Re: LF: To Ponder over the weekend

["Dick Rollema" <d.w.rollema@freeler.nl>]

To All from PA0SE:

Jim,  M0BMU wrote:


> The un-neat thing about an oil
> dielectric is its propensity for catching fire... also, I don't think it
> has particularly low loss at RF - although a lot of big TX capacitors are
> oil-filled, the oil is there to increase the breakdown voltage, rather
> than act as the main dielectric, which is usually mica, I
> believe.


The wave form of the output voltage of my 136kHz transmitter with four
HEXFET's type IRF520  in parallel-pushpull was not quite sinusoidal.
To absorb the harmonics I connected a capacitor of about 50nF over the
primary winding of the output transformer. I  tried capacitors of
different type and make but all became hot after a while.
The only one running cool was a white coloured 50nF capacitor of a type
that can be frequently found in German WW II radio equipment. These
capacitors are oil-filled....

73, Dick, PA0SE