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Ask Slashdot: DIY 4G Antenna Design For the Holidays?
eldavojohn writes "This holiday season I will return to the land of my childhood. It is flat and desolate with the nearest major city being a three hour car drive away. Although being able to hear the blood pulse through your ears and enjoying the full milky way is nice, I have finally convinced my parents to get "the internet." It's basically a Verizon Jetpack that receives 4G connected to a router. My mom says it works great but she has complained of it cutting in and out. I know where the tower is, this land is so flat and so devoid of light pollution that the tower and all windmills are supernovas on the horizon at night. Usually I use my rooted Galaxy Nexus to read Slashdot, reply to work e-mails, etc. I would like to build an antenna for her 4G device so they can finally enjoy information the way I have. I have access to tons of scrap copper, wood, steel, etc and could probably hit a scrap yard if something else were needed. As a kid, I would build various quad antennas in an attempt to get better radio and TV reception (is the new digital television antenna design any different?) but I have no experience with building 4G antennas. I assume the sizes and lengths would be much different? After shopping around any 4G antenna costs way too much money. So, Slashdot, do you have any resources, suggestions, books, ideas or otherwise about building something to connect to a Jetpack antenna port? I've got a Masters of Science but it's in Computer Science so if you do explain complicated circuits it helps to explain it like I'm five. I've used baluns before in antenna design but after pulling up unidirectional and reflector antenna designs, I realize I might be in a little over my head. Is there an industry standard book on building antennas for any spectrum?"
Something like this costs 30$
http://www.wpsantennas.com/700MHZ-LTE-4G-Antennas.aspx
Ebay has things for 20-25$
Did you look at these options before deciding to building your own?
My Aurora : http://www.youtube.com/watch?v=o91ZsGwJYyg
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Start with ARRL (http://www.arrl.org/)
Antenna Handbook: http://www.amazon.com/dp/087259694X/
*The* Handbook: www.amazon.com/dp/087259419X/
As the Jetpack is so small, could you mount it inside a parabolic dish - i.e. WOKtenna?
See: http://www.usbwifi.orconhosting.net.nz/
At the higher frequencies like 1.3GHz (LTE), the wavelengths are so small that the corresponding antenna features are also very small. They have to be extremely precise if you want the gain to actually be at the right frequency, and even then it usually takes some trial and error. Do you have a chemical or laser PCB etching machine, and a cellular antenna analyzer (Saw one SUPER cheap on ebay for $300 once). Otherwise, just making random things could result in reflections damaging your transmitter. This isn't like putting together a 1/4-wave dipole on 2 meters.
But you could try fashioning a parabolic reflector dish and put your existing antenna in the center of it. I've heard of people doing that with cell phones and wi-fi adapters before.
How about posting some pictures of the milky way? I've only barely seen it once while on Hilton Head island.
http://www.dslreports.com/forum/r27484816-DIY-3G-4G-LTE-Yagi
http://bcbj.org/antennae/lte_yagi_diy.htm
Something like this costs 30$ http://www.wpsantennas.com/700MHZ-LTE-4G-Antennas.aspx
Ebay has things for 20-25$ Did you look at these options before deciding to building your own?
If you're telling me that works and that's the best I can do, then okay, you've got it figured out and I just don't understand antennas at all.
Like I said, I googled and looked for costs. The models that I see on your link that are $30 are 7.72” in length and look like the same things that come with any wireless router. I assume the Verizon Jetpack already has an antenna of this quality. What I was hoping for by asking Slashdot was that someone would belittle me and tell me how to build something more like this but without the $120 price tag since it's probably just a bunch of metal configured a certain way connected to a balun connected to the device. I know where the cell tower is from my parent's house, I just don't know how to construct something that will function better than the little device they have.
Also, I was kind of hoping that there were really cool designs people knew of that consisted more than just "a big stick of metal you point at the tower." However, like I admitted in the submission, I don't know jack shit about antennas.
My work here is dung.
From my limited knowledge of physics, it sounds like a custom-built cantenna waveguide would be perfect for you, although I can't help you with the design - the length and diameter of the can and the positioning and protrusion depth of the tranceiver element need to be calculated depending on the frequency of the signal you're trying to pick up. I imagine there are formulae or even online calculators for this stuff online, so if you can find those you may only need to find out the frequency band you're trying to select to get the design calculated. Then it's a matter of making it precisely enough.
http://bcbj.org/antennae/lte_yagi_diy.htm
Decent instructions for an LTE yagi.
something more like this but without the $120 price tag
It seems to me that if it works, it would be $120 well spent. It would improve your parents' internet connection, which is your main goal, right? It would also require a minimal time investment on your behalf, which should also be a goal for you as you did not mention making frequent visits there. Third, if something goes wrong you have a manufacturer and a vendor to talk to - rather than having to rebuild the damned thing on your own.
One way to look at this is that if you visit once per year (you do see your parents once a year, right?) this will cost you only $10 per month. That is nothing. Besides, if you're three hours from the closest town, what are the chances you'll be able to get anything useful for building / repairing an antenna when you're out there? You seem to be about to start yourself on a project with very low probability of success for no apparent reason.
Buy the antenna and then spend your time building them a home file server to back up their important documents instead. Much better use of time and more tangible results.
Damn_registrars has no butt-hole. Damn_registrars has no use for a butt-hole.
scrap the tons of copper and steel you have, then buy an antenna.
If you get a USB adaptor for your 4G signal, and stick it outside on a long pole nice and high up plugged into a USB extension cable it'll work just fine. Remember to tape the whole thing up with self-amalgamating tape (not lx tape) to keep the water out, and leave a drip loop where you bring the cable into the building.
It's the simplest thing that could work.
LTE doesn't really mean anything for an antenna designer. It's all about modulation type, rate and protocol. What matters for antenna design is center frequency and to some extent bandwidth.
In North America, there are several LTE bands in use: 700/800, 1700/1900 and 2500 MHz. If you can, find out what bands Verizon uses in your area.
Don't buy a cheap 2dBi antenna. The antenna in the module is probably around 0dBi already so it won't help much. What you want is a directional antenna you can point at the tower to get a big improvement. The good news: this IS something you can build yourself. If you need to cover all three bands, you'll might need a log-periodic. If it's one frequency you can build a Yagi and it will do better than the log-periodic.
Books for antenna design for amateurs:
AARL Antenna Book
AARL Wire Antenna Classics
There are more books that are written at various levels. I suggest the AARL books because they assume you have some technical knowledge but aren't necessarily an electrical/electronics engineer. You can also find free designs on-line for antennas made by radio amateurs. These are often very helpful and tell you exactly how to build their antennas and show you pictures. Some engineering and science libraries will let the public come in and peruse their books. If so, you can go there with a pad and pencil and design your antenna right in the library.
Since your antenna will be bidirectional (same antenna for up and downlink) you will need to use low-loss cable to connect them up. This is very important because if you use the wrong cable or too long a cable, you may overcome the gain of the antenna! That's another reason to build a high-gain antenna.
Pointing a high-gain antenna at the tower also gets your RF out of the house where it's less likely to interfere with other stuff that might be in your house, like phones.
To answer your question about digital TV antennas:
Despite the marketing implications, there really is nothing different about antennas for Digital TV. The encoding is not important. The frequency is the main factor and that has not changed substantially. Most digital TV stations are on the UHF band around where I live. So, if you are lucky, you can get by with just a simple UHF antenna if the stations are nearby.
Here is where you can find your nearby stations:
http://transition.fcc.gov/mb/engineering/maps/#
I built a simple 4 bay bow tie antenna for UHF. Mine looks like the one pictured at the top of this thread.
http://www.city-data.com/forum/consumer-electronics/614073-how-build-your-own-4-bay.html
Here is a really nice example of one:
http://www.dtvusaforum.com/dtv-hdtv-reception-antenna-discussion/8629-kosmic-antennas-superquad-4-bay-bowtie.html
I also built a folded dipole for VHF: Here is an example:
http://crdahl.com/antennas/dipole.html
My stations were fairly close by. These two antennas are not high gain antennas. I added a Winegard preampt to bring up the signal a bit. I have been very pleased. So, in summary, there is nothing different. Just look up your local stations and pick an antenna based on band(s) and distance.
Another thought comes to mind. . . what is the cause of the interruptions the parental units are experiencing with the set-up they already have?
How far is it to the tower? what is the noise floor like between the tower and their house? [What happens at your neighbors house that may interrupt the signal gettting to your parents house?] Are they enjoying any other wireless-frequency obtained signals, like satellite? Do any of your neighbors enjoy broadcasting CB or single side band radio? Around their antenna in the home, are there any other electronics radiating interference, like wireless dvd or bluetooth, for instance? Do their interruptions happen at certain times of the day (you can ascertain what other activities happen at that time of day that may be causing interference)? Do mom & pop have metal implanted in their bodies which may be bouncing the signals coming in? If they are receiving their signal to the house, wirelessly, and then also they are wireless between their router and the device they use to get information, that presents multiple points of potential failure. Is the placement of the router in the house near a window that faces the direction of the tower? Are they then on the other side of the house away from where the router is placed? Would a signal booster work on the side of the house where the user is located? cjacobs001
To be honest, there's a time an place for homemade equipment, and this isn't it. You've admitted this isn't your area of expertise. Neither is it your parents'. If it breaks, what are you going to do? The idea of using a a Pringle's can is absurd. Get a strong, professionally built antenna and mount.
Some things to think about: the higher gain of a highly directional antenna comes from focusing the energy more tightly than a lower-gain directional antenna. The more directional an antenna is, the more precision and accuracy must be used in aiming it. It will also, presumable, but outside in the elements, with wind, rain, snow, animals, and sunlight. All of these can degrade the antenna or interfere with its aiming. Therefore, a very strong mount must be used when using a high-gain antenna.
My suggestion is to go to your parents' house well prepared, with antennas of differing gain. Use the one with the lowest gain which gives a moderately strong signal. For instance, if 5 bars means the strongest possible signal, use the antenna that gets your 4 bars. The antenna which gives you 5 bars is most likely providing unneeded signal strength, at the cost of requiring better aiming. This doesn't mean you should use the antenna that provides one or two bars, however, because the extra signal strength might be needed during strong rain or snow. you should also go prepared with a proper knowledge of antenna installation, including lighting protection and grounding, use of a drip loop, know the signal loss of the cable you are using, etc. You should already have calculated the path loss from the cell site to your parents' house, and know the receive sensitivity and transmit power of the cell site and the 4G device for your parents' house. You can then figure out if this is in the realm of possibility. When you go to do the installation on site, bring spares, the proper tools, some general tools, gloves, clothing appropriate to the task, safety gear, and make sure that you have health insurance coverage.
It's easy to do a bad job of antenna installation. Sometimes you get lucky, and it will be sufficient -for a while. But then it will fail and you're up a creek without a paddle. Spend the money and do it right, or hire a professional to do it. These are your parents, after all, you don't want to disappoint them.