USB Adapter With External Antenna

I'm thinking this might be a good versatile buy for a USB adapter:

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With a USB extension and a reflector, this seems like it could give some good leverage on the client end.

Any comments?

Steve

Reply to
seaweedsteve
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You probably wouldn't extend the coax as indicated on the website, but rather extend the USB, as you pointed out. However, these dongles are hard to deal with once they are hanging on a cable. [I've seen them tapes to windows or walls.] If you want to add an antenna with a base or some sort of mounting structure, this would do the job.

The more I fiddle with wifi, the less I like omnidirectional antennas. I am surrounded by channels 1, 6, and 11. Two or three users on each channel.

Reply to
miso

Hi. Thanks for the quick reply.

I like that the device already has a "high" gain antenna. With the zero cable loss of the USB approach, this will probably produce the desired gain if the radio is decent. However, if I do need to go to a better antenna, I have that option.

It would be on a short or no pigtail, if stronger antenna is ever used. Mounting and all that are inconsequential. This device will be tucked away with just a usb cable end showing to the user.

Still, my basic two questions are not about the approach, but about this specific device.

1) Radio guys: How do the specs look? 2) Anybody: Any experience with this product or company?
Reply to
seaweedsteve

On Jan 24, 3:27 am, snipped-for-privacy@sushi.com wrote:>

I like that the device already has a improved gain antenna. With the zero cable loss of the USB approach, this will probably produce the desired gain if the radio is decent.

However, if I do ever need to go to a better antenna, it's nice to have that option. Better yet, the external antenna allows using a simple "rubber-ducky" antenna reflector, as I mentioned. I have not had as much success so far with the "USB cookware" approach as with the "EZ-10" style. If you know what I mean.

I am now more seriously considering this for a specific client as a sheltered, but outdoor device in a marginal reception area. Mounting and all that are inconsequential. This device will be tucked away in the roof structure with just a usb cable end showing to the user.

I have two questions about this specific device:

1) Radio guys: How do the specs look? 2) Anybody: Any experience with this product or company?
Reply to
seaweedsteve

Hawking makes a USB AP that seems to be integrated with an interesting antenna. I've never played with it.

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I just set up a thinb-sized D-Link USB AP. It comes with a small base and the AP stands straight up. I put it on the end of a 20 ft USB cable and was able to put it on a high shelf and it that works fine.

Reply to
Al Dykes

On 23 Jan 2007 22:12:46 -0800, "seaweedsteve" wrote in :

Other options:

  • Hawking HWU54DM Hi-Gain Mini Wireless-G USB Adapter

  • Hawking Hi-Gain HWU8DD USB Wireless-G Dish Adapter

  • Hawking HWU54D Hi-Gain USB Wireless-G Adapter
Reply to
John Navas

"seaweedsteve" hath wroth:

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What specs? The only numbers on the page are tx power, which is fairly typical, and antenna gain +5dBi. The antenna is better than the typical USB "chip" antenna that runs -2dBi (yes, it's negative). Any manner of external antenna is an improvement over the typical PIFA antenna used in USB radios. For example, DWL-122:

With antennas, size matters.

No clue at what speed the receiver sensitivity was measured, so that's useless. If it's at the lowest speed (highest sensitivity), then the sensitivity is in the ballpark. Most access points do better but unless you're going for the DX record, it's well within measurement accuracy. My guess is that Air802LLC just used the numbers from the Atheros data sheet and didn't test it.

Not really. I have some older ZyDas/Atheros based USB dongles floating around in use by various customers. Nothing special. They work and are quite well supported.

Looks like it supports anything from Windoze 98SE and up including OS/X and Linux. I like the idea of an external antenna on the USB dongle because I can mount it directly to the antenna and use USB extension cables to attach to the laptop or desktop.

Reply to
Jeff Liebermann

The price is good, compared to a unit like the Hawking HWU8DD, which has a better, but fixed, large, and ugly, antenna.

I wonder if you can use the air802 with the external antenna disconnected? That would make it handy for travel, and you could attach the antenna as needed. You could add a reflector for the antenna. You could glue a

1/4-20 nut to the case for a tripod mount.

I went with a cheap USB dongle and a coffee can.

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Reply to
dold

Seems to be identical to:-

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has an internal antenna

Zydas were bought out by Atheros

Reply to
Rob

snipped-for-privacy@78.usenet.us.com hath wroth:

Ugly? In the antenna business, the uglier the antenna, the better it works. It's kinda like pills. If they don't taste bad, they don't work.

I don't think so. Unfortunately, you can't easily cram a 1/4 wave (3.13cm) monopole antenna (piece of wire) into the RP-SMA connector. However, a small 2dBi RP-SMA antenna can be easily borrowed from a DLink access point or wireless router. You could possibly build your own antenna, but at the price I've seen them on eBay (about $6 total), it's not worth the effort:

One possibility is to use a ceramic patch antenna, which can be very small.

It's the round white thing in the lower right of the circuit board. I have several with connectors attached. Unfortunately, the measured gain is about -4dBi, so I don't consider this to be a performance improvement. Bigger really is better.

Reply to
Jeff Liebermann

Yep, Hawking has got one that compares, but it costs more and does not have the 5db antenna. I'd say that if all else is equal, this "Air802" is the better deal by far.

Nice. I wondered if one could push the 15 foot USB extension limit with a passive cable. Sounds like you can.

Reply to
seaweedsteve

Agreed. Cheap is what caught my attention. For an external antenna device that is.

The Hawking looks great too - more expensive, higher profile and more directional. Most of all, can't change the antenna. The other Hawking is packaged with low gain antenna. Dumb.

YES

Another appealing solution. Higher profile to wind and rust, right? What kind of measured gain do you get from sticking it into the can? The "no-loss Cantenna" approach. I'm going to try it sometime with my $20 Netgear USB heater.

Steve

Reply to
seaweedsteve

Off-topic: I noticed that it's B tx power has 3dBm more power than G. Is this another clue that connecting under 802.11 B will give more distance?

Ah, so if the radio is typical and then the 5dBi antenna is actually 7 dBi improvement, then this could give FOUR times the range of a typical USB adapter? I was thinking that typical was 2 dBi.....

I see. Still that says something. Assuming the worst for the unstated variable, it's normal. Can only be better if the assumption is wrong...

I love cheap tricks ! Stock 7dBi gain not enough? Add a reflector ! Need more gain still? - optional antenna time! Need another 15' at zero loss? Add an active USB extension cable !

Reply to
seaweedsteve

"seaweedsteve" hath wroth:

Good question. 802.11b and g powers are measured at the maximum power for any frequency or mode. For 802.11b, that's at 1 or 2 Mbits/sec which operates pure FM (frequency modulation). However, the 802.11g modes, that run from 9 to 54Mbits/sec, are all combinations of both AM (amplitude modulation) and FM modulation. The AM component reduces the ratio of the peak to average power when measured according to ANSI C63.4:2003 (Measurement of intentional radiators). Therefore, 802.11b will read somewhat higher power levels than 802.11g. Also, note that the tx power will vary over about 1dB from the lowest to the highest channel.

ANSI C63.4:2003

Sorry, you gotta be a paid member to download the proceedures and specs.

Try not to use "typical" when the real numbers are available. My guess on the antenna gains are: Type Gain (dBi) USB chip -2 USB PIFA 0 PCB dipole 1.2 Rubber coax 2.1 Longer 5.0

The chip and PIFA antennas are somewhat of a guess. The gain tends to be unevenly distributed. The usually quoted figure is the *MAXIMUM* gain in some direction. No guarantee it will have that much gain in any other direction. It generally has much less gain than specified. For example, these chip antennas found in some PCB antennas quote various gains:

+2dB (whatever that means):

Centurion chip antennas:

Max gain varies with chip size from +0.8dBi to +4dBi:

Reminder: range_change = 10^(dB/20) where dB is the difference in antenna (or system) gains. or more simply 3dB = 1.4 times the range. 6dB = 2 times the range. 12dB = 4 times the range. 18dB = 8 times the range.

I like your optimism. However, in the wonderful world of system, antenna, and wireless modeling and calculations, reality is almost always worse than the theoretical models or calculations.

Reply to
Jeff Liebermann

(Steve said )> >Ah, so if the radio is typical and then the 5dBi antenna is actually 7

Gotcha. If not known, then the on-board antenna on a USB adapter may be 0dBi or -2dBi approx, depending. It's not likely to be over O..

Thanks for the clarification and the hard numbers. I thought I understood that, but probably I was mixing up power>dB relationship with dB to distance.

I like your optimism. However, in the wonderful world of system,

OK. I'll scale back my expectations accordingly.

In the end, I went to buy that one linked above, but they wouldn't give me shipping until the bitter end and it was high. I don't like to encourage the "hidden shipping income" approach, so I went and found a similar one on Ebay. Looks like this device, as well the Hawking style (SMA connector on the side), is sold as a generic commodity, rebranded by various small vendors.

When I get it, I'll post comparisons to a name-brand USB adapter I already have.

Steve

Reply to
seaweedsteve

On 30 Jan 2007 09:39:44 -0800, "seaweedsteve" wrote in :

A 5 dBi antenna is actually 5 dBi.

  • 3 dB better than standard rubber duckie (1.4x range)
  • 4 dB better than PCB dipole (1.6x range)
  • 5 dB better than USB PIFA (1.8x range)
  • 7 dB better than USB chip (2.2x range)

USB _dongle_, and more likely to be -2 dBi in my experience. Antennas on other types of USB adapters can and do have much better antennas.

Reply to
John Navas

"seaweedsteve" hath wroth:

Huh? I think you're mixing dB, dBi, and dBd. This is a common problem. dB is simply a ratio as in "This antenna has XX dB more gain than this other antenna". It's NOT an value like dBi and dBd. dBi is the gain over an isotropic radiator, a theoretical radiator where the power is distributed equally in all (hemispherical) directions from a point source. That's impossible to build (although some antennas come close). Most antenna gains are specified in dBi or "XX dB more gain than a 0dBi isotropic antenna".

dBd is an oddity that seems to creep back into the problem. I wish it would simply die and go away. dBd is "dB over a dipole antenna". A dipole antenna has about 2.15dBi gain, so dBd is just dBi minus

2.15dB.

Yep. However, note that for such antennas, the specified gain is the

*MAXIMUM* antenna gain. It's difficult to guess in what direction that will be because of the effects of the USB dongle circuit board and metal parts. It's often NOT in the direction you want or expect. The pattern can be very uneven and erratic. As always, treat the gain figure as optimistic.

It's real and based on years of suprises. The type of calculations I'm running tend to ignore a large number of potential sources of loss. For example, I tend to use a rather simplistic path loss calculation.

Closer to reality, and far more complex is one like this:

which includes topography, foliage, atmospherics, Fresnel diffraction, etc. Anyway, there's always yet another source of loss that was not part of the original calculations (e.g. adapters, antenna rot, shipping damage to antennas, manufacturing variations, water in the coax cable, interference, weird reflections, etc).

Nope. Scale them back according to your expectations of reliability. See:

and note the table with the relationship between SOM (system operating margin also known as fade margin) and reliability. You can make almost any microwave link sorta function. What's difficult is doing it reliably.

Good luck.

Reply to
Jeff Liebermann

Jeff said:

My comment, in context, was: "Ah, so if the radio is typical and then the 5dBi antenna is actually 7 dBi improvement" (over a -2dBi implied)

Just what you're saying, right? 5 dBi antenna instead of -2dBi yields

7dB difference. But putting a little i in there the second time was what threw mud on the conclusion, right?

USB _dongle_, and more likely to be -2 dBi in my experience. Antennas

Ah,imprecise labeling got me again. I forget about the non-dongle types of USB adapters. Like the ones with the folding antennas. Or the hawking USB dish.

Just trying to get oriented for what USB dongles "typically" (cringe) do, antenna-wise, in order to judge how much a 5dBi external antenna might help.

Hopefully all this has clarified the point that adding a 5dBi external to a USB dongle is a significant improvement, possibly doubling (NOT quadrupling) the range.

Correcto, no?

Reply to
seaweedsteve

On 30 Jan 2007 11:21:14 -0800, "seaweedsteve" wrote in :

Correcto, yes.

Reply to
John Navas

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