Slightly off topic, a party trick which one captain particularly enjoyed was tuning up on 512 KHz or so with knee down on key, holding a lead pencil with the thumb on the blunt end towards the copper tube antenna feeder. A gap of a few inches would produce a long hissing orange RF arc in which with the other hand you could introduce a slip of newspaper. This would burst into flames and made a good captain's fag lighter when he lost his matches.
The only downside was a small but painless RF burn the size of a pinprick on the thumb.
It is interesting to note that at higher frequencies up to HF the colour of the RF arc turned progressively purple and the audio hissing tone increased. Someone should make a study of this phenomenon .