I have found recently that my twin 36 watt preheat fitting has started to cause severe radio interference to medium and shortwave I narrowed it down to one tube I initially couldn't stop it but then I turned the tube round in its socket till it re lit and the interference was greatly reduced I also turned the tube so it's live end is swapped that didn't help so any thoughts please. The noise sounds like rapid random popping sounds also when  Itouch it a general hash noise can be heard

To stop it, try surrounding the ballast with lots of metal.

To stop it, try surrounding the ballast with lots of metal.

make a faraday cage with some metal mesh?

Quote from: wattMaster on May 31, 2016, 05:11:46 PM

To stop it, try surrounding the ballast with lots of metal.

make a faraday cage with some metal mesh?

Exactly.

The ballasts are already inside a metal fitting which is earthed to the socket

The ballasts are already inside a metal fitting which is earthed to the socket

That might not be enough.

On MW to SW the main path is via the mains connection, so a cage won't be efficient.
What may help is a capacitor directly across the mains input (normally a PFC capacitor should be enough), but it should be wired so there is no wire length common for the lamp circuit and the mains input.
So like (copy the following text into some fixed character width editor to see the "ascii-art"):
   Line o------------          ----------Ballast--------  -----
                      \       /                         ||     |
                       \     /                          --     |
                        \   /                          |  |    |
                         \ /                           |  |    |
                       ------- Capacitor               |  |     \
                       -------                         |  |      \
                         / \                           |  |    |
                        /   \                          |  |    |
                       /     \                          --     |
                      /       \                         ||     |
Neutral o-------------         -------------------------  -----

Then you may need to use ~2.2nF "Y" rated capacitors connected between each power input and PE (so Line-PE and second to Neutral-PE).

Or you may sometimes found ready made combination of two "Y" capacitors and one additional "X" (about 100nF between phase and neutral), with 5 wires coming from the device: Two are intened as the power input, two are connected to the load and the PE is supposed to be connected to the metal fixture body. Te PE connection should be as short as possible and the power input wires should not be laid out close to the other wires in the fixture (to prevent coupling). Sometimes such filter contains even a filter choke. The wiring diagram is usually on the body of such device, the only pitfall with these is the PE wire length and the eventual coupling (described above)...

Noise when you touch the lamp - That may be some little arcing in a moving bad connection there..

Try to replace the starter for the bad lamp

Is the lantern enclosed in metal as most are ?

I have cured the problem I found one of the pins was arcing that was the problem so I took out the tube turned it round and refitted it it now runs silently I will add a filter circuit as per medveds instruction I have one in my junk box so will fit it soon when I get a day off