Practical_Antenna_Handbook_0071639586

C h a p t e r 1 8 : a n t e n n a s f o r 1 6 0 M e t e r s 423
diation. As a result, it’s not possible to use this scheme to completely eliminate
high-angle radiation.
• Keep in mind that the primary radiation from this antenna comes from the
feedline, not the 80-m dipole! The purpose of the dipole is to provide a total
length (feedline + one side of the dipole) that is close to l/4 on 160 m. (And to
hold the far end of the feedline up in the air!)
Years ago, before the power limitations and interference imposed by LORAN on
1.8-MHz amateur operation had been removed, the author—whose station was located
in upstate New York—made his very first 160-m amateur radio contact with Hawai’i by
using exactly this antenna and a 30W transmitter (but without the “really good RF
ground system” recommended here). Of course, primary credit for the contact should
really go to the operator in Hawai’i who picked the author’s weak signal out of the interference
and tropical noise masking it!
Receiving on the Transmit Antenna
If your station location enjoys a low background noise level on 160 m, your transmit
antenna may well be your best receiving antenna, as well. In some respects this is surprising
because most 160-m transmit antennas in use today are nondirectional around
the 360-degree compass, just like the antennas previously described.
For most of us, who are not fortunate enough to have transmitting arrays on 160 m
or who are not blessed with extremely low noise levels, other antennas for improving
the detectability of weak signals may be necessary. Chapter 14 describes a variety of
receiving antennas—including Beverages and small loops—that can often perform miracles.
Most are very low efficiency (that’s why they’re not also transmitting antennas),
but any decent receiver of the past half-century has more than enough gain to compensate
for the low output levels of these antennas.
Other than to discuss (in Chap. 23) direction-finding antennas that can be helpful in
locating specific noise sources, and to note the existence of noise-canceling accessories
available from manufacturers and suppliers listed in App. B, noise elimination is beyond
the scope of this book.