reeseg

Ok, heres what im doing. I have a security system setup that lets me know when a employee uses the wrong access card on one side of our building. Security dispatch is all the way on the other side of the building, its about 2000 or so feet. Im gonna run the wire from one side of the building to the other.

The other thing is this device has a speaker. My thinking is if I hook this wire up to the speaker and over the 2000 feet cable and dispatch I will here the sound. Please help me. My imagination ran away from me.

Unless you guys have a better ideal or some wireless devices

zachtheterrible

Yeah, wireless would be THE WAY to go.

I'd use a pre-built transmitter and receiver module to make things even simpler, and cheaper, they're only about $7 bucks or so. Your regular modules won't be able to have that kind of range though. Although i saw a super-sensitive 433MHZ receiver module that I'd definetly use if I were you.

This might even necessitate the use of directional antennas.

Have a look around here, thats where I saw the extra-sensitive receiver http://www.rentron.com/
EDIT:Look @ RF remote control. That receiver I was talking about claims 3000 ft range.

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audioguru

If you connect a speaker to 2km of cable, the cable will need to be very heavy.
Speakerphones still work fine over thousands of km's because they use a speaker amplifier and power for it right at the speaker. Their ordinary twisted pair telephone cable is operated balanced and at about 600 ohms to avoid too much loss and interference. :lol:

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Uncle $crooge

zevon8

You could use the same system used in PA/intercoms where the signal is supplied at 70 volts, reducing to the required current through the wire. This alows for very long runs using small gauge wire. It would require a PA or paging amplifier, and suitable stepdown transformer.

A used, small say 10 watt paging amp with one speaker that has a built-in transformer could be bought.

There are likely easier and cheaper ways though.

Nigel Goodwin

In the UK we use 100V line, but mostly taps are provided for both.

But he doesn't need a PA amplifer to do this (as he already has a speaker output), just the 100V line transformers - these are freely available, use one at the amplifier end to step it UP, then one at the speaker end to step it back DOWN again.

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zevon8

Good point Nigel, as long as the device can drive the line transformer, then all he needs is 2 transformers.

audioguru

In schools here, we use only a 25V line to avoid the shock hazzard of higher voltages, otherwise the regulations require the wiring to be in expensive metal conduit. Frequently the output voltage of a high-power PA amp is stepped-down to provide only 25V, or the output voltage of a medium-power amp is used directly to feed speakers with 25V transformers.
Often an "average Joe" connects his own 8 ohm speaker to a 70V PA line, overloading its amplifier. Connecting the line to an isolated 120V mains transformer quickly "clears" it without too much smoke. :lol:

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Uncle $crooge

reeseg

actually its about 300 - 350 feet and I did go wireless, I do get a little static and can acutally here there alarm. How can I clean up the static, I got a wireless 900mhz transmitter and reciever that has a 650 feet range. Would adding a better antenna help

mstechca

your antenna length should be 1/4 of a wavelength. take 300 / frequency in MegaHertz and that gives you a full wavelength. Divide by 4.

Try changing batteries once in a while. Sometimes, adding a capacitor in parallel with the battery helps, and make sure both transmitter and receiver are on the exact same frequency.

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-=: The best low-priced components to troubleshoot with are the speaker and the LED :=-

_3iMaJ

You could empirically find a model for your 2000 feet of wire. If I HAD to use a wire, and not go wireless this is how I would do it.

First I would find a physical model for my wire. I would find things like resistance/foot, capacitance/foot and inductance/foot.

I would then draw up a model in a circuit simulation program (like Pspice) and compute a frequency response of the wire, so I knew what I was dealing with.

With that frequency response you'll be able to figure out what you need to do to adjust to the channel characteristics (the wire). But most obviously you'll have to gain your signal.

However, if you find that the wire is particularly insensitive to certain frequencies, some sort of AM modulation or some particular coherent modulation scheme would be the way to go.

Nigel Goodwin

I think my "anti-simulator" stance is well known?, but this must set a record? - wanting to "simulate" a piece of two core cable!.

Stick a 100V line transformer either end - JOB DONE - what's to simulate?, it might be a 1940/50's solution, but it's still not been bettered!.

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zachtheterrible

i still think a wireless setup would be a lot easier, and probably cheaper. 2000 feet of cable cant be too cheap.

__________________
I'm no electronics god, i just talk too much.

_3iMaJ

I like simulators, that way I do it right the first time without guess and check.