So I went ahead and connected it, but I'm not getting a reading.
I've checked the circuit over and over again, everything seems to be correct.
The only thing I can think of is that I've used the 14-pin version of the LM2907 instead of the 8-pin version.
Looking at the datasheet (http://www.emesystems.com/pdfs/parts/LM2907.pdf) I assumed that I just had to use pin 3 & 4 and pin 11 & 12 as 1 pin.
Is that correct or did I overlook something there?