St Johnstone are poorly supported in a country where supporting Rangers or Celtic because they win everything domestically is more common than supporting your local team. It's pathetic, but it's a fact.
However, of the 3000 or so regular fans, there is a loyal core that will sing their hearts out and be very vocally supportive of the team. The atmosphere in Saints away support is great, even if its only 200-300 folk.
The away support in Trondheim will make A LOT OF NOISE.