Practical_Antenna_Handbook_0071639586

332 p a r t V : h i g h - F r e q u e n c y A n t e n n a s f o r S p e c i a l i z e d U s e s
ability to copy weak signals in the presence of signal fading (QSB), ionospheric
skew paths, and/or polarization shift.
Spurred by accelerating worldwide interest in the 160-m band as long range navigation
(LORAN) systems were decommissioned and frequencies became available to amateurs,
the decade following publication of the fourth edition of this handbook has been
a fertile period for development of receiving antennas for that band. Thanks in large
measure to the use of the Internet to rapidly disseminate new design concepts and experimental
results, “folklore” about antenna performance has largely been replaced
with a solid body of good science. Today the low-band receiving enthusiast—whether
radio amateur, broadcast band listener, or shortwave listener—has available an arsenal
of antenna types to enhance his/her receiving capabilities. They include:
• Beverage and Snake
• Multiturn loop
• EWE
• K9AY loop
• Pennant
• Flag
• Short verticals
• Longwires
Many of these antenna types are employed not only singly but often in phased configurations
with duplicates of themselves. Some of these antennas cannot be analyzed
by viewing them as derivations of the half-wave dipole. All except the longwire are
generally unsuitable for transmitting purposes for multiple reasons:
• Low radiation resistance (difficult to match)
• Very low efficiency
• Easily destroyed by even modest power levels
Because of their inefficiency, these antennas generally present a signal level to the
receiver input terminals that is anywhere from 10 to 40 dB below signal levels typically
delivered by a transmit antenna during receiving periods. But because the atmospheric
noise level at MF and lower HF frequencies is so high, receiver sensitivity, per se, is
seldom an issue and preamplifiers are only occasionally required.
Beverage or “Wave” Antenna
The Beverage or wave antenna is considered by many people to be the best receiving antenna
available for very low frequency (VLF), AM broadcast band (BCB), mediumwave
(MW or MF), or tropical band (low HF region) DXing.
In 1921, Paul Godley, who held the U.S. call sign 1ZE, journeyed to Scotland under
sponsorship of the American Radio Relay League (ARRL) to erect a receiving station at
Androssan. His mission was to listen for amateur radio signals from North America. As
a result of politicking in the post–World War I era, hams had been consigned to the sup-