George, W5YR wrote:
>
> Seems like I recall that a lot of the "magic length" business originated
> with efforts to minimize the effects of line pickup and attendant
> unbalance or common-mode current in the case of coax.
>
> 72/73, George W5YR - the Yellow Rose of Texas
Nope, just chosen to make tuning easier. Predates coax by decades. Line
pickup is mostly a function of spacing and antenna balance in open wire
feeders. Feeder balance is upset by the feeder not being at perfect
right angles to the radiator.
For the general purpose ham antenna, feeder radiation is only a problem
when it kills propagation in a desired direction or causes TVI,
otherwise it can tend to cause propagation in directions and distances
the flat top didn't provide. E.g. feed radiation on 40 or 20m may be
vertically polarized and lower angle than from the flat top, better for
DX while the flat top's radiation is better for domestic contacts.
73, Jerry, K0CQ
73, Jerry, K0CQ
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