Designing an LNA with bandpass filter for 430 MHz - tutorial

Hi! I don’t know if the category is good and I wasn’t even sure if I should publish this thread but maybe someone could find it helpful :slight_smile:

I wrote a step by step tutorial about designing a simple LNA with a bandpass filter for 400-440 MHz from a beginner’s perspective - maybe there are some other beginners in radioelectronics here for whom it might be interesting. When I started this project, I couldn’t find any information about how to start designing this kind of thing - there are some photos of PCBs in the internet but no one shared their experience about how to make it from scratch (or at least I didn’t find anything - if you know any good source, you’re welcome to share it, I’m interested!).

You can find the whole text here: Designing an LNA with bandpass filter for 430 Mhz – from a beginner’s perspective | alicja • space
And the project on my Github: GitHub - alicjamusial/LNA: LNA with filter for 400-440 MHz (UHF for amateur satellites)

This LNA+filter is now connected to my test ground station (SatNOGS Network - Observations). As I wrote in the article, the observations are better than without it (and better than with cheap one bought on eBay :smiley: ).

If you have any comments, feel free to share it - remember only that I’m a total beginner and not a professional, so please, try to not be too harsh :slight_smile:. Have a nice day!


Czy posiadasz wolne plytki do LNA .Bardzo chetnie odkupilbym i przetestowal.Pozdrawiam Janusz SP7THR.

I’ve plugged range from my VHF to the website you’ve mentioned in the blog post and it gave me following output:

Basic layout seems to be similar to yours with different values on different elements.

  1. Does this mean that I could simply switch the elements on your design and get something for VHF?
  2. I see that dip in S11 for VHF is much smaller than on your design - does this mean that this particular design is not a good fit for VHF?

@sp7thr - no, I don’t have any spare parts, sorry :slight_smile: Gave them all to friends.

@michal.drzal On my newbie intuitiion it looks quite good, I’d give it a try. You can always try to change edge frequency values a bit (1 MHz up or down) and see if it makes the pink line go lower. But it doesn’t look wrong - switching elements values’ in my design should do the job.

Sorry for the late answer - I didn’t get any notification about these posts :grimacing:

Great work, thanks for sharing!

I know it can be annoying when people want more from a project that is already great, so sorry for asking: have you thought about what would be needed to add bias-tee support, so we wouldn’t need separate power supply?

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I’m pretty sure that a redesign would be needed to add bias-tee, so I didn’t consider it (as it was my first filter). But if you know electronics, don’t hesitate to take my design and adjust it to your needs, it’s on open license :slight_smile: