A FEW QUESTIONS ABOUT LOW PASS FILTERS

[M0GVZ]

But yes, clean in equals clean out. Been hearing this one a lot lately!!

I keep banging on about it like a mental person. The one reason you can give for doing it that absolutely nobody can argue with is that instead of jizzing your RF power all over the spectrum you send it out where you want it so you're stronger to the station at the other end.

 

[StrangeBrew]

Any thoughts on these:
http://www.communication-concepts.com/fl1-10/

Was wondering if sticking a couple of these on the input and output of an amp I had would be a worthwhile project.

 

[Stellasstillarat]

Of cause a negligible loss is ideal and although most low pass filter specs. show different amounts of loss their normally very low.
what is it that causes one to be rated at a higher loss then another.
And might one with a greater loss rating be doing a better job at suppressing rfi?

I use a Barker & Williamson FL1500/10. Handles 1500 watts easily, cut-off freq. of 34 MHz with max. attenuation at 52 MHz. MINIMUM attenuation is 72 dB. Negligible insertion loss.

 

[Captain Kilowatt]

Of cause a negligible loss is ideal and although most low pass filter specs. show different amounts of loss their normally very low.
what is it that causes one to be rated at a higher loss then another.
And might one with a greater loss rating be doing a better job at suppressing rfi?

Higher insertion losses can be due to several factors.Poor shielding between filter sections. Too low cut-off frequency caused by poor selection of component values and the general shape of the attenuation curve of the filter. Filter not properly designed for 50 ohms exactly. Small wire size for the coils which increases losses as well as limits power handling.

As for greater losses doing a better job of suppressing RFI? No way. Not related at all. Attenuation is all about using good quality components and assembling them properly. this should result in low insertion losses as well as high attenuation.