Bandstop Filter versus Coaxial Stub

[W4OP]

I have seen this theme before and wanted to post an image of one of our asymmetrical notch filters and a 1/4 lambda open stub comprised of RG-8X.
This filter is designed to recover more quickly on the high frequency side of the notch. The assymetry can be reversed so as to recover more quickly below the notch or the filter response can also be made symmetric. Both the filter and the stub offer about the same attenuation- around -30dB. But as you can see, the notch recovers to -3dB in about 900KHz., or about 0.5% of the notch frequency.

Dale W4OP

 

[Ubbe]

And also stub filters works at multiplets from the main frequency, that you probably don't want.

W4OP Dale = PAR Electronics ?



/Ubbe

 

[kb5udf]

W4OP where can I find more information about these notch filters? As in you mention "one of our," I'd like to view
your product line.

Thx

 

[KevinC]

W4OP where can I find more information about these notch filters? As in you mention "one of our," I'd like to view
your product line.

Thx

Dale probably doesn’t want to self-promote and possibly break the RR rules so I’ll do it.

PAR Electronics | Filters for the commercial 2 way market, MATV, FM broadcast, laboratory, marine industry, amateur radio, scanner and short wave listening enthusiasts

PAR Electronics Inc. Filters for the commercial 2 way market, MATV, FM broadcast, laboratory, marine industry, amateur radio, scanner and short wave

www.parelectronics.com

 

[kb5udf]

Thanks.

 

[G7RUX]

One neat trick that can be done with a stub filter is to make it multiple quarter wavelengths in the length of the stub. This way you can arrange for the odd multiple to fall on the frequency you wish to stop and the even multiple falls on the frequency you wish to pass.