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House A-C Wiring Used as R-F Ground

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House A-C Wiring Used as R-F Ground

Some may consider the net radiation from a conductor connecting the ground pin receptable of an a-c power line outlet to an earth ground to be low/negligible, due to field cancellation caused by the other a-c wires in the house.

However the physical separation of such wires is a very small fraction of a wavelength in the AM broadcast band, and their radiated fields have almost no cancellation.

Practical examples of this are the tapered towers used by some AM broadcast stations.  They consist of 3 or 4 essentially vertical legs along with numerous horizontal and diagonal braces along its height. These configurations may have their legs separated by 30 feet or more at the base of the tower.  Yet this structure produces almost the identical radiation pattern as that of a single conductor of the same height.

The "ground" conductors of a-c house wiring are effective radiators of r-f energy along their entire length/height from the a-c outlet to the point where they connect to the buried ground rod at the a-c service entrance.

House AC Wiring Makes Poor R-F Ground

We agree on that point. But there are more circumstances encountered in house wiring than taken into account in previous post.

Instances where AC ground drops vertically straight down to the electric panel the AC ground wire becomes the negative side of a dipole and very likely radiates RF that will increase the field strength of the signal. Agreed.

But here in the internet building the AC wiring is run from the electric panel up into the attic, across the attic, and is dropped from above to the room outlets.

Therefore if we were to attach RF ground to AC ground the upward wire in the wall would be out of phase with the transmitting antenna and actually attenuate our RF field strength.

Another example.

A real life case of poor performance from attaching to "house ground" exists right here where we have an AMT3000, loading coil and ground clamped to one end of a 60' steel I-beam below the floor. As it crosses the basement the I-beam comes in contact with metal ductwork and a heavy copper bonding wire connecting the electric panel ground and ground rod to a cold water pipe on opossite sides of the basement.

One would expect so much metal attached to RF ground would comprise a veritable ground plane that would send my signal flying throught the air but not so.

In fact our signal is strong ONLY within the building and fades out rapidly as little as 15-feet around the exterior.

My argument says that wiring schemes in buildings vary to the extent that some AC ground points add to RF radiation while others may actually diminish it.

Carl Blare

"House AC Wiring Makes Poor R-F Ground..."

But it makes a pretty good, radiating antenna component.  It is not an effective r-f ground, at all.

...Instances where AC ground drops vertically straight down to the electric panel the AC ground wire becomes the negative side of a dipole ...

Note that both sides of a dipole antenna carry r-f (alternating) current.  Neither side of the dipole has a single polarity such as "positive," or "negative."  Both sides become either positive or negative during each 1/2-cycle alternation of the r-f energy applied to it.

In fact, if either side of the dipole is long enough, it can be both positive and negative at various locations along its length.

...Therefore if we were to attach RF ground to AC ground the upward wire in the wall would be out of phase with the transmitting antenna and actually attenuate our RF field strength ...

Note than an r-f ground does not exist at the "ground" pin receptacle of an a-c power socket located a finite distance away from the buried ground rod it connects to as a ground reference.

Part 15 for AM BCB at it's beginning in 1937

when the first phono oscillators hit the market...

Hooking a record player into a phono oscillator

"transmitter" and transmitting through an

existing radio saved money in those days.

One did not then have to buy a record player

with it's own expensive audio amp.  There was

already one in the radio.  (I may not be

stating this quite correctly but you

guys know what I mean.)  

The FCC (or the Federal Radio Commission - 

whatever they were then) figured out the

first Part 15 rules, I guess.  It seems to

me that they might have been aware of

oscillator injection into the AC line and

reradiating ground wires.  Perhaps

they factored this into the rules.

(??????)  That was 80 years ago.

Was it even called "Part 15" then?

Brooce, Hartford CT

 

NOISE AND STATIC RADIO

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