[TenTec] OMN-6+ Aux ant input protection

Roy Koeppe royanjoy@ncn.net
Wed, 14 Apr 1999 09:54:37 -0500


Hello all,

Discussions on other reflectors conclude that nearly ALL transceiver brands,
including MOST TT, provided with aux rcvg ant inputs require external
circuitry to protect against front end damage occuring. This being
especially true when the separate rcvg ant is large, such as beverages on
the low bands.

The ONE possible exception might be the OMNI-6+?? It apparently uses PIN
diodes to disconnect and possibly ground the external input connector during
key down. I haven't carefully traced out the diagram. But  the question is,
just how effective is this unique feature in doing its important  job? I
have performed actual tests on 160M using two antennas separated by about 40
feet. Transmitting 100 w into one ant yielded roughly 1 w at the feedline
termination in the other (which happened to be a 40-ft circumference
resonated magnetic "army loop."

This 100:1 power ratio is interesting to contemplate when extended to the
legal limit, 1500 w producing 15 w dissipation for  the OMN-6's tiny diodes
to contend with! (My 15 w soldering iron gets mighty hot).  Simply OPENING
the circuit at the jack could limit current, but then the voltage could
build up damagingly high.

So has anyone put this to the test yet with the OMNI-6+' built in
protection? Has it really survived the beverage & QRO test?

Tnx, 73,    K6XK


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