> I assume you are referring to insertion loss from in-line bandpass
filters.
> I'm planning on using combinations of parallel 1/4 and 1/2 wave open and
> shorted stubs for bandpass filtering. In testing my particular two-radio
> setup, I found them to be more effective at supressing the broadband
noise I
> was getting with some of the band combinations. Seems to me that losses
> should be nil with stubs, although I haven't seen any data to that
effect.
I think marketing and folklore has us all convinced stubs are lossless.
Just like lumped components, ALL stubs have loss. Coaxial cable stubs can
be particularly lossy. They just have so much surface area, they spread the
heat around so the temperature rise isn't great.
The stubs in your filter contribute far more to system loss than the
SO-239's do.
When all the hyper-jargon about loss gets confusing, think heat. If a
single connector had .1 dB loss, power loss would be just over 2%. That
loss would be concentrated in an area about 1/2 inch long in a SO-239. With
1500 watts, there would be over 30 watts of heat in the SO-239.
The SO-239, since heat is concentrated in a small area, would reach
de-soldering temperatures in a matter of seconds at 1500 watts if it even
had 0.1 dB loss!!!
Most SO-239's are in the area of 0.001-0.005 dB loss at 30 MHz. With 0.015
dB loss, they would overheat and likely fail (from heat) at 1500 watts! If
you aren't burning your fingers on the connectors with high power, loss is
negligible.
73 Tom
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