<font color='#008080'>You need to make sure to run shielded cable for a run of that length. It was recommended to me that at that length you could use CAT-5(e) shielded to make a decent SVHS cable.
I personally, however, have not measured such a run with that cable. I have a 40-foot run using shielded CAT-5e for a 15-pin (HD) VGA cable.</font>