opvuller pg9hf balun

How to make a ferrite toroid suppressor

Electric fence QRM immunisation on HF radio.

  Material:               A set of Toroids
Windingwire:       Inner wire from 75 Ohm TV coax
  Project engineer:    Walter Geeraert - PE1ABR
Programming:         Cor van Soelen - PG9HF (and Walter a bit)
Photographs:           Cor van Soelen - PG9HF

Click on the pictures to enlarge them


Three toroids are wound with only one uncut wire, toroids 1 + 5 + 7

Black      10 kHz - 3 MHz
Green      100 kHz - 5 MHz
   Violet      4 MHz - 100 MHz

Acting this way filters the whole HF range from 10 kHz to 100 MHz.

Use only 1 uncut wire and 1 layer. Start and finish should not touch. Also toroids not close to each other (Don't stack them, see picture).

Toroids with a high Q (NiZn, over here the Violet) could give series resonant effect.
Lower Q EMC toroids hardly give a problem.



Toroid variations.
  • 1:   Suppressor Large (Dump)
  • 2:   Suppressor (Magnetics USA)
  • 3:   Philips Suppressor 3H2
  • 4:   3E25 Philips
  • 5:   3E1 Philips (± Amidon FT114A-73/75/J)
  • 6:   3F3 Philips (± Amidon FT114-77)
  • 7:   4C65 Philips (± Amidon F114A-61)

Only 4C65 is low AL NiZn,
all the others are high AL MnZn type ferrite

only Ring type No-1
Practical use from ± 10 kHz to ± 3 MHz.
Standard solution with 1 toroid with high inductance (MnZn).
Not adviced for use (only) on much higher frequencies.
N to high and wrong ferrite type.
Use NiZn material for higher frequencies




only Ring type No-2
This toroid can also be used as a one toroid solution from ± 10 kHz to ± 3 MHz.

But don't use the shown (yellow-green) wire for high voltage use.

Always use a wire with "fat" isolation, like the inner wire of old 75 Ohm TV coax.

The wound toroid device should be mounted directly between the electric_fence voltage generator and the outside world!
Don't stack the toroids together, just let it hang straight.
Think of the proper grounding of the arc circuit!! DO NOT connect to mains earth, but with a short wire to it's own earth pipe!!
As an extra low-pass C a piece (1 to 5 meter) old fat RG8 coax could be used close to the unit. With a very short ground wire!

Toroid supplier Barend Hendriksen.          Walter PE1ABR Ferrite Toroid information page.

mailto:pg9hf@zeelandnet.nl LINUX  2010 Cor L. van Soelen PG9HF.