I don't do RF. As Arthur C. Clarke would say, it's indistinguishable from magic. And it doesn't even require smoke or mirrors to do its magic.
Anyway, I have an old Buffalo WHR-HP-G54 "G" router, which has a single 4bDi RP-SMA antenna mounted on the top (although the DD-WRT people say there is also an internal antenna). My laptop connects to the router through Wifi, and sometimes I need to take the computer to the opposite side of the house, which is maybe 85 feet away, and going through three walls.
The computer has never performed very well at that distant location with the router antenna pointing straight up, which is the way I've always had it, and the way I see these antennas pictured pretty much everywhere.
Just to see what difference it would make, yesterday I moved the router antenna to the horizontal position, with the broad side of the antenna looking at the distant computer. So in other words, the computer is, say, due North of the router, and the antenna is horizontal, with the tip pointed East. And in this position I get a major improvement - from two bars, maybe three, to a solid five. And I can watch streaming video, which I couldn't really do before without a lot of buffering.
Does this make any sense? I thought perhaps it was a polarity thing between the router's antenna and the laptop's, but I've tried rotating the laptop all different directions, including on its side, and I still get five bars with the new router antenna location. So that's not it.
Is anyone else surprised by this, or is it just me? What is the explanation for what I'm seeing?
And while I'm at it, let me ask a related question. All of the places I use the laptop are pretty much along the same line from the router, but at different distances away. Would it make sense to use a directional panel antenna? If I ever need to replace the Buffalo antenna, would a directional antenna make sense? Something like this:
formatting link
I ask because I dropped the router once and the antenna is actually broken and repaired near the base. So if it finally dies (i.e. - I drop it again) I'll have to buy a new one, and it seemed that a directional panel might make sense.
Do you have steel studs in the walls? That'll make a big difference between horizontal and vertical polarization.
Cheers
Phil Hobbs
--
Dr Philip C D Hobbs
Principal Consultant
ElectroOptical Innovations LLC
Optics, Electro-optics, Photonics, Analog Electronics
160 North State Road #203
Briarcliff Manor NY 10510
hobbs at electrooptical dot net
http://electrooptical.net
Nope. For vertical framing studs to block the signal, the lowest frequency where blocking would ocurr would be where the studs were 1/2 wavelength apart. Metal studs are usually at 12", 16", or 24" spacing, which grind out to about 490, 375, 250 MHz respectively. At
2.4 or 5GHz, the signals fits nicely between the metal studs.
A more common problem is aluminum foil backed insulation in the walls. That will turn your house into an RF shield room and block everything. Remove a wall plate and look at the insulation. If there's foil on the back, Wi-Fi and indoor cellular will be a problem. There are also other odd indoor RF blockers. Some wallpaper has metal threads in the design. Older plaster walls are plastered over chicken wire or metal strips. For the electrosensitive paranoids, there's also RF blocking wallpaper which I've actually seen installed in one house: Cool... an "electrosmog" meter.
Even glass can be a problem. Outdoor windows are required to be coated with Low-E to improve thermal performance. However, I've seen the same glass also used indoors, resulting in yet another way to block RF. The coating is essentially an RF high pass filter. Above some microwave frequency, everything passes including light. Below that frequency, everything is blocked including Wi-Fi.
--
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
Sure, the laptop antenna is likely a PC board that is horizontal, so that the horizontal router antenna would now be in the right plane for the laptop.
When putting the laptop on its side, there are a couple ways that you can orient the internal antenna to the router.
The better routers have two (or more) antennas with totally independent RF systems for each, and can try whichever one gets the best signal from the clients.
I located my WiFi router (MediaLink) high up on the wall above Our "Open House" home-base cabinet.
Haven't had a problem even outside on the patio, and I definitely have lots of foil... one of those new "energy rated" homes. ...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.
I do RF. I also do my best to promote the illusion that RF is magic. It's not, but it pays better when those that sign the check believe it.
That's what I use at home. By todays standards, it's not the most acronym infested or performance driven device, but good enough for my needs. I have DD-WRT firmware installed:
You'll never make it through 3 walls. My rule of thumb is 1 wall is possible, 2 walls you'll get a marginal signal, and 3 walls are impossible. Much depends on what is inside the wall. I offered some comments on penetrating various materials elsewhere in this thread: Here's one of many tables and charts found on the internet that offer wi-fi attenuation figures for various materials. I don't quite agree with the numbers, but it's a good start.
Very roughly, it should be possible to calculate how much attenuation your system can tolerate. Unfortunately, the only numbers you've disclosed is 85 ft and the WHR-HP-G54 router. I'll guess(tm) the rest.
Starting at the laptop end and going to the Buffalo router end: TX power +15dBm TX coax loss -3dB (thin coax in the laptop is lossy) TX ant gain 0dB (optimistically) Distance 85ft (26 meters) RX ant gain 2dBi Rubber Ducky Antenna (It's not 4dBi) RX coax loss 0dB RX sens -84dBm (at 12 Mbits/sec) Fade margin 20dB
At 85 ft (0.016 miles) and 2.4Ghz, the path loss is about 68.3dB. The resulting fade margin is 29.7dB leaving 29.7 - 20dB = 9.7dB = approx 10dB left for attenuation through your 3 walls. At 4dB loss per drywall sheet, and 2 drywall sheets per wall, your good for about 1.5 drywall thicknesses before your signal becomes useless.
Yep. Having the same polarization works nicely in a non-reflective outdoor environment. However, indoor systems have the signal bouncing around making it difficult to maintain the same polarization along the path. Besides, you probably have cross polarization anyway. The PIFA antennas in the laptop are usually at the top edge of the screen and mounted horizontally.
It's quite difficult to tell what's happening without inspecting the rooms involved. I've had similar experiences with wireless. In one case, the customer was trying to shoot through 5 or 6 walls and actually doing quite well, but only at specific locations for both ends. They couldn't move around the room and stay connected. One look at the office make it clear what was happening. Both ends were shooting out windows, with the signal bouncing off the adjacent building. Two hops, one bounce, good signal, but only in specific locations.
Got an Android phone or tablet? Install "Wi-Fi Analyzer" and check your signal levels using the panel meter display: If it's coming through the window, down a hallway, or through the HVAC ducting (yes, I've played waveguide when desperate), it should be obvious.
No. Assuming 5 bars is all your unspecified laptop will produce, there's no way you can get 5 bars at 85 ft range on 2.4 GHz. I don't know how many -dBm a "bar" is worth these days, so I can't grind the numbers. However, if you find the signal strength for 5 bars in the laptop docs somewhere, I think you'll find that the signal levels are impossible at 85ft.
Easy. RF is magic. What more do you need to know?
No, unless you house is long and narrow. Directional antennas do not produce RF. They redirect RF in one direction, but stealing it from another. If you install a high gain antenna and point it at your Buffalo router 85 ft away, you will not have much signal left to the sides and back. The more gain, the narrower the beamwidth. So, if you're also expecting coverage behind and to the sides with a high gain (panel) antenna, you may be disappointed.
There's also no guarantee that more gain will help you "drill" through the 3 walls, especially if the current arrangement works before of reflections or indirect paths. If you are going to try to "drill" through 3 walls, I think more gain might be useful. I suggest a larger panel antenna, such as: All the antenna gain claims on eBay are lies, so just go by physical size. I picked this one because it uses fat coax cable for less loss.
broken
There's not much inside that can break: As long as the tiny coax cable is intact and connected, the antenna is fine. Just glue the plastic/rubber parts back together.
--
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
I have a cardboard box full of assorted wi-fi repeaters, range extenders, mesh system, and other band-aids that I've removed from customers systems in order to make them work. Repeaters are very good for screwing things up.
Rather than explain the details (I'm busy right now), I suggest you try an experiment. Setup a wireless network in a single room. Just a wireless router or access point and two computahs. No internet connection. One computah should be plugged into one of the LAN ports of the router, preferably with a 1000baseT interface. The other can probably be a laptop with wireless.
On the computah that's plugged into a LAN port on the router, run iperf3 in the server mode. On the laptop, run iperf3 in the client mode. Then run a speed benchmark. In theory, you will be testing for the maximum speed of the wireless part of the network as everything else is faster.
After you get numbers for your maximum speeds, plug in a store and forward repeater or range extender and set it up for the same SSID as the router. Run the benchmarks again. If you get half the speed as before, I'll be surprised. If you get consistent download speeds, I'll be even more surprised.
I just remembered that I gave two demos at the local Linux Abuser Group on the topic:
Here's the direct throughput without a repeater: and with a repeater: Retch... Questions tomorrow, when I recover from tonite's inevitable fiasco.
--
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
I use one with 14dB nominal gain to extend my Wifi to our village hall when I need to do talks there and have internet access. Range about 500m through several thick brick walls. OK so long as it doesn't rain.
Moderately sensitive to correct pointing. Simple things like a layer of aluminium foil behind the device can help in some cases.
For modest amounts of attenuation a strategically placed junior hacksaw near the receiving problem device is about the right size to boost the signal locally (or cancel it out entirely).
Directional antennae work well if you want to beam the signal to a remote location. You can get way with directional antenna on the remote end. Cheap Wifi dongles with replacable antenna are ideal for this.
formatting link
Is particularly good for this sort of thing and also for DIY cantennas. (even works with Apple kit if you get the right chipset version)
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? :-)
This post prompted me to see if I can get better data rates with my iWISP modem outside. Right now it is behind a glass door which is listed as -2dB in one of the above tables. Still, the provider is constantly saying I will get better rates if I put it outside. Sooo...
Checking inside the best I can get is about -77 dBm by moving the modem a foot to the right. Speeds are 2.5 to 3 Mbps vs. 1 to 1.5 Mbps before. Outside I was able to find a spot at -71 dBm. My roommate said he was getting over 4 Mbps. Nice improvement. I think I'll get the unit hung outside permanently.
Maker and model? Many of the radios used by WISP's have built in performance diagnostics. For example, if it's a Ubiquiti radio, you should be able to produce something like this: The key is to NOT adjust for maximum signal strength. Instead, adjust for best SNR (signal to noise ratio). You'll also need to be downloading something while running the test or it will just sit at the last value when there was data moving.
Part of SNR is interference, of which there is usually plenty in the ISM bands. I like to check for that by doing the download speed test while moving something that either blocks or absorbs RF around to see if I can improve the SNR further. I have a slab of black screen room foam glued to a sheet of box cardboard for the purpose. However a wet towel will do as well to block RF.
The -2dB is for single pane, uncoated glass. Today's sliding glass doors are double and coated with Low-E glop, that blocks RF. Try a signal strength measurement on both sides of the door.
I would say that's correct about 80% of the time. Where it doesn't work is where the improved antenna location begins to pickup more interference from other users on the frequency. Interference is a very real problem with outdoor installations. Directional antennas are a big help at reducing interference from the sides and back of the antenna. However, that creates a different problem. If the source of the interference is along the line between you and the WISP's tower, the interference will be increased by the gain of the antenna and make things worse.
Does your WISP have a rate cap in place? How fast does he allow you to go?
6dB improvement is well worth moving the radio. Think about waterproofing. If frost is an issue, maybe heating. Make sure the PCB is vertical so that water drains off the edge instead of making a puddle. I'm a big fan of pressurized enclosures, but they have their own problems. The easiest is to not pressurized with a drain hole in the bottom. Good luck.
--
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
ElectronDepot website is not affiliated with any of the manufacturers or service providers discussed here.
All logos and trade names are the property of their respective owners.