Monday, December 26, 2022


Please visit our new e-shop :)

Saturday, December 3, 2022

 Extra Virgin Can 70 - cavity filter for 70cm :)

Vodafone build new GSM site here at the roof in my job. There are three antenna systems for 800 and 900 MHz and this killed my experiments with LoRa at 433 and 868 MHz. I have found very nice cavity filter for 868 MHz at Aliexpress which works great but I need something also for 433 MHz. 

I found 5 l can in my stock with drilled holes and N connectors. Marek OK2DL drilled it many years ago when I ordered these cans for 50 Ohm oil dummy loads :) I have decided to try it. 3D printed part helped with mechanical stability and works also as a nut holder. Tunning screw is metal, what is a bad idea but I do not have better now... The result is not so bad! I focused to very low Insertion Loss where the result is lower stopband and also higher BW. There, the IL is around 0,7 dB and 3 dB BW 9MHz. By the moving the internal loops from the tunning screw you are able to obtain better stopband but higher IL.