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TomChum
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# Posted: 2 Dec 2011 11:45am - Edited by: TomChum
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ERROR in thread title ---------> requirement is "3A" (not 2A)
I'm considering mounting a cellphone repeater up in a tree where it will get an unobstructed 'view'. The wire will be 100 feet long. It has a voltage reducer that takes the 12vDC and drops it to 6vDC at the amp. The amp requires 3 Amps at 6vDC.
I have a few questions.
1) Does a 12-6 voltage reducer waste appreciable battery power? Can I tap 6volts off one of my 6v batteries? The amp idles at .5A and uses up to 3A during a call.
2) What size wire is necessary to get 6v*3A at 100 feet?
3) And/or What wire size for about 12v*1.5A at 100 feet?
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MtnDon
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# Posted: 2 Dec 2011 01:04pm - Edited by: MtnDon
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1) see below.... it is likely more cost effective to buy the 12 to 6 VDC converter and the smaller gauge wire.
In theory it is a bad idea; tapping off one 6 volt battery in a series will slowly make the series chain unbalanced as the power is drawn off the one battery over a day or so. It's not a big load but over time that battery may deteriorate more than the others. The unbalance can also cause problems with the others in the chain; they may overcharge if/when the system tries to get the tapped battery up to full charge. But if the loads drawn are small there may not be much deterioration.
2) What size wire is necessary to get 6v*3A at 100 feet?
#4WG for 3.1% voltage drop
3) And/or What wire size for about 12v*1.5A at 100 feet?
#10 AWG for 3.3% voltage drop
We use a 24 volt to 12 volt converter from these guys. {look in the Battery Equalizers/DC Autotransformers section} Very high efficiency, about 96% under our common loading. Yours may differ.
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Martian
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# Posted: 2 Dec 2011 01:39pm - Edited by: Martian
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I came up with 14ga for 12vdc/1.5amps w/3% drop at 100' using marine grade wire.
If you can live with a 10% drop, you could go down to 16ga.
Tom
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TomChum
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# Posted: 2 Dec 2011 03:20pm - Edited by: TomChum
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The min voltage is 5.75v which is 8% down from a nominal 6.25v. It's clearly not worth investing in #4 AWG copper for the 6V run. And the charging imbalance issues too. 14/3 which has 2 pairs thus double capacity, still costs $55 for 100 feet.
I'm not sure if this part of the project makes sense (positioning the amplifier at the receiving antenna). I can test it both ways (with a small 12v battery up in the tree) and prove whether there are dB gains to be had (or not, or if even necessary). I have to do a bit of planning becuse its 2:35 hours drive to the cabin when no snow. When snowing, it could add a 45 minute walk, then snowmobile ferrying etc.... So thanks for the pre-planning help!
The goal of this is to improve on the cell signal that I am getting at the cabin (for internet). I have "E" network, but am trying to get 3G coverage.
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Martian
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# Posted: 2 Dec 2011 04:06pm
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You might be in a "hole", like I am, when it comes to cell phone and internet, even though I'm on a slight hill. I can go 100' in any direction and get better reception than I do anywhere around the house; inside its even worse. I'd get one of those repeaters, but I'd hate to pay that much just to find out it isn't that much better.
Maybe its our magnetic personalities screwing up the signal............nah.:)
Tom
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TomChum
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# Posted: 2 Dec 2011 04:14pm - Edited by: TomChum
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Speak for yourself, I'm in a "shadow" ;-))
I bought a "vehicle" unit to test. There was no other way to find out, and no one to ask, because it's very specifically "location based" info.
The car unit worked pretty well, but I have to be right next to the antenna. Kind of like sitting in my car seat or like those old wall phones where the earpeice was on a 2 foot cord. So anyway I got my information (that it works!!) but ended up "tethered". If I am expecting a call I have to hang around the table. Work was not getting done.
Now I'm spending more for a unit expected to broadcast over a 25-foot radius. It's $600, a LOT more than the car unit! But driving back and forth to the cabin costs $70 roundtrip for gas alone. If my communication and productivity is better from the cabin I can do some of my work from there and save some gas and other vehicle expense.
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TomChum
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# Posted: 6 Feb 2012 09:52pm - Edited by: TomChum
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Report on the $525 cell-phone booster: SUCCESS!!
I now have 3G reception Details on "Internet with your Cellphone" thread.
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