Crystal Filter Perfection

Sometimes, just sometimes, all your ducks align in a row and you build something that is dead set on the money. I think today I have done just that with this crystal filter.

Firstly I have redesigned the PCB board and test jig setup I am using, making construction just a little bit easier and allows me to easily use the slightly larger binocular core.

But secondly, I think i hit the nail squarely on the head, with this filter. I mean its almost perfect. 5dB loss, great, good shape factor, great, -55db stop band, great, exactly 2200Hz passband PRICELESS. I honestly could not have done better even if I tried. Now to build the receiver board and pray to Jebus that it works as good as this filter looks.

As a bonus, here is his friend the CW filter, 600Hz wide. A little more lossy but still good stop band and shape. I was shooting for 500Hz, bit I need maybe another 15pF per node. Good enough for me though, that is 2 filters for a receiver, 2 filters that should perform reasonably well.

Final EDIT:

So I was going to upload the gerbers and create a great big post about how to use them. But, i went looking for the files and it looks like I have deleted them by mistake when cleaning up my project files. I got no idea how I did that, but they are gone and its a lot of work to recreate them, so there will be no release of these PCB files. Lucky for me I can reorder them easily and I also have enough board here to make 20 filters, that should be a life times supply for me. Rather sad really, because they work so well.

Rob.

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3 thoughts on “Crystal Filter Perfection

    1. Thanks Tom. Hope you are well. How is your 15m CW rig coming along? Making lots of contacts with it?

      1. Everything going well here, just waiting for spring to kick in. Haven’t done much with the rig in a couple of months… Basement workshop, and it’s 7C down there. I’ll get back to it. I’m amazed at all the stuff you’ve been up to!

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