filter RX

[radium98]

a question
Is there any Stripline filter on etched directly on pcb epoxy double side ,that can be used for reception .like the one used on rx for reception called cavity filter
like the one in this picture but in pcb mode?

[Albert H]

Yes, but only at UHF and higher frequencies

[radium98]

Thanks.And why in VHF it can not be acheived ?

[Albert H]

Simply because the striplines are too large at lower frequencies. It's possible to do minor impedance conversions at VHF using board tracks, but the values of inductance available with even quite long tracks are far too small for useful filtering.

[radium98]

thanks Albert.And what an easy diy filter will you suggest me to try for frequency 200-250

[Albert H]

The traditional pi filter - two coils that show 50Ω impedance at your frequency of interest, with 50Ω impedance capacitors at both ends and 25Ω impedance capacitor in the middle. Design for a frequency about 15% higher than the highest frequency you want to pass.

Get a copy of the ARRL Handbook. There's all the design notes you'll ever need for 225MHz (an amateur band in the USA)

[radium98]

thank you . ARRL Handbook what issue ?

[Albert H]

Get one of the ones from the 90s - you can get them cheap on Ebay. There's a wealth of useful info in there!

[radium98]

if you can scan me some pages ,because i cant buye anything . sadly we have issues