>Please explain stagger tuning.
>Do you tune the other stub to CW and the other to SSB
>part
>of the band, and in between a mid-band quarter wave
>line to
>provide at least 25+dB over a broader range of
>frequencies?
A single stub (RG213 type coax) will give you +/- 30
dB attenuation on the targeted 2nd harmonic. (notch
depth and width vary based on frequency). If you use
smaller coax like RG-8X, the notch may only reach 25
dB attenuation on the 2nd harmonic.
If you use a dual stub, cut one stub for the SSB
portion of the 2nd harmonic band, and the 2nd stub for
the CW portion of the 2nd harmonic band. Then
separate the stubs by 1/4 wavelenght on the 2nd
harmonic you are trying to notch (center of band is
OK, and not critical).
So, if your 40m station's 2nd harmonic is causing
problems to your 20m station, here's an example of the
stub for the back of the 40m TX to minimize the 20m
harmonic: (I didn't keep notes on the exact
frequencies I cut them to...)
Cut first 1/4 wave stub for 14050
Cut spacing coax to 14150
Cut 2nd 1/4 stub for 14225
If you use RG213 type coax for the stubs, your
resulting attenuation will be about 50-60 dB across
most of 20m. If you have access to a network
analyzer, you can experiment on the best frequencies
for the 1/4 stubs. The spacing coax length is not
very sensitive to the band segment.
I hope that helps.
Kenny K2KW
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