[TowerTalk] Shack wiring

Pete Smith 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.

73, Pete


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