Howdy all,
OK, now I have some time to write my ferrite material comparison on type 43
and type 77 material. This is taken from Amidon's literature.
>From page 14:
Material 43 77
==============================================================
Initial Permeability 850 2000
Max Permeability 3000 6000
Max flux density 2750 4600
14 oer, gaus
Residual flux density 1200 1150
Vol. Resist (ohms/cm) 1E5 1E2
Temp Coeff 20-70 deg C 1% 0.60%
Curie Temp deg C 130 200
Resonant Cir. Freq (MHz) .01 to 1 MHz .001 to 1 MHz
Wideband Freq (MHz) 1 to 50 MHz 0.5 to 30 MHz
Attenuation RF Noise, MHz 20 to 600 1 to 50
And then quoting from their text on page 15 of their brochure:
"We recommend the #73 or the #77 ferrite bead material for the attenuation
of RFI resulting from transmissions in the amateur band. The # 43 material
will provide best RFI attenuation from 30 to 400 MHz and the #64 material is
most effective above 400 MHz. The #75 material is recommended for RFI from
1 to 20 MHz, but they can also be very effective even below the AM broadcast
band."
Also from page 13:
Material 43 (u=850) Nickel-zinc. High volume resistivity. Widely used for
medium frequency inductors and wideband transformers up to 50 MHz. Very
good frequency attenuation from 30 mHz to 400 MHz.
Material 77 (u=2000) High Saturation flux density at high temperature. Low
core loss in the 1 KHz to 1 MHz range. Suited for power conversion and
wideband transformers. Widely used for noise attenuation in the 0.5 MHz to
50 MHz frequency range.
Also again from page 14 the Al (mH/1000 turns) values are given:
Type 43: Using the FT-240 torroid size (2.4" OD, 1.4" ID): 1240 mH/1000
turns
Type 77: Using the FT-240 torroid: 3130 mH/1000 turns
So it's clear that the type 77 material provides far more inductance (my
comment).
Anyhow, to me, it's pretty clear from this that type 77 IS the material to
use for HF common mode chokes. Perhaps Palomar or Fair-rite materials
numbered 43 or 77 are different from Amidon's.
Given this, I would like to know why people have found type 77 material not
to work at HF.
Comments?
73,
Jon
KE9NA
--
-------------------------------------
Jon Ogden
KE9NA
http://www.qsl.net/ke9na
"A life lived in fear is a life half lived."
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