At 07:19 AM 10/14/2005, Carcia, Francis A HS wrote:
>Since most transmitters have a coax connector output referenced to chassis
>ground. Say that chassis
>Is not grounded. Some of the energy will show up as a voltage between
>chassis and ground.
If we are speaking strictly of RF, that statement is not correct,
given a properly designed antenna system. All of the RF energy
generated by your transmitter appears between the coax connector's
outer conductor and the center conductor. Your job, as Chief
Engineer, is to keep it that way.
> I prefer my energy located between the center conductor
>of my coax and the inside of the coax shield.
Absolutely.
>To reduce this voltage offset a good ground reference is required.
Not for RF. The voltage present at the coax connector has no desire
to flow to some external ground unless there is an unbalance problem
in your antenna system. It wants to flow into the coax and thus to
the antenna. Again, your job is to make sure 100% of the RF at the
coax connector flows into the coax only and not be diverted to some
external ground. The way to accomplish this is to maintain electrical
balance in your antenna/feedline system.
> Also,
>lightning, since it is God's RF pulse needs a good path to where it is
>going. A poor path results in lots of voltage across that path. To keep
>God's system happy and the ham radio system happy a low Q low Z ground is
>required.
>Multiple connections and heavy connections make both systems happy. OH yea
>your insurance co loses their excuse to pay if you ever get hit.
Those statements are correct for lightning ground and for AC mains
ground, but not for RF.
73, Bill W6WRT
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