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dubman 10-25-2007 03:07 AM

250 meters run of electric cable?
Hi, I want to install an antenna for internet which need 220 volts - 50/60 hz, but the house doesn't have coverage, so I'm thinking of running a cable about 250 meters to a point where there is coverage. I understand that there would be a voltage loss of about 47 volts in 100 meters? And that this loss would lead to overheating of the cable, which obviously could be a fire risk.
So, is there a convenient and SAFE way to use step-up / step-down transformers to correct the problem, and what cross section of cable would be needed?
Thank you in advance.

Speedy Petey 10-25-2007 06:12 AM


Originally Posted by dubman (Post 69813)
I understand that there would be a voltage loss of about 47 volts in 100 meters?

OK, who told you this MYTH!

Voltage drop is directly affected by amperage. Also, VD @ 240v is MUCH less than at 120v.
With a load of one amp there would be NO noticeable VD @ 240v. With a load of 16 amps VD would be dramatic.

1) What is the ACTUAL amperage of the unit you would be installing.
2) Where are you located, Canada or the UK, or somewhere else?

slakker 10-25-2007 12:21 PM

I'm interested in your configuration... how is Internet running on this?

NateHanson 10-25-2007 12:59 PM

250 meters is a loooong run! That's gonna be very pricey. Have you thought about going up a bit? Perhaps you'd get reception by going up 50 feet, rather than going sideways 800 feet. Are you going to dig 800 feet of trench?

dubman 10-25-2007 03:13 PM

I think the info about voltage loss came from a Canadian site, so maybe not 220 volts there?

The internet system is called LMDS - sort of broadband via radio signal.
I'm based in a mountainous region in the north of Spain, and the repeater is hidden behind a peak (around 1 km distant), but there is at least partial line of sight about 250 meters from the house. The idea is to erect the antenna there and resend the signal to the house via WIFI.

I don't know the exact amperage of the antennas, but I assume it would not consume more than about 50 watts. I will try to get more precise info from the installers.
For such a long run of cable what cross section would be best?

As regards having a high antenna at the house,,, I think it would need to be very high, maybe 30
meters. or more not an option.
My idea is to erect the cable on standard type electric poles on private land. Im trying to find out about the feasibility of the project . and may even look into a solar panel solution.... thanks

Oh..just saw on the broadband website the following info about power consumption of the antenna:

Internal equipment : 220 volts AC / 47-63 Hz.
Electrical consumption: 30 W.

That doesnt include the WIFI antena - but I imagine the consumption would be very little. I did email the company for more exact details... So maybe a 40 watt solar panel may be a cheaper option.

Andy in ATL 10-25-2007 06:16 PM

If I was gonna do it...I'd do it right and run #10AWG. Wanna guess what the A in AWG stands for??:laughing: Ill get my codebook and convert that to Spanish ...oops I meant MM squared:laughing: :wink: Lets see.. I THINK it is 5.261 mm2 If I'm looking at the table right. Stubbie????

It looks like you would be drawing much less than 1 Amp.

dubman 10-26-2007 03:53 AM

is that 5mm referring to the cross-section of the cable? If the power consumption required is so low, I'm still wondering what kind of cable to use: 1mm, 1.5mm,2,5mm, 4mm. Though I suppose a strong rigid cable would be needed to resist weather, wind etc... obviously the cost would vary a bit depending on cable cross section. That's why Im wondering if a solar panel set up might be cheaper, and look better than over head cables...

dubman 10-26-2007 06:43 AM

I had another look at the land layout and now I think that a 40 watt solar panel may be a better solution, and may be cheaper too. Thanks.
btw the info I got about the voltage loss referred to a 10 amp load....

NateHanson 10-26-2007 07:11 AM

You'll need a much larger panel to supply a 24 hour 40w load. You probably need something around 200 watts or more, considering that the panel is only at peak output for 5 or 6 hours of the day, and inneficiencies of the storage battery, and inverter. Still I expect that a solar installation would be much cheaper than installing your own overhead cable for 800 feet. You can get a 200 watt panel for about $1000, and the regulator, battery and inverter would probably cost another $500.

Have you looked into satellite internet service? If it's available in your part of the world that would probably be the simplest solution. Around here, when people are beyond the range of cable and DSL, they use a satelite internet service that is not quite as fast as broadband, but much much faster than dialup.

robertmee 10-26-2007 01:24 PM


Originally Posted by NateHanson (Post 69947)

Have you looked into satellite internet service? If it's available in your part of the world that would probably be the simplest solution. Around here, when people are beyond the range of cable and DSL, they use a satelite internet service that is not quite as fast as broadband, but much much faster than dialup.

The 2-way systems I've seen are not close to broadband. They're in the 512kbps download to 128kbps upload speeds, compared to 2Mbps for most Cable broadband. Some still require terrestial connections for uploads. And the plans I've checked into are pretty pricey ($125 to $150/month) plus equipment purchase. It's been about a year since I checked into these plans so maybe they've gotten faster and come down in price. Another option would be cellular, however, given the OP is in a mountainous range, that might not be an option either.

NateHanson 10-26-2007 01:27 PM

Yeah, my friends who use it say it's certainly not broadband, but it's workable.

My impression was that it's about $100/month, but the situation this guy is trying to install would be so expensive that I don't think a monthly cost like that would be hard to justify. This has to be a many thousand dollar project, with poles, and 800 feet of cable, plus the receiver, long range Wifi transmitter, etc. Yikes!

dubman 10-26-2007 03:49 PM

at the moment I have an internet connection similar to dial up, It also uses radio signals - using a cell phone card -it's fine for most internet use like emails and general browsing...but not for VOIP.

But I was hoping to upgrade to the LMDS system - the package I was interested in is 512mb (at least in theory), upload and download the same I think - symetric system. Price here about 45 euros a month. But alas I have the coverage problem.
Looking around ebay, I saw some solar panels around 180 watts for about 300 British pounds. There's also the slight hesitation about mounting such expensive equipment over 200 meters from the house...

A Satellite system would need to be 2 way in this case because there's no normal phone line in the house. But I'm not convinced about satellite, being so expensive etc.
Another possible option is the 3G cellular one. But in this remote area there is no 3g coverage, so the 3g USB modem would only work at about dial up speed (maybe a bit faster) in this area. regards the option of the 250 meter cable run I still dont know what cross section would do the job, since I think the price would vary a lot depending on the cross section.

Andy in ATL 10-26-2007 03:57 PM

It certainly sounds like a pickle...I'll tell you what.... If you fly me over to the mountains of Spain I'll take a look at it and not even charge you my normal $29.95 estimate fee.:whistling2: :yes: :laughing:

dubman 10-26-2007 04:49 PM

BTW Andy, thanks for the AWG table.
You mention 5.261 mm˛ , so would that mean 2,5 mm diameter cable would be ok for the 250 meter run?

#10 (Awg) 2.588(mm)5.261 (mm˛)

Would the above conversion line be correct?

Andy in ATL 10-26-2007 06:07 PM

MY OPINION ONLY yes, the conversion line is correct. I would think the 2.5mm would be more than sufficient. I would also think the 1.5mm would work, also. Ohm's law: I=P/E where I= Amps P= Watts E=Volts

I=0.14Amps :)

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