Rev. Robert makes a very good point about the composition of hot and cold water pipes. You may know all about the plumbing in your own home, but if you are a cliff-dweller, you are living on someone else's property, and you have no idea about the history of your residence.
Thank you for your important observation, Robert. I was naive enough to thing that a length of corroded copper pipe would be replaced with copper pipe. That is what happened when I had to get corroded pipe repaired at my house.
I am unfamiliar with pvc water piping, but I can think of a pipe device that can interrupt a pipe system ground path, and that is when a special connector is used when copper is joined to iron, which serves to isolate the two metals which will corrode very rapidly at the join if connected directly. The solution is a bypass strap clamped on each pipe.
Good points about possible interruption to water pipes. Here code requires that the pipes be electrically grounded. I installed a deductor meter and had to strap across it with a wire to keep everything grounded. One of the reasons for not using the hot pipes for electrical grounding is for the safety of plumbers who may disconnect the water heaterfor service and they can end up between an electrically live pipe and a grounded pipe. Sounds good but by experiences working on plumbing and electrical systems I don't bet my life that things were done right.
Back to the original question I suggest that conductors placed along baseboards or under carpet or even on the ceiling can perhaps be defensible providing they run equal lengths and opposite directions from the transmitter ground connection. The idea here being that such radials would not have a net radiation yet will function to return current to the transmitter.
Neil
Radio8Z reminds me of something more about using wire strung along baseboards, which he mentioned.
In a ham book, article or website, I read that a common ham method for getting a usable ground plane up in apartments is precisely that: string a bunch of wire along baseboards running in both directions away from the transmitter, wrapping around into other rooms to get the desired length.
I think I'll test that idea later.
Mr. Fry posted a link on another site in reference to your question and other's comments. A very good read.
i am still looking for that mentioned post on
the other website. I will eventually find it.
i have to agree with Neil about the counterpoise
wires, and how they would cancel each other
out and not radiate. (And still provide a return path.)
That sounds workable to me, and also comes along
with a sensible explanation as to why it would be
legal.
Bruce, DRS2
P.S. I'm not a broadcast engineer, but I play one on TV.
The links are:
http://boards.radio-info.com/smf/index.php?topic=213307.0
http://boards.radio-info.com/smf/index.php?topic=213356.0
Neil
The concept came from twin lead configurations, which in twin lead both lines cancel each other out. Unbalanced to balanced toroid, out to antenna system.
Worked for me..don't see why it would not work for anyone else.
RFB
RE: Submitted by radio8z on June 7, 2012 - 17:05.
>The links are: (snipped)
Thanks, Neil.
Throughout the radio age many AM stations have had towers way up on top of buildings. What did they do for grounding and radials?
Was it, however they did it, as effective as radials buried down at ground level?
Once we know what they did, can we not do the same thing from an upstairs apartment?
Carl Blare wrote:
Throughout the radio age many AM stations have had towers way up on top of buildings. What did they do for grounding and radials? Was it, however they did it, as effective as radials buried down at ground level?
____________________
Approximately so, but then the FCC Rules applying to the minimum radiation efficiencies of such building-top antenna systems used for licensed AM broadcasting are different than the FCC permits for legal Part 15 unlicensed systems operating in the AM broadcast band.
Rich, I am not sure what you said, but it doesn't seem to be an answer to my question.
How do AM towers on buildings solve grounding? I am not asking about FCC rules.
For reasonably high radiation efficiency, all monopole "AM towers" installed atop a building or with their bases barely above the physical earth need a suitable r-f ground reference to be driven against, in order to meet/exceed the FCC Rules for the minimum fields applying to licensed AM broadcast stations.
For AM towers atop a building, such a reference can be supplied by a counterpoise of several, symmetrically-arrayed horizontal wires at the base of that vertical radiator.
Whether or not this antenna system configuration is acceptable to a given FCC inspector with respect to Part 15.219(b) depends on the engineering background and FCC training of that inspector.
Buildings are constructed from earth materials. It seems to me the top of a building, especially the top of an industrial office type building, is similar to a man-made cliff and that radials up there would be the same thing as radials down below on the ground.
Can anyone argue against that obvious comparison?
Well, you answered that... "It depends on the engineering background and training of the inspector." But by that we are saying that it might be possible for a given inspector to be unreasonable. In that case the conversation would not be about electronics, but about the ability to make reasoned conclusions.
Monopoles need to be "driven against" another conductor or conductors in order to radiate efficiently. If a monopole is installed with its base close to the earth then those other conductors can take the form of a few horizontal wires installed symmetrically several meters high around the base of the monopole -- or a set of buried radials. Of course radials buried in the earth usually are not practical for monopoles atop buildings, so a few horizontal wires must be used as a counterpoise. Such horizontal conductors have high r-f voltages on them, and must be protected from accidental contact. The radiation pattern and system efficiency from the building-top system is essentially the same as if that system was installed with its base just above the earth.
Most of the materials used to construct the outside of a typical building are not very good conductors, and if used as part of a monopole antenna system would not result in good radiation efficiency, aside from the safety considerations of applying r-f power to the outer part of that building and/or to its steel framework.