Hf filter for ballast

Hello John,

Here is a free (ad-supported) program to calculate LC filters in the HF range:

Have you considered common mode measures? For example, looping the cable as a whole a few times through a big #43 ferrite toroid at each end?

Hi Joerg

Yes, I tried individual ferrites and common mode, it seemed to change the points at which the radiation peaked but did not suppress over the range. Just about also to try a foil and braid screened cable, as teh original was just braid, but it seems that hf ballast manufacturer's in general are not paying much respect to EMC on the output of their ballasts. It is annoying bacause I was paying for test house time. Thanks for the web site suggestion

JohnS

Hello John,

That's what happened to most (new) clients of mine, blowing through the first EMC lab visit and fail. But not all is lost because then you have the baseline plots. You can rent an antenna set and possibly an analyzer if there is none in the lab and experiment on your own until you reach enough margin. There is never a guarantee but this greatly increase the confidence level for the next round at the EMC lab.

Shielding will help but only if there is a tight shield connection at the generator, ballast and preferably at least the frame of the load.

For the ferrites make sure it's indeed #43 material or similar. #77 looks deceptively similar. Unfortunately what I find a lot during visits is that all the ferrites have been placed in bins and after a few trial and error sessions the cores of same sizes are often mixed. The only way to re-separate is an inductance meter, some wire and lots of time.

For what it is worth.

Buy some cans of spray enamel and paint them after sorting. Do the same with new stock.

Small beads and cores can be strug on wire and dipped in a thinned mix from a can of paint.

You can even use this for threaded cores.

Jake.

Hello Jake,

I usually write the material code onto them with a silver or gold indelible ink pen. Then I don't have to remember colors. But those pens dry out quite quickly.

Nail polish works as well but my wife wouldn't appreciate that ;-)