a length of 7/8” wooden dowel will prevent stray RF coupling to the mast, a condition that could
cause detuning and result in element measurements deviating from those prescribed in the chart.
Warning: Never assemble or install your antenna in close proximity to
power lines or entrance cables. Accidental contact with utility lines can
result in serious injury or death.
Tuning Procedure:
Three adjustments tune the antenna (see diagram). When following the
tuning chart, note that dimension
E1
always refers to the whip that is mounted on the
loading coil
assembly
(
L1
), and
E2
refers to the whip installed directly to the feed block. On 30 Meters, E1
and E2 are not equal and, if reversed, the antenna will not tune properly
.
Tap
Whip #1
Whip #2
Balun
Coax
EL1
EL2
Loading
Coil
Tuning Chart:
E1
and
E2
are measured from the face of the feed block to the element tip
(E1
length includes the loading coil assembly).
When setting E1 and E2, extend each whip from the
feed block toward the tip, so the element always has maximum diameter.
To estimate the
L1
slider setting on 40 and 30 Meters, count the
exposed turns
between the end
of the coil and the face of the slider tube. Alternatively, you may measure the distance from the
end of the coil to the face (both provided). Then, fine-tune the slider position for minimum SWR.
Above 30 Meters, move the slider to the outer end of the coil, shorting out all of the inductor turns.
Frequency E1 E2
L1 .
7.15
Full Length
Full Length 26-t
10.11
Full Length
9’ 9”
16-t
14.15
Full Length
Full length
Shorted
18.11
13’
13’
Shorted
21.20
11’
11’
Shorted
24.93
9’ 3”
9’ 3”
Shorted
28.50
8’ 2”
8’ 2”
Shorted
50.10
4’ 3”
4’ 3”
Shorted
Optimum dimensions for minimum SWR may vary at your location, depending on ground
conductivity, nearby objects, and antenna height. Note that the “Big Ear” is a continuous
coverage antenna. By scaling the length of E1 and E2 to the nearest ham-band settings, tuning
should be possible on any frequency between 7 and 55 MHz.
In Case of Trouble:
If you are unable to obtain low SWR, if settings deviate widely from the
chart, or if SWR jumps intermittently, check the following items:
[ ] Are the coil assembly and each whip seated firmly?
[ ] Is there damage to the coil or attachment wire?
[ ] Is the coax feed shorted, open, or intermittent?
[ ] (30-M) Are dimensions for E1 and E2 reversed?
[ ] (Above 30-M) Are all of L1’s turns bypassed by the tap?
[ ] Is a metal mast making contact with the feed block and detuning the element slightly?
