For a long time there have been plans to establish an outdoor antenna site with radials, but the clearing of yard space is going slowly, but steadily.
For a long time there have been plans to establish an outdoor antenna site with radials, but the clearing of yard space is going slowly, but steadily.
One final clearance issue will be filing for a digging permit to allow safe planting of a ground rod, but prior to that time I wish to explore the ground with a metal detector.
Tell me your metal detector experiences.
Radio Shack has an astounding variety in their online catalog, ranging from around $40 to over $200. Is there really a difference in performance among so many models, or are they more or less alike.
Bottle Caps and Juicy Fruit wrappers…
I was gifted a VLF2 metal detector last Christmas. Their website is http://www.detecting.com . Mine is the Bounty Hunter Metal Detector VLF listed with the Starter models.
It is a simple detector with a control to discriminate/eliminate specific metals from the search.
So far my grand daughter and I have located $1.27 in change, several bottle caps and pull tabs, two Hot Wheels cars and other obscure items.
see my link. i have a metal
see my link in fs/ft forum. i have a metal detector for sale as well.
it was one of radio shacks 100.00+ models at the time. asking $50.00
Buried radials
The only real reason for burying radial wires is only in regards to a safety/snagging issue. You want to get them below the surface so they won’t get caught by your mower and won’t be a tripping hazard. Otherwise the radials will work just as well when they are just laid out on the surface.
You don’t need to be concerned with what’s under your ground as long as you don’t go more than a few inches deep with your radials. Any important stuff like electric, phone, gas or sewer is a lot deeper.
A lawn edger, or a rented wire trencher (2-3″ deep) will cut grooves. Or you can just “staple” the wires to hold them long enough for the natural lawn growth and decomposition to bury them. See: http://www.eham.net/reviews/detail/8163. The staples are even available from Home Depot for laying out dog fence perimeter wires.
Those Are the Staples
The staples just posted by PhilB are officially designated as part of the upcoming antenna installation. I had not previously seen such ideal staples.
I bought a bag of much shorter staples at the hardware store, but was certain that they would pull loose because of their shortness, and plan to return them.
I do want to have a ground rod along with the installation for lightning safety.
Chicken Fence
If your worried about strings of wires being tripped over or sliced and diced by the mower, lay down chicken fence and anchor it with 4 inch nails. Interconnect each and you got you a ground “mesh” or “screen” which will have far better results than plain wires.
RFB
Good Practice
“I do want to have a ground rod along with the installation for lightning safety.”
Very good practice. Lightning can arc over from where it strikes very easily. If your setup is nearby a tall object that’s subject to being hit by lightning, bet your lightning bolt that strike could arc over and hit your stick too. You will want that to go somewhere besides dance around inside your TX or down your coax.
RFB
Big Ideas of Western Man
Tonight we reach a solution to the “long ground lead issue”, once and for all.
Go back and re-read RFB’s advisory about lightning safety.
In the case of an elevated antenna, I would say that safety PRE-EMPTS the restriction on “…exceeding 3-meters”
The term “pre-empts” is the same as SUPERSEDES.
That settles it. An elevated antenna MUST have a long ground lead connected to a grounded copper rod FOR SAFETY.
The United Nations agrees with me on this.
Safety vs Regulation
“In the case of an elevated antenna, I would say that safety PRE-EMPTS the restriction on “…exceeding 3-meters”
I fully agree. Revision in the rules should include elevated installs that NEED a ground path for lightning protection.
That choke for the Rangemaster, will prevent the long ground wire or mast from radiating. It will also choke off the return path for RF to the TX. But it’s better than having no ground at all or having that strike travel down your power/audio ground paths and into your studio.
Time to start writing drafts for proposed rule making.
Up to it guys? (ALPB)
RFB
..lay down chicken fence..
..lay down chicken fence.. and you got you a ground “mesh” or “screen” which will have far better results than plain wires.
RFB did you say chicken fence wire provides far better result than plain copper wires?
(I know you said that, but would you say it again?)
Comment on Protective Gnd
The idea of including a choke in the tx. ground path to prevent RF radiation negates the protective function of the ground. If the path is open for RF then it is also open for part of the lightning energy. A ground choke is no solution.
Neil
Not Quite So
“The idea of including a choke in the tx. ground path to prevent RF radiation negates the protective function of the ground. If the path is open for RF then it is also open for part of the lightning energy. A ground choke is no solution.”
Hardly. That choke provides a DC path just as it would if it was a simple straight wire. The only thing your choking is the RF return to the TX, not DC arc from a strike.
Take your DVM and do a continuity check and see for yourself. A .1 ohm resistance isn’t going to block a 4 million plus volt jolt.
RFB
Lightning is not Just DC
A strike is a pulse or a series of pulses which necessarily contain energy at many frequencies as a Fourier analysis of pulses will reveal. The higher frequency components of lightning can be heard on an AM radio for hundreds of miles illustrating that there is RF energy in a strike which will not be passed by a choke and which will seek and find other paths to ground. A choke is no solution.
Neil
Irresistible Force Meets Immovable Object…
Think of it this way, a choke reacts to a change in current flow offering resistance (reactance) to that change.
An instantaneous change (lighting) equates to an infinite frequency. A choke would react with an infinite resistance.
As such, the current would seek another path, your transmitter.
Yes, the choke has a very low resistance to DC but a very high resistance (reactance) to a high frequency (instantaneous change.)
From Wiki: “In electrical and electronic systems, reactance is the opposition of a circuit element to a change of electric current or voltage, due to that element’s inductance or capacitance. A built-up electric field resists the change of voltage on the element, while a magnetic field resists the change of current. The notion of reactance is similar to electrical resistance, but they differ in several respects.
Capacitance and inductance are inherent properties of an element, just like resistance. Reactive effects are not exhibited under constant direct current, but only when the conditions in the circuit change. Thus, the reactance differs with the rate of change, and is a constant only for circuits under alternating current of constant frequency. In vector analysis of electric circuits, resistance is the real part of complex impedance, while reactance is the imaginary part. Both share the same SI unit, the ohm.
An ideal resistor has zero reactance, while ideal inductors and capacitors consist entirely of reactance.”
As such, the choke will bleed of a static charge build up (DC) which lends itself to a lightning strike. The choke, however, would vaporize with a direct strike along with most anything around it.
Lightning response of ground choke is irrelavent
… irrelevant because the concept of using a ground choke is bogus to begin with.
The RF displacement current circuit consists of the path: loading coil -> antenna -> earth -> back to loading coil. This circuit must be unbroken and have as little resistance as possible for maximum efficiency. The one exception is the radiation resistance part, which should be as high as possible.
A choke (inductance) inserted in series with the transmitter earth ground wire will be in series with the loading coil inductance. The inductances are additive. The loading coil inductance must be reduced by the added inductance of the choke to maintain resonance. When things are adjusted back to resonance, all inductive reactance is cancelled and the choke ceases to impede RF ground current. At that point the choke isn’t doing what you wanted, so you might as well remove it and toss it in the trash.
To complicate things, the misguided attempt to impede RF ground current is complicated by the RF ground paths through the power and audio wires, which are in parallel to ground across the added ground choke. Some have proposed adding chokes in the power and audio wires. If you do that, you end up with 3 chokes in parallel. The resulting combined parallel inductance is then in series with the loading coil. The inductance of the loading coil must still be reduced by the combined inductance of the chokes to maintain resonance.
The simplest way to reduce ground current would be to detune the transmitter output circuit. Another way would be to keep the transmitter tuned and add series resistors in all the ground paths. The goal would be the same: cripple the transmitter output, if anyone really wants to do that!
A Twist Of Tales?
Well now, unless everyone’s memory is that far gone, seems a few here are talking a double standard with that long ground lead.
Dang if you do, dang if you don’t.
Interesting.
RFB
Twistedness
seems a few here are talking a double standard with that long ground lead.
My post was accurate as to the technical realities it addressed, but did not consider how the FCC might react to such elevated systems using narrowband filtering of a long “ground” conductor.
Lately I’ve been trying to avoid posts referring to FCC issues, when I can.
Good Point
“My post was accurate as to the technical realities it addressed, but did not consider how the FCC might react to such elevated systems using narrowband filtering of a long “ground” conductor.”
No one said your response was not accurate or valid. However there is obviously a double standard here about a long ground lead. Either you should have it, for obvious reasons, or you should not have it, again for obvious reasons.
Here lies the conundrum eh. So…what to do..oh what to do!!
Maybe get the FCC to define the long ground lead nonsense and finally put it to rest.
RFB
Part 15 AM Ground Leads
Maybe get the FCC to define the long ground lead nonsense and finally put it to rest.
FCC §15.219(b) has defined the total radiating length permitted for unlicensed operators legally using the AM broadcast band — which includes the conductor to r-f ground (a.k.a. the ground lead). Granted that an accurate understanding of the means needed to meet that FCC Rule may take a lot of study.
Only physics provides the definition of an r-f ground — and such does not exist at the top of a “massive” wire, flagpole, tower, the steel frame of a billboard or building, a water tower etc etc, regardless of whether or not such a conductor is connected to an earth ground at its base.
ALL such uncoupled/unfiltered conductors will radiate when incorporated in an elevated Part 15 AM installation.
More on Lightning
Generally there are two approaches to lightning protection, one being to divert the strike energy to ground and the other being to prevent the strike. A combination of both methods can reduce the chance for damage.
Consider the reasons for lightning “protection”. Primarily it is to protect life and property and is generally done in such a way as to keep the energy from entering buildings. One approach is to use a fusible link of wire (a fuse) in series with the conductor at the point of building entry in addition to a voltage clamp shunt (MOV or spark gap) to ground connected at the building side of the fuse. This won’t protect the outdoor equipment but that can be replaced.
Two stories for yesteryear. I lived on a farm with a wall mounted crank phone. The line was fused and spark gapped at the house entrance. The fuses “popped” so often that the phone man left a handful for us to replace when needed. Being the 7 year old electrical whiz of the family it was my job to replace the fuses. These fuses were a wood tube with copper caps which were about 4 inches long so the length, I presume, was to block the high voltage of a line strike.
We later moved into town and our house was about 50 yards from the city water tower. This tower provided a “cone of protection” which I have read is out to about 1/3 the height of the tower. We never had any lightning strikes or damage at our in town house. Maybe build a water tower in your yard???
Neil
Maybe build a water tower in your yard???
Maybe build a water tower in your yard???
Heck yea and then put our antenna’s on the water tower and ground the system to the tower and transmit for miles with a Part 15 Transmitter!
More Nit Pick
” A choke is no solution.”
It does two things. 1. Prevents that ground lead or metal support structure from radiating. Which amazes me no one is pointing that out considering KENC and
2. Provides a DC path for that strike.
Now without it, which is less of the two evils…a popular question lately that should be easily answered.
RFB
Choking
“A choke is no solution.” It does two things. 1. Prevents that ground lead or metal support structure from radiating. Which amazes me no one is pointing that out considering KENC …
IIRC the measured field radiated by KENC wasn’t much different with the “choke” installed than when it wasn’t.
The Elephant’s Ghost
The elephant in the room at all times here at part15.us is the rules we follow to be legal radio stations. Since we all know the rules, they seldom need a recitation as if we were in bible school.
When I posited that safety pre-empts the long ground lead rule, I put that thought into discussion with obvious self consciousness about the rule with which we struggle. I was not being dogmatic nor setting policy.
Always embedded in these interesting discussions about the part 15 elevated ground quandary is the slim hope of hitting upon some new idea that will solve the problem for all future elevated installations.
Not being a schooled RF engineer gives me and some others the advantage of having free use of our imagination all the way until we’re found to be wrong about some brilliant thought.
More Nit Pick
RFB wrote:
” A choke is no solution.”
It does two things. 1. Prevents that ground lead or metal support structure from radiating. Which amazes me no one is pointing that out considering KENC and
2. Provides a DC path for that strike.
Now without it, which is less of the two evils…a popular question lately that should be easily answered.
Did you read my post above titled “Lightning response of ground choke is irrelevant”? Did you read Radio8z’s post “Lightning is not Just DC”?
If you did read those posts, then I suggest you go back and spend some time on Wikipedia reading and understanding such topics as “electrical circuits”, “AC circuits”, “Inductance”, “AC impedance” and “resonance”. Once you understand what is said there, then maybe you can come back here and make a more significant contribution.
Read Them Just Fine….Did You Read Mine?
Yes Phil I did read both your posts and Neil’s.
Problem here is both of you and another are singing a double standard, totally ignoring the primary point.
And that point is the choke prevents the long ground from radiating, something all of you keep preaching about to not have a long ground because it will radiate.
And the second part of that point, you will have a better direct path for that strike going through that long ground rather than coming down your audio/power lines and into your studio.
So dance around the points all you want. It’s quite clear where the diversion is coming from.
I believe I have made significant contributions far more than either of you have..beings you keep doing that double step dance around the main point.
Now..go play with your simulators and run the numbers and see for yourself that the choke provides two important functions with long ground leads/paths/wire.
Do either of you deny that?
Or perhaps just wont admit that I am correct.
I’m sure Hamilton would agree..beings he sells a toroid choke for the Rangemaster. I suppose it’s there just for looks and kicks? No..it serves a purpose.
RFB
Purpose Being?
And that point is the choke prevents the long ground from radiating … I’m sure Hamilton would agree beings he sells a toroid choke for the Rangemaster. I suppose it’s there just for looks and kicks? No..it serves a purpose.
Just curious… if the customer installation of such a choke as reportedly was provided by the manufacturer of an AM transmitter that was/is certified for unlicensed use under FCC §15.219 might not have produced an installation compliant with FCC §15.219 — then what purpose did/would that choke serve?
Read Them Just Fine….Did You Read Mine?
RFB, let me make it absolutely clear from the start that I don’t give a rat’s tail what kind of antenna anyone chooses to install, or whether it is legal or not. That’s all up to the user. My various posts on the subject of antennas in the past have been technical and factual, and I have always been careful not to pass any legal judgements. If I did, it was not intended.
In this thread I am simply trying to convey that a choke in the ground line is a bogus solution to reducing ground line radiation.
bo·gus [boh-guh s]
adjective
not genuine; counterfeit; spurious; sham.
It’s bogus because it de-tunes the antenna matching network. You can do that without a choke. When you re-tune the matching network, the choke no longer impedes the ground current flow, other than to add some additional coil loss resistance to the matching network, and becomes useless. You can impede the ground current flow with a resistor, or a stick of dynamite for that matter, if that’s the goal.
If you still don’t believe me, consult with someone else who has actually studied and understands the basic fundamentals of AC circuits. Be sure to report back on what they say.
Even if I can’t convince you (likely), I hope that others reading these posts will be convinced not to waste their valuable time playing with chokes in their ground lines.
You said “I believe I have made significant contributions far more than either of you have”. Well, I wouldn’t put it quite that way. I would say you have made a LOT of contributions. Some have been “significant”, most have been just contributions, and some have been just plain wrong and counterproductive. You sure got a bunch of people chasing their tails playing with carrier current after you made that initial wacky claim about covering your entire town (Casper, WY?) with a carrier current transmitter! Was that excursion fun for you?
Whew
Just read all the posts and I have to say it’s time to stop the arguing.
the Choke did not work for KENC because it was still radiating.
Lets work on changing the rules for Part 15 with the ground issues.
The Long Grounds are not hurting anyone and there should not be any issue with them as long as the station does not interfere with the police or TV’s or the Fire department or cause any planes to crash down , then we need to change the rules for Part 15 stations.
And for the most part the FCC wont be bothering most part 15 stations due to the fact most of them have such a tiny signal , whats the point ?
There is way to much arguing going on over the ground stuff.
You have to have a ground just to stop static build up.
Trust me when I say this as I got one hell of a shock when I disconnected the ground from my ATU.
I now have it grounded VIA the Coax and it seems to be working just fine.
However I plan to go to ground level with my next system to avoid all of the Ground issues that are talked about on this forum.
I don’t think a choke is the answer , I think the answer is to work on changing the rules.
Lefty Speaks Truth
As founder of the ALPB, Lefty Gomez has gone to the heart of the matter on this ground fuss.
If the Mission of the ALPB is to bring “Radio Back to the People”, we need to be able to “Get Radio to the People”.
How silly would we be to promise something we can’t deliver.
It Can Work
“The Choke did not work for KENC because it was still radiating.
The choke did reduce that radiation, later Hamilton produced another choke that kills the radiation completely and is the current choke being sold by them.
“I don’t think a choke is the answer
It’s not a complete answer, it is part of the whole answer.
I think the answer is to work on changing the rules.
I’ve been saying that since day one of ALPB. Couldn’t agree more.
RFB
Full Circle
Back to Carl’s original query, I have an el cheapo RS metal detector and it is useless for finding underground lines which could be subject to damage or cause injury if punctured with a ground stake. If this is your concern, beyond treasure hunting, here are two ways I have dealt with this issue.
You should have a “Utility Protection Service” (UPS) in your area and you can ask them to mark (for free) the locations of underground utilities such as power, phone, cable, and gas. Though the intent of UPS is good they are not 100% accurate in their markings. They often use plat drawings as a guide and sometimes miss or mislocate things because utility workers don’t always follow the drawings, and it is still worth doing but I wouldn’t bet my life on it.
Another method which I have used with success borrows an idea from the location folks’ equipment and also from carrier current. The best way to make this work is to inject a signal into the house neutral using a modulated RF source. I use a RF signal generator set to the low end of the AM band on a “clear” frequency and modulate the signal with an audio tone. The “detector” is a portable AM radio and as it is moved around the lot the audio tone strength changes with proximity to underground wires. With a bit of practice and using the somewhat directional nature of the loop antenna it is possible to locate lines very accurately. I did this for a contractor here who was hand digging footers for posts and I had a rough idea of where the underground power drop line was buried but with the radio I located the line which was buried 24 inches to within two inches as confirmed when he carefully dug there. Even if it is not located with such accuracy, this method can alert to the presence of something conductive underground. Though pretty reliable I wouldn’t bet my life on this method either.
Neil
What’s Under There
Thank you Neil, for your comments.
Actually, I will be calling the “dig right” service, as they call it in the TV ads, for a legally required utility marking of the ground prior to planting a ground rod.
My hunting the area with a metal detector could actually be done before or after that utility check, but I think should be done before I install radials (for obvious reasons).
The planned antenna area has no electric nor water pipes, which are all in the front of the property, but I am not sure about gas.
A next door neighbor had his yard flagged for utilities and has a mysterious backyard gas line which is not the same one that serves the front of his house, and perhaps whatever it is also passes through my yard.
The signal line check for buried wires could probably be done with my carrier current system, except that I don’t have any buried electric lines.
When I had some foundation work done the workers found a large number of antique bottles from long ago which may have re-sale value. Therefore I think we should invent a glass detector so people can hunt for old bottles.
Say What?
“Well, I wouldn’t put it quite that way. I would say you have made a LOT of contributions. Some have been “significant”, most have been just contributions, and some have been just plain wrong and counterproductive.”
Heck of a thing to say for someone who rarely shows up once in a blue moon. But at least there is a fraction of that statement true.
More like stirring up hornet’s nests.
I see what’s going on here, as has happened on other forums.
No wonder new membership is down to nothing.
Keep dancing around the point. Eventually even you will get tired of it and disappear for weeks again.
Once again..since obviously the point is being ignored. The choke prevents the long ground lead from radiating. The long ground lead provides a better direct path for a lightning strike and preferable to have that strike go down that long ground line instead of the power/audio lines, which without that ground line going into the dirt, that strike will go into the studio and fry it.
This has nothing to do with compliance..everything to do with preventing lightning from zapping your studio to a puff of smoke.
The ground riff raff all over again. Old song, worn out record, time to change the channel.
EOF
RFB
Say What?
Being a frequent poster is not necessarily a good thing! I post here occasionally when I have time and when I have something meaningful to contribute. I have other things to do too.
I strive to post factual information as opposed to some who troll randomly for responses. This board is lightly moderated and is still remarkably free from trolls. I don’t classify you as a troll, unlike one other previous poster, not “Rich”. I just classify you as a blow hard who likes to make stuff up for whatever reason. Your credibility rating is zero because you never provide any information substantiating your myriad of claims. Your “real world” does not seem to include common sense. Why on earth should anyone believe all the stuff you say? I suppose the moderators could interpret this as a personal attack, but I see it just as a simple statement of fact. You are free to go on with your endless stuff. Just don’t fault me for not being a frequent poster.
And, once again..since obviously the point is being ignored. The choke does not prevent the long ground lead from radiating. Given that fact, there is no better path for a lightning strike than a direct wire to earth ground instead of the power/audio lines, which without that ground line going into the dirt, that strike will go into the studio and fry it.
You Do Your Thing, Let Others Do Theirs
Well I suppose the simulator says it won’t prevent the ground line from radiating.
Whatever.
Funny how the laws of physics change from one location to another.
Nuff of this nonsense.
People, learn by doing, not by simulating.
So back to the very beginning. And that is to get the rules changed and clearly defined.
Or…the teeter totter back and forth debate can go on for another decade.
Time to move on.
It’s obvious your transmitter is intended for simple antennas, like a single wire and can’t match up to anything beyond that. Glad I was able to pry it out of you..in not so many words…but enough for anyone to get it.
RFB
Chicken wire
Chicken wire is now properly called “poultry netting” or “poultry fencing”.
Using it can be considered environmentally responsible. It will return itself back to the earth in the form of a reddish-brown powder in just a few years. To install it properly, make sure all of it is securely in contact with or below the surface of the earth. This will help to ensure even decomposition and prevent pesky, unsightly patches from lingering for a few more years.
I can’t say using the cheap plastic substitute would be as environmentally responsible. It would probably take many more years to decompose, unless it specifically says “bio-degradable”.
Birds Of A Feather
“Chicken wire is now properly called “poultry netting” or “poultry fencing”.”
Semantics and political correctness. Same puppy.
And yes it is environmentally friendly. Though I am sure some might tell you that climate change is because of humans having babies and eating too many beans..never mind that the Sun is entering it’s 11 year maximum cycle and that Pluto has warmed up a whopping 3 degrees.
When the…poultry netting/fencing returns itself to the bowls of where it came from, it’s usually time anyway to check that ground system and replace/repair.
Point is however, it does work far better than single wires laid on the ground or buried. More area to catch that return RF.
RFB
Ground Conductor Choke for Elevated Part 15 AM Installations
That choke provides a DC path just as it would if it was a simple straight wire. The only thing your choking is the RF return to the TX, not DC arc from a strike.
However a tuned (narrowband) r-f network optimized for the center frequency of an elevated Part 15 AM transmitter+whip can prevent most radiation by that transmit system from a long “ground” conductor — and without much affecting whatever lightning protection is provided by that long conductor and whatever it connects to at its base [ground rod(s), etc].
However the radiated fields produced by an elevated system using such a network probably will not be as high as if the system was installed with the base of the transmitter a few inches above the earth WITHOUT that network, when using a very short conductor connected to the same ground rod(s).
The reason for the reduced fields from the elevated system with the decoupled ground lead is due to the much higher impedance in the return path for radiated r-f earth current back to the “ground” terminal of the transmit system.
An analogy for d-c circuits is the brightness of a “stock” flashlight to that when a large-value resistor is added in series with the flashlight bulb.
Once Said Twice Repeated
“RFB did you say chicken fence wire provides far better result than plain copper wires?”
Yep I said it because I tried it and it does work better.
More of the real world results. 🙂
RFB