Try a signal amp or a good video filter.

Those two items are a problem with interference though I am surprised at fluorescent lights. Try checking your ground plus 500' is a lot of cable. Check the signal before and after the dist. amp. with a scope if you have one.

maveric manic

I eliminated the distribution amp and went direct to a single monitor but it did not eliminate the interference.

Also, according to the specs for most baluns, 1000 feet for color transmission and 2000 feet for black & white over Cat 5e UTP is not exessive.

In researching various baluns, I have just learned that there are baluns available for isolating groud loops which supposedly eliminate rolling hum bars and picture instability which apparently are comon problems. I guess I'll try some provided they are not too expensive.

VGA/DVI display devices over long runs of CAT-5/CAT-6 cable. Runs over 400 feet may lose quality due to attenuation and variations in the arrival time of each signal. A skew control and special low skew or skew free cable is used for runs over 400 feet.

500' is to long, place a repeater every 300'

I believe I have found the solution.

I'm not having any problem with picture color or detail, only a rolling hum bar which according to on line info is caused by ground loop potential difference between the camera and the monitor. This supposedly can be eliminated by use of a ground loop isolator. http://www.eql.com.au/videogli.htm

In the event that a ground loop isolator does not solve my problem, what brand/model repeater do you recommend?

As far as distance using Cat 5e cable, the following sites all claim over 1000 ft:

http://www.cablestogo.com/product.asp?cat_id=3115&sku=41151

http://www.seco-larm.com/EVPPT11.htm

http://www.svideo.com/cctvbalun.html

http://www.dalco.com/ProductDetails2.aspx?sku=71772&OVRAW=cctv%20balun&OVKEY=500022&OVMTC=advanced&OVADID=2148872022&OVKWID=20367872522

The potential to correct depends upon at which end the ground is lifted, ask about that when you buy.