I have made stubs from LMR-400, RG-213, RG-400 and RG-58 for various home and
field applications over the years. In general, they all work; the difference
is in depth of the null and in the bandwidth of the null. As W4EF pointed out,
the lower-loss cables produce higher-Q traps; i.e., sharper, deeper nulls. My
RG-58 stubs attenuate the second harmonic by about 24 dB; the RG-213 stubs by
about 29 dB; and the LMR-400 stubs by about 31 dB.
In Field Day, where no station is running more than 200 watts and there is some
physical separation of antennas, the RG-58's are fine, and they're pretty easy
to transport in a carrying bag. At the Caltech station, where side-by-side KW
stations feed yagis stacked on the same tower, I went with the LMR-400 for the
extra 7 dB it provides. Since they reside behind a desk, their greater bulk
isn't an issue.
73,
Marty N6VI
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