Murata CFWS455 Resin MoldedCeramic Filter SOLVED

How can I test the above component. Can you please supply instructions. Cheers

September 10, 2018

2 Answers

Answer by mikerogerswsm

This link will give the datasheet:

There is a test circuit shown.

Ideally you need a wobbulator but any good tuneable source of around 455kHz will do.

The output should be measured with an RF voltmeter, but almost any 'scope will do.

Connect the test circuit. The resistors are shown as 2000 ohm but 2k2 should be okay.

Connect one beam of the scope to your source, the other beam to the filter output, and sweep the frequency, You should see the output, flat at 450-460kHz, and nothing at lower and higher frequencies.

Testing can be carried out with the device in-circuit and power on or off. Keep the signal kept down to a safe level, say 100mV.

The filter will normally not degrade except from extreme physical stress.

Thanks for the interesting question. mike

ACCEPTED +1 vote
by mikerogerswsm
September 10, 2018

PS - I'm in the UK, first time I've contacted Tasmania! mike

by mikerogerswsm
September 10, 2018

Answer by VK7LAZ

Thanks Mike, I am retired and took up amateur radio for a hobby and I want to learn more about electronics, especially testing and repairing electronics.

In the test circuit, what is the Rg in what looks like a signal generator.

I have a RF voltmeter I built as per VK5JST design. What should the rf voltmeter read? I also have a Tektronix 2213 oscilloscope, but haven't learned to use it yet.

Thanks for your assistance.

+1 vote
September 10, 2018

Rg is the sig gen output impedance, usually 50 ohms at RF.

The output is shown as 0dB, the same voltage as the input, with max insertion loss shown in the table as 6dB, half the input voltage.

The RF voltmeter circuit diagram looks okay, it has a nice high input impedance.

The Tek looks nice. I prefer analog 'scopes. The controls are intuitive and should be easy to learn. Plenty of vids on YouTube.


by mikerogerswsm
September 10, 2018

Map showing Tasmanian ham radio clubs:

Well worth joining one of these, they will have lots of interesting events.

by mikerogerswsm
September 10, 2018

Thanks Mike

September 11, 2018

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