The signal was clear - and so was the message: travelling with a mobile phone changes everything.
The example above means 'the signal was clear and the message was clear'. Very often, we use structures like the above to avoid repetition (in this case, to avoid repeating the phrase 'was clear'). Note the structure: 'so' + verb (was) + noun (the message). Here's another example: I generally work from 10am to 7pm, so does my sister. (Meaning 'my sister also generally works from 10am to 7pm'; note that we don't say 'so works my sister').
1. 'I am hungry.' 'So _____ I. Let's order lunch.'
2. I went to the beach over the weekend and so _____ my neighbour; I bumped into her at the beach.
3. It was rainy yesterday and so _____ today.
4. Helen loves dogs and so _____ Jessie.