I will check all of those this evening, although I pretty confident that they're right, only because I would have had to make a pair of matching errors in order to not end up with a missing / extra component at the end. I'll double check the actual values with a multimeter just to be sure.

With the antenna mismatch possibility - I'd be surprised because (a) that aerial + amplifier works really well with other radios and (b) the noises that the tuner makes are completely unrelated to what antenna is attached. Also, reception in this area (Oxford) is pretty decent normally. Would you expect the signal strength level to be high if reception was the problem?

A further data point - when the tuner is scanning frequencies it makes a fairly loud clicking noise as it passes each frequency. I don't know if this is normal, but it doesn't sound right to me. The noise that the radio makes when "tuned" isn't what I'd normally associate with poor reception - it's very quiet, as well as distorted, but in a different way to a poorly tuned FM radio. What is the format of the MPX signal - presumably it's digital audio, but is it multiplexed with other data? I'm just trying to understand what might cause what I am hearing.

I believe that the problem is most likely poor soldering on my part, but I'd be interested to know if Geoff is seeing exactly the same symptoms - that is quiet, poor reception, and clicking when changing frequency.

Paul