Omni VI & VI+ Aux Antenna Input

From the Ten-Tec Reflector September 16, 1998

The front end of the Omni-VI and Omni-VI Plus receiver is protected by two diodes at the AUX RX ANT input jack. It is possible, when using auxiliary receiving antennas like loops or Beverages to have transmit RF energy from your own radio come back into the rig through your receiving antenna. It is possible to blow these diodes doing that; they are there for protection of the receiver. That does not lessen the aggravation of having to replace them should you have this problem, but at least you're not going to cook the receiver itself.

Yes, it is possible even with small amounts of transmit RF to pop the diodes at the AUX RX ANT jack. You may want to investigate the possibility of adding an external protection circuit between the receive antenna and the input to the AUX RX jack. There was an article about this in the February 1997 (Pg 32) issue of CQ. A very simple solution is to use a low voltage, 10 mA light bulb in series with the receive antenna. Too much RF down the receive antenna jack results in a burned out light bulb rather than burnt diodes. Much cheaper and easier to replace, too!

Here's another caveat about the diodes at the AUX RX jack: It is possible (so possible, in fact, that this happened in my own shack last year), for receiving antennas to send a quick static discharge down the coax. Like any other antenna, receiving antennas need to be disconnected during lightning storms. You may encounter a small static buildup on a receive antenna as a result of a nearby lightning storm, that will discharge at the moment the antenna is re-connected to the transceiver. Connecting the receive antenna to ground immediately before re-connecting to your transceiver can prevent this from happening.

Happy DXing,

Scott Robbins, W4PA

Amateur Radio Product Manager

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