[Top] [All Lists]

Re: [Amps] Ferrite Core for 160M PI Output

Subject: Re: [Amps] Ferrite Core for 160M PI Output
From: Manfred Mornhinweg <>
Date: Thu, 15 Jun 2017 17:20:24 +0000
List-post: <>

##     #61 ferrite is  UHF material and semi useless for an HF balun.

Not right. 61 is good for absorption in the UHF range, and for relatively low loss applications on HF. It works great as balun, for example in the form of an FT-240-61 core with 12 turns of RG400 on it. Instead it's not good for a bead balun, because its permeability is too low for that.

#77  ferrite is out of vogue these days for HF baluns.....even though
Hy-hain still uses it on their  BN-4000 balun. Both have been
replaced with type 31 ferrite.

77 is low frequency, high flux density ferrite for power supply applications. It can be pressed into HF balun applications, but is far from optimal. Many people have used old TV flyback transformer cores and even TV yokes for winding baluns - that's much the same material.

31 is formulated for absorption in the HF range, not for transformers. It can be used in baluns only if enough turns (or beads) are used to provide a really high impedance, because the impedance it provides is almost purely resistive. It makes for a VERY lossy balun if used to provide a moderate impedance.

61 provides a lower impedance than 31 or 77, but it's mainly inductive in the low and mid HF range. So its far less lossy. If used in a way that provides too little impedance, though, it can detune an antenna.

So, it all boils down to selecting the material best suited for the balun on intends to build, and then design it correctly. 31 cannot fully replace 61 nor 77, nor can 61 fully replace 31 nor 77, etc. Each has its applications.

Some companies offer several dozen different ferrite mixes, so that designers can select the optimal material for a given application.


Visit my hobby homepage!
Amps mailing list

<Prev in Thread] Current Thread [Next in Thread>