There are multi band dipoles such as fan dipoles, trap dipoles, stub
detuned dipoles, and linearly loaded dipoles.
It's been mentioned that with fan dipoles the lowest frequency band has
it's band width increased, but on the higher frequency of say 160 and 75
we find the band width narrows. Remember this is also the second
harmonic of the 160 segment and the bands tend to be harmonically related.
Is it this function that tends to cause the higher bands to lose usable
Some swear the praises of trap antennas, but they are relatively
inefficient compared to others and it takes some beefy traps to handle
the legal limit. These traps can see some pretty high voltages at the
legal limit and when used with a tuner these traps can see some even
I'd think stub tuning, or decoupling would be easier to do with ladder
line than the "fan" approach of parallel wires.
I really don't know much at all about the linear loading aspect.
Then there is the *balun* at the feed point. Most of the commercial
multi band wire antennas use a voltage balun at the feed point and for
75 and even 40. Many rigs require a tuner to cover the whole band. Most
of these baluns are incapable of handling the legal limit with much of
an SWR and a tuner will allow the balun to get hit with more power,
generally cooking it when operated outside it's SWR limits. I think many
of these are pushed to handled the legal limit PEP, let alone higher
duty cycle modes even with a low SWR.
There is a lot of equipment out there that is generously rated even when
it comes to PEP, let alone digital modes.
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