What ignition system are you running? Stock or aftermarket? What spark plugs? (Some plugs cause radio interference).
If it works fine with the engine off, it's not the antenna, it's engine electrical interference (electrical "noise") aka RFI (radio frequency interference).
Have a read on this:
Dave F. aka the Librarian
Car and Mods:
93 S4, 1.8t coil pack conversion (First in world using integral POS coil packs (??)), CF (OE), S6 steering wheel, RS2'd, Samcos, MRC, TDS-1, Apikol FMIC, Eibach/Bilstein, BIRA Sys 1, relayed FP
Click here to link to the UrS FAQ Thread Start
Uncle Dave says "You want my 'high horse, elitist' opinion ?(IMHHEO(tm))Then just post something stupid."
Unofficial Chief Cat-herder Vancouver UrS-car club
Last edited by UrS4boy; 02-03-2014 at 06:33 AM.