Setup of my Receiving System

Improperly connection of a computer to a rf-receiver may introduce a lot of noise into the receiving system. From my experience, there a three things to take care for:

I am using the following setup:

Diagram: wiring of the receiving components

There are two antennas in use: Outdoors the active antenna DX-500 from RF-Systems with its own earth system, which is different from the ground the computer is connected to. Indoors a broad band magnetic loop antenna of 0.6 m diameter, feeding a HDLA-3 amplifier build from Charly Hardt. Galvanic insulation of the serial connection (A) is achieved by means of an optocoupler (Gude USB-RS232 OptoBridge). The galvanic insulation of the af connection (B) is build by means of an af-transformer. If it is intended to use the detector output of the AR5000 an additional amplifier is needed to drive the af-transformer (Conrad 5W af amplifier). Capacitors should be soldered parallel to the input / output of the af-transformer to build a low pass filter. In my setup I use a 30 ohms : 30 ohms af transformer connected to the earphone jacket of the AR5000.

The rf noise generator (QRPprojekt PWRRgen) is not necessary for the normal operation of the system. I use it for measuring purposes (e.g. if-bandwidth, spectral responsivity of the AR5000).