Here is my question.
Say we have the 8 foot antenna like the range master uses. That leave 2 feet
for a ground wire to be ran to a ground.
Most grounds are 8 ft long under the dirt. That 8 feet under the ground
does not count . Only the 8 ft Whip and the 2 feet of wire running to the
ground pole correct.
Now I know woeking for large profesional AM Station we ran a ground plain
under the ground. 128 ft copper wires 10 guage. Now this would be no different
than the 8 foot copper rod under the ground. Even a house ground is larger
than a 8 foot copper rod in the ground.
So here the question would it be legal to place 16 wires equally spaced
under the ground to serve as a ground plain. Since it burried and would
serve as your ground.
Still you have only a 8 foot whip and 2 feet of lead wire to your ground.
This places your antenna only 2 feet off the ground but you now have a very
large ground plain under your antenna system.
This does fall in accordance to the FCC rules part 15. There was nothing that
stated how your ground had to be done. Only that your ground wire and
antenna could not exceed 3 meter in total. (10 feet).
Really people use to use cold water pipes on Crystal radios to receive back
in the day. Those pipes coud run for hundreds of feet under the ground.
Well since AM radio travel by ground wave and not sky wave it would be better
to have a antenna near the ground with a really good ground system.
So is it legal to have 128 ft wires burried under the ground to serve as a
ground plain??
That is my question
SKW40
"So is it legal to have 128 ft wires burried under the ground to serve as a ground plane??"
SP is important these days.
The rules do not regulate what kind of ground system you use. You can lay down 500 radials a mile long if you got the real estate to do that if you want. Even if those radials are just lying on the ground surface, they are on the ground and not sticking up in the air.
RFB
I think the idea is that radials on the ground surface do not radiate, but serve to ..... reflect? ........ Guide? .... the radiated signal from the vertical antenna in a strong ground plane path.
The radials do nothing more than to provide the return path for the RF circuit. When buried, they extend that radial's ground effect by direct coupling to the dirt, in effect extending their lengths and conductivity to the dirt, which as we all know MW loves to hug the ground (ground wave) and at flea power levels we want that as much as possible.
The ground return footprint must be as large as possible, ie more radials, longer radials, high conductivity of the dirt itself.
Its the same with a CC setup coupling to the neutral. We want a large ground footprint (conduction) via the isolated ground rod or rods to provide that large conductive footprint for the return path. The larger, more conductive that return path point is, the better the system will perform.
RFB
"Therefore I think the consensus would be that there is no legal way to elevate an AM part 15 antenna and have a legal ground."
Except for the TH ATU/Antenna combo. It's grounded to house ground thru the cable shield, the PS, and audio connections. Seems like it might be a wise idea to make an extra ground path with spark gap or one of the mfr'd parts... doesn't connect to ground unless enough voltage.
The best solution would seem to be to get property on a high hill, mount close to the ground, and enough space for ground radials and bonded rods to work against.
How about a rooftop with a metal vent pipe?
"How about reviewing all of the NOUO's and NAL's over the last 4 years.
OK ...
"The two stations with clusters of Rangemasters, KENC and it's metal structures at two locations.
And that is just of recent years."
INDEED! I say it doesn't amount to a hill of beans.The point I was making about FM busts is that the 'agency' has a lot of man-hours wrapped up in dealing with FM pirates. You have to be fairly seriously violating the rules for them to be coming after a wee Part 15 AM station. Of the few AM Part 15 violations, virtually all (except KENC) were cited because of interference complaints.
Range and RF energy are tied together, but rarely in a stable relationship. If there is one huge standout I've learned, it's that there are quite a few other factors, to where one perfectly legitimate Part 15 station will get much more range than another.
Location, ground conductivity, climate and weather, traffic conditions, high tension wires, transformers, etc., etc. Here's just one example: Out the San Juan valley on nice day after a rain, my station can occasionally be listenable for 2-3 miles on a good car radio ... but less than 1000' in other areas. It makes the station directional in that sense.
IOW, even as small as it is, the propagation coverage pattern can fluctuate wildly. Under certain conditions, which are nearly impossible to predict, and in one direction, for a few hours, I'll be out of compliance ... then it changes, and things will be hunky-dory.
Another one: T-storms 100 miles away can generate so much static, it doesn't matter where I'm listening. A block away is still noisy, and nothing significant can help ... it's just AM radio transmission.
... and how-the-heck could my station be heard, 5 miles from the Port, for a tight 8 foot stretch along a 200 foot-long underground power line going from a building to a floodlight on a roadside sign? The only thing I can figure is that there is (or was ... I haven't been able to repeat it) a very narrow 'slot' between hills with maybe a couple soggy ditches or creek beds in line with that spot.
I'll probably never know ....
"and how-the-heck could my station be heard, 5 miles from the Port, for a tight 8 foot stretch along a 200 foot-long underground power line going from a building to a floodlight on a roadside sign? The only thing I can figure is that there is (or was ... I haven't been able to repeat it) a very narrow 'slot' between hills with maybe a couple soggy ditches or creek beds in line with that spot."
Same is applicable to a 250uV FM signal. It could extend further by induction onto nearby power lines, other metal objects and such. AM is no different, or any other band or frequency.
Only real difference with your setup Ken is the fact you got salt water area to work with, the most perfect conductive ground you could ever have. THAT alone is the reason why you get 5 miles of coverage. There is no equal to that whatsoever, other than another pond of water or lakeside shore or in your case, on an island surrounded by sea water.
As you put it numerous times..location location location..and not everyone's location is on an island surrounded by salty sea water! Lucky whale! 😉
RFB
THEORETICALLY, since salt water is a better conductive medium than plain dirt or common moisture, WHAT IF we got bags of road salt and buried our AM radials in a blend of salt and dirt, hosed down well.
I know all the plants would die, but would the transmission be good?
My spectrum analyzer is showing reception of AM signals as received on the 13" telescoping vertical attached to the front of the unit.
When I bring my hand close to adjust the controls, the signals on the screen raise as much as 10 extra dBm, depending how close my hand is to the antenna.
Think of this capacitance effect in reverse. Imagine placing a 10-foot legal Part 15 AM vertical within an inch-and-a-half or so from an isolated 100-foot vertical wire.
It would most certainly not tune properly with Part 15 transmitters because they are intentionally scaled for short antennas, but a 50-ohm transmitter say the Ramsey25B, might light the night sky!
Seems legal to me.
Imagine placing a 10-foot legal Part 15 AM vertical within an inch-and-a-half or so from an isolated 100-foot vertical wire. ... It would most certainly not tune properly with Part 15 transmitters because they are intentionally scaled for short antennas, but a 50-ohm transmitter say the Ramsey25B, might light the night sky!
A standalone ~10-foot, legal, base-loaded/fed Part 15 AM antenna system installed with its base a few inches above the earth and using a loading coil to make it resonant no longer will be resonant when relocated close to a separate, longer vertical conductor.
The reason for this is the mutual coupling between such physically adjacent conductors. Nearby physical isolation of such conductors does not equate to their adequate electrical isolation, in terms of wavelengths.
After relocation, the impedance matching of the transmitter output to the base of the ~10-foot "antenna" conductor hard-wired to it could be re-configured to make that composite antenna system resonant again, so as to maximize radiation efficiency.
But as a technical reality that composite antenna system configuration no longer would be compliant with FCC §15.219(b), whether resonant or not.
Sorry.
On the one hand I believe Rich is correct about my latest brilliant idea not being acceptable by FCC standards.
But over on the other side of the brain I have a feeling that my idea is a great loophole in the rules and there'd be no way it could be banned except by writing one more line of Part 15 regulation.
But I'm not going to try it because I have no way of holding a 100-foot wire vertically upright.
for testing.. maybe a weather balloon?
i dunno.. I seem to recall someone talking about using one to hold up a bit of thin wire once..
Such a balloon would need to be large to support the weight of the long-wire.
Also, the balloon would be buffeted by wind and keep that antenna roving at all angles, totally throwing out the capacitive relationship with the 10-foot resonant antenna.
Details Details Carl. 🙂
ok - so I know this was done, and the pic i saw showed multiple tethers.. I don't think it has to be too heavy wire, and those balloons were designed to carry weather sensors.. so.. meh..