getting better 3G connection. - Page 1
Forum section: electronics / projects

author: Unordung
author_rank: Contributor
timestamp: November 25, 2021, 04:44:17 am
content: Hi folks,I have an interesting issue that I was hoping someone could assist with.I work for a company which has devices all around the country and are used as roadside furniture (not armchairs of course but powered signs to warn of situations etc) all of which connect to 3G.I'm having an issue with a particular sign which simply can't get a reliable connection.Thinking hardware may be at fault I moved all of the hardware from a sign across the road (no more than 15M away) which works flawlessly in its current position.Sadly when moving the known working internals over to this location the sign still can't get a reliable connection.The sign is close to the Telstra tower which is at 22 Annely road Dutton park (Tower 4102018).Sign is located at the Schonnel bridge heading toward University of Queensland.I have tried a omnidirectional high gain antenna which had no effect. I'm considering a Yagi which I can aim toward the tower.Note: there is no line of sight to this antenna as the cemetery between the two locations is quite woody.Is there another option?Telstra only use the 850MHz band so we can't switch bands.What other options are available in this situation?Kind regards,Unordung.

author: jonpaul
author_rank: Super Contributor
timestamp: November 25, 2021, 06:32:48 am
content: Bonjour, the issues of cell transmission in the face of interference are well studied and involve the cell tower TX design, antennas in the TX and RX etc.You have a classic radio transmission problem.You cannot change the Cell tower TX or antenna nor the interference.You options:Better RX and antenna eg a repeaterRemote locate the RX and antenna eg on a towerRéorientâtes RX antenna for improving the signal to interference ratio.Kind Regards,Jon

author: EPAIII
author_rank: Super Contributor
timestamp: November 26, 2021, 06:41:16 am
content: 3 GHz and woods? Can you say attenuator? Real good attenuator!You changed the "internals" but not the sign. The working sign is only 15 meters away. Move the non-working sign across to that location and see if it works there. When there are obstacles in the way, even a one wavelength difference in location can mean the difference between a good signal and a bad one. At 3 GHh the wavelength is 0.1 meter or 10 cm or 4 inches. At 15 meters your two signs are 150 wavelengths apart. That is a long, long distance; enough for reception to be completely different. Anyway, move the whole sign, not just the internal circuitry. Connectors and cables and other things do go bad.After doing that, you will know if it really is the location or just the sign itself. If it is the sign itself, some kind of repairs are needed. If it is the location, look for a big metal object nearby. A water tower would be nice or a big building; the higher the better of course. Aim at that with a directional antenna (Yagi). If there are no obvious reflectors try every direction, even directly opposite from the straight line path - strange things do happen with RF.Another thing that you can try is the polarization of the antenna. Since those woods are blocking your direct path, you are looking for an indirect one. When a signal is reflected often the polarization can change. Switch between horizontal and vertical polarization and try the two 45 degree positions between them. You do this simply by rotating the Yagi antenna about it's long axis.Finally, you said it when you said "height". It may not be practical, but the higher you can locate your antenna, the better the signal strength can be. One standard for measuring broadcast signal strength is with an antenna at 10 meters above ground. That gets above most single story buildings and a lot of trees and other plants. I have seen this work in a very dramatic fashion while making field strength studies in VHF and UHF bands. Of course, the same applies for the antenna you are trying to connect with, but you may not have any way to change that. But it is possible that just moving the antenna one or a few wavelengths can have a big effect on the signal strength. When multiple paths are considered, one wavelength (10 cm) or even a half of one wavelength (5 cm) can be a completely different location.

author: Whales
author_rank: Super Contributor
timestamp: November 26, 2021, 11:19:08 pm
content: Quote from: EPAIII on November 26, 2021, 06:41:16 am+1This might not be a TX power or radio path issue. It might be interference from other electronics in the sign.Does your 3G modem provide diagnostics? Link quality measurements, SNR, signal strength, etc?

author: johnboxall
author_rank: Unknown
timestamp: November 26, 2021, 11:34:59 pm
content: Odd. You can't connect to the cell on UQ?https://www.rfnsa.com.au/4067004From my hazy memory of UQ attendance it's quite elevated and should be line of sight to the bridge. Could be wrong.

author: connectTek
author_rank: Regular Contributor
timestamp: November 27, 2021, 10:20:02 pm
content: https://www.ebay.com.au/itm/3G-4G-Cell-850-2100MHz-Phone-45dB-Signal-Booster-Data-Repeater-Kit-for-Car-Voice-/144177483036?mkcid=16&mkevt=1&_trksid=p2349624.m46890.l49286&mkrid=705-154756-20017-0

author: connectTek
author_rank: Regular Contributor
timestamp: November 27, 2021, 10:20:44 pm
content: Got a 900mhz one for my workshop.Works great.

author: johnboxall
author_rank: Unknown
timestamp: November 27, 2021, 11:16:14 pm
content: Quote from: connectTek on November 27, 2021, 10:20:02 pmThey're illegal and interfere with network usage. The only legal units are the Cel-Fi systems.

author: SL4P
author_rank: Super Contributor
timestamp: November 28, 2021, 04:38:05 am
content: https://usermanual.wiki/m/3fb8089a0a32312a9e6a3aef5957c80df8c2041cde15f08105c87f1fe0cf4fcc.pdf] https://usermanual.wiki/m/3fb8089a0a32312a9e6a3aef5957c80df8c2041cde15f08105c87f1fe0cf4fcc.pdfhttps://www.seeedstudio.com/Motor-Shield-V2-0.html] https://www.seeedstudio.com/Motor-Shield-V2-0.htmlhttps://github.com/Seeed-Studio/SeeedMotorShieldV2] https://github.com/Seeed-Studio/SeeedMotorShieldV2First search.