Passive longwire cellphone antenna to inside dead area? - Page 1
Forum section: electronics / rf-microwave

author: Circlotron
author_rank: Super Contributor
timestamp: June 20, 2018, 12:30:08 am
content: At work I am stuck inside one of those portable site office buildings that is all aluminium clad, and this in side a concrete walled factory. Phone reception is zero inside my little Faraday cage, but reasonable in the factory area. Might there be some improvement if I strung a length of wire outside in the factory area and passed it through the window to my work area? Not expecting amazing results, just something better than zero.

author: Yansi
author_rank: Super Contributor
timestamp: June 20, 2018, 12:46:01 am
content: Strongly doubt it would help anything, apart from catching few thunderstorms.Get a proper external phone antenna, if you phone supports connecting it.

author: Marco
author_rank: Super Contributor
timestamp: June 20, 2018, 01:04:13 am
content: I doubt many modern smartphones have external antenna inputs any more, but older ones did (google tells me Samsung S4 had it for instance).You might be able to get a cradle for your phone with an external antenna port though which I assume just puts another antenna right next to the phone antenna to couple the signal. Which you can then connect to an antenna in the factory hall.

author: rx8pilot
author_rank: Super Contributor
timestamp: June 20, 2018, 01:17:36 am
content: This is a task for an active amplifier. A number of years ago, I purchased a system from a company called Wilson. It was pricey, difficult to install, and did not do much to help signal strength.Maybe modern options are better and lower cost.

author: thermistor-guy
author_rank: Frequent Contributor
timestamp: June 20, 2018, 03:00:45 am
content: Quote from: Circlotron on June 20, 2018, 12:30:08 amGood question. RF isn't my area, but your post did bring to mind these concepts:https://en.wikipedia.org/wiki/Leaky_feederhttps://en.wikipedia.org/wiki/Passive_repeaterI'm keen to read what RF experts here advise.

author: babysitter
author_rank: Frequent Contributor
timestamp: June 20, 2018, 06:43:37 am
content: Either you use the already recommended leaky line (Preferrably directional antenna outside, inside the leaky), or you use a path which i think is even easier to DIY in my opinion but obscure technology from days gone.Gubau line:This consists of a single wire, preferrably isolated, wire strung to to the "dead" area. Coupling from coax is done by a kind of trumpet like this:<------------------------------------------------------------------------------at the small opening of the trumpet you attach the coax to the outside antenna. The trumpet shape shall actually be trumpet-like, not like a funnel.

author: Circlotron
author_rank: Super Contributor
timestamp: June 20, 2018, 06:52:18 am
content: Looked at using a waveguide but the crosssection needs to be about 12x6 inches for 950MHz. No good.

author: thermistor-guy
author_rank: Frequent Contributor
timestamp: June 21, 2018, 12:40:50 am
content: Quote from: babysitter on June 20, 2018, 06:43:37 amFascinating concept. Thanks.https://en.wikipedia.org/wiki/Goubau_linehttps://en.wikipedia.org/wiki/Single-wire_transmission_line

author: CopperCone
author_rank: Super Contributor
timestamp: June 21, 2018, 01:07:34 am
content: how do those amplifiers work since their bidirectional antennas? Do you have a active circulator or something (to keep size down at 900MHz?)

author: jmelson
author_rank: Super Contributor
timestamp: June 21, 2018, 09:02:18 pm
content: There's a thing called a passive repeater. It has a Yagi antenna on the roof pointed at a cell tower. They run heliax down inside the building, and then have a small antenna in the area where people need cell connection. I sometimes am in a building where they have this, and it does work. Both antennas are tuned for the cell frequencies. A piece of wire is not going to do the job.Somewhat more sophisticated systems have directional couplers on the heliax and multiple small antennas in different areas inside.Jon

author: David Hess
author_rank: Super Contributor
timestamp: June 21, 2018, 09:39:22 pm
content: Install a passive repeater. Place a phone band antenna on the roof and connect it to another phone band antenna inside the room through coaxial cable.

author: jmelson
author_rank: Super Contributor
timestamp: June 21, 2018, 10:25:31 pm
content: Quote from: David Hess on June 21, 2018, 09:39:22 pmBut, that's the rub. 900 MHz, or even worse, 2.4 GHz requires some really GOOD coax! The system I saw had some roughly 1" diameter semi-rigid coax that was likely pretty expensive. But, it DID work!Jon

author: CopperCone
author_rank: Super Contributor
timestamp: June 21, 2018, 10:26:25 pm
content: a directional to omni converter is new to me, it reminds me of a disco ball stimulated by a laser, or those high end solar panel optics

author: thermistor-guy
author_rank: Frequent Contributor
timestamp: June 22, 2018, 12:35:14 am
content: Quote from: jmelson on June 21, 2018, 10:25:31 pmor a G-Line (single-wire transmission line), which apparently has lower loss than coax.

author: David Hess
author_rank: Super Contributor
timestamp: June 22, 2018, 12:36:14 am
content: Quote from: jmelson on June 21, 2018, 10:25:31 pmIf a directional antenna is used on the roof, then its gain makes up for some of the coaxial cable loss. An RG-8 sized cable like LMR400 is not too large for convenience or too lossy.

author: Lord of nothing
author_rank: Super Contributor
timestamp: June 29, 2018, 10:15:45 pm
content: Call your Operator and order an Active Repeater!Why is that legal? Thats simple because the amply fie only your Operator Frequency.

author: Karlo_Moharic
author_rank: Regular Contributor
timestamp: June 29, 2018, 11:54:49 pm
content: Buy GSM amplifier , it's around 30$ on ebay and comes with receiving antenna that can be put on the outside

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 30, 2018, 04:01:30 am
content: Do they provide Wifi that allows the connection of personal devices?

author: Circlotron
author_rank: Super Contributor
timestamp: June 30, 2018, 05:16:05 am
content: Quote from: NiHaoMike on June 30, 2018, 04:01:30 amYes, and iMessage and FaceTime is usually quite okay. Sending SMS to Android users is a problem. And normal phone calls to them also.

author: johnkenyon
author_rank: Regular Contributor
timestamp: June 30, 2018, 10:13:42 am
content: If this is having an impact on your ability to do your job, then speak to/lean on your employer and get them to speak to their mobile service provider and get a femtocell installed.Of course this only works if you are permanent staff.Otherwise speak to your mobile provider and see if they have some kind of "Home zone" femtocell offering that you can plug into a network somewhere in your cage (rather than at home...)/john

author: Lord of nothing
author_rank: Super Contributor
timestamp: June 30, 2018, 01:06:51 pm
content: QuoteIts illegal in the most country.Quotenever heard that any European Company give it to customer. I head in Germany one was offer then for a very hight Price.

author: NiHaoMike
author_rank: Super Contributor
timestamp: June 30, 2018, 10:57:07 pm
content: Quote from: Circlotron on June 30, 2018, 05:16:05 amGoogle Hangouts handles texts and voice calls over IP.

author: CopperCone
author_rank: Super Contributor
timestamp: July 01, 2018, 01:35:56 am
content: How much signal will a wire carry?I am asking because I own a USB isolator that does not isolate the power (it uses fiber link), so I can drill out the power wires with a fine drill, but there will be still a wire in the vicinity. How much energy can something like that couple from a computer to a SDR or other USB device?I would drill it out on both ends so its just a floating bit of conductor between the two USB ports. or I might sell the thing because it irritates me now that I got this thread in my head.

author: FlyingHacker
author_rank: Frequent Contributor
timestamp: July 02, 2018, 04:10:05 am
content: Sounds like you have an iPhone. Did you try enabling WiFi Calling? Don’t know if that works where you are, but here I can make and receive normal cell calls that are actually us8ngmy WiFi instead of the cellular connection.

author: wolferl1210
author_rank: Contributor
timestamp: July 02, 2018, 05:57:32 am
content: A wire will do nothing at all for mobile phones. Stories about 'reflectors' or twoantennas, one inside, one outside, connected by a cable are wasting money.The only solution - and I did several installation of this - will be a GSM repeater.But before you invest you have to check two things:- what system you want to extend: GSM, UMTS, LTE ? You need a repeater thatwill handle the transmision mode & frequency of your mobile phone provider.You did not say in what country you live. Yes, you find some on ebay, but:- A GSM repeater (or UMTS, LTE) is a receiver with an antenna outside and antransmitter + antenna inside. And in most countries 'transmitter' need a licenseor an approval. Or, in some countries, they simply don't care...Good luck!