[TowerTalk] Shack wiring
n4zr at contesting.com
Mon Jan 24 11:28:03 EST 2005
At 11:07 AM 1/24/2005, W8JI wrote:
>So you need two meters Pete...you need to measure the true
>peak and you need to measure the true RMS. Capacitor input
>supplies run off the peak, and are more sensitive to line
>ESR at a given power load than resistive loads like choke
>input supplies or filaments.
Thanks to Tom and everyone else who wrote. Yes, Tom's right about 110 vs
120 -- somewhere 50 years or so ago I formed the mental habit of calling it
"110." That was appropriate at the time, I think. I'm told the current
ANSI spec is 120/240 +/- 5 percent.
Not having either a true RMS and true peak meter, I intend to follow the
advice of some others and verify that the two legs of the service are
within a volt or two of each other at the panel, and let the power company
put a recording voltmeter on the service to see if the problem is
there. Frankly, I'm betting on that, because our power company is in
Chapter 11 and the county's population is growing fast. I'm only a couple
of miles from the substation, but it's one that serves a lot of the
population growth. The extreme lows I've noticed are all relatively early
in the morning, which suggests a peak load for heat pumps, lighting, etc.
I just measured a 110 outlet close to the panel and the voltage was
111.1 Upstairs, about 60 feet of wire away, with the two radios on
receive, I measured 110.1. Turning off all the "radio" side (radios,
rotator and stack controllers, etc.) it went up to 110.8. Just now it hit
111.7 in the shack for a moment -- now 110.2. Lots of fluctuation. I
don't know if these are either RMS or peak voltages (most likely some
fudged version, because it's not a Fluke).
Assuming the wiring is #14, my Handbook says the resistance is .252 ohms
per 100 feet. Measuring at an outlet in the shack, equipment in the shack
is drawing through ~120 feet of that wire, right? That doesn't sound
wildly off to me.
Or have I misunderstood something fundamental? Wouldn't be the first time.
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