Post by thread:[OT]: External WIFI antenna

rad0 wrote: > Do any of you know how to hook up a Bufalo outdoor antenna to > a WAP? With good quality cable. At 2.4 GHz, if you try to use standard RF cable (like RG-8 or similar) the loss is very high and you'll end up with very little RF actually reaching the antenna. Typically at microwave frequencies, something like LDF or hardline is used with N-connectors. > My question is, do you need two antennas or is everything in the Bufalo? Don't know what a Buffalo is, but most outdoor 2.4 GHz antennas are single antennas and most access points have a way of defining which antenna port is used if they have two for receive-diversity. Access points that actually transmit through both antennas are extremely rare if you can even find them, so you need to wire to the correct one. Most manufacturers do not tell you which is which, so you'd be best served by either searching online for someone who's done it already or opening up the AP and looking for the transmitter to see which antenna connector it's attached to. > A link to a step by step would be nice, thanks. Google. This is definitely the wrong list to ask this of, and you didn't even mention which AP you have. Watch out for what I would call "RF Voodoo" from online sites. Pringles can antennas are stupid (virtually no gain, and only directional, not gain antennas), and most of the hobbiest 2.4 GHz 802.11b sites show people using real crap for feedline, etc. Find a ham operator who does very high frequency (not VHF per-se... but REALLY high stuff) or microwave guy in your local area and ask around for some spare hardline or LDF or similar cable (this stuff can get very expensive) and get some help making low-loss VERY short jumpers from whatever connector your AP has on it to the hardline and you'll get GREAT performance. Build it with junk co-ax and it will seem to work well but you'll never know how well it can really work. Also - a note of caution - DO THE MATH and make sure you're within the legal ERP limits for Part 15 802.11b devices. You are on a shared band with others and there are hundreds (if not thousands) of people running illegal power levels out of their 802.11b outdoor antennas using 1W amplifiers into directional high-gain antennas. They don't bother to do the math and they're generally naieve about the actual spectrum issues. Don't be one of those. Nate, .....nateKILLspam@spam@natetech.com -- http://www.piclist.com hint: To leave the PICList piclist-unsubscribe-requestKILLspammitvma.mit.edu

Alright, the WAP is a linksys BEFW11S4 wireless router, it has two antennas on the back. I thought one was transmit and the other recieve. Is this not true? And the outdoor antenna I was going to use is a Buffalo Technology outdoor directional antenna, WLE-HG-DYG. Are you saying that I only need to run one, a single, coaxial cable to this type of antenna? And is there any likely chance that this will be over any power limits? The antenna doesn't 'add' power does it? I was going to buy it and hook it up. I didn't know if I needed two antennas or just one. Thanks. I'm aware that you need to use low impedance coaxial cable, I'm assuming this is just high quality cable, or is there a brand or nomenclature for this type of cable? I will put it on a pole so it is above a story and a half house. 25 feet maybe. {Original Message removed}

> Alright, the WAP is a linksys BEFW11S4 wireless router, it has two > antennas on the back. > > I thought one was transmit and the other recieve. > Is this not true? No. BEFW11S4 has two antennae for diversity mode. If you are using an external antenna, you will need to go into the router configuration page and change the settings (Wireless..Advanced, IIRC; I no longer have that router). > Are you saying that I only need to run one, a single, coaxial cable > to this type of antenna? Yes. > And is there any likely chance that this will be over any power limits? > The antenna doesn't 'add' power does it? No. Cheers, Ishaan -- http://www.piclist.com hint: To leave the PICList EraseMEpiclist-unsubscribe-requestspam_OUTTakeThisOuTmitvma.mit.edu

Harold Hallikainen wrote: > Also have a look at www.hallikainen.com/FccRules/2002/15/203/ > regarding the legality of using an antenna other than that supplied by the > WAP manufacturer. The "responsible party" in this document above is the owner of the AP. The owner is allowed to change the antenna, but they then take on the responsibility of maintaining the ERP limits for Part 15 devices -- if I remember correctly. Nate, natespam_OUTnatetech.com -- http://www.piclist.com hint: To leave the PICList @spam@piclist-unsubscribe-requestKILLspammitvma.mit.edu

Hi, Don't know what the FCC rules are or what power the AP transmits at but yes, the antenna does add power in that your ERP can be greater than the applied power. Done some calcs (using an online calculator)based on 25ft, 0.25W and 14dB gain (as specified but very optimistic) and RG8. The results were: Online Coax Cable Loss / Antenna Gain Calculator ================================================ Cable Loss per 100 ft at Operating Frequency = 13.188 dB Cable Length = 25 Ft. Calculated Loss = 3.3 dB Power into Cable = .25 Watts Power out of Cable = 0.1 Watts Gain of Antenna = 14 dBd ERP of Antenna System = 2.9 Watts Calculated 12/12/2003 at 9:59:25 PM Which as you can see for a TX power of 0.25W gives you an ERP of 2.9W which will almost certainly fall outside the FCC guidelines and cause interference to secondary users (us poor Hams....) Silly question but why do you want your AP to have a huge range in one direction ?? The aerial quoted is directional (Probably a yagi in a plastic tube) and will therefore only give gain in one direction and if well designed huge losses on the nulls. Cheers, Dave (G0GMK) ------------------Big Snip-------------- -- http://www.piclist.com hint: To leave the PICList KILLspampiclist-unsubscribe-requestKILLspammitvma.mit.edu

Ishaan Dalal wrote: >>And is there any likely chance that this will be over any power limits? >>The antenna doesn't 'add' power does it? > > > No. Wrong. There are both power and ERP limits. Effective Radiated Power being a function of the antenna and how much power it focuses at the horizon or direction you pointed it if it's a directional antenna. If you use a gain antenna you could very well exceed the limits. ESPECIALLY if you do like a lot of people and add a 1W power amplifier. The Linksys has a 150mW transmitter, I believe. So you'll have to do the translation to dBm with your specific feedline loss and antenna gain numbers to find out if you're over the limit. You can't just say "no" it won't go over them without doing the math. What are the gain figures of this Buffalo thing in dB? Nate, RemoveMEnateTakeThisOuTnatetech.com -- http://www.piclist.com hint: To leave the PICList spamBeGonepiclist-unsubscribe-requestspamBeGonemitvma.mit.edu

From: "Ishaan Dalal" > > The antenna doesn't 'add' power does it? > > No. Hmm.... I respectfully believe this advice to be "effectively" incorrect. ;-) ERP is what counts when transmitting and it makes little difference whether you put 100 watts into a unity gain antenna (isotropic point to be precise) or 10 watts into a 10dbi beam. One nice thing about using high gain antennas vs. more power is that they work in reverse just as well. IOW it doesn't do much good to add a power booster to a WAP if it already can't hear the clients. michael brown -- http://www.piclist.com hint: To leave the PICList TakeThisOuTpiclist-unsubscribe-requestEraseMEspam_OUTmitvma.mit.edu