tech.am

No pun intended, honestly, but Tony Smith’s article on The Register’s RegHardware ‘How to get your Wi-Fi working again‘, while making a nice and broad effort at examining the problems plaguing WiFi nowadays, and reviewing several options to improve your experience around WiFi, also uses somewhat pseudoscientific methods to measure things like signal strength.

Not that the N1 is a poor choice. Belkin’s software makes set-up a doddle and it’s handily compatible with both 802.11b and 802.11g for older, un-upgradeable devices. I hooked the N1 up to my cable modem, and was quickly up and running with the 802.11n USB adaptor plugged into my Vaio in the next room. Here, the signal registered as four blocks, two higher than the 802.11g RangeMax router yielded in the same location, albeit at a different time.

What exactly is four blocks? -60dBm? -110dBm? Cutting Tony some slack, he attempts to explain the issues and measurements in layman’s terms, so that as many people reading the article as possible will understand what he is talking about, but still, there are better ways to measure performance of WiFi networks. Signal strength readings are as reliable as my 90-year-old granny at the shooting range, save for a few cards which provide pretty accurate figures. A good measure of the performance, or lack thereof, in the various setups he studies, could have been net throughput. There are various tools to do this, such as the excellent yet very simple NetCPS from Netchain Communications. In WiFi, throughput is proportional (amongst other things) to available wireless bandwidth, that is, theoretical bandwidth minus artifacts such as interference and background noise – thus, between two particular machines, NetCPS would provide a good sense on how good a combination of routers, bands and adapters is performing.

You probably have seen the video on YouTube about a molten Fonera, apparently due to overheating, which shows the plastic case completely deformed. Gizmodo (also in spanish) and other sites are also reporting on this. As usual, Fon has censored the post on their forums that broke the story, but alas, thanks to their partners at Google, here is a cached version. Even Martin Varsavsky seems worried about this. It seems the damage is obviously from heat, but could it have come from the Fonera itself?

I, and others, have our doubts about wether this video is a fake stunt, or a true story. It is true that the Fonera overheats, much more than would be expected from a consumer-electronics product, but to the point of causing physical damage to the plastic case?

The heat problem

Heat in electronics mostly comes from dropping voltage by converting current into it, in our case, the voltage regulator in the Fonera drops 5V to 3.3V at 500mA, resulting in the dissipation of 850mW. That’s right, we are dumping 850mW right into the atmosphere in the form of heat. This brings the operating conditions very close to the maximum ratings for this regulator, which has a maximum rated thermal resistance of 90ºC/W, my calculations put the operating conditions at 88ºC/W. Additionally, the wireless section of the Fonera is also converting a lot of energy into heat.

The measurements

After I finished my tests, I got a comment from Pobletewireless, regarding his own measurements of the heat problem, which are shown in very cool thermographs (no pun intended!) – much nicer than my rather rudimentary method.

I measured the temperature of the Fonera using a thermocouple connected to a Fluke 123 Scopemeter via an 80TK thermocouple module. The thermocouple was placed in between the heatsink and RF shield, the case closed, and the Fonera powered, as can be seen in this picture:

After 10 minutes operating normally, the temperature had risen to an average of 72ºC, with a peak of 80ºC.

The second batch of measurements were performed drilling four small holes to allow the thermocouple into the casing, the locations are shown in the following picture:

Maximum temperature at one corner was 43ºC. Next, an attempt was made to melt the white lid of the Fonera, by exposing it to a high temperature airflow from a paint-stripping gun, and at the same time, applying slight pressure from below. The thermocouple was used to measure at which point the plastic became maleable, and deformation started. At around 100ºC, the plastic was soft enough that a solid object could change its shape – this is in line with ABS plastic thermal properties, which state a deflection temperature around 100ºC, depending on specific material composition.

As the deflection point test resulted as expected, the lid was then exposed to an airflow at 280ºC for two minutes. The result of this exposure is shown in the pictures below:

It’s obvious that some deformation has taken place, with discoloration and charring on the point where heat was directly applied. However, the front side of the lid had mostly retained its shape.

Conclusions

The Fonera does indeed run very hot, much hotter than it should, if anything, for the good of the internal parts. Electronic components are sensitive to heat, with maximum ratings given by each manufacturer in terms of storage and operating conditions. The higher the temperature, the lower the service life of any given component. Some are affected more than others, most notably, electrolytic capacitors have a high sensitivity to heat, as it can evaporate the electrolyte quicker, causing it to fail. The capacitors in the Fonera are made by Taicon, a taiwanese manufacturer, and are max-rated for 105ºC. From the datasheet [PDF], at this temperature, the capacitor will fail after some 2000 hours, around 83 days. Following Arrhenius’ Law, and since the area around the capacitors was found to be at around 52ºC, their expected life would be 7800 hours, or about 325 days – what a coincidence, almost a full year, after which your warranty has expired. Comparing the Fonera to a Meraki Mini, one realises that there is a serious design flaw, as apart from the Mini having a switched-mode regulator, the wireless section shares exactly the same design as the Fonera. The temperature measured outside the casing of the wireless section indicates that the junction temperature of the components inside has to be ridiculously high. So, one conclusion is that the Foneras will eventually fail due to overheating, and it will probably happen sooner than later.

On the deformation / melting video – in my opinion, it’s not real. At least, it couldn’t have happened without the Fonera reaching temperatures around the whole casing that would have caused some components to blow up (for example, the capacitors). The Fonera could not have undergone such an extreme temperature, and still function as shown on the video. The temperature gradient between the heatsink and one corner of the case is almost 2:1, thus, to reach a deformation temperature of say 200ºC at the corner, the heatsink must have been running at 400ºC! A final bit of evidence – the sticker. If you look closely at the video, the sticker on the bottom of the Fonera looks almost unscathed. Here is a picture of what it looks like after applying a 250ºC airflow for 30 seconds, which causes the plastic to deform:

Obviously, a more prolongued exposure would have damaged it even more. In all honesty, I would love to get more details from the guy who made the video, as it stands right now, I’d call it a hoax.

I wrote before about the Logitech MX5000 Bluetooth keyboard & mouse combo, and there are plenty of posts around the web that confirm that the product sucks – badly.

To recap a bit, the problems are random reboots of the keyboard, disconnections of keyboard and mouse, erratic mouse behavior (including spontaneous motion of the cursor), and repeated keystrokes after the keyboard has not been used for a few minutes (resulting in things like “aaaaaaaafter the news…”). In all, a very frustrating and annoying experience, for a rather expensive combo. Logitech seem to acknowledge the problem, but I have not yet seen any form of update that could fix this, and my theory is that the problem cannot be fixed with a simple software update.

Declaring the keyboard and mouse defunct, I performed an autopsy, which revealed a few interesting facts (details after the jump):

• The Bluetooth dongle has a very very strange RF design – it uses a normal groundplane meander PCB antenna, but then it has a copper-wire loop antenna on top.
• Dongle and keyboard use Bluetooth chipsets from different manufacturers (CSR and Broadcom), in theory interoperable, in reality…well.
• The touchpad uses a very crappy sensor design, which explains the lack of responsiveness and uselesness of the scrolling controls.

Let’s start with the dongle. Below are a couple of photos of the opened device, the first with the loop antenna in place, the second with it removed, showing the meander. If someone with better RF knowledge than me can explain why this makes sense, I would be grateful. The design of the loop itself is wrong for 2.4GHz, having a wire length about 10 times larger than what would be required given its size.

The dongle uses a Broadcom BCM2045 chipset, with a 4Mbit flash memory onto which the firmware is loaded. The meander is a PCB track designed for 50ohm impedance, coupled to the chipset via a normal inductor-resistor-inductor matching network. Noticeable is the lack of baluns or filters, I’ll have to check the datasheet (if it’s publicly available) on this aspect.

Let’s take a look at the keyboard, starting with the touch controls. These are built into the keyboard as a separate module, linked to the main control board with a flat ribbon cable, and consist of three main pieces – the PCB and touch sensors, external case with printed cover, and a plastic support with built-in LED light pipes. The controls are made with a layer of gold-plated copper, printed on the underside of the PCB, and on the top side lives the control chip, made by Synaptics (who also makes touchpad systems and other stuff).

The principle by which these type of controls work is capacitance changes. When you place your finger near the sensor, a capacitive effect takes place (using the air and any other material in between as dielectric), which can be measured. It is very small, but enough to give an indication that a finger is present. There are a few rules that one must follow when designing such touchpads, as any interference in the capacitive effect can have negative results on the ‘feeling’ of the controls. Namely, ground planes have to be carefully controlled, and usually placed away from the sensor area, the sensors have to have a minimum size in order to be effective, and any trace routes from the sensor pad to the control IC have to be kept tight, avoiding cross-overs and other disturbances.

I am not familiar with the Synaptics chip, but I have worked with Quantum Research QProx devices, and I cannot see how the physics of capacitance could be avoided in either case. The MX5000 design violates all these rules. The sensor areas are irregular, with a gaping hole in the middle to allow for LED light to pass through, there are ground planes all over the PCB, the tracks meet and part at various spacings and passing right next to ground planes. The biggest joke seems to be the ’sliding’ sensors for the volume and zoom. These are depicted on the face of the keyboard as smooth analog paths, as if one could go from minimum zoom or volume to maximum by sliding the finger to each end of the vertical scale. The truth is that to change the volume in any significant way, one has to repeatedly slide the finger along the whole path of the scale several times, and in some cases, the detection doesn’t work. You end up looking demented, rubbing away the side of your keyboard repeatedly! As is shown on the photo, the sliding scale has only 7 distinct sensors, thus giving you a maximum of six detectable steps in either direction (each step is signaled by the triggering of one sensor, then the one adjacent, determining direction of finger travel). It would be a bad idea to place the whole volume or zoom range on a scale of six steps, and so they settled for the crazy-monkey-rubbing-keyboard action instead.

The next two pictures show the PCB inside the plastic assembly that houses the faceplate. Notice how the cutouts allow for light from the LEDs to be piped towards the labels and icons.

And finally, the last part of the broken equation – the Bluetooth module on the keyboard. It uses a CSR BlueCore3 ROM, which is cheap but cannot have its firmware modified after the die has been printed, meaning whatever bugs you had in the device will be there forever. Again, the module uses a meander antenna. Now, I am not too familiar with the Broadcom chipset, but I have worked with CSR chipsets quite a bit, and know they provide a balanced antenna output, this means that to use an antenna such as a meander or chip, you have to go through a balun. I don’t see a balun on the MX5000’s module, and so it appears they have attempted to balance the antenna with another set of meanders, which can be seen between the chip and the large main meander in the picture below:

Again, this design doesn’t seem to be the best in terms of RF performance, specially when you have a large inductor nearby (L1).

Conclusion? Don’t buy one of these, if you want to go wireless, get one of the non-Bluetooth (some also work at 2.4GHz) keyboard/mouse combinations, and I would still say get a Logitech, as they make some very good ones, such as the MX3000. I’ve always used Logitech, but the MX5000 has been a real lemon.

I got a tip today that Fon is looking at launching a new router with a LAN port, apart from the WAN port found in the current Fonera (they seem to privately admit not having a LAN passthrough was a rather big mistake).

With the current Fonera, you cannot access devices on the wired side of the network (such as a SAN drive or printer) from the wireless side, be it using the public or private SSID, you are effectively NATted from your own network. A LAN port would solve this the same way as it is done in higher quality devices such as the Linksys WRT54 series.

What really surprised me was to see that these routers have already been shown by Accton, the OEM that manufactures the Fonera on their website for a few weeks. Check out these links, datasheets in PDF available, for a white-label Fonera, a Fonera with LAN passthrough, and what looks to be the Fon Liberator, having a USB port and BitTorrent client built-in! Martin Varsavsky recently put the release date of the Liberator back a few months, originally scheduled for Christmas 2006, citing technical difficulties.

Now, either Accton wants to score a goal taking advantage of the publicity offered by Fon, or Fon didn’t pay an exclusivity fee for the design of these routers, or both. One million routers by 2010 is nothing by asian manufacturer standards, but they do allow buyers to secure exclusive designs. Copies could still be found, but not as prominently and by the same manufacturer making their own.

I wasn’t sure that Accton was the designer behind the Fonera, and gave Fon the benefit of the doubt of actually having developed something themselves in the electronics field, but now it seems clear that Accton is the designer of the hardware platfom, so there wasn’t that much development by Fon after all (the firmware was created by the hackers behind DD-WRT and OpenWRT).

It was only a matter of time until the developers of open-source firmware OpenWRT and DD-WRT managed to port the OS to the Fonera, which is based on an Atheros chipset. As described in this thread of the DD-WRT forums, there is a firmware package available for download, which can be flashed onto the Fonera, thus replacing FON’s original firmware and functionality. I think it will be a matter of time until we see reflashed Foneras on eBay, just like we saw Linksys once upon a time.

The hack is not for the faint-hearted, and so you risk bricking your router if the flashing fails – there is still a way to de-brick using the serial port, but in any case, don’t try this at home unless you know what you are doing. We are on the cutting edge of the development, which eventually trickles down into easier-to-follow HOWTOs and step-by-step guides.

Not much point to .mobi domains in the realms of Verizon, it seems – the New York Times reports that starting 2007, ads will be placed on sites that are accessed using their mobile phones. The Verizon Wireless release claims that certain types of ads and video clips will not be allowed, as they may not be compatible with the limited browsers found in the phones, but this is not very encouraging – meaning that they will allow video clips. Will this not hugely increase the amount of data used during browsing? I believe Verizon offers all-you-can-eat data plans, but if you are not using one of those, you could feel the pain. In any case, having to wade through a mobile website rendered on a tiny screen is hard enough as it is, with some devices not being able to cope with the amount of processing required, resulting in a very slow and frustrating experience. Add videos, which require much higher resources to be played back, and you have a recipe for disaster.

Leaving aside regulatory issues that may turn this particular setup into an illegal operation, I will better not describe the quality of the installation to be polite. Check out this picture:

Spotted the problem yet? Radio antennas are affected by any element that is present around them, even non-metallic elements, such as the ground. In this particular case, kanijo, a Fonero, has attempted to provide more “range” to his FON hotspot, which is in itself commendable, however, the means may not result in the desired end – original FON forum thread here.

You can see that the vertical omni antenna, a carefully tuned radiating element, has been strapped to a metallic pole, which also runs a coaxial cable into a TV antenna right on top. The router is inside a sealed plastic box, with power and Ethernet going into it from below. There is no way that this antenna is radiating correctly, as the pole that supports it is probably grounded (if it has been installed according to regulations), and even if it is not, it is inducing an imbalance into the tuned element, causing a large amount of RF to be attenuated. The user reports good results with it, which are most likely due to good luck.

The second problem with this type of setup is that vertical antennas don’t emit downwards, and thus will provide very limited coverage to users below the antenna. There is some downwards bleed of course, but it will only reach lower users that are some distance away from the antenna.

Recommendations for these sort of setups: install the antenna right at the top of its own pole, and ground the pole. If you have no choice but to use an existing pole, get a T arm fitting and mount the antenna at least 1 meter (3 feet) away from the pole. A perfect example of such as setup, in this case with two supports as the antenna is rather large and care for wind load is needed, is this (credit to Roger Halstead):

Check out Roger’s page, it is a very good read if you are interested in radio installations.

Reading an article in The Register by Bill Ray, he thinks the Apple iPhone will fail, actually, fail badly. I somewhat doubt his conclusions.

The main argument to support his analysis is that since network operators have to like the phone, then Apple has to do a good job convincing them. Remember the ROKR? It was rather a failure due to the fact it could only be loaded with iTunes music over cable, and thus mobile operators were left out of attractive data chargers levied when buying music directly from the phone. There was even speculation that Apple allowed it to launch on purpose, to protect their audio player market.
Where Bill goes wrong in my opinion is that the handset market is heavily controlled in the US, but not in Europe – go to any shop in the latter and you will have a very large variety of handsets to buy unsubsidized. Why? Because a lot of people value the ability to switch operators as they see fit, without having to enter into contracts involving their soul. In the US, there isn’t a culture of operator hopping, but rather of staying with one just to get a phone $50 or $100 cheaper.

One thing I have never understood is why people get themselves tied into a two year contract for a $50 saving. If they worked out how much they could save by moving operators taking advantage of special offers, they may think twice.

There is a very large number of paths Apple could follow, first, they have a nice distribution network with excellent shops placed in key areas, second, they have a large and loyal crowd of followers, who would probably not mind paying an unsubsidized device, and third, there are already a number of MVNOs and fixed-line operators that are willing to take a bite from the large networks. As for the subsidy, I wonder…are iPods subsidized by anyone? Apple costumers are used to pay for quality, and in my view, the iPhone will be no different.