If your SWR is already low and you wish to reduce feedline radiation (RFI) and improve reception, DX Engineering Maxi-Core® Feedline Current Chokes are highly recommended. Note: Whenever the DX Engineering "Documentation" tab is available, please look at the associated files for additional product information. In other cases, as the coax feedline travels through the near-field of the antenna, the current can be reintroduced to the feedline after the balun. A ground loop can be a source of interference that can induce a noise voltage between the grounds on either end of the transmission. While the most common advice is to improve the station's RF ground, the root of the problem is in the poor isolation of the feedline from antenna currents. This article explains how ground loops occur and discusses how galvanic isolation has been used to eliminate them.Transmitting data over long distances is fraught with potential problems. It is a telescope antenna connected to your normal one and a box between that can alter the phase. This results in higher power handling with lower loss, improved antenna bandwidth, and reduced RFI, and compensates for a less-than-optimal grounding system. Having the antenna indoors will let it pick up more interferencies than the coax ever can do, so a common mode choke filter will not do anything for you. This symmetry cancels, to first order, all effects of external electromagnetic fields. Coaxial cables have fairly good natural immunity to external noise, due to the physical symmetry of the signal current conductor and the returning current conductor (the concentric shield). It behaves as a 1:1 Current Balun, even though it is connected to the antenna feedpoint with a short piece of coaxial cable.ĭX Engineering Feedline Current Chokes have significantly higher common mode impedance and a larger effective core area than similar line isolators, including conventional enameled wire or bead baluns. 10.2.2 Coax: Radio Frequency Interference. This inline choke is also known as a Line Isolator, so it works very well when placed at the station end of the feedline or it may be used at the antenna end of the feedline. A ground loop can be a source of interference that can induce a noise voltage between the grounds on either end of the transmission. The new DXE-FCC050-H05-B has both SO-239 connectors isolated from the aluminum case and no stud, which replaces the original DXE-FCC050-H05-A that had only one isolated connector and a rarely used grounding stud. This means that effectively, your RF return path is already isolated. The return current for a signal propagating down the centre conductor will return exclusively down the inner surface. 5.) We have poorly installed connectors or defective cables. 3.) The problem is not RF at all, but is a DC power supply ground loop back into the audio system. 2.) The antenna is too close to the operating position. At 1.6GHz for GPS, they will absolutely dominate. The antenna system has a design, engineering, or installation flaw. They provide excellent feedline decoupling and low loss performance from 1 to 60 MHz and are power rated for 2 kW continuous, 5 kW intermittent on antenna feedlines with an SWR below 2:1. These effects kick in even at tens of MHz. DX Engineering Feedline Current Chokes, using Maxi-Core® technology, prevent unwanted RFI by eliminating feedline current and radiation in 50 ohm, coaxially fed antenna systems.
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