[Al Skierkiewicz]

Jeff,
Are you going to substitute H and V sync from the original monitor? Adding sync back to video is a difficult process unless you have some good electronic design experience.
It sounds like you are pointing the antenna at the screen to get radiation data and then amplifying it to be able to display the effect on another monitor. This will be very difficult if you are expecting to see actual video demodulated from the radiation of the screen. The radiation occurs at baseband video and can have a bandwidth of at least 10-20 MHz. Remember that the radiation is a function of brightness and electrons striking the phosphors on the face of the tube. The electron stream varies with each of the colors as each of the phosphors have a different sensitivity to electron bombardment. Red, Blue, and Green streams occur simultaneously as there are three guns in the back of the tube so there is no way to separate the radiation. A VGA or Super VGA or higher res tube does not operate at the standard sync rates that normal TV demods operate at and so even a high quality tuner will not give you any valid data to look at since it is not occuring at the same frequency of a standard tv channel.
That being said, you might be able to get a watchable signal (black and white) with another monitor and an amplifier. Feed the same sync to both monitors and a video signal to the first monitor. A loop of wire in front of that picture tube with a wideband amplifier might give enough signal to feed into the video input of another monitor. There is an electronics kit mailorder called Ramsey Electronics that used to have amplifier kits for pretty cheap prices. They had a website but I haven't gone there recently. You are looking for a wideband preamp and as I remember that had several in the under $50 price range without a box.