Cheap wifi antennas

Let me see if I understand what you've done. You replaced the stock

2dBi rubber ducky antenna with a bigger rubber ducky antenna that claims 9dBi. Well, a vertical colinear with 9dBi gain would be about 400mm long. Close enough: However, there are a few problems. Both antennas are far too close to the metal case of the computer to not have the case interfere with the pattern, VSWR, and mechanical mounting. The case acts as a shield. So does the traditional tangle of wires behind most PC's. In addition, most PC's seem to live under a table, on the floor, or buried inside a cabinet, which are not the best RF locations.

What you should have bought is a lower gain antenna with a length of coax cable terminated by an RP-TNC. That will position the antenna away from the metal box, tangle of wires, and miserable location. Something like the antenna base at:

this uses the stock 2dBi antenna. It would be nice if the antenna had some gain to compensate for the coax cable loss. So, a better combination would be: are other combinations.

Share the results instead. How much farther or better can you go with the new antenna?

Or the freeantennas variant, with a chunk of coax:

think this was reported in the thread "EZ10 antenna results" a week ago in this newsgroup.

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

Yeah, I saw that. Very clever. However, I noticed something odd. The sex of the connectors don't make sense. The antenna is probably a common RP-SMA. The right angle connector on the cable can be either SMA or RP-SMA. However, the barrel adapter doesn't make sense. I've never seen an RP-SMA to RP-SMA barrel, and certainly not an RP-SMA to SMA barrel. Looking at the area between the barrel and right angle SMA, there's far too much thread exposed for a proper fit. Something odd about this connector derrangement.

On Tue, 20 Jun 2006 06:08:13 GMT, Jeff Liebermann wrote in :

My own preference would be a USB Wi-Fi adapter, which makes it easy to position the adapter properly without any signal loss. High-end unit:

Assuming the specs aren't fantasy. :) Here's another:

Or Hawking HWU8DD

John Navas hath wroth:

20dBm (sic) of omni gain from a 1ft long antenna? No way. Typical 5dB (sic) antenna found on a standard router? Try about 2dBi and what's a "standard" router? Price is $120. 802.11b only. The claimed 15x range improvement would require an antenna gain of about 23dBi[1]. No way with that small an omni antenna. Price is $170

Price is $62. I ran the numbers previously on the antenna and it apparently really does have 8dBi gain.

The two Dlink antennas I suggested are $44 and $24 respectively. Think cheap.

[1] Range doubles for every 6dB of gain increase. Range gain power gain incr. (dB) (linear) 2x 6 4x 4x 12 16x 8x 18 63x 16x 24 251x 32x 30 1000x

On Tue, 20 Jun 2006 22:20:47 -0700, Jeff Liebermann wrote in :

Perhaps the gain figure is being artificially boosted by amplification (as compared to standard products). FWIW, C.Crane is considered to be a fairly reputable outfit. Still, I'd probably go for the Hawking product.

I have used the "Hawking HAI6SDA Directional 6dBi 2.4GHz Antenna" with good success on a Netgear WG311 PCI card. $20-30.

John Navas hath wroth:

Perhaps the product description is somewhat incoherent? Just about every term in the short product description is misused. 20dBm is probably the transmit power, although it's difficult to deduce from the description. I hadn't seen the term "range booster" applied to a USB wireless client, but I guess someone has to be first in the creativity department.

The concept of a suction cup, stick on window, USB radio with an omni antenna is rather interesting. Similar integrated USB radio/antenna combinations usually use a patch or panel antenna. The idea of putting it in the window is usually to be able to hit a remote access point, where antenna gain is most important. With a directional gain antenna, inside coverage is usually of no interest. However, an omni in the window offers the worst of both worlds. The omni has much less antenna gain for hitting remote access points. Located in the window, it will pickup more interference from the outside, making it a rather odd choice for indoor coverage. In other words, an omni in the window doesn't make much sense.

I will admit that it's a rather clever method of mounting. It's described as "... the best indoor, Mobile or RV WiFi antenna made". Most RV's have window screens which might be metal. I guess this might work in a vehicle if the windows aren't coated with metalized mylar and are fairly vertical. Indoor coverage is a problem because of the outside interference problem, but also because the spacing between the antenna and whatever it's stuck to is insufficient to prevent interaction. For example, sticking it on a metal refrigerator is probably a bad idea unless the spacing is about 1/4 wavelength, making the fridge into an improvised reflector.

The total lack of specs and relatively high price makes me rather suspicious. The device seems to labeled "Fly High" which is probably the product name, not the manufacturers name. I couldn't find anything in the FCC ID data pile, Wi-Fi certifications, or with Google. Looks like they have an exclusive on this one.

I've never bought anything from Bob Crane, but agree that he seems reputable. It's not listed in the current printed catalog or on any of the "new products" web pages. My guess is that this is a very new product, with zero documentation, that was rushed to the web page in great haste. I suspect the description will be fixed and spec supplied after the questions come in from prospective buyers.

Incidentally, the name "SUPER USB WIFI ANTENNA" kinda turns me off. Anything super, amazing, magic, miracle, turbo, enhanced, and ultimate, rarely lives up to the superlative.

I did anlso buy a small magnetic mount with 1 metre coax for it... that puts the antenna ontop of the PC casing.. no idea what the output is..

I believe that the bright boys at CCrane know more about radio than Jeff.

CCrane has exclusives on AM radio design as well, don't they?

Oh, well. It fits with your general disdain for engineers.

Jeff Liebermann wrote in news: snipped-for-privacy@4ax.com:

Pasternack,

, has ALMOST any adapter.

RP-SMA-M -> SMA-F = $17.95 RP-SMA-F -> SMA-M = $26.95

They also have RP-SMA-(F or M) -> RP-SMA-(F or M)

Of course, I'm not too fond of adapters for permanent installations. I'll use adapters all day long on the test bench, but I prefer to make coax's with the correct connectors on each end for everyday use. Especially figuring in the cost of the odd-ball adapters.

Now what did I do wrong? Are you still mad at me because I didn't like your wrinkled aluminum foil and carboard reflector?

Lots of people know more about radio, RF, antennas, and magic than I do. Let me know when they're interested in answering questions in usenet newsgroups.

What might I do to make you happy?

I don't know.

Huh? I are an engineer with a sheepskin signed by Ronny Reagan (when he was governor of Calif). The CCrane product description was not written by an engineer. An engineer would never have invented terms, called a radio an antenna, or misused decibels.

Amazing and y'er right. Thanks.

However, they do NOT have: SMA-F to RP-SMA-F which is what I would guess is the adapter in the photo.

'm still wondering about the large amount of exposed thread on the SMA barrel adapter.

Likewise but only because of cost and aesthetics. One of my favorite demonstations is to take almost every coax adapter I have in my collection and string them in series. I usually do about 4 ft of adapters for the demo. I do cheat a little and not use any UHF adapters. I place a wattmeter at each end of the string. A 440MHz ham xceiver at one end and a dummy load at the other. I then ask the audience to guess the loss through the adapters.

(Spoiler: It's about the same as an equivalent length of LMR-240 and much lower than what the predictions of attenuated disaster found in the books and magazines.)

I sometimes have to reverse the two wattmeters to convince the non-believers.

Jeff Liebermann wrote in news: snipped-for-privacy@4ax.com:

Yes that is correct. And why I purposely didn't write in a price.

My chart says 5.3 dB/100 ft. for LMR 240, so that would calculate out to .212 dB. Even though I never did buy the loss numbers that some people claimed on connectors, that does sound a little low. One bench tech claimed .25 dB per connection, which would mean 1 barrel inline was .5 dB. I'll do a test later on the Network Analyzer if I get some time.

Regards,

DanS

DanS hath wroth:

Yep. I have a 4ft chunk of LMR-240 available for the demo. It has TNC connectors on each end. I use adapter to UHF connectors as found on the wattmeters.

In most cases, I see about about a 10% loss in power for 4ft of adapters, which I guess is more than the equivalent piece of coax. However, it's certainly much less than what one would calculate based on a rule of thumb such as 0.5dB per connector pair (or 0.25dB per connector). With about 60 connectors in line, that would be 15dB of loss, which is obviously not happening.

Unfortunately the accuracy of my Radio Shack wattmeters is not that good. The first time I ran the demo, I had the embarrassing situation of having the output power increase, rather than decrease. I tweaked the guts of the wattmeters until they read the same for a variety of power levels and frequencies. The directional coupler is adjusted by bending a brass shield. Yech. The exact calibration wasn't as important as the consitency.

Another demo that I include is stringing a mess of BNC T connectors together. I think I have about 40 of these in series. One would expect the multiple "stubs" to be rather lossy, but it's only a bit worse than the chain of adapters. The TDR looks awful, but the loss is minimal.

I'm suppose to give another demo sometime later in the year. I plan to try some additional frequencies. I'll see if I can throw together a video clip or some photos.

I think it depends on the connectors. It's been a while since I experimented with odd connectors. That's why I cheated and didn't use UHF, phono, and F connectors. Also nothing with a phenolic insulator, whcih can absorb some moisture. Most of the adapters are N, BNC, TNC, and SMA. I'm also careful not to make drastic changes in diameter, such as from SMA to N, which I suspect (but haven't verified) are slightly more lossy than others. A network analyzer verification would be nice.

They also have the very lowest quality of any RF bits I've ever seen. Probably OK for audio frequencies, if mechanical strength is not required, but using them on 2.4GHz is asking for trouble.