Stryped wrote:
"If I use a conductive boom and ground it, is there no need for a
coaxial lightning arrester?"

That is my experience, provided that the driven element is a
short-circuit for lower frequencies, such as a folded dipole or a
short-circuit 1/4-wave stub.

My company had countless examples in high places over the world with no
damage to radios, including many solid-state models, operating 24-7.

W6SAI, Bill Orr gives plenty of examples of "plumber`s delight" Yagi-Uda
antennas in the eighteenth edition of "Radio Handbook" (1970). He also
warns on page 548: "Short large-diameter elements have low Q and are not
practical in parasitic arrays. Orr also says: "The Yagi antenna,
however, remains "the antenna to beat" for the 50-,144-, and 220-MHz
amateur bands."

Best regards, Richard Harrison, KB5WZI

Richard Harrison wrote:
Stryped wrote:
"If I use a conductive boom and ground it, is there no need for a
coaxial lightning arrester?"

That is my experience, provided that the driven element is a
short-circuit for lower frequencies, such as a folded dipole or a
short-circuit 1/4-wave stub.

My company had countless examples in high places over the world with
no
damage to radios, including many solid-state models, operating 24-7.

W6SAI, Bill Orr gives plenty of examples of "plumber`s delight"
Yagi-Uda
antennas in the eighteenth edition of "Radio Handbook" (1970). He
also
warns on page 548: "Short large-diameter elements have low Q and are
not
practical in parasitic arrays. Orr also says: "The Yagi antenna,
however, remains "the antenna to beat" for the 50-,144-, and 220-MHz
amateur bands."

Best regards, Richard Harrison, KB5WZI


What do you mean it is "short circuited for low frequencies?"

I am trying to decide whther to go with two antennas or one.

I would like to build at least one of them, but can not find plans for
one with a conductive boom.

Stryped wrote:
"What do you mean it is a "short-circuit for low frequencies?"

A folded dipole, you might agree, is essentially a short-circuit for
d-c, also for 50-60- Hz a-c. At some high frequency, the folded dipole
is no longer a short-circuit, but offers considerable opposition to
current at its input terminals.. Its impedance is very high at its first
resonance where its overall length is 1/4-wave, and its impedance is
often about 300 ohms near its second resonance where its overall length
is about 1/2-wave.

At frequencies much lower than the resonant frequencies of the dipole
(most of the energy contained in a lightning stroke) the opposition of
the folded dipole is very low, or almost a short-circuit. This puts the
voltage at both terminals of the dipole to the same value and makes the
lightning applied to the transmission line a common-mode phenomenon.

Best regards, Richard Harrison, KB5WZI