- 11 -
Low Frequency Response - Internal Jumpers
The sensitivity response of the
ARAH
System
does not
need to be changed for most installations
above 3.5 MHz.
However, if you are interested in
primary frequencies below 3.5
MHz, some adjustment may be
required to increase sensitivity or
eliminate interference from strong
broadcast stations. Refer to
Figure
8
for various jumper settings.
Figure 8
For access to the jumpers, remove
the two #2 Phillips Screws on each side of the
ARAH
unit and remove the bottom. The circuit
board and jumper headers will be visible as shown in
Figure 8
.
The
ARAH
has five internal
jumpers that modify frequency versus gain response. The L jumpers change the inductance values
and C jumpers change the capacitance values.
As shipped, all jumpers are deactivated.
Installing jumpers in L1MF, L1HF or both, will configure the antenna for a sensitivity peak near the
frequencies listed in
Figure 8
. The frequency response above the peak frequency does not change
significantly. Below the peak frequency, sensitivity reduction is reasonably fast. Installing a jumper
in any C1 position when jumpers are being used in L1 will move the peak response lower in
frequency, decreasing sensitivity at higher frequencies.
To enhance weather resistance after the jumper settings are finalized, run a bead of non-corrosive
silicone (
PTX-82180
) along the upward facing seams of the aluminum housing. Leave a small
opening in the lower seams to function as a condensation drain.
