there's probably alot I don't know about wifi antenna's.. I found some good sites how to make.. but wow, some is confusing as hell. And scary part is some things I haven't found a howto for at all.
First case being crimping. To make a long story short, I bought a wifi antenna years ago and made a mistake on connector. Now I have an external wireless if my laptop's builtin cannot connect. IT has rp-sma and I want to crimp a new connector to use it instead of chucking it. I have basic knowledge of crimping and I have a rp-sma being sent to me.. BUT are there extra steps or anything else I should know before doing so? are there any howto/videos to make sure I can follow and have my first attempt work?
second problem I have is if this antenna isn't enough to extend the wifi to my camp trailer (in the yard) should I go with a larger antenna? shorten cable first?.. is a cantenna or yugi worth the money or time making?
what sort of signal loss should I expect from the cable on this antenna? It is a 7db antenna roughly 8 inches tall, the cable itself is "hdf
-100" "50 ohm coax" and is roughly 5-6ft long.. is it advisable to shorten it?
What is "IT"? I'll guess a USB wireless contraption with an RP-SMA connector?
SMA connectors are particularly difficult because they usually use fairly small diameter coax (RG-316/u) or the PTFE version (RG-188/u). The first step is to identify the coax type used by that antenna coax you apparently are about to destroy, so that you can buy the correct matching connector.
What is "this antenna"? Manufacturer, model, and other numbers are usually helpful.
How long is the coax now and how short were you planning on cutting it? Also, what number coax. Attenuation can be rather large for the small diameter coax cables. That's why most external antennas use big fat heavy coax cable (LMR-400) between the antenna and where it enters the room, and then converts to a fairly short length (usually about
12") of smaller diameter coax which is called a "pigtail". The benefit is that it gives you some flexibility so that the big fat heavy and stiff coax doesn't drag your computer off the table.
You're also going to have some entertainment learning how to strip the insulation off the coax without making a mess. The small diamter coax cables are kinda tricky. You can do it with an xacto knife of razor if you're careful. However, if you plan on making a habit of this, get a thermal wire stripper.
Cheapo crimping tools:
Anything is better than the stock rubber ducky. Therefore a can antenna will be a plus over the rubber ducky or built in laptop antenna. Figure on about 8dBi of gain for the typical coffee can antenna, minus coax cable losses. 6dBi will double your range. 12dBi will go 4 times as far. 24dBi will go 8 times as far.
A yagi is just too complexicated to build yourself. There are some cheap ones available:
I personally don't like Yagi antennas and prefer patch, panel, biquad, and dish antennas.
None. The cable does not radiate.
HDF-100 is probably the same as LMR-100 which has an attenuation of about 1.3dB/meter. At 6ft (2m), that's 2.6dB of attenuation. Cutting the coax in half will gain you a range improvement of about 5%. Don't bother cutting it.
The 7dB mystery antenna, that's 8" tall kinda sounds like an omnidirectional rubber ducky antenna. These are not suitable for long range. Look into panel, patch, biquad, yagi, or dish antennas. Favorite vendors:
cable is roughly 6-8ft long now. I was thinking it may help signal to shorten to pigtail size and use a usb extension cable instead. I've so wanted to get a cantenna but I'm worried of screwing it up and scrapping the project. The usb wireless contraption DOES have a rp-sma connector and came with an antenna that looks like this:
I wanted a crimper for a bit. I think I'll get a cheapo for now. I have a coax stripper (rg6) that swivels around the cable but I need to say if I can adjust the diameter, if I cannot than an exacto is good idea
when you say 8dbi gain does that mean from the normal 4db antenna? (cantenna)
thank you for the link to the yugi. thats cheapest I've seen them so maybee that'll be something to try later. How about the wi-fire? Has anybody tried one?
says it'll extend your distance by 1000, and the author of an engadget article said it was pretty good. but didn't compare it to other solutions like yugi, cantenna, bi-directional, etc...
Good idea. USB cables offer no RF loss. The official limit for USB
2.0 is 5 meters, but I've gone furthur without problems. There are also low loss cables, USB hubs, and absurdly long USB extension cables that will work for longer distances. The catch is that the USB device will now be outdoors, and should be protected against the weather.
Do it anyway. There are plenty of plans online. Anything is better than the stock rubber ducky. I prefer something better, but if your requirements are minimal, it should constitute an improvement.
About $25 or less each. Prices are all over the place.
That style of cable stripper will work well for 0.25" diameter cables and larger. The 0.100" dia cable (LMR100, RG316/u) that is used with SMA connectors is too floppy to be stripped that way. I use a thermal stripper:
However, I use rounded stripper blades. If you're going to work with tiny cables, PTFE insulation, or have no luck with a razor blade, this is what you want.
No. The "i" means over an isotropic reference, which is a mythical antenna, with a sperical pattern, and a gain of zero. This is the most common reference found when designing and specifying antennas. There's also dBd, which is dB over a dipole, which has a gain of
My guess is the rubber ducky antenna has a specified gain of 4dBi which is about what you would get with a 7" long colinear antenna. The cantenna might have a gain of about 8dBi. Therefore, your net improvement from the rubber ducky to the cantenna is 4dB. In terms of range improvement, that's about 1.6 times. (6dB is twice, 12dB is 4 times, etc).
The MFJ yagi is junk but can be made to work. A friend used one on a local tower that was in the coastal fog belt. The copper folded dipole driven element corroded through in about 6 months. Replaced it with a $70 panel antenna, which has lasted now about 5 years.
Incidentally, you can sometimes find MFJunk from other vendors cheaper:
The tech specs are lacking. It's just an ordinary USB wi-fi adapter that belches +27dBm (500mw) of xmit power. That's quite a bit of power for a USB device. However, unless it's matched by a similar increase in xmit power at the access point, the added power is worthless. The result of high power is an "alligator" which is an animal with a big mouth and small ears. Everyone can hear this thing transmit, but it can't hear the relatively low power replies. See if you can find the FCC ID number, and look it up on the FCC ID pages to see what's inside.
Baloney. They also don't specify what they're comparing it with that would produce a x1000 increase in range. Let's assume it's a fairly disgusting MiniPCI card, with an insipid internal antenna in a laptop, with an effective radiated power of 10dBm. That's the usual +13dBm xmitter and +2dBi antenna, minus 2dB of coax loss. In order to obtain a 1000x increase in range, the combination of antenna gain and tx power would need to provide a 30dB gain increase. Assuming the same style antenna (based on similar size antenns), the xmitter would need to belch +13dBm + 30dB = 43dBm which is 20 watts of xmit power. I don't think so. I really doubt the USB dongle has a much more gain than the average internal laptop antenna, but if you attach the biggest external dish antenna that's commonly available, which has a gain of +24dBi, the resultant tx power required to get a x1000 range improvement is +13dBm + 30dB -24dBi = +19dBm or about 80mw. That's entirely possible but the antenna is about 3ft across, which doesn't quite fit inside the USB dongle.
The above calcs may seem a bit confusing, but if you read through the technobabble one line at a time, and use an online calculator:
to convert from dBm to milliwatts and back, it should be fairly clear.
thank you for your replies. you seem to know alot of this sort.. or been playing around for some time lol. I guess I'll take a look at my own cantenna. worse case senario is I go through a few cans.
Thank you for the link to the wire stripper. I hadn't looked that up yet, so know now what to look for and didn't waste time with my stripper.
Calculations on ducky to cantenna db seems right.. I wasn't sure which it would start with (eg. laptop antenna, builtin/output usb) so thats cool. it helps in determining what will be needed if things don't work.
Thats exactly what I was thinking. I was disappointed there was no comparison or graphs on signal gain, etc.. And it doesn't make sense that such a small receiver should give you a gain like that when I hear cantenna for eg is only around 2x and so much larger surface area.
I was thinking if I stuck the usb just inside the window, the cable in between and the antenna outside it would help. I have a usb hub that would be ok for now.. but problem is if I moved the pc and that sort.
Note: I only have a vague idea of what you're trying to accomplish and what you have to work with. So far, all we talked about are connectors, yagis, and the usual inflated claims.
If you have a window view available, try a corner or dish reflector with your USB device:
(site down again)
More on cantennas:
mostly its an internet sharing excercise. a test for my aunts who'd be trying to extend around 1km. My setup now is a cantenna (homemade) thats a teeny bit bigger than pringles can. My Attempts are probably pitiful because I'm getting roughly 77dbi/45% signal right now at .10km distance and around 10kbps (distance approximation from a "wardriving" attempt down the road which is mapped in google earth).
Its the first time I could get a connection but I'm rather disappointed atm. I'm currently using vistumbler as a signal tester so maybee I can "dial it in" with a realtime signal check.
thanks for the links again. LOTS of info. Getting a laugh or two at the umbrella antenna. I've been seriously thinking later of using an old satelite dish but yet to figure out what could be water proof and stable but thinking pill bottle that could house the wifi usb and go from there. OH, and I tried - unsuccessfully - the "mesh"/collinder setup but that was more than a failure. maybee its because signals are pill poor?