[Mikey405]

Hi Hamish and G6Tanuki.

Many thanks for the comments.

Re Hamish's comment - The loud "buzzing" is only there when the Spitfire is on - There is a little bit of noise from various electrical devices around the place between stations but not too much to speak of - and I can always find a "quiet" part of the spectrum. If I move the whole setup (including the aerial) outside then everything is quiet - but as soon as there is a sniff of anything to do with mains powering the Spitfire or the MP3 player then the buzz is back. Other local stations come in on the radios without any buzzing noises too.

The "Modulation Hum" thing sounds promising - Although I have tried turning off every electronic device in the building (including fridges, freezers, computers, the 19" rack and all its bits-and-bobs) - in fact everything except one AM radio and this device running on its batteries - but still the problem remains. In fact there is almost no discernible difference at all between everything "on" and everything "off".

One thing I did notice is that if I have a mains lead lying near to the Spitfire then it seems to pick up a lot of hum from that, so I wonder if shielding the device in a metal tin might be the answer.

So, I think I might be resigned to using the device in the garden with perhaps a small 12V lead-acid battery, the aerial in a tree, a 1200mm ground-spike, and a Bluetooth receiver, to which I can transmit music etc. It's just such a shame as my SSTRAN AMT transmitter works perfectly with virtually no hum whatsoever.