Balun tips

Although ferrite cores do get used to wind baluns, powdered-iron

rings are often more suitable because they are less likely to saturate and get less hot

due to their lower losses.

The power ratings listed in the web shop with the ring cores are strongly dependent on 

correct construction and possible adaptation. In case of strong mismatch due to incorrect 

cable or totally different antenna impedance, there can be such high currents, 

that the core MUST get hot...

By the way, Amidon recommends parallel winding instead of twisted,

so for baluns, the three wires are laid neatly side by side.

The "bundles" are neatly distributed over the circumference, however, of course without

that the first and last bundle touch each other.

Number of windings n= 100 x (root of) nH : AL (L and AL in µH).             

Mix 6: low TC so good for oscillators. The great advantage of toroidal cores    

for resonant circuits is besides the simple way of winding the fact that

the field remains largely confined in the core so that a shielding is not necessary

is needed. The windings as well as the core itself can be well secured with a heat

glue gun.

Frequencies are in MHz.

....

  1.-----------50R ball.---.
  2.----------- mass        |                               
  3.------------------------'                              The the one and only ball-un 
   .                               |                              (balanced/unbalanced)
  1.----------- ground     |                              50 ohm - 50 ohm
  2.------------------------'                             For this, three trifilair
  3.----------- 50R unbalanced---mass           wound wires are used for this purpose
...

....
  1.---------200R----,                        For this 4:1 transformer,
  2.----massa        |                        2 bifilair wound wires are used.
   .                 |                        
  1.----massa        |
  2.-----------------'---50R----massa
....

source and Author of this information is Barend Hendriksen (voorheen http://www.xs4all.nl/~barendh/Indexned.htm)