"Richard Harrison" wrote
ON4UN says on page 9-29 of his 1994 edition of the Low-Band DXing
book: "Over sea-water the 5/8 wave has lost 0.8 dB of its gain already,
the 1/4-wave only 0.4 dB." (It`s less than one dB).

I think you should question that conclusion. Sea water (or any path of
fixed parameters) attenuates every groundwave by the same decibel amount for
the same path, conditions, and frequency. For example, using the FCC curves
for groundwave propagation from a radiator with 1 kW of power and 120
1/4-wave radials, over a seawater (only) path at 1MHz...

- a 1/4-wave vertical produces a field of 190 mV/m at 1 mile,
and 85 mV/m at 2 miles.
- a 5/8-wave vertical produces a field of 274 mV/m at 1 mile,
and 137 mV/m at 2 miles.

This is as expected. Doubling the distance reduces field strength by 6 dB
in each case. The absolute value of the groundwave signal has no bearing on
the percentage of it that is lost as it propagates.

Even a disappearingly small radiator produces radiation less than 1/2 dB
weaker than a 1/2-wave dipole, or a 1/4-wave vertical. In lossless
antennas, the only difference in radiated signal between the full length
antenna and a too-short antenna comes from the slight difference in
their patterns.

The difference in peak gain between an isotropic radiator and a reference
dipole in free space is 2.15 dB. Practical antennas in real-world
applications can show greater than 0.5 dB losses for shortened radiators.
In my example above, the 1/4-wave radiator would need about 2 kW of input
power to produce the same field as the 5/8-wave radiator with 1 kW, over the
same path -- which is a 3 dB ratio.

In 1949, I worked in a transmitting plant where two stations, KPRC, 950
KHz, and KXYZ, 1320 KHz, shared the same transmittinng tower. Both
stations had identical RCA 5-C, 5 KW transmitters. Regional coverage was
almost identical despite many more degrees in the tower at 1320 KHz than
at 950 KHz.

If the tower was 90 degrees at 950 kHz it would have been 125 degrees at
1320 kHz. The FCC efficiency for 90 degree towers is 190 mV/m at 1 mile for
1 kW, and about 210 mV/m for 125 degree radiators. So the 1320 kHz signal
was launched with a greater groundwave, but that advantage would be lost as
the signal propagated over whatever the ground conditions are for the path
(higher freqs have greater losses). Using the FCC curves and a conductivity
of 8 mS/m, the 5 mV/m contour should be about 35.5 miles away for the 5kW
950 kHz station, and about 27.5 miles away for the 5kW 1320 kHz station.
But close in probably few would know the difference.

Bill Orr writes on page 78 of "Vertical Antennas":
"A helix length of about .05 wavelength or more provides good results
as a substitute for a full size quarter wavelength vertical antenna."

Was 0.05 lambda the pitch of the helix? If so, how many turns? How were
the two installed? How were the antennas oriented, and In which direction
from the antennas was he comparing them?

+ + +

And thanks for some serious comments on this subject.

RF