Hawking 8db gain Dish woes.

"Don W. McCollough" hath wroth:

Well, the numbers I calculated are for an idea dish antenna. My guess(tm) is that this thing is anything but idea. Did you read my Google Groups reference to what happens when you use a USB dongle as a feed for a parabolic 18" satellite dish? The illumination pattern of the feed (i.e. the dongle) is VERY lossy, with much of the signal going off in useless directions. My guess(tm) is only about 15% of the RF that leaves the USB dongle, hits the reflector and goes in the general direction of the access point. 0.15 is about: 10 log (0.15) = -8dB of loss. That makes the antenna gain about: 8dBi (theory max gain) - 8dB (illum loss) = 0dB In other words, this contrivance is slightly better than the USB dongle by itself.

Reply to
Jeff Liebermann
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Ok. I purchased one of these silly 50s sci-fi looking adapters to see if I could lock onto more wi-fi routers in my neighborhood; I was going to go with a cantenna but I didn't want to buy a new PCI card and pigtail.

This is the dish

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So, I hooked it up to my computer which has a cheap Wireless B PCI card. Normally, I get about 7 or 8 neighborhood wireless networks and can connect to them sometimes with "Very Good" or "Excellent" signal readings. My own Wireless B router usually comes in "Excellent."

I was expecting to see more networks and pull better signals from the preexisting networks (routers) with this dish, but after installing the driver and using its networking configuration software, I found that all I could get is "Low" "Very Low" and rarely "Good" signals.

The dish should have a 8db gain. I tried pointing it in all directions and angles...outside my windows...but this thing would not get any additional router signals and when it found the older signals it didn't connect very well. The cheap wireless B PCI card did much better without having to aim it.

I've contacted their tech support...and the thing might be defective, but am I missing something here?? Do these "gain" antennas only connect to networks that are normally out of the distance of typical wi-fi adapters and do little to lock onto to closer signals? One would expect that these kind of dishes would be useful in determining from which direction a signal is coming from...especially with built in signal locator LEDs.

This Hawking dish is a big let down. Its supposed to be Plug and Play. Any input would be much appreciated.

Don

Reply to
Don W. McCollough

Chuckle.

I can't really tell what's inside or how it works, but let's pretend it's a properly designed parabolic dish. Could you measure the dish diameter? My guess(tm) is about 15cm.

The theoretical power gain of a dish is roughly: (circumference / wavelength) ^2 (Pi * 15cm / 12.5cm ) ^2 = (3.14 * 15 / 12.5)^2 = 14.2 Converting to decibels: Gain = 10 * log(14.2) = 11.5 dBi However, that's assuming perfect illumination and efficiency. Well designed dish antennas have about 50% efficient or a -3dB loss. Do the maximum gain of this contrivance is: 11.5 - 3 = 8.5dBi Yeah, 8dBi is theoretically possible.

The beam width would be: 1.2 * wavelength / dish diameter) in radians (where 2 * 3.14 radians equals 180 degrees).

wavelength = 3x10^8 meters/sec / 2400x10^6 Hz = 0.125 meters Dish diameter = 15 cm (my guess) 1.2 * 0.125 / 0.15 = 1.0 radians 1.0 radians * 180 / Pi = 57 degrees. With 57 degree beam width, this is not a very directional antenna. Of course this assume that's its really a parabolic reflector. My guess is that the feed is anything but ideal for illuminating such a small dish. Methinks that the USB dongle at the center has a PIFA or meandering 1/4 wave element for an antenna. These radiate roughly in a spherical pattern, where the energy goes in all directions roughly equally. That means a large part of the signal goes in directions other than hitting the reflector and going in the direction of the access point. I previous ground through the numbers at: |

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Reply to
Jeff Liebermann

Thanks for the calculations. The dish is actually (more like) 12cm. And

57 degrees isn't that directional, which makes me wonder why this thing won't pull in a better signal than my standard PCI card. It should, if aimed at a nearby broadcasting router give *some* gain in signal...but nada. I've contacted Hawking Tech tech support, lets see what they say.
Reply to
Don W. McCollough

That's dissapointing to hear. Hawking tech support claims that the thing is defective...send in for a replacement etc.

Out of curiosity would the output of a PCI card be significantly better than a USB dongle?

-Don

Reply to
Don W. McCollough

Jeff,

Something like this would probably be a better bet eh? 24db gain.

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But could I mount this thing indoors?

TIA

-Don

Reply to
Don W. McCollough

Your dime. I would ask for a refund and buy something that works.

No, not really. The typical USB dongle and PCI cards vary between

+13dBm and +17dBm, mostly towards the lower end. However, there is a difference in antenna gain. The typical USB device, with a PIFA or meandering monopole antenna, has a gain of about -2dBi. The PCI antenna is much better at about 2 dBi. The 4dB difference should theoretically yield about 70% more range.
Reply to
Jeff Liebermann

Yep. Much better. That's the old PacificWireless antenna. I have a pile and use them for point to point links. It has a rather narrow beamwidth (about 5 to 7 degrees) and may be difficult to aim and keep stable.

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Are you married? Are you planning to stay married? Technically, you can mount it in a window and use it indoors. If the walls are like paper, you might be able to shoot through them.

Reply to
Jeff Liebermann

Of course, unless your PCI card has a cable allowing repositioning of the antenna, the dongle has the advantage of being able to position it for best reception.

Bob

Reply to
Bob Alston

Reply to
frankdowling1

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

Yeah, something like that. Some more guesswork. What I found interesting is that the "dish" was 12cm in diameter. That's almost

12.5cm which is 1.0 wavelengths at 2.4GHz. If the dish were measured along the curved diameter, I suspect it would be exactly 12.5cm.

Well, that's a simple 2 element "yagi like" reflector. You can take any dipole antenna and fasten a reflector at a distance of approximately 1/4 wavelength and get some gain. Instead of a dish, it could have been a flat plate and achieved the same results. Any multiple of 1/2 wavelength diameter will work. In other words, this is not a "well designed" reflective dish antenna. I may be a "well designed" flat plate reflector antenna where the aesthetics department decided would look better if it were a dish instead of a flat disk.

I'm not sure how much gain such a flat plate reflector will produce. I'll try to shove it into 4NEC2 and see what happens. It will probably be over 3dB but surely less than the promised 8dB. I'll assume a common USB dongle with a ceramic backed antenna feed (-2dBi gain).

This the 2nd time that Hawking played games with the specs. Last time, it was specifying the gain of their external patch antenna at

6dBi without the slightest consideration for the 3dB loss in the 3 meters of tiny RG-316/u coax cable.

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Reply to
Jeff Liebermann

I have used the "Hawking HAI6SDA Directional 6dBi 2.4GHz Antenna" with good success on a Netgear WG311 PCI card.

I wouldn't expect their 8db USB widget to be junk. Jeff's calculations indicate that their claim could be correct, but then he wanders off claiming that it is no better than the New Zealand dishes, which are rather artsy, but lack the real design that Hawking might have done.

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If you just bought it, why can't you return it and get a replacement. If the replacement is the same, then you should return that for a refund.

Did you remove your original PCI card? Are you sure that you are looking at the signal from the new gadget? Did it come with a USB cable? Could you try another cable?

Reply to
dold

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

Like Sherlock Holmes, I don't know all the answers until the investigation is done.

Yep. I used it to extract some dimensions from the photos.

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'SOYHWU8DD'The test report shows that it was made by Edimax in Taiwan. The antenna gain is claimed at 8.00dBi with +17dBm output for 802.11b modes, and +15dBm output for 802.11g (OFDM) modes.

The construction was not what I expected. I previously guessed that there would be a USB dongle hanging in the center feed area. Instead, the USB radio is all in the base of the unit, with a coax cable going to the antenna feed in the center cylinder. There are no details or photos that show the type of feed. It could easily be a ceramic backed 1/4 monopole, PIFA antenna, or some manner of loop or squashed dipole. I can't tell without breaking the center cylinder open.

I have an NEC2 model constructed that seems to show that it is possible to get 8dBi of gain out this 12cm dia reflector using a simple dipole feed. I get slightly less gain with a flat plate (circular) reflector. The gain will be less when I try it with a smaller (and lower gain) center feed antenna. I'm having some problems getting the VSWR down to below 2:1 so I'm not quite ready to post quite yet.

Except for not specifying the coax loss, I don't have any objections to that antenna.

Reply to
Jeff Liebermann

Jeff Liebermann hath wroth:

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I gave up on getting the VSWR down and simply cheated by using a 75 ohm feed instead of 50 ohms. I'll play with the optimizer later. I also couldn't figure out what was inside the Hawking antenna feed, so I just left it a simple dipole. It's probably a circuit board with some manner of loop, PIFA, meandering 1/4 wave line, or something similarly miniature that will fit. That will reduce the gain somewhat.

The 1.0 wave diameter dish antenna yields a gain of about 7.7dBi. The 1.0 wave flat plate reflector yields a gain of about 8.3dBi. However, that's well within the tolerances of my guesswork as to the location of the feed in the flat plate reflector and f/D ratio on the dish. However, if I use a shortened feed, the gain will drop about

2-4dB, putting the antenna well below the advertised 8.0dBi gain. I'll do a shortened feed model later.

FCD ID web page:

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'SOYHWU8DD' Hawking HWU8DD web page:
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NEC2 data files (not optimized):
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4NEC2 antenna modeling program:
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Reply to
Jeff Liebermann

Jeff Liebermann hath wroth:

Oops. I reorganized my web pile a bit.

Hawking Dish:

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Same thing with flat plate:

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Reply to
Jeff Liebermann

Reading you draw conclusions is like reading Sherlock Holmes.

Did you look at the FCC sheet for it? That would show whether there's an active USB element in the "feedhorn", or if it's just an aesthetically pleasing dipole.

Hawking didn't seem to have a problem with the flat plate on the 6dBi that I bought. Marketing could have appended an empty "pointer" to that one too.

Reply to
dold

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

When you have eliminated all which is impossible, beaten to death that which is improbable, pounded into the ground that which is unproveable, contemplated the rediculous, denounced the political, dubunked the miracles, removed the personalities, and read the FAQ, then whatever remains, however absurd, must be the truth.

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Not me. I just answer the techy questions and avoid the politics. You're welcome to provide moral support or legal direction if required. Incidentally, I read somewhere that the term is now "Wi-Jacking".

Reply to
Jeff Liebermann

I expected Hawking to be better than the gang in New Zealand.

I am a bit surprised by that. I guess we don't typically "see" what's inside the rubber duckie on a WAP either, but this seems different. I expected to see an inside photo.

Sherlock on the trail again. Maybe it's a perfectly optimized feed. After all, these guys do this for a living. ;-)

The HWU54D is my flat panel HAI6SDP + HWU54G USB in one unit. A little less Sci-Fi looking than the HWU8DD mini-dish, at 6dBi, and $10 cheaper.

But the OP never said what kind of PCI card he had. Maybe he could just add the external antenna.

And then we could talk about which of his neighbors' connections he intends to poach.

Reply to
dold

Well at least it lives up to its claims...

Now if only the company can ship one that actually works to me.

Have you ever done a bench test of a Super Cantenna?

"Hi-Ho-Hi-Ho...its off to poach I go."

Reply to
Don W. McCollough

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