Anyone know how to build a Cell Phone Repeater or Booster for a tower?
I'd like an economical way (if that's possible) to build a cell phone repeater or booster that can work for multiple cell phones, and be mounted on top of a tree or some other tower or pole. (Boosting signals here is legal). The reason I'd like to do this is because we use a cabin that's located deep in the forest and currently cell phone signals are spotty. (Move down the road 100 feet or stand on a stump and it works, but not where you really need it to). My concern is for safety as many of my family members use this area, and if there were ever a problem, I'd like to know that we could get a call out for help.
I've done quite a bit of searching on this already, and have found several methods to improve the cell phone antenna, or the coffee can method, but what I'd really like is something that can work for ALL of our cell phones (that are with different cell carriers), and therefore (as I understand it), can be on different frequencies. The only thing I could find were devices that were out of the box ready and at a hefty price.
Does anyone have any advice? or can point me in the right direction in order to build something like this that will work?
Thanks, canucksgirl
Edit: Let me clarify that the intended purpose isn't to be able to contact 'emergency services' from camp. We're a few hours from the nearest town and it isn't conducive to 'sit and wait' for help to arrive. Our group has been extremely safe, competent and self sufficient in that area for more than 30 years. Without getting too personal, we have an "in town" family member with a serious illness. If there were ever a reason, we'd like to be able to reach family at the camp to let them know that they needed to return home.
I've done quite a bit of searching on this already, and have found several methods to improve the cell phone antenna, or the coffee can method, but what I'd really like is something that can work for ALL of our cell phones (that are with different cell carriers), and therefore (as I understand it), can be on different frequencies. The only thing I could find were devices that were out of the box ready and at a hefty price.
Does anyone have any advice? or can point me in the right direction in order to build something like this that will work?
Thanks, canucksgirl
Edit: Let me clarify that the intended purpose isn't to be able to contact 'emergency services' from camp. We're a few hours from the nearest town and it isn't conducive to 'sit and wait' for help to arrive. Our group has been extremely safe, competent and self sufficient in that area for more than 30 years. Without getting too personal, we have an "in town" family member with a serious illness. If there were ever a reason, we'd like to be able to reach family at the camp to let them know that they needed to return home.
Visit Our Store »
Go Pro Today »
Steve
http://cell-phone-booster-review.toptenreviews.com/wilson-electronics-mobilepro-review.html
This one has the adapter for USB, AC or lighter adapter:
http://www.futureshop.ca/en-CA/product/wilson-wilson-cellphone-signal-booster-wi801242-wi801242/10122403.aspx?path=33a0b79ddf9fb53a8a5e3666b9a8a38fen02&SearchPageIndex=1
You might not get fantasic range but as long as your phone is close to the base (might have to leave the phone near the signal booster and use speaker phone)
http://en.wikipedia.org/wiki/Femtocell
Recently there was a prize offered in the Instructables Extreme Challenge, called "Spot Connect". Unfortunately, I didn't come up with a winning extreme project, but I had my eye on that prize specifically for the reason I'm asking about.
I just ran across something that might be of interest to you. It does require an internet connection to work but if you don't already have that you could get a satellite connection like "Wild Blue".
No It is not voice over IP, its something different that the cell phone company is using to relay cell signals and rebroadcast them at a local point using the interent as the transmission medium. I didn't know anything like this was even out there.
It's on sale too, I get their sale e mail notices and saw it for that reason.
Here is a comment I copied from Amazon, they also sell them.
Verizon Network extender-Awesome July 8, 2011
By Wen2buy
I live in a "blackout" are were there is no cell phone service. (Let me repeat that..No cell service at all)
I purchased the Verizon Samsung Network Extender for my house and my Mom's apartment building. We get full bars within a two house radius. Never drops a call, works with our texting too. It's as if we were standing next to a cell phone tower. You can set priority callers so the tower can be shared with the neighbors (if you wish)but your phone will override everyone else. It states that it can only do 3 calls at once, but we have never had any issues with this. If you live in an area with weak or no service this is for you. I have had my extender for 2 years now and still love it! We have had a few purchased through the town now and everyone loves them. Works great for repair men and emergency people too... I can't say enough about this product. Verizon sells it for $249 but it is much cheaper on Amazon..Oh most important part...you never have to pay another thing for it. No monthly fees, just the original charge for the equipment thats it (plus you must have internet service, This works so well because it is hooked up to your internet. So internet is an actual cost, but nothing to run the extender). Great present that keeps giving too. Got one for my Brother, so now everytime they use the phone they think of how cool I am!
To pick a frequency to design for, take a poll of the phones there and see where they transmit. If they are close enough, use the mean/average. If they are spread out to far, you may need to build more than 1 antenna size for the group. Another thing to think about is if the signals are differently polarized. Some may be vertical and the others may be horizontal. If that is the case, you'll need another antenna set that follows the polarization.
All I can say is that may be your least expensive proposition. It should work, but it may not be enough. Only a competent engineer that has done a thorough assement of the site and it's requirements can truely say what would be the best course of action.
Maybe you guys should set up a shortwave / ham shack. They can reach a heck of a lot farther than cell phones, and there are protocols for emergency phone connections. Just a thought.
Qa
From what you described for 'many mountain area towns' is precisely the configuration of the 2 towers located at a neighboring town about 30 kilometers (or 18 miles) directly North of our camp. There is also another tower about 45 kilometers (or 27 miles) to the South-East, and based on our South-East mountain location, I assume we're accessing that tower versus the ones to the North.
I've already determined that all our carriers have access to the North and South-East towers, which use the frequency band GSM 850 (824.2 - 849.0 Uplink | 869.2 - 894.0 Downlink). I know that we need our antenna length calculated to work that band (so I will definitely check out the link you gave for the calculator).
I'm not entirely understanding the concept of the different polarities (and more so how that factors in), so if you could point me to some literature, I would appreciate it. (The first 2 articles I read left me more confused then informed).
I also appreciate the suggestion for the shortwave, but it isn't right for our situation. If I need to contact my family who is at the camp, while I'm at home, there is about a 600 kilometer (or say, 360 mile) distance between us.
Thanks again for your help. ;)
Looking back at that thread, it seems that the calculator I pointed to, N3DNO's 3 element yagi calculator, is inaccessible. Going back through the same site, I found W4HN's antenna calculator, which has 3 of the most common types: Dipole, Yagi, and vertical. The one you should be most interested in is the Yagi. The simplest way to explain one is this:
There are a minimum of 3 elements: Director, Driven, and Reflector.The Director is just that, an element that is in front and helps direct the radio wave to the driven element. It is shorter than the driven element. The Driven element is actually 2 elements placed so that they look like 1 single element. It is the 2 close ends of these driven elements that you actually attach the feed wires. The Driven element is between the Director and the Reflector. The Reflector is behind the driven element and is longer than the combined length of the driven elements and the gap between them. It's job is to "reflect" some of the radio waves that go past the driven elements.
The frequency you are trying to optimize for sets the size and spacing of all elements.If you avg. the upload, you get 836.6, download, you get 881.6, and the avg. of both is 859.1. The driven element sizes will be, in ascending order, 3-13/16", 3-5/16", and 3-1/4". As the frequency goes up, the wavelength is shorter, so the elements are shorter. I'd try for the 3-5/16" driven elements (don't forget you need 2) to start. Use the calculator link above to get the rest of the measurements. Make 2 antennae exactly the same and connect them together with some cable. Check out SkyScan to see how to put it all together, substituting your dimensions. Now pick a tree or other tall object that has a good view of the tower you want to point toward. Mount 1 antenna there and mount the 2nd one pointing toward a spot where you want to be to use your phone. Totally passive, and since the yagi has at least 3dB gain, it should help get your signal out there. These should be able to be built and installed in a day for dirt cheap.
Polarization means that the radio wave travels in either a horizontal way, like a wave on top of a pond, or veritcally, as if that same wave was turned on it's side. If you don't get good results with the antennae in a horizontal/flat position, spin them 90 degrees on their axis and see if that helps.
Now, on the 2nd page of the link in my original post above, isa link to another reflector type of antenna. It may be worth looking into. As for other good info, the ARRL is one of the best. See what you can find there.
Hope this helps.
Qa
I'm going to go through all the links and start making some notes and plans. I hope you don't mind some follow up questions (if I run into trouble). ;)
Qa
As to your cell phone not having an external antenna... it is possible to find the internal antenna on a cell phone's PCB, but you may not be able to get a good connection to it. "It all depends" is all I can say about that. IF you can get a physical connection, that is the best way to go as there is very little loss. Almost all of the signal goes to and from the external antenna. All other ways have greater losses. Some, like the commercial "boosters" try to make up for that with bi-directional amplifiers. If you cannot get a direct connection, the redirection and focusing of the cell phone's signal would be the next step (as above). If that doesn't work (well enough), then a commercial solution might be necessary. Like I stated above, it should only cost a few dollars to build a pair of antennae and maybe $20 more to get the correct connectors and cabling.
I like the idea of having something that is self-contained, passive, and useable to more than 1 phone at a time. That is my line of thinking. Maybe a search of your phone model and external antenna together can unearth someone's success, or failure, at that modification.
Keep the dialog going...
Qa
I took a look at the SkyScan link you gave and they mention a "ladder line", (but the link doesn't go to the specific product). They say its suppose to be available at ham radio shops... Do you happen to know what ladder line is? I'm not sure where the heck we might have a "ham radio shop" around here (in the Vancouver, B.C. area).
From what I've looked at so far, I'm going to have to sketch out the plans and make the actual construction at my parents house. We're planning a trip there in the next week or so, which is a good thing as my dad has all the necessary tools and room to work in. I'll just have to get the cable and other material (minus the lumber) here.
I'll let you know as soon as I've made some progress. ;)
Build info:
Get several feet of 12 Ga house wire - the solid copper stuff. Strip the outer cover off and separate the wires, leaving their insulation on. Use one color for the Director and the Reflector. Use the second color (if there are only 2 wires inside) for the Driven element. Make that wire 2 times the total length plus a couple extra inches. Mark the center of that wire and then measure out the 3-5/16" on each side and bend the wire back on itself. Where the ends overlap each other, bend them out at 90 degrees, strip off some insulation and form some loops on the end to allow a nut and bolt to attach to the Balun leads.
How you attach the elements to the main boom is up to you, but since they are so small, they would be quite stiff all by themselves. You may only need a 1" square piece of wood about 8" long. A couple of staple "nails" could hold each element on the boom. The mount is your design to suit your particular situation.
If you want to use RG59 cable or similar, you can try to find a couple of those old cable tv adapters (300 ohm to 75 ohm) that they used in the old days to hook up the boxes to the antenna input. The upper channels were in the specified range. Or, if the run is really short, a couple of feet or 10 ;) , you can hook the antennae together with twisted pair. At least 18 Ga should do. If you can't find twisted pair, you can make your own. Just get solid core wire, pair it up and secure 1 end in a vise. Put the other end in a drill and start twisting. Twist it tight, but not so tight you cannot bend it. Take out of their respective holds and make loops on the ends like the ones on the driven element. Bolt together and seal up the ends. Good as gold.
Any more questions, just ask.
Qa
I intend to sit down and work on this over the weekend when I can really spend the time to get my head around this project, and to understand the parts I'm still trying to learn.
In the mean time, I was given this link, and I thought I'd share it with you. Perhaps you can tell me whether or not I should bother using the site as a source of info. (When you're learning, it's hard to tell if a website is giving you good information or not).
http://www.k7mem.150m.com/Electronic_Notebook/antennas/yagi_vhf_quick.html
If this actually works out for you, maybe your group can make more and "blanket" the camp. Or, you can do as the Amish do, keep the phone "out in the shed" (use one narrow spot for all calls - a communal thing).
Here's to the challenge!
Qa
Clearly there is much to learn...
Design Frequency - the radio wavelength you are designing for expressed in the number of cycles per second (Hz = Hertz) - MHz = Mega Hertz = Million Hertz.
Forward Gain - The amount of gain, or perceived amplification (in this case due to the focusing of the passing radio waves) shown at the active or driven element as compared to a standard Dipole antenna, expressed in dBd, deciBel dipole. Wikipedia, second listing under Antenna Measurements. More is better - to a point. 12 dBd is a pretty good antenna gain to start with.
Reflector Spacing - You can chose from DL6WU or ARRL. The first one is named after the call sign of a German radio operator, Gunther Hoch, who did extensive testing to come up with universal antenna design parameters to match to a 50 ohm cable "without the need for adjustment" (see link above). The second is the American Radio Relay League's design criteria for antennas. The ARRL is the premier radio information source and licensing body in the northwest hemisphere with approximately 100 years of service/experience. If ever in doubt about something radio related, check here.
Director Element Spacing - See Reflector Spacing.
Boom Type (mounting) - You will most likely be using either PVC pipe or some sort of wood, so use non-metallic. If you want to get into metal booms like the big manufacturers use, look up the difference. I won't get into that.
Boom Diameter - You will see some text below this that tells you what the maximum diameter "could be", but if you use rectangular x-section wood, try to make the skinny mounting side (where the elements sit) this width.
Boom Correction - This changes with the boom type. Just accept what comes up.
Driven Element and Parasitic Element diameters - The short paragraph to the right gives you the minimum and maximum suggested sizes for these elements. Measure the diameter of the material you have and enter it in the boxes.
If you enter a numeric designator in certain boxes that are outside the recommended design parameters, it will let you know.
You could spend a lot of time reading up / studying about the design of specific antennae, but you really don't have to do all that. These "hams", as they are called, have taken the time to do just that and they take pride in their ability to do such design work.
Qa
BTW, just wanted to point out that the driven element in a YAGI is actually a DiPole antenna. What makes the YAGI work so much better is all the extra elements that channel the RF (radio frequency / radio wave) energy to that DiPole. Thus, the YAGI is a directional antenna that works best when pointed directly at the chosen transmission tower / radio "station". In this case, it is the cell tower you want to pick up.
Oh, and previously when I said yard sale search for a TV antenna, I meant a set-top antenna "bunny ears" type. The kind that has the flat cable with the open spade lugs on the ends. That is the 300 ohm type. If you aren't sure about that, ask your father. He'll be able to tell you about it.
I'll be in touch, as soon as I figure out what materials I can get.
(oh btw, if there was any doubt, you'll be getting the best answer. I didn't want to mark it yet, because we lose the "reply" button).
Anyway, here's a rough concept of what I see as a possible build with mounting to a tree. Note that this is only for 1 of the 2 needed antennae, no need to be redundant. Feel free to use as much or as little as you want.
The boom can be either wood (something that can stand the weather and not warp) or some sort of PVC pipe or even fiberglass rod / rectangular stock. Whatever you can get. I still think that 12 Ga solid copper wire is a good element material, but that is just me. Cheap too, if you get a small roll of 2 or 3 conductor Romex at the big box home store.
Here's to a fruitful build.
Qa
Anyways, I got to it again, and drew out the plans (1:4 scale) to get a sense of how this will work, and expectedly, I have some questions.
Here's a link to view the plans I drew out, including all the specs.
I had some confusion when measuring the cumulative spacing. You'd think it would be straight forward, but I couldn't find the answers I needed.
1. Most Yagi Antennas show the Reflector a few inches off the end of the boom, but the plans that I got (from the website link I posted), indicates the reflector is at 0. So do I conclude that the reflector sits directly on the end of the boom? (One site I visited, the guy said to measure 10 inches from the end of his 6 element Yagi to position the reflector, but I couldn't get any reference to how this measurement is generated, and how that effects Yagi's with a different number of elements).
2. The driven element and the directors: Are they also measured directly off the end of the boom (from the back where the reflector is)? And if so, should the elements be placed "on center" to that measurement, OR, should the element be placed off this measurement?
I hope that my questions don't sound incredibly uneducated, but I spent quite a bit of time trying to find the answers, but couldn't find anything helpful. So, you'll have to excuse me if I seem like a student asking the teacher to checkover my homework. ;-)
I tried to get back to that site you used, but it seems to have disappeared. From what I remember, everything should be just about right. The only thing I would have any reservation about is the choice of diameter for the boom. 1/2" might be a bit small and deflect too much. Maybe something a bit larger for more rigidity.
Your points:
1.) Since you are using a non-conductive boom, it really doesn't matter about the "overhang". You probably should have a little bit of extra boom on each end just for ease of element mounting. The dimension of "0" for the reflector means that all other elements are in relation to "it". So, since measurements are usually center to center, take all subsequent cumulative measurements from the centerline of the reflector rod to the center of the respective element. For total boom length, use the longest cumulative dimension, 36-7/8", add a couple extra inches/cm and split the difference for each end.
2.) See #1.
No need to feel that way. I always remember what one of my teachers said (oh so long ago): "The only stupid question is the one not asked."
Qa
So, I just checked the link, and you're correct, the site's gone! I'm so glad that I did all the calculations and (even took screenshots), so I should be okay, as long as I stick to the same formula.
Thanks for the clarification. I assumed the measurements should be on center, but I couldn't find anything that said either way. Since I'm using a non-metallic boom, and can add some length to either end and mark the element spacing off the reflector, does that also mean that changing the diameter to something larger than 1/2" conduit be okay? I didn't try the calculator with anything other than a non-metallic 1/2" boom, so I don't know if the measurements would change; do you know if they would?
The only last part that I'm unsure of is the positioning of the dual yagi's. If one is pointed toward the tower and another on a slant toward the camp, is that all I would need to do?
No rush on getting back to me. I do want to do this soon, but I don't want you to go out of your way when you may have other things to do. - You've been a fantastic help! ;-)
Hope it all goes well,
Qa
Thanks again, for all your help!
If it's for the health and safety of my family I would not depend on a DIY solution for this problem. I'll change my own brake pads but would not design my own braking system.