You could certainly have an increased field strengt due to a combination of both the increased radiation resistance of elevated antennas and constructive interference from synchronized wavefronts.
No. 1, I recently asked about using an I-beam as a ground plane, and a question I included didn't get commented on: I asked if the I-beam would radiate to its side like a horizontal antenna, or out the ends, as I'm sure this same rule-of-thumb would govern the directionality of buried radials;
No.2 - I've heard talk of radials laid on open ground, unburied, for experimental purposes. Is burying them simply a matter of getting them out of the way or is contact down in the dirt an important factor? I think I know, but this is a review.
1. I-beams in the base frame of a mobile home (welded construction only) would act as a counterpoise for the radiating system of a transmitter. These rails to be compliant with most codes would be connected to earth ground separate from neutral or service ground in the AC panel of the home. This is mostly to help with lightning protection. In some homes in some states all the grounds are tied together, but it depends on the state you live in and the building codes. If the I-beams are separate from the service grounds then you would have to connect the transmitter ground to the rail directly. The wire between the transmitter and the rail would radiate most likely. The beams would radiate perpendicular to the beam.
2. Historically one of reasons to bury ground radials in to protect them from being moved or destroyed. They are also buried to keep people from contacting the ends of the radials that exhibit a very high impedance therefore a very high voltage potential that could cause burns or high frequency shock. The primary reason to bury radials is safety.
I'm not sure I agree with your comment in totality. Unless you know something about complicity between an FCC agent and a radio station, I'd say you're painting with a wide brush. FCC Rules are just that, rules. So in other words if your station is compliant, it's compliant. 🙂
Dead on... As business profits decline, the licensed stations will be wanting to get rid of unlicensed operators more urgently and will use every trick in the book. We are already seeing this everywhere. Here in Canada, the over the air TV stations want cable/satellite operators to pay for feeding the free OTA programs. The CRTC intended for the cable/satellite folks to pay, but they simply passed it on to the consumer and are now running newspaper and TV adds blaming the OTA stations for trying to gouge the public. It's becoming a dog-eat-dog world with nasty tactics and it's only going to get worse. If IBOC doesn't trample over Part 15 with excessive interference then these licensed stations in their survival mode will.
Gerry
Chezradio.com
John,
It is not a question of complicity. It is more to the question of an entity or person submitting a "written complaint" as to the operation of a radio transmitter. The complaint does not have to have any substantiation or cite any section of the rules. How do I know? With this same inspector, I sent a written complaint to his Vancouver, Washington office, involving a commercial broadcaster, that resulted in a fine. Before the inspection and after, the The inspector called me on the phone to explain his progress with the complaint. He then sent the inspection report to the San Diego office who issued the ruling and the NAL.
The rest of the story is that the commercial broadcaster is still in violation 3 years later.
"FCC Rules are just that, rules. So in other words if your station is compliant, it's compliant." John-wdcx
I wonder if the opposite is true? Of course it's true. Members of SBE chapters in the Northwest talk about how this guy gets away with murder and has continued this way for decades. Just pay the fine and keep running. Now who's being complicit?
My philosophy for Part 15 broadcasters is to be proactive with listeners and other people on the band, to keep complaints to a minimum, and try to solve them before they become legal challenges with the government. Be responsible and be a pro. If you're going to put a signal on the air, do it right.
You do make a good point. There is an AM here in town that's directional and is authorized 1KW day and 500 at night. Guess what, the power never changes, and the phasor is broken.
I've watched over time this subject of grounding and occasionally it is suggested that a choke or inductance of some kind be inserted in the ground line and it makes me cringe.
IF lightning protection for the transmitter, building, or personel is the reason for the ground then a choke of any kind including coiling the wire is a very bad idea. Lightning is a very short high energy pulse that likes to go in straight lines. Anything that "impedes" it (pun intended) , makes it show it's anger in the form of a deadly arc. The arc is caused by the voltage building to an extremely high value behind the resistance/impedence point (choke,coil,bend, etc). So.. do not insert anything in the ground line. period...
In fact run it as straight as possible and with as big a diameter of smooth conductor as possible to the best ground or ground plane (in the soil.. if bad soil the ground plane will hold the pulse while it slowly bleeds into the bad soil) as possible. It is a waste of time to run an earth ground if it's going to bend all over or have any choke, coil, etc. in it.
Now if you do run a good earth ground to the transmitter then it's a very good idea to insert chokes in the power and audio leads going into the studio to discourage lightning from going in that direction and frying everything in sight, it will instead choose the easy path.
If you run the ground lead to a plate with radials in the soil be sure and attach the ground lead to the SAME side of the plate as the radials. Lightning doesn't go through the plate it tries to go around the plate trying to make a 180 degree turn at the edges of the plate (can you say impedance).
Now the good news... The transmitter signal follows most of the same rules and likes the same connections to work best. As to FCC rules, well the national electrical code requires grounding for radio transmitters and if you do it like above you have a good shot at protecting your equipment.
The longer the ground lead above ground the more it radiates signal so really the rules are contradictory between the electrical code and part 15 unless you mount the transmitter at ground level and then they agree.
More random thoughts...
Try not to use stranded wire for your ground. Use a single lead conductor if possible.
Copper tubing is just as good as solid wire because all the current flows on the skin of the conductor, the center is totally wasted.
Very gentle large radius (ugly) bends where necessary. You want a few million amps flowing to ground not a few million volts building up where the ground turns the corner at the eaves of your house!
Dave
I emailed Ken Cartwright of KENC Radio and let him know that we are here and discussing his station.
here is his reply which he gave me permission to post......
------------------------------------------------------------------------
Good Morning Robert,
What a long strange adventure this has been with our low power AM
community radio station. We do not know who turned us in, though I
have filed a freedom of information act request with the FCC to try
and find out who and why. I think I know, but can't say at this time.
So far our choice has been to leave the transmitter/antenna atop the
40' tower. We disconnected the ground wire that we thought was
compliant from the tower.. As the FCC inspector defines ground leads,
the ground has to be directly connected to an earth ground at no more
than 3 feet in length. That means that the transmitter has to be
either on a ungrounded metal roof as a ground plane or no more than 3
feet off the ground, or in our case elevated, but no ground. But
that's not enough, he is requiring that we get a field strength
reading of no more than 14.2 micro volts at 30 meters from the
antenna or tower.. I don't have a field strength meter and most don't
have one that will read the small of voltage that is calibrated that
will satisfy the FCC.. I have very strong opinions about this
inspector but will reserve my judgement call at this time. We are
consulting a FCC attorney in Washington through the efforts of
several individuals including Keith Hamilton, the designer and maker
of the Hamilton Rangmaster, of which we have three in operation ....
It is imperative that we keep the station on the air... There are two
other stations licensed to this community. One is for sale at
$350,000 (out of our price range) that is AM 1460 KCKX a spanish
christian station, and a low power FM, KPIK, that is a hobby station
and does not serve the community with public affairs or news. At this
time all I can say is that we are working on the problem. The FCC
inspector said that "No one complained and that we are not
interfering with anyone else's signal, but that we are getting too
much range". We have always been diligent about making sure the
transmitter were installed and tuned to legal specs. Perhaps if more
low power FM frequencies become available we would apply for it, but
right now, this all we have to work with and it does work.. Ken
Cartwright
You do have my permission to post this and if anyone can help, we
sure would appreciate it.
Ken Cartwright
Program Director of AM 1620 Community Radio. "It's not how big your
watts are, It's how you use them!" www.kencradio.com
Agent inquiries about installations come up from time to time but this has been an odd one. One thing that may explain partly what is going on is that I think there was a FCC “memo” that went around to agents some time ago saying that Part 15 units on towers “somehow” were getting “incredible” ranges.
The dangerous thing here is that the agent is talking like he wants Ken to comply with 15.209, this basically requires a test lab. If Ken had a TH or procaster he would not even be able to comply since these units have auto power adjust.
I spoke to the agent on Tuesday about this. It is important to note it seems the agent did not seem to have a problem with Ken’s other two installations.
Someone on the board said to make friends with local Broadcasters, Amen, to that, because that is where objection probably will come from.
I agree with the comment about the choke on the ground, I only suggested it trying to appease a FCC agent at the time, Lighting safety should be the first priority.
Another thing I wanted to say, things change from time to time, just because FCC agents were telling me such and such was OK ten years ago, that doesn’t mean that is the current thinking, I try to keep my website legal section updated.
So when you hear Hamilton said this and that about a massive ground or long wire radiation, this or that, keep in mind that I rarely post these days, and you are most likely are hearing about something that is a morph of something I might of said years ago, when the FCC thinking was different. Again see the website for current info, the FCC checks out my website regularly and believe me, I hear about it if they don’t like something.
The problem is not whether Ken Cartwright has a field strength meter or not. The real problem is that the FCC inspector has decided to play hardball in this case, and his field strength requirement simply can't be met.
Limiting the field strength to 14.2 uV/m at 30 m is the same as telling Cartwright to turn his transmitter off. It takes a field strength of about 150 uV/m (over 20 dB above the inspector's field strength limit) to receive an AM signal in an urban area, and a lot more in downtown areas. You can't even get a field strength reading in the AM BCB if the field strength is only 14.2 uV/m. The signal would be swamped by the background noise, and would not be detected.
It looks like Ken will be shutting down for now. I think it is a travesty of Justice that Ken cannot operate considering he is compliant with Part 15, and is not interfering with anybody.
I am VERY hesitant to allow a reposting, but in light of the discussion I'll let it go this time only.
If there is a need to have information shared here, please have the original source create an ID and post the information as the original source rather that pasting something into your own post and attributing it.
If you have any questions about this, please send me an email at scwis (at) yahoo (dot) com
I am VERY hesitant to allow a reposting, but in light of the discussion I'll let it go this time only.
first time i have ever heard of this being an issue on any of the forums i frequent.
except if you are reposting for someone who was previously banned.
Quick reply
Since a number of replies have popped up since your post I'll post the answser inside your post. Our forum guidelines include a provision that members post only their own intellectual property on our site. Reposting something from another author is simply not your own intellectual property. There are also obvious issues with attribution, accuracy and in extreme cases, even whether or not the work is actually from the person to whom the intellectual property is attributed.
i suspect this rash of AM busts while infrequent compared to FM seem to be forming a trend.
most if not all were running rangemasters supposedly under part 15.219b
i think something is coming down the pipe and they want to clear the band of part 15.219b users.
who knows what the NAB and FCC are cooking up behind closed doors.
i find it curious that for 10+ years this ground lead thing was not an issue and now it's a huge issue within the last 2 or so years. also for every public FCC bust there are probably at least a couple of informal busts.