If it's a speccy 16K/48K/+ then you should turn the TV sound off anyway because it won't output audio thru the RF. Only the Speccy 128K and later could do that.
You lucky sod.
You'll probably find Channel 5 is interfering with them slightly - like JDsony says, adjust the RF output freq from the inside (but carefully because they tend to crumble after all this time, that happened to me on a spectrum +3, the modulator adjustment screw thing just fell apart).
