Here are some measured numbers for the subject of this
discussion.
Loss through the Top Ten A/B relay box at 28 MHz is 0.02 dB. The
path through it includes 2 SO239s and 2 relay contacts.
Losses through one of the popular commercial switching bandpass
filter assemblies range fro 0.5 dB minimum to 1.0 dB maximum.
The higher losses are at 160 and 10 meters and the lower losses
are at 40 and 20 meters, typically. The rejection of unwanted
frequencies range from 18 to 55 dB.
Loss introduced by a shorted quarter wave stub made from RG-213
is 0.06 dB at 14 MHz. Rejection of 28 MHz is 31 dB.
Loss introduced by an open 1/2 wave stub made from RG-213 is 0.05
dB at 28 MHz. Rejection of 14 MHz is 34 dB.
Double stubs will typically more than double the dB rejection.
George
W2VJN
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