slot design

hi, have you seen the multi-polarized antennae(some call em snake-oil!) on

I've seen at least a couple units made like that! Designed to be externally mounted, with power and data fed over CAT5 cable. Of course these things cost a good bit more than the consumer grade products that most of us talk about here... :-)

I wonder about that restriction on USB cable length too. I have no idea just exactly what limits it to 15 feet, but I suspect it might be the power leads rather than the data. If that is true, it might be that a device which uses significantly less than the maximum power could actually be used on significantly longer cables.

I've got a couple of 15 foot USB extention cables here somewhere, and someday I'm going to test that to find out... But I don't have any USB wifi devices, so whatever tests I might do wouldn't necessarily apply to those.

I'll assume 2.4GHz. 4 slot antenna:

Wanna disclose what you're trying to accomplish, what you have to work with, and why you think a horizontally polarized slot antenna, which is normally used as a sector antenna, is the "ticket"?

I assumed horizontal polarization because vertically mounted slot antennas are almost always horizontally polarized. That's because you can build a vertically polarized sector antenna, with similar characteristics, much easier and cheaper using a vertical colinear.

It is possible to design a vertically polarized slot antenna, but the geometry and pattern are rather odd looking. These were used for early WWII era aircraft night-fighter RADAR, where the antennas were waveguide slots on the leading edge of the wings.

The link above is horizontal polarization. The various examples of Alford Slot antennas are all horizontally polarized.

Good luck, whatever you're trying to do.

Why? Well, your ISP's terms of service may restrict redistribution of bandwidth off the property limits. Of course, few enforce such restrictions and everyone does wireless, so I think you're probably safe.

Watch your tolerances. See the ACAD DWG on Trevor Marshall's site. Note the tolerances. They're tight. I worked out the numbers in another posting but the total error to drift out of the 2.4Ghz band for a 1/2 wave dipole is something like 1.5mm max. This is not something you can build with a drill, file, and tape measure.

May I recommend you build a pair of biquad antennas instead.

Good luck.

Yeah. You mentioned using 15 meters of coax. That's 9.3dB of loss for 9913 or about 85% of your power gone up in smoke. Methinks that's way too much coax. If you switch to LMR-400, you'll still lose 3.3dB or a bit more than half your power, which is much better. Lose the

This you call monster invisible?

One more slot antenna:

I used to work with lots of aluminium jacketed CATV coax of various dimensions. Bending the larger stuff requires an EMT bender. That's hard line. 9913 is aluminium foil and braid, which is NOT what I would call hard line. It's usually listed as "low loss RG-8/u".

yeah, that will work if you mount it in the middle of the window. One problem with such a sector or omni antenna is that you can't really put it next to anything metallic or reflective as it will wreck the pattern and possibly increase the VSWR. So, you plan to spoil someones view by planting it in the middle of their view? Actually, that's not a bad idea. Plant the lower end into a flower pot, add some soil for stability, decorate with plastic plants, and it will be invisible.

Incidentally, some "energy efficient" tinted windows are aluminized and block RF. I suggest a fast test to make sure they'll work.

Agreed. I do badly with insufficient information. I like numbers.

I guess math isn't part of the job requirement. You're installing 15 meters of fairly high loss coax cable to a 1.5 meter long antenna that is being used for a point to point link and delivers perhaps 15dBi gain on a 180 degree sector. Meanwhile, a 14dBi panel antenna is perhaps 200mm x 200mm for the same gain and a narrower 35 degree beamwidth (so you don't have do deal with reflections). You "found" the 9913 which is not commonly used at 2.4Ghz as a simple loss calculation will show.

It took me a while to find Belden 1573A data. It's not in the online version of the Belden catalog. Google found one reference to Belden

At 600meters link distantce, your proposed arrangement should sorta work as described, even with the lossy coax. Range: 0.373 miles (600 meters) TX power: +15 dBm TX ant gain: +14 dbi TX coax loss: -9dB (15 meters 9913) RX send: -83 dBm RX ant gain: +14 dbi RX coax loss: -9dB (15 meters 9913) Using:

I did some disorganized tinkering with extension cables and can offer some anecdotal evidence. I was able to locally power a WUSB54G with

There are also rise time and timing delay specs, which I don't claim to have read:

I had trouble trying to figure out why my local 5V power would stick the device in USB 1.1 mode instead of 2.0. It seems that one has to have a common DC power ground so that one of the data lines can be pulled high (3.3v) to indicate it's a USB 2.0 device. Grrrr...

Incidentally, the WUSB54G apparently functioned down to an applied voltage of about 3.8VDC. However, I kept getting stuck with USB 1.1 mode instead of 2.0 so that's not really totally functional.

I can re-measure any of the above. However, I'm down to my last scope probe and can't really measure the signal levels without pair of probes with the scope in differential input mode.

Can save you the trouble... I have one of those little "dongles" that plug into a USB port on a computer or other device (a few oz'z and an inch or so long). I was experimenting and trying it with USB extension cables rather than plugging it in directly into my laptop. When the USB extension cables are added on, you start getting more errors (at about 45 FT it becme so error ridden it was unusable), that's when my partner at work suggeted ethernet (they make and sell Power over Ethernet devices) and can go about

As for cost, the USB dongles are about $35 (ethernet to USB converter is about $18), with economy of scale, I would suspect they would be under $50 if made together in one package, and rather than an internal antenna, a mini-uhf connector to hook to external antennas to it, should make a negligable difference in cost. Just to be clear, they make consumer grade USB "dongles", adding ethernet and POE options, Seems like it would be a perfect consumer grade device.

Good Lord, *don't* entice him! Jeff's CV is probably 2000 pages long and lists the path margin on every system he's ever implemented... ;-)

....

With a little difference too. Jeff is doing the systems engineering, not just installation. He's figuring out *what* to install, not just how and where.

A *very* significant difference...

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Any one got information as I need to shoot a link about 600 metres and am thinking a home made slot would be the ticket . (and ues its los if I go up 10 metres whixh means 15 metres of coax all up)

no I don't , I do know its the way to go , for my purposes. nice link but Ill have to find more as I said I intend making one or two of then , now why you assume its horizontal in polarisation ?

From the house to the office , why buy two dsl 3 mbs ? I've opted for waves because I can make them in the neighbours shop , with a corner refletor and a vpn should do the trick and it will be cheap Im sure .. plenty of 9913 here and lots of connectors so I figure about an hour each plus install at almost nothing each with coax . looking at the retail prices Im glad I have the facilities .

it may , but there are ways , and seeing I have a fiscal interest it doesn't matter ..

didn't read it did you . he has a serious machine shop , so a vertical cnc and 20 minutes to set it up. easy

I'm a contractor and install all sorts of things as part of my business, just found 40 metres of hard core .. any other problems ?

not interested in quads , been there and they work but because of the situation at the office the slots will be almost invisible so that's what I'm using , thanks anyway ... will have them made in another hour or two and fit tomorrow...