-----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
