Tag Archives: Adam

137MHz Bandpass filter for NOAA / Meteor Satellites

Yesterday I saw a new blog post by Adam (9a4qv) in LNA4ALL. The post (here) talks about a band pass filter he did for Weather Satellites and I decided to try as well.

Unfortunately I don’t have a exact match for that components at home, so I tried to do something with the components I have. So the lower value I had for capacitors was 10pF, and the needed values for Adam’s Filter is 1pF, 4.7pF and 15pF. I decided then to use 10 in series to do the 1pF, 2 in series for the 4.7pF (that will be 5pF) and then one in parallel with two in series to give me the 15pF. Its a very close match, and I’m unsure about the effects of serialization of capacitores in the filter (increase inductance maybe?). So here is the results.

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New way to measure filters and my new filter

So I’m still mad about the FM Spectrum (88-108MHz) noise I get when using a LNA or something else. So I’m still looking for a nice and easy way to filter out these signals.

Last time I posted about a TV/FM Diplexer, that works great, but doesn’t attenuate enough the signals. So the solution would be cascading several of them, but I found that is very hard to find one Diplexer or FM Trap filter those days.

So I started looking out how to make my own filters. So I reopened Adam’s Website (LNA4ALL) that have a small filter he did for FM Trap and tried (again) to make my own.

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