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Forum Index : Electronics : Aerial pursuits
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Gizmo Admin Group  Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
A few months ago I signed up for internet at my new residence. At the time I had no land line, and even if I did, I was too far from the exchange to get ADSL, so mobile internet was my only real option. Ended up with a little rebadged Sierrra AC760S. It's a 3G/4G wireless hot spot device. I'm in a very poor mobile reception area, my mobile phone only works in a few places around the house, so I wasnt't expecting much better for my internet hotspot, not with its standard internal aerial anyway. The AC760S does have some basic screens, and signal strength indicator, but I soon discovered this has little to do with actual internet speed. By relocating the 760 around the house, I could get up to 4 bars of 3G signal, but my internet speed was very poor. Here's the 760 hanging on a wall, the best location for it. 
I used http://www.speedtest.net to measure my internet speed, and the best I could get was about 400kBs. 400kBs is OK for checking mail, light intenet surfing, etc, but I knew I could do better. A few years ago I had a similar set up at my last home, built a 3G Yagi aerial, see http://www.thebackshed.com/forum/forum_posts.asp?TID=1992&PN =16, which gave a vast improvement in internet speed. Unfortunately, it looks like I've lost the Yagi somewhere between there and here, so I had to look into building another, or trying something different. After reading a few forums ( http://whirlpool.net.au/wiki/nextg_3g_satellite_dish_antenna ) where members used old satelite dishes to improve their 3G service, I decided to give that a go. I purchased a small dish from the local recycling centre for $15, and mounted a dipole at its focal center, then started testing. 
I have 3 mobile towers I can use, Oakey and Pittsworth are about 15km away, in opposite directions, and behind hills. Dalby is about 50km away, with no hills in the way. Using a map I worked out the direction to point the dish, and then using speedtest.net, fine tuned the direction until I got the best internet speed. Speed was best with Dalby, and I could download at around 4 to 5 MBs, about 10 times faster than before. Oakey and Pittsworth would give about 3 MBs. With the dish my internet speed was now very good, I could stream youtube videos and use remote desktop on my clients computers, so I thought that was the end of the project. But I was soon having problems with the internet dropping out. It would be fine for hours or days, but then die. Dissconnecting and reconnecting the 760 didn't help, the only solution was to turn the dish to another of the 3 towers, reconnecting, and it would be working again. It got to the point where the only way to have reliable, if slow, internet was to dissconnect the dish, and use the 760's internal aerial. I guessed it has something to do with the dishes directional width. A few degrees one way or the other would kill the signal, and maybe the terain between me and the towers was having an effect. Plus if a tower is having "technical" problems, the dish meant the 760 couldn't switch to another tower, since it was focused on one tower only. The fact the 760 could work reliably with no dish meant it could pick and choose which tower to use. So I needed to abandon the satelite dish and use a unidirectional aerial, something I could make myself. More interent research found lots of unidirectional aerial types, but the one that caught my attention was the Collinear aerial. http://www.rason.org/Projects/collant/collant.htm http://wireless.gumph.org/articles/homemadeomni.html The plans I found were for the 2.4GHz wireless band, so I modified the dimensions to suit the 850MHz band of Telstra's 3G network. I built a 8 element type, and it ended up about 1.1 meters long. The finished aerial is pretty flimsy, so I slid it into a piece of 15mm conduit, and held it in place with a couple of cable ties. Finally I added a string loop at the top so I could hang it off the wall of my house. 
Performance if pretty darn good. I have a 3 to 4 MBs download speed now, and its proven reliable. Now if I could only plug my mobile phone into it 
Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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Tinker Guru  Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
Which one did you build Glenn, the coax or the copper wire version? You should be able to build one for your mobile phone too, I'm sure it would be better than those commercial long range mobile antenna's of which I keep one in my car in case the phone is to be used in a marginal location. Klaus |
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BobD Guru Joined: 07/12/2011 Location: AustraliaPosts: 935 |
This can couple a mobile phone to an antenna http://www.jaycar.com.au/productView.asp?ID=AR3316 Not sure how practical it is though. Use a smaller antenna like this one http://www.jaycar.com.au/productView.asp?ID=AR3313 I think you can get all this stuff on eBay too. |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
It's the coax version Klaus. My mobile is a old iPhone 3GS, no external aerial socket so would need an adapter like the one BobD suggested. But then its no longer very "mobile", and I think I would be better off with a new mobile phone, somethng that works better in poor signal area's. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
Just realised one of the links I put in that post pointed to a copper wire type Klaus asked about. Changed it to the correct link.... http://wireless.gumph.org/articles/homemadeomni.html Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| BobD Guru Joined: 07/12/2011 Location: AustraliaPosts: 935 |
If you are on Telstra then get a Blue Tick certified phone. It is an indicator of better performance in marginal conditions. |
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yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
This is mine, I have no phone signal at all at ground level. Whip antenna is mobile phone, yagi is internet. I have no bars of signal on my modem (-94 dBm) but the low noise gets me 80 - 270 KiloBytes of data depending on the day, roughly 55 Km to the tower, no latency, no dropouts. I have done some trials with a commercial modem/gateway it was rock solid 500kByte+ speed at 85 Km, where I could not get a Telstra gateway to even handshake with the tower. Yes, there is a catch, $1500
The little telstra 21M usb modem that most people have is quite deaf, fitting an antenna to one of these will boost the performance out of sight!, they need maximum signal (5 bars)to work well. Hope this helps someone Yahoo I'm confused, no wait... maybe I'm not... |
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| Warpspeed Guru Joined: 09/08/2007 Location: AustraliaPosts: 4406 |
Glenn, one type of omni antenna that is very easy to make and non frequency critical might be the "discone" type. http://www.northcountryradio.com/Articles/discfig2.htm It is also possible to improve the performance of a discone in specific directions by fitting one or more reflectors behind the antenna to "beam" the antenna in one or more preferred directions. Cheers, Tony. |
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| domwild Guru Joined: 16/12/2005 Location: AustraliaPosts: 873 |
Glenn, If the Yagi did not work and the sat dish did not work as they are both directional, then a "WOK" antenna will also not work. The wok serves as the parabolic. It looks like it is difficult to get a new NextG phone with an antenna jack. What I am using is an older Samsung A411, Telstra T100 and a later Coles $49 smartphone LG (model no. not handy, 490?). The LG phone has an antenna connection which is blanked off; why I ask you? One has to drill a hole into the back cover and then scratch off a plastic cover to get to the antenna jack. You also need to buy a connecting cable to fit the antenna jack; a tail. Sorry, me no can help! Taxation as a means of achieving prosperity is like a man standing inside a bucket trying to lift himself up. Winston Churchill |
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| Gizmo Admin Group Joined: 05/06/2004 Location: AustraliaPosts: 5078 |
I had to look up WOK antenna to work out what you were talking about. Now I get it, using a wok as the reflector  http://en.wikipedia.org/wiki/WokFi
Thats right, any directional aerial was not suitable where I currently live, as I have 3 towers in different directions that I need to access to get reliable internet. My house in Mackay was different, I had a hill behind me, and could see Mackay in the distance, so by pointing the Yagi at Mackay, about 20km away, I was aiming at a dozen or more towers. Good tip about the mobile phone, and yeah I agree, all mobile phones should have an external aerial, like a slide in/out afair, or a jack. Its especially hard to find a smart phone, which I need, that comes with an aerial jack. There are a couple of "blue tick" smart phones on the market, iPhone isn't one of them. Glenn The best time to plant a tree was twenty years ago, the second best time is right now. JAQ |
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| yahoo2 Guru Joined: 05/04/2011 Location: AustraliaPosts: 1166 |
Glenn, I think your original problem with the dish is not just signal, but a software glitch. Some towers will periodically shed a percentage of the live connections and make them re-handshake to shift some of the load to other towers. Some modems (and phones) will freeze and not reconnect if it does not see an alternative tower. If you can restrict the modem to Telstra's country network by blocking 3telstra or setting it as a non preferred connection and setting it to manually select the 850 Mhz Freq, it will usually keep polling till it re-hooks and not just give up. Having said all that, throwing the modem in the bin and installing one that does work is still the best solution. I'm confused, no wait... maybe I'm not... |
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| Tinker Guru Joined: 07/11/2007 Location: AustraliaPosts: 1904 |
Hey Gizmo, this design works very well as a TV antenna too  .
I needed an omnidirectional TV antenna, to be used on my boat while at anchor so anything directional is a waste of time. The TV is viewed on my laptop using one of these cheap USB dongle things. Mine came with a tiny telescopic antenna and works well enough for SBS but nothing else. I had experimented with two dipoles at 90 degrees - made from telescopic radio antenna's as the lot has to be stowable in the cabin when underway. This still was too directional but better than just a single dipole. The Collinear antenna is much better. I just tested it inside my house leaning vertically against the wall and it received almost all the TV and music channels, certainly CH2 which I watch most. To keep it short I used only 4 segments, cut for 200Mhz from RG213 coax. This made it just over 2m long, its in a plastic conduit and I can stow it easily enough in the boat cabin. I made the top 1/4 wave section from the tiny telescopic original antenna which happens to be just about the right length. This part unscrews for stowage. Thanks for posting your antenna and giving me ideas. Klaus |
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