I seem to recall that some railway systems use at about 16 2/3 Hz (one third of 
50 Hz) for traction. Historically, some systems used about 33 Hz. I read 
somewhere that on-board power converters on some railway systems work at about 
33 Hz/275 V at full load, rising to 50 Hz/415 V when lightly loaded.

Can someone say whether my recollections are correct, please?

73 John F5VLF

> On 15 Mar 2016, at 08:42, Markus Vester <[email protected]> wrote:
> 
> Occasionally I'm getting a new kind of interference with strong 33 Hz spaced 
> lines all over the LF band. Variable RDF colour indicates that it could be 
> emitted from power converters on moving railway vehicles. Several tracks for 
> freight tranis are passing about 400 m south of my QTH.
>  
> Grabber screenshot: 
> http://df6nm.bplaced.net/LF/screenshots/test1603150730.jpg  
>  
> Best 73,
> Markus (DF6NM)

[email protected]

Researching history of RABSON, BLACKSHAW, GAUNTLETT, VERLANDER and ROBSONNE