The "ground" pin of a 3-terminal a-c outlet in a house might be nearly at earth potential for d-c and extremely low a-c frequencies -- but it is not a very good earth ground reference for frequencies above ~50 kHz.
So the wire connection from that "ground" pin receptacle to a ground rod near the a-c service entrance will radiate, if r-f current is present on it -- which might make an unlicensed AM system using such to be non-compliant with FCC §15.219(b).
Mr Rich generalized: "The "ground" pin of a 3-terminal a-c outlet in a house might be nearly at earth potential for d-c and extremely low a-c frequencies -- but it is not a very good earth ground reference for frequencies above ~50 kHz."
Actually, this is sometimes true, but not in all cases. Mr. Rich knows this when he says "might be".
Many variables are involved in what actually takes place, such as:
1.) The gauge of the AC wiring... heavier wire provides more efficient ground;
2.) Proximity to the electrical earth rod... AC recptacles near the electrical panel will have much better earth ground than those higher up and farther from the panel.
There's no room for shortcuts in part 15.
Mr Rich generalized: "The "ground" pin of a 3-terminal a-c outlet in a house might be nearly at earth potential for d-c and extremely low a-c frequencies -- but it is not a very good earth ground reference for frequencies above ~50 kHz."
Actually, this is sometimes true, but not in all cases. Mr. Rich knows this when he says "might be".
Wrong. In NO case above ~50 kHz are the r-f characteristics of the ground terminal receptacle of a typical 3-terminal a-c outlet in a building close to being equal to the r-f characteristics of the earth.
The "might be" phrase in my post applied to the lower limit of that resistance for d-c and and extremely low a-c frequencies, ONLY.
Many variables are involved in what actually takes place, such as:
1.) The guage of the AC wiring... thicker wire provides more efficient ground; ...
An invalid conclusion here, in practical terms. You might wish to research "skin effect" as it applies to the conductors of r-f current.
We disagree on this point.
I held a memorable conversation once with an electrician who'd installed a very heavy duty electric service into an old studio building.
He told me that very up-to-date electric systems can show an impedance to earth approaching zero ohms, whereas old wiring can often be so shabby it only achieves 300-ohms from outlet to earth.
Anyway, the AC "3rd-pin" ground or a copper rod earth ground only provide safety and, although it'll contribute to reaching "resonance" it does surprisingly little to extend radiation.
Only ground radials benefit range outreach.
The last few posts have taken this thread off-topic.
The construction of any individual power outlet is immaterial. The Talking House transmitter was certified under Part 15.219 with its power cord ground. End of story.
True Artisan, and I think this clears up any confusion. It's another line posted above: "So the wire connection from that "ground" pin receptacle to a ground rod near the a-c service entrance will radiate, if r-f current is present on it -- which might make an unlicensed AM system using such to be non-compliant with FCC §15.219(b)."
Note especially "... will radiate IF r-f current is present on it..."
That's the same as saying that it might not radiate.
Bottom line... IT'S CERTIFIED!
- A conductor carrying r-f current while attached to the r-f ground terminal/chassis of a Part 15 AM transmitter does not need to be connected to any form of an r-f ground (buried rods or radials) at the opposite end, in order for that conductor to radiate
- The FCC has issued citations to users of commercial AM transmitters having Part 15 certification, based on their installation details
While some may consider these points to be "anti-Part 15," that does not change these realities.
Rich claims: "The FCC has issued citations to users of commercial AM transmitters having Part 15 certification, based on their installation details"
When was that, how many instances, and was it because of using the ground pin on an AC power socket?
Are you saying that using a AC ground connection is not permitted under part 15?
"Are you saying that using a AC ground connection is not permitted under part 15?"
Not necessarily, but a legal Part 15 AM system doing so would have to be in compliance with FCC §15.219(b) -- while realizing that the length of the conductor leading away from the ground terminal of an a-c outlet to a buried ground rod is part of the length included in §15.219(b).
If legally operating under §15.209 then any antenna configuration may be used, as long the field intensity limit for that Part 15 system is not exceeded.
One well-known example of an FCC citation to the operator of a certified Part 15 AM transmitter is that of KENC.
IIRC there was another example of this involving the user of a Talking House.
Resident Rich: "...while realizing that the length of the conductor leading away from the ground terminal of an a-c outlet to a buried ground rod is part of the length included in §15.219..."
Those are your words, sir, not from the rules, which makes it your opinion.
There are others who believe that true ground starts at the AC ground pin and is therefore not an extension of the 3-meter measurement in 15.219.
The KENC example is removed in time and is not known by today's hobbyists, with several different versions of the story. Because there haven't been hundreds of such citations and given that most historians believe the circumstances at that time were based on personal vendettas, it does not stand as a point of reference.
"There are others who believe that true ground starts at the AC ground pin and is therefore not an extension of the 3-meter measurement in 15.219."
Belief does not equal Fact.
A good price for that I'd say $20. Not worth much more than that for a TH2.
Said: "Belief does not equal Fact."
At times beliefs prove true.
Legal language has been known to stretch fact.
The "fact" that the 3rd blade of an AC outlet is called "ground" sort of makes it true.
It is also possible for a reasonable person to arrive at a different "interpretation" than another reasonable person.
An "authority" on FCC rules without a law degree stands the risk of being questioned now and then.