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Old 25th Oct 2022, 11:13 pm   #189
G0HZU_JMR
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Join Date: Sep 2010
Location: Cheltenham, Gloucestershire, UK.
Posts: 3,077
Default Re: 6-gang FM stereo tuner heads

Quote:
I didn't bother with his Butterworth LP filter as I am not convinced either. I thought it is not necessary. Funny enough this guy also copied his LP filter idea:

https://electronicprojectsforfun.wor...quency-probes/
To be fair, that circuit uses a LPF with a more sensible L to C ratio for a 50Ω design so the LPF will appear fairly transparent up to the cutoff frequency. It looks like a regular 50Ω LPF design. I don't really have an issue with that LPF as it probably won't have much (if any) impact on the input impedance of the probe.

By contrast, the LPF in the thesis has tweaked component values and this will cause the issues I described in my earlier post because it isn't a 50Ω filter anymore.
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