Why so thick? Banging your head against the wall only requires a single layer of sheet rock.
True, if it were the size of the entire wall. However, it makes a great waveguide. During the early 1990's, I had a problem installing wi-fi at a local hospital. I could do anything I wanted except to add, move, or change anything. Right. So, I put a wireless router antenna inside the HVAC ducting, and walked around the hospital to see what kind of coverage I could get. The rectangular cross section sheet metal ducting worked over several hundred feet. The round flex stuff, maybe 50ft. That was enough to light up a waiting room, a few offices, and some odd equipment rooms.
However, when I proudly demonstrated my feat of improvised engineering, the bureaucracy was aghast. I was allegedly "irradiating" the patients. Someone mentioned ionizing the air in the ducts. Fearless leader was on the phone calling some attorney to check if the hospital had created any legal exposure. The IT person stood there like a statue and said nothing.
It was about 5 years later that the hospital finally installed wi-fi, mostly because the doctors were buying early smartphones and could not connect their Blackberrys from inside a poured concrete structure. So, wi-fi finally arrived via the back door.
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Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
The "house" is a cell in an insane asylum >:-} ...Jim Thompson
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| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
On Fri, 11 Sep 2015 17:09:25 -0700, Jeff Liebermann Gave us:
You should have directed them to a wiki page on Tesla.
Or is it Johnnie Cochran?
Seriously, if it were a problem folks would already be dropping like flies all over the planet.
We could hack the cell towers and remotely up the wattage on all of the ISIS phones and win the war from an analyst's desk chair.
Aghast indeed. The world is full of overpaid, undereducated, less than deserving bureaucratic idiots. THAT is where the wealth re-distribution should start.
On Fri, 11 Sep 2015 17:17:48 -0700, Jim Thompson Gave us:
The tripeson retard is an example of someone the KKK or some other faction should have 'visited' and wiped out decades ago. Him AND all of his pathetic spawn.
They should all have participated in the purple gym shoe comet reception.
I did that, and don't find as much difference between the vertical and horizontal positions of the router antenna as I did with the laptop. The laptop continues to show a strong preference for a horizontal router antenna pretty much everywhere.
Other things you mentioned:
I was wrong about the distance. The maximum distance is 65 feet, at which point the computer gets four bars. But at about 55 feet, it gets five bars. The tablet app shows it barely out of the green at 65 feet, and just into the green at 55 feet. But in both cases, it's definitely going through three walls, but I guess it could be bouncing around and going through off-line open doors.
I remember checking this back in the day with Buffalo, and they said the WHR-HP-G54 comes with a 4 dBi antenna. On the box it just says "High gain antenna for extended range". It's six inches long from the swivel point near the base, but of course I don't know how much of the plastic is empty, or what the gain really is.
The problem with the existing antenna is that the plastic part that broke off, and I didn't save, is right at the base, and is part of the threaded socket that screws onto the router connector. I've only got a little over half of the threaded socket left, so I cant screw it down tight, and can't be sure it's even making a good connection. I don't see a good way to fix it without the missing part, and would kinda like to get a replacement that attaches correctly.
Of ocurse I can just get a replacement omni antenna, but as I said before, almost all the places in the house where I ever use the computor or tablet are along one line from the router - within 15 degrees either way from that line. The only exception is the base location of the computer, but that's six feet from the router, so not likely to be a problem even if the antenna is directional.
The directional panel I'm looking at ($9) is shown in the first half of this video:
formatting link
I wonder if his understanding of how the parts go together is correct, and I wonder which side is the front. It seems to me that the metal plate should be behind the antenna elements, but Alfa says the side with the logo is the front, so I don't know. Well, I guess it would be easy enough to test when it arrives. Anyway, would this be worth a try, or does it just look like junk? Or both? :-)
Bingo! The exact unit is the NanoStation loco M900.
Uh, best SNR *is* the highest signal strength. The noise floor never wavers. I'm not seeing much difference in signal strength, about 6 dB total with most of that from finding a "sweet" spot. Trying to optimize the last 1 db is not of much value.
Notice in your illustration the noise floor is -90 dBm? Mine is -101 dBm right now. I guess I have seen it as bad as -99 dBm. I will note the noise floor if I play with it again tomorrow.
Also notice the airMAX Quality and airMAX Capacity readings. I can't find anything about how they are calculated. I expect they take into account the current usage on the air link since it is shared. On my unit they are always pretty poor, barely into the orange, never yellow even.
I can barely measure 1 dB diff if I try hard. I think the real difference is just a matter of finding a sweet spot with the highest signal strength. That happens to not coincide with my glass door.
The Antenna has very little gain. The pattern is roughly cardioid
other than cell phones? Not many of them about really, this is the dead center of nowhere which is why I'm using the only game in town, iWisp.
BTW, a directional antenna can't make the interference *worse* unless it is pointed away from the desired signal source. It just won't give
*any* improvement. I might hit the guy up for a unit with more antenna gain, but I think the outside mounting will do ok.
I'd like for him to do the work. I have a *very* bad hip and getting on the ladder today almost ended badly when I stepped off wrong. A hole needs to be drilled through the top of the basement wall and I don't think I have a bit both long and wide enough to admit the RJ45 connector. It will also require a longer cable and he specifically said it needs a "special" cable with shielding. I guess that helps with self interference.
He doesn't cap anything, that would be work! I run computers 24/7. One says it transfers some 50 GB in a month, well over the limits most wireless providers cap. My roommate does a lot too. The rate cap is whatever the airlink will allow. The best we have measured when the leaves are gone is 5 Mbps.
On the weekends, we may see functional rate limiting. When lots of people are down it seems like the rates drop noticeably. I expect it is due to bandwidth limits in parts of his system or his Comcast connection.
The radio is designed to be outside, just not in the driving rain I think. Unit is sealed with a bottom cover for the RJ45 jack. All the other units are outside, so I expect he knows they aren't complete junk.
He did have weather trouble with *his* end once. We had an ice storm which covered his equipment. He seemed surprised by the fact that his antenna didn't work so well when covered by a quarter to a half inch of ice. lol I don't know how much water and ice absorb in the 900 MHz band, but I know it's not zero.
Probably. It's very quiet in the forest. I can carry on a conversation without yelling at a distance of about 50ft. I like really quiet and would certainly notice if a dog with indigestion passed by. The down side is that I have to be careful when I do something noisy. My propane powered casting forge had to be disarmed because it made too much noise. My piano pounding turned into synthesizer pounding with earphones. Leaf blowing is effectively banned. If I want it quiet, I also have to be quiet.
If you really want it quiet, two layers of drywall will certainly work, but methinks a layer of lead or spent uranium is better. Also, a poured concrete wall is more quiet. The higher mass barricades are better at attenuating the irritating lower audio frequencies from boom boxes. It's probably too late to redesign your house, but you might consider these materials should you remodel.
Sorry, but your short comment did not include any reasons for why you would use two layers of drywall. Presumably, it was not for RF attenuation. While it's generally more effective to ask, I thought it more entertaining to speculate on a possible rationalization.
I don't normally pound my head against the wall, although it does feel much better when I stop. However, I have been known to throw computers and computer components against the wall. I had a neat slot in my office wall where I was playing frisbee with some PCB's and missed the designated target. It's not exactly banging a computer against the wall, but might be close enough. I have repaired laptops that look like they were pounded against a wall, so I know it's possible.
--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
Back in the days when I rolled my own speaker enclosures I used the box-inside-a-box method: 3/4" Plywood boxes with 4" of sand in between... gets rid of any wood resonances... ought to work for walls too ;-)
Bwahahahahaha >:-}
[snip] ...Jim Thompson
--
| James E.Thompson | mens |
| Analog Innovations | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| San Tan Valley, AZ 85142 Skype: skypeanalog | |
| Voice:(480)460-2350 Fax: Available upon request | Brass Rat |
| E-mail Icon at http://www.analog-innovations.com | 1962 |
I love to cook with wine. Sometimes I even put it in the food.
Though to be perfectly precise, reflection is still reflection -- and if the studs are quite evenly periodic (hmm, dubious for a construction job really), it acts like a diffraction grating, which will lead to multipath problems inside, and fading outside.
If you find a fence of similar construction (metal poles or bars, wood pickets with enough spacing), try stomping your foot and listening carefully: you should hear a falling chirp due to the acoustic diffraction grating. :)
As I recall, 802.11(alphabet soup) is made to address multipath (automatic reflection filtering), but the sheer number of paths may overwhelm the method, so I'd be wary of this being a "gimme" situation.
I'm kind of interested in doing this, in one room, just so I can have an RF-quiet area for EMC work. Brass screens in the windows, foil on the walls, ceiling and floor, spring stock around the door... ;-)
It'd be something of a pain to filter all the AC line entries, though.
That comment was in your 2nd reply. Your original comment was: "This house has two sheets of 5/8" wallboard per wall, per side for four each wall." which fails to offer any explanation, context, logic. So there's no misunderstanding, I really don't care about your opinions or actions. However, I do care why you did it, hopefully including the logic and economics involved. In the future, some additional detail would be nice.
--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
In early college, I was working for a tape recorder, hi-fi, and camera repair shop and a large hi-fi dealer. I also did sales. Many of the customers were audiophiles, which meant they were willing to burn inordinate amounts of money on extreme components. Even back then, I could smell money.
One of my sales gimmicks was to connect a portable transistor radio to a really big expensive speaker system. Customers would invariably walk around looking to see which tuner/amp was playing. After some initial dialog on which hi-fi components are the most important, I would pull out the transistor radio by it's leads and proclaim that it was producing the sound. I sold an impressive number of high margin and high commission speakers that way.
During this time, I began to partly understand what made audiophiles function. It didn't need to sound good. It only needed to impress their friends and associates. Some were impressed by specs and features, but most simply wanted an impressively high price. Anything that expensive just had to sound good. I decided to dramatically improve both the function and performance of the speaker systems.
The basic design was a fairly conventional (bass reflex enclosure) about 5ft high and 3ft across and deep. However, instead of the usual plywood and fiberglass insulated cabinet, this was made from two layers of 1/4" thick Plexiglas, cross bracing, stiffeners, and with water in between. It looked enough like a fish bowl that I decided to add gravel, plants, fish, aerator, and heater. It actually sounded quite good and there no obvious enclosure resonances. I have some old B&W Polaroid photos somewhere.
After assuring the manager that the enclosure would not leak, I was allowed to drag it into the store and demonstrate it privately to a few select customers, to get a feel for whether it would sell and what price might be considered reasonable. The first customer wanted it immediately and offered $300 for it. That's about $1500 in todays inflated dollars. Sold.
However, like all student projects, there wasn't enough time to do exhaustive testing. I had never tested the completed speaker under sustained full power. The customer hauled it to his lavish Bel Air (near Smog Angeles) mansion, filled it with water, added some fish, and turned up the volume. The fish went insane after a few minutes, and soon died from the overpressure and vibration. After a few days, the glue joints holding the Plexiglas together began to crumble. Eventually, the entire enclosure fell apart. I'll spare you the details of my sudden departure and how I avoided getting sued (by helping with the cleanup).
If one had to do it over again today, nothing less than concentric plastic molded tanks would suffice. Also, lose the fish.
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Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
Yep. With the advent of 802.11g, the modulation became OFDM (orthogonal frequency division multiplex) which split the approximately 22 MHz wide signal into 52 carriers: If the reflected signal was 180 degrees longer than the incident (direct) signal, the two signals would cancel in the receiver. However, with 52 carriers, the cancellation would only wipe out a small number of channels, the others working normally but slower because the phase difference is something other than 180 degrees. This is called "frequency selective fading".
802.11n or MIMO did one better. Instead of dropping phase cancelled channels, spatial division multiplexing allowed using the same channels that had previously cancelled, but now with separate transmitters and receivers, could be combined and used to increase throughput. The catch is that the path for each "stream" had to be different. In effect, the reflections are now beneficial.
The RF filtering wallpaper is made to be frequency selective. Mostly it's used to eliminate cell phone base station interference, but is also made to work on other frequencies. However, if you want to block all RF, I suggest looking at how RF screen rooms are built. You'll probably find yourself working with brass mesh or brass sheet metal. I've built a few of these over the years. The hard part is getting the door to seal, and filtering any wires that go through the walls.
If that's too much, think about a smaller shielded box:
Bulkhead filters are easy, but not cheap. There are commercial AC line filters in all manner of size and shapes. Because of the large difference in frequency between 60 Hz and whatever RF interference you're trying to remove, the filters are fairly simple.
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Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
A bit more on the cabling. Ubiquti sells and recommends shielded and gel filled cable: However, it's not for EMI/RFI problems, but rather from ESD (electrostatic discharge), where a nearby lightning hit will induce enough power in the cable to blow up whatever is on either end. I've had it happen from a ground hit, about 200 ft away. For fairly short runs I don't think it's necessary, but you might as well play it safe.
Looks like their cable is not waterproof and gel filled. Gel is a slimy silicone goo that makes terminating the cable a messy operation. However, it's necessary to keep the cable from delivering water into the house via capillary action. It also seems to deter the mice. I've had them bite through the outer jacket and braid, but stop when they hit the gel. The cable is also rather stiff and does not like to go around corners.
The cable I previously suggested is NOT gel filled (the description and picture are in conflict). I think this will be a better choice.
--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
On Sat, 12 Sep 2015 18:24:40 -0700, Jeff Liebermann Gave us:
The house is valued higher with added features such as that one, and things like a 22kW backup generator...
Which our neighbors can hear when their power is out, but we hear
*less* because our walls are thick.
The builders of multi-dwelling "condos" use dual panels between units for noise abatement as well as calling them a "firewall". Were there a fire in one portion of the house, it would spread much more slowly..
On Sat, 12 Sep 2015 19:05:19 -0700, Jeff Liebermann Gave us:
$ inches of sand would make each speaker cabinet assembly weigh like
50 Lbs or more.
Not to bright. And piss poor design if there were no efforts made to negate parallel wall reverberations within the inner cabinet.. IOW, NO parallel walls.
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