At 03:12 PM 7/24/2003 -0400, SGTOKIE@aol.com wrote:
>i am looking for a source of information about providing ac power to my
>radio room. i have probably missed it somewhere in the arrl handbook.
>
>wanting to run supply @220v for 3 amplifiers and 2 power supplys. also
>want about 10 or so outlets for 110v.
>
>i need information sources so i can isolate componets and computers as
>much as possible to try to avoid RFI....
>
>a few questions that come to mind:
>1. the main power kill switch-should i use fuses instead of breakers to
>lessen RFI?
Fuses aren't a power kill, they're "overcurrent protection", designed to
keep the house from burning down.
Breakers or fuses, all the same, except bear in mind that for 220V, for a
disconnect (not overcurrent protection) you want to interrupt both sides,
so you need a double pole switch. A double pole breaker does this nicely.
>2. should i have a seperate supply circut run for computer?
This is an area of MUCH discussion, particularly with respect to the value
(or not) of an isolated ground (which merely means that the green wire runs
all the way back to the service entrance). A separate circuit for the
computer(s) is nice in that if you get a trip on one of the other circuits,
the computer stays on.
From an EMI/EMC standpoint, you're much more likely to get problems from
ground loops/potential differences in the various interconnect cables
(RS232, USB, audio cabling, control signals, etc.)
Just keep in mind that there are 3 grounds to worry about:
1) Electrical safety ground (the green wire)
2) Signal common (RF ground in your shack)
3) Lightning protection ground
What's good for one isn't necessarily so for the others. There is much to
learn from the IEEE Grounding Specs (aka the Green book (IEEE Std
142-1991) and the Emerald book (IEEE Std 1100-1999), if you can find them
in a library (or fork over the bucks to buy a copy). There's a good
summary of grounding for LowVoltage and Communications systems stuff from
Mike Holt Enterprises, for free, on the web. http://www.mikeholt.com/ is
the URL, I think.)
>3. 2 or 3 or 4 supply circuts for 110v?
Up to you, really... There are some NEC rules about number and kind of
receptacles on one branch circuit. There's also the issue of what your
wiring topology will be: are you running a heavy feeder to a subpanel from
your main panel, then breaking out the 220V and 110V circuits. Or, are you
running separate branch circuits from the main panel.
When devising branch circuits, think about what happens when a trip
occurs... what will be left powered, and what gets powered down. For
instance, room lights should be on a separate breaker from the electronics,
so if the electroncs trips the breaker (when you turn the QRO knob to
"11"), you can still see what you are doing. Also think about where a UPS,
if any, will go. What happens if the 110V circuit for your rig trips, but
the 220V linear remains powered on?
You also want to balance the load across the two phases of the 220V, as
much as possible, although, in most houses, all the other loads are going
to swamp whatever loads your radio has.
Think about Ground Fault Circuit Interrupters (GFCI).. they're cheap and no
reason to not have that extra bit of insurance. If you miswire a cable, or
you've got the cover open on something, and you ground the line, the GFCI
will catch it long before the overcurrent protection.
>thnx to all, i just need a reference to start looking
>
>73 de kd5qwo, david EM15
>_______________________________________________
>
>See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
>Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with
>any questions and ask for Sherman, W2FLA.
>
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