You will need to select a channel that you don't use on your 2nd tv, then do a UHF scan as if you were searching for terrestial tv, this will pick up the frequency of the Satellite signal being sent through your cable & you should get a picture.
You may have to check your Digibox to make sure the RF out function is set ON.
Triple Dragon, Dreambox 8000, Echostar AD3000ip, TBS6522,6925,6983 PCie cards. Gibertini 1.25m motorised dish driven by the AD3000, with either Inverto BU Quad or Norsat / XMW Ka LNBs . SMW 1.05m + 3 other dishes. Speccy: Promax HD Ranger+
If you can't change your TV to accept Pal I transmissions then you might want to investigate buying a videosender. This would plug into one of the scart sockets on the digibox and the other unit plugs into a scart socket on the TV.
Another possibility is to use an old RF modulation unit off, say, a games console to send the TV signal down the TV aerial cable. Obviously you would have to get one with European Pal B/G capabilities rather than UK Pal I specification.
IDD CI24 ECONO MM Penta 1.20 Galaxy II 1.2Mtr Polar MTG yes it has been on the arc for 25 years and is now fixed on 13 East using two pairs of rusty molegrips. Unlike me they never groan but always perform.
You could of course just get hold of your mums tv in the bedroom that hasn't been switched on for years next time you visit her:-tree Assuming of course she is still in the UK ... maybe not but you get the principle
The other option (if you have no PAL I setting on the TV) is to run it from your VCR and set the VCR to whatever AV connector the Sky runs into. The VCR doesn't need to be fully functional, as long as the loopthrough and RF modulator works.