SO2R RX Loop Antenna

Todays work included installation of the SO2R RX Loop Antenna and associated devices. The W6LVP relay will provide switching for the SO2R RX Loop Antenna. I’ll also install some front end protection.

Here are some of the items on the agenda:

SO2R RX Loop Antenna
The wiring is nearly complete.


The SPE Expert 1K-FA amplifier allows connection of two transceivers, four antennas, and, an SO2R RX antenna. When the OP is transmitting on radio#1, radio #2 is connected to the SO2R RX antenna. This enables the operator to listen on radio #2 while working the latest DX on radio #1, and vice versa.

SO2R RX Loop Antenna for low noise

Operating in SO2R mode presents the possibility of overloading or damaging the sensitive RX front ends of the two connected transceivers. The 1K-FA manual warns of this possibility and cautions the user about antenna separation and it is suggested (and makes the most sense) that receiver front end protection devices be considered.

The Flex transceivers have built-in RX protection, but adding an RX front end protection circuit offers one more level of protection.

From the May 2014 QST article:

The RXFEP uses multiple devices to soft limit input signals starting at –1 dBm and outputting a specified maximum signal level of +10 dBm to the re-ceiver input.While manufacturers do not generally specify the maximum safe input levels for their equipment, it is worth noting that ARRL Lab re-ceiver dynamic range tests include input signals as high as +10 dBm, and we haven’t lost one yet.

An obvious place to install this device is at the RECEIVE ONLY ANTENNA port of a receiver. By having it as close to the receiver as possible, any pickup on the cable between the device and the receiver is minimized. There is another potential application in some installations, however. Some receive-only antennas include a remote preamplifier at the antenna termination. A protector at the remote preamp input would also be appropriate, although consideration should be given to the preamp input impedance, with a transformation to 50 W, if needed. If there is a long coax run from the remote preamp to the receiver, a second protector could be used at the receiver in case of loose coax connectors or other shield impairments. It should be obvious, but I’ll say it anyway. This unit cannot be used on any antenna feed that is also used for transmitting. Damage to both the unit and the transmitter would be likely consequences.

The low noise RX Loop Antenna is hereby considered a major station improvement!

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