[Elecraft] antenna question

[Stuart Rohre]

Folks,
George hit it on the head.  There are more reasons to use non resonant
antennas fed with parallel line than to worry about measuring and cutting
them to resonant length.  You are using the transmatch to make that
unneeded.

Many handbooks and introductory texts start out talking about resonant
dipoles just as a way to teach the basic theory.
But that does not mean they are more efficient than a transmatch and
parallel line fed doublet of some length.  That early intro to resonance
gets misinterpreted by new hams as giving resonant dipoles some magical
property over non resonant lengths.  The resonant dipole is an advantage
only on a single frequency, and you need a transmatch everywhere else, so
why bother with measuring to resonance? Who works only a single spot in the
band?  Or a single band?

A resonant antenna is higher Q, and might spike the impedance such that the
transmatch has to be adjusted if you try to cover another frequency in the
same band that is nearby.  With a broadly tuned doublet that is not resonant
on any band you are using, except perhaps the lowest, you can move around
not only on frequencies in a band but from band to band with some easily
determined settings of the transmatch, that can be returned to when you QSY.
A simple chart sets you up to return to any spot on any band.  A few
settings work over any one band for our Field Day big loops and Double
Zepps.

The losses of parallel line are much lower feeding broad coverage doublets
than if you tried to use coax for multibands.
The measurement of doublets for many bands is simply as George says, have
wire to stretch from one support to the other.  Fold it in half to find the
middle, and cut it there and insert feedpoint insulator, and your feeder.
That way you do not need to carry a long tape measure to field days, or
emergency set up locations.

If your doublet is long enough at a given band, you can realize gain over a
dipole. It is the truly multipurpose antenna.
72,
Stuart K5KVH