG
All continued to work, but at reduced signal levels that were
insufficient to trigger LoS alarms.  We realigned them eventually.

As Rob mentioned, the 60GHz Mikrotik dishes are self aligning and
should survive a shake that leaves the building intact.  (I didn't
know that it had that feature).  It also makes realignment much
easier.

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The common 20" DBS dish is quite light.  However, the J mount is not
very secure.  It doesn't take much to ruin the alignment as I've found
when helping friends and neighbors with their installations (in the
trees).  The usual problem is that lag bolts used to secure the dish
to a wooden part of the house.  The bolts loosen over time.

If you need some entertainment, attach an accelerometer to a wood
mallet and beat on the dish at its center of mass.  Watch the peak
acceleration on an oscilloscope:
<https://www.tandfonline.com/doi/pdf/10.1080/00288306.2011.641182
   Ground motions during the earthquake were unusually large  
   at near-source distances for an earthquake of its size,  
   registering up to 2.2 g (vertical) and 1.7 g (horizontal)  
   near the epicentre and up to 0.8 g (vertical) and 0.7 g
   (horizontal) in the city centre.
Aim for 1.7g acceleration and see what happens to the dish.  Loma
Prieta 1989 was 0.64g horizontal.


--  
Jeff Liebermann     snipped-for-privacy@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
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Re: Monkey Brains
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This was a 89cm dish - 36", with a J mount and two stay bars. It's
held down with high tensile roofing screws, not cruddy mild steel lag
bolts.

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Apart from that being impossible - the center of mass is located in a void.
I'm sure I could get different figures depending on the size of the
mallet chosen... what's this going to demonstrate?

with 2g acceleration the mounting needs only to withstand three times
the normal weight of the dish. and the bolts are all at-least torqued  
five times harder than needed to hold the dish on target during
adjustment.

--  
     ?

Re: Monkey Brains
wrote:

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This is seriously embarrassing.  Most of what I wrote above is wrong.

In 1989 we did not have Wi-Fi and DBS satellites.  The antennas that I
was running around realigning in 1989 were 460 and 900MHz yagis and no
dishes.  All of what I wrote above actually happened and are not
fabrications, but occurred over about a 15 year period and not in
1989.

What happened was that my sense of time failed.  It was as if
everything over about a 15 year period happened at one time, in this
case in 1989.  I've had this problem erratically for much of my life.
At the time when I write something like the above, I cannot tell that
my sense of time is distorted.  However, I can usually tell by simply
waiting about 30 mins and double checking what I wrote or said.  This
time, I was in a hurry and didn't wait.  A recent change in my heart
meds might have also been involved.  

I'm not sure what to do next.  Of course, I just sent email to the
doctor asking if I can change back to the previous meds.  I'll
probably take a break from posting on Usenet and various mailing lists
until I'm sure there will not be a repeat performance.  This is all
rather painful.  Having trashed my own reputation, the best I can
offer is this apology and explanation.

My apologies (again).

--  
Jeff Liebermann     snipped-for-privacy@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
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Re: Monkey Brains
wrote:

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This business is so complex that it's hard to remember what happened
when. After my first hundred designs, I could remember every
schematic. After the first thousand PCB designs, one starts to forget
details. That's why we write stuff down.


--  

John Larkin         Highland Technology, Inc
picosecond timing   precision measurement  

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Re: Monkey Brains
Jeff Liebermann wrote:
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I think your reputation is more resilient than that.  No one bought or  
sold stock based on your post.  The pain is all yours, and is part of  
the pain of aging, so there should be no embarrassment or guilt to go  
with that pain.




Re: Monkey Brains

Jeff Liebermann wrote:
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I think your reputation is more resilient than that.  No one bought or
sold stock based on your post.  The pain is all yours, and is part of
the pain of aging, so there should be no embarrassment or guilt to go
with that pain.
==================================================================

x2.  I've always prided myself on my memory, and one of the things I was  
good at was having a pretty accurate sense of how sure I was of any given  
specific memory.  Once past about 45 that accuracy data seems to have stuck  
on "I'm sure of everything", and sadly over the last 15 years or so I either  
can't remember stuff at all or think I remember it correctly but I'm wrong.  
I've embarrassed myself a few times with friends and family, once much worse  
than your episode.  Getting old sucks, it's worse than everything but the  
alternative :-).

--
Regards,
Carl Ijames  


Re: Monkey Brains
On 23/08/18 01:41, Jeff Liebermann wrote:

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That's never happened to me. Oh, no. Never. Ever.


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The mistake means you fit in with far too much of
usenet :(

Admitting it means you don't fit in - and your
reputation is enhanced. :)


Re: Monkey Brains
Jasen Betts wrote:
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My friend maintained the system that linked the WTC to the NY metro area  
airports.  It never went down until the collapse.




Re: Monkey Brains
Jeff Liebermann wrote:
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Lower cost could allow sufficient redundancy.  If the dishes are a few  
hundred dollars then you could have several directional dishes on the  
roof of each large building to link them in a wider mesh, each aimed at  
a different elevation and direction.  Small buildings in between could  
use omnidirectional antennas to form a smaller local mesh that links to  
several of the larger buildings.  The small buildings could also have  
multiple antennas with intermediate angles each.

Of course it would suffer to an extent when any part goes down, but that  
happens when a router fails somewhere.

And of course I know I'm missing something.




Re: Monkey Brains
On 08/21/2018 12:34 AM, John Larkin wrote:
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I recall reading somewhere that in the distant past, in time known as  
the Sixties, the telco companies knew that consumers would eventually  
start demanding wider bandwidth channels than copper links could provide  
for, but fiber optics was still in its infancy and it was unknown to  
materials science if such a medium could actually support wide bandwidth  
communications.

So it seems they spent some time investigating the properties of  
relatively large-diameter spiral microwave waveguides that would be run  
under the streets to homes like water pipes, like an actual "tube" for  
the Internet


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