Ed,
Steward ferrite discusses this question their website. Other than noting
it was there I didn't read it so I can't speak to the quality of the article,
but one would assume these guys should know how to make such a measurement.
Gary
From: Price, Ed [mailto:[email protected]]
Sent: Thursday, December 18, 2003 11:43 AM
To: 'Grasso, Charles'; '[email protected]'
Subject: RE: Measuring a ferrite performance
-----Original Message-----
From: Grasso, Charles [ mailto:[email protected]]
Sent: Thursday, December 18, 2003 9:40 AM
To: '[email protected]'
Subject: Measuring a ferrite performance
Greetings all:
I have a requirement to test the performance of ferrite bead (one that
that can fit over a power cord) to 500MHz for qualification of
alternate vendors.
I have an impedance analyzer - but it only goes to 40MHz. Does anyone
have a good way to verify ferrite impedance.??
Thanks
Best Regards
Charles Grasso
Senior Compliance Engineer
Echostar Communications Corp.
Tel: 303-706-5467
Fax: 303-799-6222
Cell: 303-204-2974
Email: [email protected];
Email Alternate: [email protected]
Chuck:
Assuming that you have a signal generator and a spectrum analyzer, you could
try the following:
1. Get a small RF project box. Mount two N or BNC or SMA coax connectors on
opposite walls of the box. Solder a short wire directly from one coax
connector center pin to the other.
2. Decide on system impedance. If 50 ohms is OK, then just connect a 3 dB
attenuator to each of the coax connectors. If you want another impedance, then
put appropriate resistors (carbon comp preferred) into the project box.
3. Connect the signal generator to one attenuator, and the spectrum analyzer
to the other.
4. Now set the generator to 0 dBm and sweep or step the frequency range,
noting the spectrum analyzer response.
5. Now open the box, break the wire, thread the bead onto the wire, and
re-solder the wire.
6. Repeat step 4. The amplitude differences will be the insertion loss due to
the bead performance.
7. Repeat steps 5 & 6 with any other bead samples.
This isn't an exhaustive test, but it's a good A to B comparison of RF loss.
Ed
Ed Price
[email protected] WB6WSN
NARTE Certified EMC Engineer & Technician
Electromagnetic Compatibility Lab
Cubic Defense Applications
San Diego, CA USA
858-505-2780 (Voice)
858-505-1583 (Fax)
Military & Avionics EMC Is Our Specialty
