Here's a nice little circuit that the man who originally owned this box of "stuff" I was given built. As I could tell before I opened it, it was probably a low pass filter. I know you all know most of this but we have a lot of readers here on the TEA thread.
After opening I saw a 15 uH inductor, two 4 nF caps, and two older style inductors, which looked like a butterworth filter. It was made using good construction methods. I looked on the internets but wasn't sure I found the proper color codes for the two inductors on the input/output, can anyone check on the values? The color codes are gold-red-gray-silver (or vice/versa). I'd like to verify the actual factory values. (Yea I could measure it but I want to know the factory-stated value).
I went to a butterworth filter design tool -
http://www.calculatoredge.com/electronics/bw%20tee%20low%20pass.htmand plugged in the value for the cutoff the man had labelled on the top plate - 1.3 MHz (-3 dB). I got these values -
L1: 3.8 uH (unverified)
L2: 12.2 uH (15 uH installed)
L3: 3.8 uH (unverified)
C1: 4 nF (same as installed)
C2: 4 nF (same as installed)
I also did a sweep of it and it matches up to it's specs pretty well. What would it be used for? Well it passes most of the AM band and VLF. Most of the time I've been concerned with blocking strong AM stations, but I suppose if you are interested in low band DXing you might want this? Any other ideas?