Cores for baluns

 I have this printed out as I refer to it often enough so I reproduced it here (I cannot recall the original source tbh but all the values are in several reference books anyway) I got loads of torroids from GQRP club sales and W8DIZ.

The  different material works at different frequencies. These are often used in common mode chokes and wide band baluns.

Material	Common mode choke frequency range (single turn)	Common mode choke frequency range (multiple turns)	Impedance transformer	1:1 Balun (Choke)
#31	3,5 - 100 MHz	1,5 - 50 MHz	-	1,5 - 30 MHz
#43	25 - 600 MHz	2 - 60 MHz	2 - 50 MHz	2 - 30 MHz
#52	150 - 1000 MHz	4 - 150 MHz	1 - 60 MHz	1 - 60 MHz
#61	200 - 2000 MHz	5 - 200 MHz	15 - 200 MHz	10 - 100 MHz
#77	200 kHz - 10 MHz	100 kHz - 10 MHz	0,5 - 8 MHz	1 - 8 MHz

31 Material

Property	Symbol	Value	Unit
Initial Permeability	µi	1500
Flux Density @ Field strength	B H	3900 5	Gauss Oersted
Residual Flux Density	Br	3200	Gauss
Coersive force	Hc	0.28	Oersted
Loss Factor @ Frequency	Tan δ/ µi	20 1.0	10^-6 MHz
Temperature Coefficient of Initial Permeability (20 -70°C)		1.6	%/°C
Curie Temperature	Tc	>130	°C
Resistivity	ρ	3000	ohm-cm

31 Material

Property	Symbol	Value	Unit
Initial Permeability	µi	1500
Flux Density @ Field strength	B H	3900 5	Gauss Oersted
Residual Flux Density	Br	3200	Gauss
Coersive force	Hc	0.28	Oersted
Loss Factor @ Frequency	Tan δ/ µi	20 1.0	10^-6 MHz
Temperature Coefficient of Initial Permeability (20 -70°C)		1.6	%/°C
Curie Temperature	Tc	>130	°C
Resistivity	ρ	3000	ohm-cm

43 Material

Property	Symbol	Value	Unit
Initial Permeability	µi	800
Flux Density @ Field strength	B H	2900 10	Gauss Oersted
Residual Flux Density	Br	1300	Gauss
Coersive force	Hc	0.45	Oersted
Loss Factor @ Frequency	Tan δ/ µi	250 1.0	10^-6 MHz
Temperature Coefficient of Initial Permeability (20 -70°C)		1.25	%/°C
Curie Temperature	Tc	>130	°C
Resistivity	ρ	1×10^5	ohm-cm

52 Material

Property	Symbol	Value	Unit
Initial Permeability	µi	250
Flux Density @ Field strength	B H	4200 10	Gauss Oersted
Residual Flux Density	Br	3300	Gauss
Coersive force	Hc	0.6	Oersted
Loss Factor @ Frequency	Tan δ/ µi	45 1.0	10^-6 MHz
Temperature Coefficient of Initial Permeability (20 -70°C)		0.75	%/°C
Curie Temperature	Tc	>250	°C
Resistivity	ρ	1 x 10^9	ohm-cm

61 Material

Property	Symbol	Value	Unit
Initial Permeability	µi	125
Flux Density @ Field strength	B H	2500 15	Gauss Oersted
Residual Flux Density	Br	1000	Gauss
Coersive force	Hc	1.1	Oersted
Loss Factor @ Frequency	Tan δ/ µi	30 1.0	10^-6 MHz
Temperature Coefficient of Initial Permeability (20 -70°C)		0.1	%/°C
Curie Temperature	Tc	>300	°C
Resistivity	ρ	1 x 10^8	ohm-cm

77 Material

Property	Symbol	Value	Unit
Initial Permeability	µi	2000
Flux Density @ Field strength	B H	5100 5	Gauss Oersted
Residual Flux Density	Br	1800	Gauss
Coersive force	Hc	0.25	Oersted
Loss Factor @ Frequency	Tan δ/ µi	15 0.1	10^-6 MHz
Temperature Coefficient of Initial Permeability (20 -70°C)		1.2	%/°C
Curie Temperature	Tc	>200	°C
Resistivity	ρ	100	ohm-cm