Powering Through The Coaxial Cable; Connecting The Power Supply - DX Engineering RPA-1 HF Manual

3. Replace the antennas with a resistor load of the same impedance as the antennas.
4. When the load is substituted for the antenna, a noticeable decrease in noise should occur.
It is advantageous to have receiver AGC action begin just above noise floor, while avoiding
excessive levels of background noise. This usually occurs when there is a perceptible increase in S
meter reading, when the antenna is connected. If background noise is high or your receiver is
overloaded, you can add an attenuator pad or remove power from the DXE-RPA-1. Removing
power bypasses the DXE-RPA-1.

Connecting the Power Supply

The DXE-RPA-1 requires a well-filtered 12-18 Vdc @ 130 mA source with a negative ground.
Many inexpensive wall mounted transformer DC supplies are not 'clean' and have RF noise
components on their DC output. Place the fuse at the power supply, rather than at the DXE-RPA-1.
The DXE-RPA-1 power connector uses a standard 2.1 mm barrel type plug (included). You can
use a well regulated +13.8 Vdc supply provided it supplies 12-18 Vdc negative ground (has the
power plug shell connected to negative) and has an inline 1A fuse.
WARNING! Be sure the supply polarity and voltage are correct.

Powering Through the Coaxial Cable

The external power connector is normally active, but components are inside the DXE-RPA-1 to
allow powering through the coaxial feedline. To change the power feed, refer to Figure 2 and do
the following:
1. Unsolder RFC1 - 100 uH RF choke lead that connects to the power jack.
2. Connect the free choke lead to the PC board indicated by the RFC1 choke outline.
NOTE: A 12-18 Vdc low noise positive power source must be inserted in the feedline center
conductor through a feedline voltage injector and the voltage must be blocked from
appearing at the receiver.
Caution: Do not nick, scratch, or break
the fine wires on the RFC1 choke. Do not
grab the RFC1 choke body with pliers.
Figure 2
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