Zepp and 630M
An Antenna for 630 to 10 Meters.
When my old Wilson telescoping antenna tower collapsed several years ago I decided
not to rebuild it because of extensive damage to the tower and antennas. I am
fortunate having three tall trees in excess of 100 Ft. in my yard so I
decided to use them to support a couple 20 meter Extended Double Zepp (EDZ)
antennas. As Ward /Silver, N0AX pointed out in the February 2014 issue of
QST, a 89 foot horizontal dipole fed with 74.7 feet of 540 ohm balanced feed
line prouduces a low SWR on both 20 and 15 meters. I have found the Zepp's to
be very effective antennas on all bands 40 to 6 meters. Being the average
horizotall height of each antenna is 80 feet or higher helps too!
Since vertical antenna are negetively impacted by being close to metal and
other structures, locating the feedpoint away and above surrounding homes,
power power lines and poles increases the radiation effeciency. Since the end
of the 74.7 feed lines did not reach the entrance point to my radio shack, I
decided to mount a water proof box under the roof overhang of my house where
all three feedlines met. This puts the feed point for the Zepp's above the
house wiring. I then built a remote relay switching system so I could select
between the three Zepps.
As a bonus, by shorting the bottom end of the balanced feedline together and
feeding this point against ground I had a top loaded vertical T antenna that
was resonance on 160M at 1845 Khz. Perfect. A heavy #6 copper wire runs from
the remote switching box to ground rods and radial wires which I run under
roof overhang of the house and also along the perimeter of my yard fence. The
ground wire is also attached tothe the house AC ground, copper water pipes
etc. A current balun is added to the feed point at the coaxial lines which
goes to my ham shack antenna switch.
With another relay I added a separate length of 450 Ohm balanced feed line
that allows selecting one of the Zepp antennas that directly connects to the
Balanced Antenna tuner in my ham shack. This allows tuning the Zepps for all
other bands besides 20 and 15 meters for a low SWR including 80 meters. I recently
purchased a Palstar Model BT1500A balanced L network antenna tuner. I found
that using a true balanced antenna tuner with balanced feed line elliminated
all common mode RFI pickup and BCI intermod.
Since I have recently became interested in 630 Meters, 475 KHz operation I
began trying different antenna combinations to increase the effective
radiated power ouput ERP, on 630 Meters. By joining all three 450 Ohm
feedlines together at the base I was able to reduce the amount of inductance
in the base loading coil significantly. This increased the ERP because base
loading alone is the most inefficient method of resonating a short vertical
antenna. Remember that a quarter wave length vertical on 630 meters is 518
feet long so significant loading is required. Combining all three Zepp
antennas as one antenna helped achieve this.
Here is a photo of my control panel for antenna selection and SWR monitoring.
This remote 630 to 10 Meter Antenna System described here was accepted by
ARRL and published in July 2018 issue of QST beginning on page 36. To my
surprise I received a plague from ARRL voting my article as the best article
from the July 2018 QST.