I had some ferrite cores in a envelope marked FT50-43. To check that these
cores are actually FT50-43, I put a test winding on one and calculated the
inductance. Using a Booton 260A Q-Meter, I tried to verify this. I got no
indication over a wide frequency range on the Q-Meter. The Q-Meter stayed at
zero.

Doing the same thing with a FT50-61 core, the Q-Meter gave a accurate
indication. Is there something about the 43 material that does not allow a
indication on the Q-Meter?

On Mon, 11 Aug 2003 15:03:57 -0700, Roy Lewallen
wrote:

Depends on the frequency. The Q of type 43 ferrite is 1 at a few MHz,
and less than 1 above that. It's unlikely that your Boonton will measure
Q that low. You'd be able to measure a decent Q at a few tens of kHz if
the meter goes that low.

The low Q is fine for broadband transformers and definitely a good thing
for RF suppression (one of the primary markets for type 43 material).
But you wouldn't want to make a tuned circuit inductor out of it at HF.

See http://www.fair-rite.com for more information about the frequency
characteristics of various types of ferrites.

Roy Lewallen, W7EL

Bart25 wrote:
I had some ferrite cores in a envelope marked FT50-43. To check that these
cores are actually FT50-43, I put a test winding on one and calculated the
inductance. Using a Booton 260A Q-Meter, I tried to verify this. I got no
indication over a wide frequency range on the Q-Meter. The Q-Meter stayed at
zero.

Doing the same thing with a FT50-61 core, the Q-Meter gave a accurate
indication. Is there something about the 43 material that does not allow a
indication on the Q-Meter?


Roy is correct, the Q is too low to register on a Boonton 260A Q-meter
or, for that matter, on the 4342A Q meter. I've had success, however,
measuring coils wound on Type 43 material with both the GenRad 916 RF
bridge and a Boonton 250 RX meter. In both cases, you are measuring
R+jX of the inductor, so you can then go back and calculate the Q.
(Series with the 916 bridge, parallel with the 250 RX meter, so you
may have to do a little extra math if you take the data with the 250
RX meter.)

(I was measuring leakage and magnetizing inductance of some broadband
transformers I wound.)

Jack K8ZOA

On Mon, 11 Aug 2003 15:03:57 -0700, Roy Lewallen
wrote:

Depends on the frequency. The Q of type 43 ferrite is 1 at a few MHz,
and less than 1 above that. It's unlikely that your Boonton will measure
Q that low. You'd be able to measure a decent Q at a few tens of kHz if
the meter goes that low.

The low Q is fine for broadband transformers and definitely a good thing
for RF suppression (one of the primary markets for type 43 material).
But you wouldn't want to make a tuned circuit inductor out of it at HF.

See http://www.fair-rite.com for more information about the frequency
characteristics of various types of ferrites.

Roy Lewallen, W7EL

Bart25 wrote:
I had some ferrite cores in a envelope marked FT50-43. To check that these
cores are actually FT50-43, I put a test winding on one and calculated the
inductance. Using a Booton 260A Q-Meter, I tried to verify this. I got no
indication over a wide frequency range on the Q-Meter. The Q-Meter stayed at
zero.

Doing the same thing with a FT50-61 core, the Q-Meter gave a accurate
indication. Is there something about the 43 material that does not allow a
indication on the Q-Meter?


Roy is correct, the Q is too low to register on a Boonton 260A Q-meter
or, for that matter, on the 4342A Q meter. I've had success, however,
measuring coils wound on Type 43 material with both the GenRad 916 RF
bridge and a Boonton 250 RX meter. In both cases, you are measuring
R+jX of the inductor, so you can then go back and calculate the Q.
(Series with the 916 bridge, parallel with the 250 RX meter, so you
may have to do a little extra math if you take the data with the 250
RX meter.)

(I was measuring leakage and magnetizing inductance of some broadband
transformers I wound.)

Jack K8ZOA