If by 'uncovered' you mean 'uninsulated', I would not do that.

And if I understand what you are saying, you want the 'fencer' control transformer to be located at the house while the actual fence is located at the barn 500' away. So the wire you wish to run is a single insulated wire to the fence.

You will require a ground rod sunk at the house for the fence control unit ground.

Aluminum uninsulated wire is what we were told to use with insulators. We know about the three grounding rods, etc. I feel insulated 12 gauge copper wire is what we need but worry about the resistance over such a long distance.

Another solar panel and possibly a larger battery might be cheaper options.

The current is normally very low on the high voltage wide of the fence charger, so voltage drop is not as much of an issue as simple leakage through the insulation.

Typical wire insulation is only rated to 600 V, far less than most fence chargers.

I don't think I'd want to run high voltage 500 feet through the woods. Leakage is the problem. You'll have to tend the line regularly. There are too many places where weeds, dirty insulators, and the like can bleed voltage off. You'll also need more lightning protection for it.

I suggest that before you spend any money at all, you make sure you have a good ground with what you're using now. The ground rod should be sunk 10' into damp earth. Use two if in doubt.

Then, check all your insulators. I trust you've gone over the fence line in the dark to check for arcing over. A meter can help in this process.

http://www.parmakusa.com/Baygard/access/tester.htm

If that doesn't turn up anything, I'll second Brick's recommendation. Get a better charger with more sock.

Parmak makes a good solar charger. You'll find these at the co-ops. This is not the usual feeble made-in-China solar powered junk the chain "tractor stores" usually sell.

http://www.parmakusa.com/Fencers/solar2.htm

If that's not enough you might try their 12-volt battery powered fence charger.

http://www.parmakusa.com/Fencers/battery-operated-fencers.htm

Power it with a good 12v gel battery, preferably group 24 or even group 27. U1 size is lighter, but will need more frequent charging. I get excellent service from East Penn Deka brand. You can either get two batteries so you can charge one while the other is in use, or buy one battery and a PV panel to keep it charged.

I have two of the 12v Parmak chargers and have been using them (in separate areas) with portable fence for several years. So far the coyotes and foxes are leaving the sheep and chickens alone. A group 24 gel battery powers each for weeks.

Where you have aggressive predators (or curious critters), you can't cheap out on fencing materials.

Hope this helps.

Gallagher makes chargers that are claimed to be premium quality at premium prices. Charger outputs of about 5000 volts pulsed are effective for most animals.

Here is a link that might be useful: Click here

I agree with bus... get a 'New Zealand' style charger like a Speedrite and there are a few others. I recommend the Speedrite as we have used them for over a decade with no issues.

A New Zealand style is one that is designed to operate in the sheep country on animals with very insulating wool and long distances. Voltage 7,000+ and even with a 'T' post grounding out the fence the meter was reading over 3k.

This is on 12v models with an automotive battery and stand alone solar panel not a all in one unit. I think they do make a quality solar unit but most tend to have too small of a solar panel that is built in. I would recommend a deep cycle battery and solar panel off to the side that can be purchased off Ebay.

ONE other alternative is to buy the wire that is designed to be run across the ground or buried for electric fences and run it from a 120v unit in the home to the fence.

Also put lightning arresters on your fence at least one furthest away from the fencer and one close to it. We put one close and one at any end point. They will greatly increase the units longevity if you have much lightning at all, even if they are designed to handle a strike.

Here is a link that might be useful: Speedrite Fencers