antenna compatibility

The higher gain rubber duckie antennas are only higher gain in the plane perpendicular to their axis. Off this plane they are actually lower gain. Try pointing the antenna so that this high-gain plane hits your wireless client. If that still doesnt' work any better, then there is something else going on.

-wolfgang

"JWD" hath wroth:

Yep. That can happen. RF is magic.

That's correct. The FCC part 15.204 clearly mumbled that you can legally replace an antenna only if it is the same type of antenna (omni, dish, panel, yagi, whatever) that was originally type certified with the equipment, and only if it has equal or less gain. What you're doing, by increasing the antenna gain is in violation of Part

15.204. Please surrender yourself to the FCC enforcement bureau for correction.

I'm not sure what he could tell you. Antennas are just one component of your system. If there's a problem, it can somewhere other than the antenna. Unless you're prepared to supply a complete description of your topology, environemnt, and equipment, there's not much anyone can suggest.

It should work with other products and manufacturers. It's just that DLink support isn't terribly interested in supporting other products and manufacturers.

Sure. I just got through an interesting exercise where adding a higher gain antenna actually *REDUCED* the coverage. The problem was that this location overlooked a large part of the city. Netstumbler showed about 50 access points. The higher gain antenna increased the interference pickup from the city (through the window). Although the signal strength to the various laptops and PDA's were increased around the house, the not-so-minor detail that the main access point was picking up crap from all over the city made it look like the connection was unreliable anywhere in the house. I moved the main access point to a more protected location, setup a direction antenna (reflector), and it worked well enough (unless the laptop or PDA was in the window).

Another common problem is antenna orientation. That Dlink antenna claims 7dBi of gain. Unfortunately, it comes with 5ft of tiny coax RG-316 or RG-174 cable which is good for about 43dB/100ft or about

2.5dB of loss. Therefore, the antenna gain is really only 4.5dB gain.

Range doubles for every 6dB of gain, so this antenna should yield about 2.8 times the range. However, that's only in the horizontal plane. If you are positioned above or below the antenna, such as on a different floor of the house, the signal will actually be less with the DLink antenna.

I think you misunderstood what the support personality from Dlink was saying. He didn't say that it wouldn't work. He probably said that he could not help you make it work.

The basic assumption of WLAN antennas is that they are all 50 ohms impedance and are tuned to the 2400-2483.5MHz band. As long as the connectors match, any antenna should function on any 2.4GHz access point. Whether it will do what you expect is another story. Unrealistic expectations are all to common. Since you haven't described your environment, topology, or what you're trying to accomplish, it's difficult to deduce why the better antenna didn't work.

What setup? All we know is that you have an MR-814 router and a Dlink antenna. How about some clues as to the environment, construction, topology, client radios, and interference potential?

See:

see if the reflectors give you some ideas.

It's hard to say how much improvement you should see.

He used to be correct. Radios and antennas needed to be tested in pairs to receive FCC certification, part of the reason they have supposedly unobtainable connectors on 802.11 radios. But that was relaxed to allow various antennas, as long as they don't exceed certain parameters. It might be that he is still correct, and Netgear never tested their radio with anything but their stock antenna.

indicates that is true, the 814 is not listed. If it were listed for a Netgear 7db omni, my understanding is that a DLink 7db omni would also be legal.

On the other hand, the FCC doesn't seem to care any more, and the DLink page for the ANT24 says: "Works with Virtually Any 802.11b/g Compliant Devices with a SMA or TNC Connector"

That's the spirit. It ought to work, assuming the connector fits. It probably does work. How are you measuring the signal, and how much did you hope to achieve? This is a 7dB antenna, so it's not going to shoot your signal through walls to where there was no signal before, although it ought to improve the signal that was already there, if it was of marginal strength.

That's all. No protocol, no vendor ID, other than the half-hearted attempt to have unusual connectors.

The signal pattern looks like a donut slid onto the antenna. The best strength is going to be broadside to the antenna. The 7db antenna will have a flatter donut than the stock antenna, stretching the signal farther out, but less thickness. Maybe it isn't aimed correctly.

If you had no signal in your desired location, maybe you still won't.

If you have some signal with the stock antenna, you should see some small improvement with the new antenna, but maybe not enough.

You could add a directional reflector. Instead of squishing the donut to make it reach out farther, this reshapes the signal so that it heads more off into one direction. This should work with either antenna.

EZ-12, Windsurfer reflector. printed on photo paper for thick stock, with aluminum foil glued to the sail, provides a substantial boost in signal.

Thanks for the posts received so far. I did a bit more testing today and although I do see a minor improvement in signal strengh, it does not seem to be enough to help my situation. To measure the signal, all I'm doing is opening up my wireless card's utility program and monitoring the dB levels in the Link Status window.

Anyway, here's more on my environment. I live in a townhouse/condo where there are 4 houses connected together. The walls between each house are cinder block which I know is not easy for a signal to penetrate. My brother-in-law owns the house on one end and I own the house on the other. The router is in my brother-in-laws house and I'm trying to use his signal. I do get a signal in certain locations of my house, but it is very weak (-85 to -90 dB) and occasionally drops out.

There are no cordless phones in our complex and noone else has a wireless signal so interference should be minimal. The biggest obstacle is the two houses in between.

It seems as though my best bet might be the directional antenna that was suggested in one of the posts, but maybe this environment is just to difficult get a wireless signal working.

Thanks, John

Explain how your stuff is laid out. What type of building construction? Are these on different floors? What sort distances are there between the devices. All these things matter and the wrong antenna can CERTAINLY make things worse.

For example, I've got a 50's era rambler, brick on block with an early variant of drywall. I've also got a 90's era sunroom attached to the back. The coatings on the windows actually BLOCK most of the WiFi signal! But even with that I've got a Linksys WRT54G with it's factory rubber ducky antennas installed in a basement window well. It has line-of-sight up to the sunroom. They have to be pointed at about a 75 degree angle to spread their beam upward into the sunroom and downward enough to hit an office area downstairs. The far upper corner of the house, a guest room only barely gets coverage but everything else is ok. The 'donut' pattern of the beams radiates enough to cover what we need. I swapped the 5db units with a 9db pair. The coverage at the desk and in the sunroom was better but only by a scant amount. But the coverage at the vertical fringes of the donut we dramatically reduced. Now most of the rooms upstairs didn't get covered, not just the far guest room. Not an improvement.

In the past I used a pair of parabolic reflectors around them and pointed one toward the sunroom and one downward toward the office. Worked pretty well, but this was for a lower performing BEFW114 (or something like that) and the WRT54G that replaced it didn't need 'em. Made 'em from scratch using cardboard, a glue gun and some 1/4" hardware cloth. STFW for more.

Sure, but Ford parts don't explictly say they won't work in a Chevy either. While I sympathize with the confusion it's not like one company would go out of their way to say if it worked with anothers units. That and the FCC test issues explained in other posts would certainly affect the situation.

It's not about protocols; they're all the same. It's about the beam pattern. Better explain your setup and perhaps some suggestions can be made.

-Bill Kearney

"JWD" hath wroth:

That's usually sufficient. Netstumbler running on a laptop is good for finding the hot spots inside the house.

OK, so this is essentially an outdoor network. You're not going to see much improvement going from a 2dBi rubber ducky antenna to what appears to be a 4.5dBi antenna (7dBi minus coax cable losses). There should be some improvement, but nothing spectacular.

Cinder block is well, a brick wall. Little goes through it. Are you able to find a window with a view of the opposite end of the link?

How far away? What manner of hardware and antenna does the bother-in-law have? Is there line of sight?

As a general note, numbers are always better than descriptions. I can make a good guess as to the gain of the direction antenna you'll probably need to make this work if you supply some numbers.

That's very weak. You'll need line of sight and a directional antenna. You might get a connection, but it will dropout as soon as you start moving data.

Are you sure? Did you run Netstumbler, or better yet Kismet, to be sure? I've been suprised many times.

Two houses? Are you trying to "drill" though those obstacles? There's no way this is going to work without line of sight. Worse, even if you do conjur enough antenna gain to get a connection, if anything moves in these two houses, your signal will go up and down. I read a story where someone was able to drill through an office building that had opposing picture windows. That worked just fine until someone moved a file cabinet in front of one window. Try to get line of sight, even if it means antennas on the roof.

With 2 houses blocking the RF path, I would say it's impossible. However, you are apparently getting some signal through so some tinkering might make it marginally useful. The reflectors on:

very easy to build and produce impressive improvements in directional antenna gain. Methinks it's worth a try.

Incidentally, if the houses in question are sufficiently close to run wire, it's fairly easy to run 10baseT-HDX over CAT5 or coax cable up to about 1000ft. Details on request.

The hardware is a NetGear MR-814 and the antenna is the basic antenna that came with it (unless I use my ANT24-0700 of course). The houses are small. They are only about 17 feet wide. There is definately no line of sight between my house and the brother-in-laws. The router is in a closet in his first floor. I can get a signal on my first floor if I get very close to the wall.

I downloaded Netstumbler and there is only my brother-in-laws router listed.

The antennas on freeantennas seem simple enough to make. Maybe I'll give them a try.

Yeah, I thought about this, but we wouldn't be able to run the cable through the other houses either inside or out.

Thanks, John

You've got three cinder block walls? I'm surprised it works at all. Have you tried things like putting your antenna in the attic (and maybe your BIL's too)? Maybe each of you sticks an antenna out a back window in sight of each other? Maybe you just pony up for your own broadband? [If you start doing file sharing, he's gonna kick you off anyway for eating all his bandwidth, and then all the money you spent on gain antennas is wasted...]

Unfortunately we have no attic, they are flat roof houses. What about adding a repeater in one of the houses in-between? What exactly is a repeater? Is it a access point configured in a special way or is it a separate device? How much would a repeater cost ?

John

"JWD" hath wroth:

How far away in feet?

I'm amazed that it even works going through at least two cinder block walls, two additional houses, who knows how many bushes, and an inside closet wall. Methinks you're going to need some help from the brother in law. Have him move the router out of the closet and into a window.

OK, you're probably safe from interference problems. There are other sources of potential interference. See:

a checklist of possible interference sources.

It's worth a try. However, I'm not very optimistic about your chances considering the lack of line of sight.

So, go around them. I've done trenching along a fence line for exactly that purpose. Just make sure that whatever you bury is gopher proof.

Repeaters don't work very well, IME, though if you had to try if I'd go with a Linksys WAP54G in the middle house. If it works the neighbor in the middle is going to want/expect access to the broadband as well, and now you've got three households using one broadband feed, and your BIL finds it's too slow and cuts the rest of you off...

If you can talk to your neighbors, how about running a wire thru their basements? How about you and your BIL each sticking an antenna out the back window? How about getting your own broadband and not spending a lot of time and money trying to engineer an imperfect solution?

Unfortunately, these are small, cheap vacation condos. There are no attics (flat roofs) and no basements so antennas out the back window and/or a cable through the other houses are the only alternatives. Thanks for your opinions and suggestions. I'll try a few more things like the free directional antenna and investigating the repeater a bit more. I was trying to avoid getting my own broadband since I only live here a total of a few weeks a year.

Thanks, John

Building electrical and fire code generally frowns up on that idea.

Unless you own the lands that 'go around them' then you'd run afoul of municipal right of way issues.

Short of leasing a 'dry pair' from the phone company there's little you can do to wire two different houses together, especially when there's other structures and property owners between them.

There's also the vertical coverage area to consider. Unless you're willing to setup two additional routers, one on each end, you're going to have trouble trying to get a router you'd expect to use for other in-house wifi coverage. But given how cheap Wifi units are these days it'd be better to just get the dedicated set.

-Bill Kearney

-Bill Kearney

If it's a flat roof you could put antennas up there. But if you're in a complex that has a condo or home owners association you may not have the right to do so without approval. The outside of the buildings is essentially jointly owned in that situation, and the roof is usually included. But if they're individually owned and not governed by such a contract then you might consider using the roof.

Otherwise it might be 'easier' to just rig up a pair of panel or other style of directional antennas and hang 'em out a convenient window or balcony. Make a bracket of some kind so you wouldn't have to leave them installed permanently. A pair of small panel antennas might not look too obvious. Going with sector, yagi or the 'cantenna' style might be a bit unattractive and raise unwelcome attention from the neighbors. If you've got flower boxes on the outsides of the house then consider using the side of the boxes as a mount for the panels. There's probably a number of ways to set them up in ways that don't draw too much attention to them.

-Bill Kearney

"Bill Kearney" hath wroth:

Actually, it's worse than that. In the People's Republic of California, anything that crosses the property line is frowned upon. Such adventures in creative wiring are the exclusive domain of the public and private utilties and require forming a special utility district.

Running UTP (unshielded twisted pair) CAT5 is fairly safe as long as there is no common ground at both ends, as in STP (shielded twisted pair). The danger is that each building might be on a different ground return for AC power, which will cause some current to flow. I had this happen in the 1970's at my employers, where the metal conduit run between two buildings literally disolved. There was only about

1VAC ground differential between buildings, but there was LOTS of current behind it. Don't run a common ground between buildings. Otherwise, the ordinary ethernet transceiver is quite well isolated and protected. If you're paranoid, there's always fiber optic cable, which is inherently safe.

Coax cable has the same ground "loop" problem as STP. The common

10base2 to 10baseT converter is quite well isolated and protected to prevent any problems. 10base2 (cheapernet) requires that the coax shield be grounded at one end. That's fine. Just don't ground it at both ends. Use a proper water pipe or ground rod similar to CATV grounds.

In the 1970's, I installed and ran an unauthorized CATV system around the neighborhood. At it height, there were about 20 houses on the system. The municipal authorities didn't seem to care (or undestand) too much. The cable company went nuts and dragged in the "agencies". I agreed to dismantle it if they didn't arrest me for some unspecified crime. (This was before the "theft of service" laws).

True. There's little that can be done legally. In the process of removing my neighborhood bootleg CATV system in the late 1970's, they also demanded that I remove the wires used as a neighborhood "intercom" so the kids can yack with each other without tying up the phone. Basically, anything that crosses propertly lines is legally "discouraged".

I've found a rather marginal way around the problem. Many years ago, we established a special utility district with the purpose of maintaining our private road. When I ran my bootleg CATV and later internet system along and under the road, I justified the wiring as a "burglar alarm" in case someone was attempting to steal the road. It's in the road committee charter and road agreement and was approved by LAFCO (local agency formation commission). I suspect it would fall apart if challenged, but so far, has not attracted any municipal or regulatory interest.

Additional wireless routers are cheap compared to the effort of customizing the antenna patterns to deal with both vertical and horizontal coverage. However, the philosophy doesn't scale well beyond 3 wirless routers as one runs out of non-overlapping RF channels.

"Bill Kearney" hath wroth:

There are also "stealth" antennas and radomes that are not easily visible. I know of several cell sites that are hidden inside fake plastic chimneys. Unfortunately, one of them was so badly done that it looks like Santa Claus had tried to squeeze down the pipe. You might want to look through the camouflaged cell site phots at:

see if you get any ideas.

There are also clear plastic dish antennas which are difficult to see. They're not found in the US, but are apparently fashionable in UK.

down to the 60cm transparent dish).

Only if they're on different phases. Even then you can do it, with suitable earthing.

Depends. I could toss a bit of CAT5 into my neighbour's study from where I'm sitting. Heck, I can practically reach to plug it into his PC for him.