Aliexpress 20m Band Pass Filter

[@fastradioburst253]

Thanks for posting this. Was great to get a look inside.

[@adventurelaus]

Your welcome. I was curious about how it looks inside and how it performs as well.

[@jwchancey]

so.. how well did it work?

[@adventurelaus]

Ok, I think. I did have it out on a pota event where we tested the filter with an Icom IC-7300 while another station next to it transmitted on 40m. Without the filter the OVF indicator lit up. With the filter it didn't.

[@y_x2]

Using ferrite core instead of power core for filter is absolutely ridiculous!

[@adventurelaus]

I'd be interested to know how you can tell what toroid material / mix is used by looking at it, especially with unmarked ones like these.

[@y_x2]

@@adventurelaus The color of the ferrite is black and will saturate easily with power that why they use very big ferrite.

[@adventurelaus]

@@y_x2Thanks for your reply. Being ignorant, I'd still say it's inconclusive. Coming from a low cost manufacturer, the cores might never have been painted. Or the larger size makes it work just fine. We probably can agree that at very low receive power, in the micro watts range, the filter works as tested. The question is what will happen when some significant power is applied. I think I might have some ideas on how to test that. I'll try to make a follow up with that and would love to get our feedback on it.