Practical_Antenna_Handbook_0071639586

C h a p t e r 1 0 : W i r e A r r a y s 255
Random length
( ) 4
Coax
to
XMTR
Antenna
tuner
4
Radials
Figure 10.2 Radials improve the “ground” of random-length antenna.
chassis of the ATU (or the transmitter if no ATU is used) and run outside. Of course,
this effectively converts your longwire into an off-center-fed wire of unpredictable
performance, but it’s far better than having no defined ground at all.
If you intend to use your longwire
on more than one band, a single
radial is of limited help. However, at
Tuner
least one company (MFJ) sells a tuner
for the artificial ground. The MFJ
Coax
model MFJ-931 artificial RF ground
is installed between the radial wire
and the ATU or transmitter chassis
ground connection, as shown in Fig.
10.3. With every band change, the
tuning controls will need to be adjusted
for maximum ground current
MFJ-931
as indicated by the built-in meter.
Keep in mind, however, that use of
an artificial ground—with or without
a tuner—falls in the category of
trying to make the best of a bad situation.
Antenna wire
Ground
system
Figure 10.3 MFJ ground line tuner
installation.