After reading the article in the latest QST (April 2003) on the Hinternet, I started a quest to find out how one attaches an external antenna to a WiFi device. First thing I noticed is that there seemed to be no way to hook antennas to a PCMCIA card, and lots of the Orinoco access points etc, seemed to have no antennas at all, and no sign of a connector.
I use Orinoco stuff because at UHM that is the card they supported when they started Wi-Fi experiments on campus. I tried a LinkSys card, and it was a nightmare. I gave it to a person who had several ICS students fiddle with it and after a lot of aggravation, they also gave up. It took the big dive into the dumpster quite some time ago. No one ever did get it to configure, or recognize signal, much less login.
The key for a lot of Wi-Fi is that the PCMCIA cards are the radios. They apparently have the modems and the transceivers for 2.4 GHz, or if 802.11a, for 5 GHz. The g is some kind of new standard. So cards are typically 802.11b, 802.11a, 802.11g or a combination. In the Orinoco line, the silver cards have 40 bit encryption and the gold cards have 128 bit encryption.
From what I understand, Wi-Fi is 802.11 a/b/g and Bluetooth is something else. Airport is a Mac version and is related to Wi-Fi. It is supposed to be interoperable with Wi-Fi. The new standard 802.11g is called Airport Extreme and the port they are selling even has an external antenna connector. Two external antennas, a flat panel and a vertical are available for order for this Airport Extreme hub. The 802.11b operates in our 2.4 GHz band and I believe the 802.11a operates up at 5 GHz. I think 802.11g is another protocol for 2.4 GHz.
Recently, I was looking at a PC catalog. Lots of stuff coming out for 802.11g. From a note I read however, they said that even though this is alleged to be 54 megabit at best, it has huge overhead and is lucky to get 24 Mbit actual throughput.
The basic unit, at least for Orinoco, is the radio/modem, which is what is sold as a PCMCIA Wi-Fi card.
The interesting part is that most other Orinoco products use the same PCMCIA cards as the radio part! They consist of a "trick" board with a PCMCIA connector and a PCMCIA radio card, usually an Orinoco gold card, plugged in. This seems to be the scheme with a lot of the makers.
What this means is they do not re-invent the wheel. Also some units can be upgraded by swapping the PCMCIA radio card. Some even support more than one PCMCIA puka and can have more than one radio installed. Some support both an 802.11b card and a 802.11a/b card for instance, or even an 802.11a/b/g card. Tricky and clever. Think of the access points, gateways, routers and other Wi-Fi stuff as specialized computers with PCMCIA pukas for the PCMCIA radio cards. Some may have dedicated on board radios, but a lot seem to follow this scheme of using the PCMCIA radios.
So if you take a unit like the AP-200 Orinoco access point, a good low end way to interface Ethernet with Wi-Fi to make an access point for laptops which have a Wi-Fi radio PCMCIA card, and you crack it open, you find a trick board. This trick board does the conversion from Ethernet hardware and protocol, to the signals the Wi-Fi radio card needs, and has a PCMCIA connector on it. Yep, plugged into that connector is an Orinoco Gold card.
The higher end units, like the AP-2500 has more tricks than a drunk pet monkey. It is designed for "instant wireless internet cafe" and will do all kinds of protocol conversions, accept multiple cards and so forth. But the mysterious line in the add that says "comes with Orinoco gold card" now starts to make sense! Some cards even have been reverse engineered to discover that they have software settable power, and it is possible on some of them to turn the power up! To as much as 100 mw. Underground hacking has been going on for some time, so no telling what you might Google, in an amongst all the typical sex sites any search inevitably finds.
So the card is the game. For the Orinoco card it is a little plug. It looks like a tiny button on the very end of the card. This bulge on the end of the PCMCIA card, the part that sticks out if you push it into a laptop, has a little thing in the middle of the end that looks like a tiny button. I have tried this and with a pointed Xacto knife the little button popped right out. It is in fact a tiny plastic cork.
So when I did pop the top on my Orinoco card, it does in fact have the tiny connector inside. fab-corp calls this an MC connector and "Proprietary Orinoco Connector". There seem to be about three other ones common. This one is certainly super sub miniature compared to the typical SMA. In the picture of the mating connector on the pigtail I bought, the marks on that ruler are 1/16ths of an inch. So the entire cubical body of this right angle, mating MC connector is about 1/8 inch on a side.
Underneath the plug the tiny RF connector is in common with the machined slot antenna inside. Sure enough This tiny dot pops right out. I used the point of an Xacto knife. It is in fact a small plastic plug or cork, and offered little resistance with the right tools.
What you need next is called a "pigtail". And companies fortunately make them! I was not thrilled about the prospect of mounting one of these miniature reverse right angle SMA connectors on decent coax to work at 2.4 GHz. Even with the coax and the right connector and the crimping tools, one has to wonder if it is just easier to order the pigtails.
One such company is Fleeman, Anderson and Bird, www.fab-corp.com. They have a wide range of goodies for this sort of thing, including a wide selection of pigtails with what they call the proprietary Orinoco connector. Also other types for other cards. Some use a set of tiny pins, like a miniature PCB connector.
To add an antenna to a laptop to extend range, you plug the pigtail into the end of the card and mount an antenna on the N-series connector on the other end of the pigtail. Even a simple antenna should help. It will get the signal off your lap, and you can raise it up a bit. You will not get a big or even noticeable increase in horizon, but you can get the 2.4 GHz energy above all the nearby absorbers like other people, foliage and anything organic. I was thinking of another paint pole application, but any kind of small mount to lift up a small external antenna a bit should help. I have seen paddle antennas with the Orinoco connector on them that would be ideal and probably double your range just from better exposure of signal with a laptop and card..
The picture shows a 12 inch MC to female N bulkhead mount that is destined for modification of the AP200 access point, and a 60 inch MC to male N which is destined to be part of my arsenal of laptop portable hookups. Also a female chassis mount N is shown.
The tiny right angle connector for the Orinoco card slips on. As a push on it has a nice property. It will rotate rather freely which helps a lot with relieving strain on the connector from even the miniature coax that is used in pigtails.
To modify an access point, you first have to get it open! And with the AP-200 it was somewhat difficult. I took pictures and have details.
But once you see the card you know what to do. You drill an access hole in the outer AP-200 case, plug an appropriate pigtail into the Orinoco gold card inside, and leave the N-connector part of the pigtail hanging out. Close up the case and hook up the external antenna to the new N-connector thus created.
The disassembly starts easy enough, you slip off the cosmetic connection cover. Then you have to attack two case closure snaps. One of the snaps was under a stick on foot, hidden on the bottom of the unit. There seemed to be two you could actually release and then you just had to go around with a small stick, or screwdriver blade, and force the case open the rest of the way, starting from the back after you slip off the cosmetic cable cover part. It was not easy and sounded very "breakey" but seemed to eventually come open like a clamshell towards the front where the status light indicators are.
You can easily add a commercial 1 watt power amp and zoom right into illegal operation!, well not for us Hams, who are licensed to run this stuff. 1 Watt vs. the 30 mw typical of a card, and the typical 17 dbi gain of antennas quickly adds up to extended range far beyond 150 feet.
For reference here are some values of dBm vs milliwats. Card makers
rate their cards "power" in dBm, so one needs to be able to convert. The
scale is log, just like working with db loses in coax:
FCC says you should not have more than 36 dBm of effective radiated power to be part 15 for WiFi. That is 30 + 6; or 1000 * 4 * 1 milliwatt, or 4 watts ERP! A typical card output of 15 dBm works out to about 30 milliwatts of power at the card connector after you allow for a typical 2 dB antenna gain for the builtin antenna.
Antennas are of course the big item since their gain works on both transmit and receive. There is an entire line of so called barbeque grate antennas. And they look like bent grill tops indeed. They go up to 24 dbi gain easily, and are not that expensive at 2.4 GHz. Particularly attractive for portable operation with a laptop are panel antennas. There are some cute ones that have enough gain to overcome the coax losses and then a bit. One of them is only 5 inches on a side and about 1/2 inch thick.
I am waiting for goodies recently ordered and hope to experiment with this from my lanai using an external antenna on the AP-200 access point and my Viao laptop with an Orinoco card and external antenna.
I got some decent photos of the dissection of the AP-200 and also of the puka in the laptop card. UH wireless standardized on Orinoco cards, which is how I got started using Orinoco as my standard. Lots of home hubs are showing up now with pairs of external antennas on the back, I do not know how they attach, if they are slid into connectors for which pigtails can be purchased or if they are hard mounted and you have to get inside and probably find a card to put the pigtail on directly. One thing is clear, people have been vigorously hacking this stuff for quite some time and 2.4 GHz is every bit as populated as CB on 10 meters.
Orinoco now has a gold 802.11 a/b/g card for sale and because of their strategy, it can be used to retrofit and upgrade some of their existing access points, routers and gateways which came with Wi-Fi.
Also www.fab-corp.com sells a Pringle kit. One of their pigtails and a chassis mount female N connector. You may have seen the article in the recent QST about the creation of a pyramid horn antenna for AO-40 use? That is just a better Pringle Can. Pringle Can WiFi antennas are kind of a cult icon and legend.
But researching the Pringles antenna on the web, I find this is not an urban myth, though it does have some basic problems. You can check out this nice cantenna site, which has some great information. The underlying idea is quite sound, but the biggest problem is that Pringles cans only look metallic inside but are not really metal enough. The can idea is just a standard method of using a section of circular waveguide to transition from RF energy inside Coax to RF energy in "ether". It involves a 1/4 wavelength probe inserted about 1/4 wavelength from the closed end of the circular waveguide stub. This sets up standing waves in the circular waveguide and they escape out the open end. Added flares and horns and such are just ways of trying to match to the 380 ohm or so impedance of clear open air and get more gain with a bigger mouth. Another good website on this subject is the Finnish cantenna site, which has some more details on the exact dimensions which work best.
I am trying a cantenna made from an ether can, appropriately enough. It is pressure formed, one piece aluminum and contained diethyl ether. The only other part you really need is the chassis mount N connector. N is a standard for UHF and is much superior to the PL-259 which was actually designed to hook up TV cameras way back when, and was intended for frequencies up to about 100 KHz. BNC connectors are better for VHF and the N series connectors though bulkier are favored when it gets higher. Of course at microwaves waveguide is the real way to go, but coax is so much easier to use if you need flex, and so one has to keep the lengths as short as possible. In very few feet at 2.4 GHz, you can eat up all of your new found antenna gain.
Example is LM-100A, similar to RG-174 and what a good pigtail might be constructed from. It has a loss of 38.9 dB at 2.4 GHz! In case you cannot relate to that, 10 dB is a loss of 90% of your power, 1/10th makes it to the end. 20 dB means 1/100th makes it. 30 dB means 1/1000th makes it. 40 dB means that 1/10,000th the power makes it to the end of the 100 feet! Per foot, that is a loss of .39 dB. For a five foot or 60 inch pigtail, that is 1.95 dB loss. This we can live with. For longer runs you just need better. LM-400 which is an RG-8 cable only has 6.6 dB loss in 100 feet. That means a bit less than 1/4th of the power makes it to the end, much better than 1/10,000th. A cantenna waveguide antenna might be worth about 6-8 dbi.
To get the system effective radiated power you would take the card output, any amplifier gain, any coax losses, and any gain in the antenna system and add it all up to get the final answer. In one setup case I used I had about 30 mw from the card, lost about 2 db in coax and pigtails and gained about 15 db from a very nice yagi. That is 13 db gain or 10 db plus 3 db, or 10 * 2 * 30 mw = 600 mw effective radiated power. Or about 27 dBm.
As a bit of lilly guilding, I am fitting an "exponential horn", to my home-made cantenna mouth. Well actually it kind of looks right and turned out to be made of aluminum. It is in fact the top of a scrapped trumpet lamp, that kind that flares out and points at the ceiling with a three way bulb inside.
A great book I have discovered is "The Wireless Network Starter Kit" whose subtitle is: The practical guide to Wi-Fi networks for Windows and Macintosh, by Adam Engst and Glenn Fleshman, published by Peachpit Press. Their chapter 8 called "Going the Distance" is full of good information. Their recommended supplier of pigtails is Seattle Wireless.
It has a chapter on antennas, connectors, pigtails and why the FCC required such bizarre and non-standard connectors to discourage installation of antennas etc. to these devices which are sold as Part 15. Their web address is : www.peachpit.com
I also felt the need for a reference antenna. A basic antenna of a type we could all understand to serve as a base reference for any gain testing. Of course one can use the card antenna on the laptop. But for a base station set up with a pigtail and an exposed external antenna, it would be nice to be able to slip on a reference antenna to get a baseline before attaching the latest and greatest gain antenna.
I settled on a simple quarter wave vertical worked against a solid 3/4 wave in diameter, circular groundplane. One might argue that a 10 wavelength groundplane would be better, but 3/4 wave is similar to the three inch groundplane of a commercially available design and a very reasonable size.
The vertical is constructed the same way as the probe for a cantenna. It is the 1.21 inch total protruding part of a wire installed in an N series chassis connector. The other part is just a circle of aluminum sheet, 1/8 inch thick, and cut a bit less than 3.5 inches in diameter. The central hole is cut to clear the base of the N connector and beveled to deal with a second larger step that my connectors possess. The mounting hardware is carefully countersunk using stainless steel flathead screws on the top surface. I could have drilled and tapped, but through drilled and countersunk was simplier to produce. I also wanted to avoid using too many fancy tools to make it so it would be easy to reproduce.
It is cute as a bug, and a really new experience to make antennas like model airplanes, with tiny tools, and vernier calipers and diminsions measured in 1/100ths of an inch. The scrap panel I cut up ended up having the ATT logo on it. I just left it for decoration, it was entirely an accident, and I did not realize it was there until I flipped over the disk after cutting it out. After putting up an 80 meter dipole, one has to love the size of 2.4 GHz antennas.
It seems to work just fine and is hooked to the new pigtail installed on the Orinoco AP-200 access point. The pigtail goes in through a pair of holes, one in the plastic snap on cord cover and one in the postage stamp sized square plate at the top of the access point cover rear. both were first drilled and then filed oblong to allow the tiny connector on the pigtail to keyhole through.
My first success was with my 15 dbi commercial Yagi. Since they are fragile they are often enclosed in thin plastic pipes which are great for protection from the elements as well. It was mounted on an old salvaged based for a pole or trumpet lamp. Hooked up with four feet of LM400 coax and a 19 inch pigtail onto a standard Orinoco card on my ME laptop, I was able to connect to our network on the UHM campus from my condo.
Survey by GPS indicates this is a line of sight path of .68 miles with some palmtree and building obstructions in the way. The on campus network is not pervasive. It mainly covers two corridors of clear space in long Malls. It has a range of a couple of hundred feet and you often have to know just where to try your laptop to connect with a naked card.
I was able to connect, check email and web brouse. Of course I had the encryption code, network name and legitimate account on the systems. A bit un-nerving is all the other networks Boingo, the sniffer software that comes with an Orinoco Gold Card now days, could find! From my lanai panning about with the Yagi/Polelamp mount I could easily find nearly a dozen at any given time, all of which the Yagi thought it had adequate signal to try to access.
One sobering note. Just when things were going well I got myself in a mess by silly "lily guilding". I tried to upgrade from an Orinoco silver card on my Sony Viao Laptop to an Orinoco gold card with its improved encrypton. I just stuck in the new CD and went for it. What a mess. Everything more or less quit working. Hours of effort could not back out of it. I had two wireless icons in the control panel. Orinoco client insisted there was no card or driver. Hardware manager said there was a card and could report its driver version but said it was not working right and needed an upgrade, but could not upgrade. Boingo (a new sniffer program) would work fine at finding networks but nothing else. A very large mess.
Apparently the Orinoco installer script does not check for existing card installation or clean up the registry. Perhaps a full uninstall would have helped a bit. The root cause seems to be failure to clean the Registry. Even carefully following the instructions from Orinoco support on cleaning the Registry by hand did not help. Eventually I upgraded the Viao to XPpro from ME, a very long process that needs to start with the detailed documentation at the Sony website. If it work's don't fix it!