My main objective was to be able to see the passbands of various ceramic and other filters, and it turns out I have the equipment to make it happen. A frequency generator (VC2002 function generator), a sweep generator (Heath 1274 sweep function generator, and a scope (Tek TAS465). The setup:
The other two pix show the low end freq and the high end freq.
I can adjust the amplitudes on both generators. I can see the shape of the bandpass (linear, not dBs though) and I can also see the amplitude of the marker frequency outside the passband of the filter on the scope. The scope is triggered from the sweep gen. The marker is always on. But the marker has to go thru the filter to get on the scope, and changing the marker frequency I can see when it drops to half amplitude and thus the 3dB points, high freq and low. The marker also beats with the sweep generator (which doesn't really show in the pictures) when the frequencies of the two happen to coincide.
The Device Under Test (DUT) is a ceramic filter at 455KHz, and has a little more than 20KHz bandwidth at 3dB. Which would be good for 10KHz of AM radio station audio, the max the FCC allows. Hifi AM.
Okay... Yes, channel spacing is 10KHz, but not in the same town.
03-10-2016, 06:52 PM
Threaded Mode