Paul,
Thanks for the reply comments. Your switching configuration is exactly
the sort of scheme I had in mind for protecting the station when wire
feeders are used. Over the years, I have just seen way too many instances
of wire feeders going straight through a drilled (or replaced with wood)
window pane and into the shack. A very scary thought!
I totally agree with your thoughts on lightning performance of wire
feeders. Again, the chief problem is that too many ops do not make the
effort to do the job right.
As for the switchers, those intended for communications usage have no
choice but to cleanup their act or be destined for a short market life.
Sadly, the general purpose switchers are so often real junk from a design
or construction viewpoint - especially when cost-cutting vendors leave out
parts intended for EMI reduction. That's very common with cheap, third
party power sources.
73 and thanks again for the comments,
Dale - WA9ENA
"Paul Christensen" <w9ac@arrl.net>
10/19/2010 05:05 PM
To
"Howard Lester" <howard220@gmail.com>, <dgsvetan@rockwellcollins.com>
cc
"RFI List" <rfi@contesting.com>
Subject
Re: [RFI] Noisy or Quiet Power Supplies?
> 2. Let me ask: How many people on this
> reflector who use wire feeders of any type have any form of lightning
> protection on those feeders?
I do. Two Jennings 75A @ 10KV vacuum relays form a knife switch at the
antenna feed point in my outdoor, motorized ATU. When the shack ATU
controller is powered on, the relays close. When I QRT, the relays open.
See my QRZ.com page for photo details of the relays in the ATU.
Approximately 80-feet of LMR-400 is run from the shack through the attic
to
a homebrew motorized ATU located outside at the back of the house. The
coaxial line to the ATU point is bonded/grounded via a bulkhead and tied
back to the service panel.
Also, I'm not sure the use of open lines is any more susceptible to
lightning damage than coaxial cables. Some of us are used to seeing how
well a heavy-duty, well-bonded/grounded cable entrance bulkhead can
perform
when using coax during a lightning event. But if the open line can be
remotely disconnected (and antenna grounded if that one's preference), I
see
no reason why a balanced line cannot achieve the same level of protection
with little work. The argument sometimes heard is "lightning just
traveled
a mile to earth, what's another couple feet when the line is
disconnected?"
The answer is that it depends on how the line is disconnected.
I used to detest switching power supplies until I found a model that does
not affect my current station. For me, common household appliances
(switching wall warts, the DVD player, the switching PSU in my router, the
switcher in my stereo amp, and several switching devices owned by
neighbors)
were all producing more RFI than the shack supply.
Adding a really good panadapter was one of the most rewarding days in this
hobby -- it was also one of the most painful after spending months
eliminating all the noise to achieve a flat scope baseline so that I
didn't
see, nor hear the sequential; switch-mode "bumps" on the display.
Paul, W9AC
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