... design LPFs.
Used a FeelTech FY6600-M60** function generator and O'scope to evaluate two filters assembled with standard parts. The results indicated that the filers meet the design requirements.*
The filters were developed with Elsie then tweaked to use standard value MLCC 5% capacitors. The inductors use T50-2 and T50-6 wound and measured for the same inductance.
Elsie tweaked model values: Transmission loss = -0.226 dB 7.1MHz, RL -17dB***, VSWR 1.33, Knee -2.89 dB @8MHz, -3dB @9.19 MHz, -63dB @14.2MHz, -80dB @21.3MHz.
The amplitude of the generator is 'flat' from 2 to 20 MHz. That is, lining up the peak of the sine wave on one horizontal line, the peak remained constant.
Using the generator sweep function from 5 to 10 MHz, the filter load (50ohm) voltage remained flat to about 8MHz for both filters: close to the model value. The amplitude changed quickly then to the end of the sweep range. The sweep time used was 25 seconds and the sweep cycles so you can get repetitive 'looks' at the frequency and amplitude values. The scope measurement window is a little help too.
I wasn't able to measure the notch attenuation or insertion loss. The sweep can be stopped and started but it's awkward and not precise. Here's where a much large screen and continuously adjustable settings would be needed (or a spectrum analyzer... :-)
*I would use the MFJ-259C to make other measurements.
**Bangood $87
Fun Stuff...
Chuck, W5USJ (ex K2OFN)
ARCI 5422, SKCC 19956
EM22cv, Rains Co., Texas
