[TowerTalk] Isolation Transformer

Tom Rauch w8ji at contesting.com
Sun Mar 20 16:30:17 EST 2005

A transformer _can_ provide some protection against HF
signals &
transients that may come in on the line, but most
transformers aren't
designed for that kind of isolation.>>>

I agree with that. My tower lights are fed through an
isolation transformer because:

1.) I would rather have the wiring grounds independent,
since the tower is 500ft away.

2.) If lightning hits I want some additional surge isolation
for whatever makes it that 500ft into the barn.

  The best ones are carefully
shielded between primary & secondary to reduce capacitive

Now here's something to think about. If you put a shield
between the primary and secondary, what do you do with the
connection to that shield?

If you connect it to the station ground, it actually
increases the capacitance from primary to station ground.

If you connect it to the power line ground, you increase the
capacitance from power line ground to the secondary.

The ONLY way a shield reduces capacitive coupling is when it
connects to a separate isolated ground that connects to
nether station nor power line grounds.

In most cases, I don't see any advantage either.

73 Tom

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