Well Tim.. You just must not be googling right!...
I tried googling "saltwater ground transmitter am", here's a few excerpts from the results I got;
A pdf artilce entilted:`Seawater Grounding for High-Frequency Radios
Communications No Need to turn your boat into a copper mine. Just tap into the ultimate ground---the sea of salt water that surrounds you
http://sfbaysss.org/resource/doc/SeawaterGroundingFor_HF_Radios_byGordonWest.pdf
"..The Ground Conductivity can have a major impact on the station's coverage. Salt water is considered the "best" with a ground conductivity of "5000" ..."
http://www.oldradio.com/current/bc_am.htm
"...The same factors that made New Orleans so vulnerable this week made it an easy place to put radio stations. AM stations function best in low-lying areas with a salt-water ground..."
http://www.fybush.com/sites/2005/site-050902.html
Federal Communications Commission
Rule sections 73.183 and 73.184 refer to AM groundwave field strength ... The bottom set of curves covers distances between 10 to 5000 km from the transmitter site, ... with the best conductivity (5000) corresponding to seawater (salt water) and ... Ground conductivities in the United States typically fall between 0.1 and 30 ... (link broken, there's also more at the FCC's screwed up website)
"...Despite all these variables, it is found that terrain with good conductivity gives the best result. Thus soil type and the moisture content are of importance. Salty sea water is the best, and rich agricultural, or marshy land is also good...."
http://www.electronics-radio.com/articles/antennas-propagation/ground-wave/basics-tutorial.php
"...Conductivity can range from 5,000 mS for salt water as an extraordinary high (little loss) to a miserable low of near 0.5 mS, such as you have on the moraine field called Long Island..."
http://www.radioworld.com/article/what-determines-how-far-your-signal-goes/50789
"...As you can see, salt sea water provides the best conductance by far (5000 mS/m)...'.
http://radio-timetraveller.blogspot.com/2011/06/field-strength-calculations-ground.html
A paper concerning the matter from the notorious R Fry:
http://www.radioworld.com/article/am-coverage-frequency-vs-conductivity/23739
"..WABC's transmitter position might be considered less than ideal, since it doesn't sit on salt water like so many other New York stations..." http://www.musicradio77.com/transm.html
Here's a large collection of free pdf 'Radio' magazines from 1922...
"...In this system a conducting fluid such as salt water is used for the antenna.."
https://books.google.com/books?id=IGpOAQAAIAAJ&pg=PA17&lpg=PA17&dq=salt+water+ground+transmitter+am&source=bl&ots=cR4_yF83Ig&sig=pV6YG2IDid49bjo5w3naGX1h4Og&hl=en&sa=X&ved=0ahUKEwic9ZXTv9jJAhUG5CYKHb8XBuoQ6AEIYTAN#v=onepage&q=salt%20&f=false
AND That's just scratching the google surface!
I just come to realize that Ken Norris is no longer broadcasting from is boat.. Right here on Part15.us are some results for "boat" and saltwater which i should have search myself to start with..
Ken Norris:
"..As some here may remember, I was on a boat and had the ocean for ground and counterpoise...which is as good as it ever gets. On some days, I could get the ol' Talking House 5 listenable to nearly 3 miles depending on interference..."
http://www.part15.us/forum/part15-forums/antennas/ground-planting-questions-now-time
Other search results on part15,us include...
Philb:
"...As others have said, salt water has the highest ground conductivity. There have been many reports of extraordinary range over salt .. ...I would recommend something other than just throwing a wire over the side. The ground should be physically stable. A wire over the side would work but as it drifts around, it will likely affect the tuning. I see nothing wrong with grounding the transmitter to the boat's common electrical ground as long as there is ample contact with the water. I assume there is a ground plate or something on the bottom that is submerged."
Scwis:
"...Note the conductivity of salt water (5000!) relative to that of earth - no wonder Ken is experiencing such great results up there in the harbor!..."
RFB;
"..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! ;).."
Dave:
"..if I remember correctly with salt water being almost as good as 360 radials of wire...."
Thelegacy:
".. If you live near salt water as we know that makes for super conductors here for ground...'
And Rfry even metioned a few post back that grounding in salt water is far better than any other method of grounding.
And I have mentioned a few times in the past, about 10 or so years ago when I had my transmitter mounted on the roof of the Tybee Pavilion, and grounded to it's elaboarte copper grounding system which went deep in the sand to where it hit the water of the salty Atlantic Ocean.. I was getting at least 10 miles range for several weeks with a clear strong signal, untill i disconnected it before getting into trouble!
Here are some numbers for a typical, land-based Part 15 AM system.
- Frequency: 1700 kHz
- Height of Vertical Radiating Conductor(s) Above the Earth: 3 meters
- Earth Conductor (buried vertically, directly below the radiating conductors): 2.5 meters
- Earth Conductivity: 5 mS/m, d.c. 13 (average)
- Transmitter Output Power at Loading Coil Input (unmodulated): 50 mW
- RF Resistance of Loading Coil at System Resonance: 25 Ω
- RF Resistance of Ground Path: 60 Ω
- Effective Radiated Power: 0.07 mW
- Field Intensity for a 30-meter Horizontal Path: 2.6 mV/m
- System RF Bandwidth, 3 dB: 50 kHz
If the earth conductivity above is changed to that of sea water (5,000 mS/m, d.c. 81) and other parameters are unchanged, then these other changes might result ...
- RF Resistance of Ground Path: 2 Ω
- Effective Radiated Power: 0.22 mW
- Field Intensity for a 30-meter Horizontal Path: 4.7 mV/m
- System RF Bandwidth, 3 dB: 16 kHz
Other things equal, a Part 15 AM "sea-water system" would produce higher ERP and greater coverage area than for a land-based system, but would be more difficult to tune/set up, and probably not as stable.
Of course it isn't practical to exactly duplicate this physical configuration on a sailboat, but does illustrate the difference between a sea-water r-f ground and one using the terrestrial earth.
So if I interpret correctly, with seawater ground, the radiated power triples, the field intensity almost doubles,.. and not sure the meaning on the rf bandwith differences, but in general, your calculations further confiirm that there would be a very substantial improvement in range.
Every time you point out something positive it makes me regret my differences towards you..
I'm not exactly sure what you mean of it being impractical to duplicate the configuration on a sailboat.. With the install I described the transmitter in a dry spot, would be maybe 3-4 inches above the waterline with ground in the water and the antenna having no obstruction around it.. The only substantial difference I surmise would be the tides rise and fall twice a day.. not sure what that would do to tuning.. other than that would be rough weather and or heavier waves, but fortunately my boat has a spoon bow with a rather heavy water displacement, and a heavy keel, so it really doesnt incline much swaying back and forth - it's more likely to just go up and down.
There's always tradeoffs, and I guess I'll just have to try it and find out, but based on Ken Norris's experience, the final results is likely to lean more heavily towards the positive.
I wonder if there is any information out there about how the offshore radio pirates did their grounding systems. Several of them like Radio Caroline ran several hundered if not thousands of watts.
If the hull is metal, they bolt the tx earth connection to that.
As the hull area is large, it does not matter if it is painted as the capacitance of hull to water is large.
Paul.
Rich Powers posted about me in Reply 18 (in part), "... Every time you point out something positive it makes me regret my differences towards you. ... "
Thanks for stating so, Mr Powers.
The purpose of my posts is to provide technical truth.
Understandably such posts -- no matter who makes them -- may be viewed by some readers as being either positive or negative, depending on the personal concepts/hopes of those readers with respect to "Part 15."
If you're just going to be broadcasting while docked, why not use an anchor tossed over the side as the ground (attach the ground wire to the anchor chain). Note that I don't know what an FCC inspector might say about that arrangement.
Well.. I suspect the surface of the water is equalivant to the surface of the earth in respect to where the ground lead ends.
As for attaching the wire to the anchor, that might be problematic since it would tend to pull on the wire this way and that. I think the better method would to attach a plate to the underside of the hull with epoxy or something so the wire would be secure and stationary.
Do you really think the FCC is going to send someone out to a boat in the water to inspect the ground lead? 🙂
No life jackets on. That's a no no.
First @timinbovey.. I just re-read your comment above before I posted that slew of links i response, and realized how I had somehow missed the point of what you were saying! , so apologies for that.
Anyway, here a some good tips specifically concerning rf ground on sailboats for any one else interested..
"The thing to be careful of with ANY RF ground advice you get, no matter who you get it from, is to be skeptical and be ready to test carefully to be sure that it really works ON YOUR BOAT..."
http://www.sgcworld.com/sailboatgroundtechnote.html
and a couple others..
Marine Grounding Systems - http://www.westmarine.com/WestAdvisor/Marine-Grounding-Systems
Seawater Grounding for High-Frequency Radios - (pdf) http://sfbaysss.org/resource/doc/SeawaterGroundingFor_HF_Radios_byGordonWest.pdf
Ok, I realize most of you really have little interest in this topic, but the following is particuarly interesting, and could prove invalueable to others in the future who set out to do the same thing. You never know, someday you might be moving your transmitter a boat on the ocean to.
This has got to be the most useful information anyone is going to find in regard to effective rf grounding on a boat. I've read it several times to soak it in, and what I take away from it is that a small simple seawater ground is just as effective (or at the least, nearly so) in producing a strong transmitting signal, as would be an elaborate, more complicated and expensive grounding system..
Or to put it another way; You don't need much surface area contact with the seawater to create an potent rf ground and inturn produce a strong transmitting signal.
This is a big releif to me, because I was begining to greive over having to run a bunch of copper foil or mounting plates on the hull of my boat for the sake of the transmitter as other sources I have found on the internet deem to be neccesary to accomplish top performance.
This guy has a strong reputation, so he probally knows what he's talking about, and the described following test performed appear to confirm it.
Below is a heavily edited down version of his paper, to highlight the key points in relation to my situation. A link to the entire article is shown below.
I think you'll find it interesting even though most of yours are land based transmitters..
(The selected excerpts, spacing, and bolding is mine, to better highlight the points)
`Seawater Grounding for High-Frequency Radios (from Sail Magazine.)
http://sfbaysss.org/resource/doc/SeawaterGroundingFor_HF_Radios_byGordonWest.pdf
Communications No Need to turn your boat into a copper mine. Just tap into the ultimate ground---the sea of salt water that surrounds you....
My latest test of a marine-radio ground system took place last May in Long Beach, California. I
brought an old friend, Art Godson, aboard a sailboat with a brand new 100-square-foot capacitive ground system to verify my results. Art.. designs and builds unique mobile marine-antenna systems that put out monstrous signals.
The Test
Our 40-foot sailboat... ground system was a professionally installed copper-foil strip that went nearly all the way around the boat, capacitively picking up metal fuel tanks along the way.
Our comparison grounds were made up of 3-inch-wide, 3-mil-thick copper-foil strips. ..
The boat's capacitive ground system, estimated to exceed 100 square feet, was connected to switch position 1.
Switch position 2 was connected to copper foil running to a single un-bonded underwater through-hull 4 feet from the automatic antenna tuner in the lazarette. --(((Me: This would be a viable option for me)
Position 3 connected to a copper-foil strip temporarily run over the side and immersed in seawater to a depth of only 6 inches. --((Me: or this one)
Position 4 was connected to a large fully immersed foil strip.
Our tests were with sky wave stations as far away as Hawaii and as close as San Francisco; all were asked which system sounded best.
We were careful to retune the antenna tuner each time we switched ground systems, and the results were as anticipated.
The seawater ground improved antenna power output, decreased the noise floor while receiving on board, increased sky wave signal strength,..
We saw only half as much signal strength with the capacitive ground.
Using ANY of the seawater grounds, the output-antenna current meter jumped up, sky wave stations reported a much stronger signal, and the fluorescent tube lit up from one end to the other on modulation peaks.
When tuning we could also see a difference in how hard the antenna tuner was working when we switched from a capacitive ground to a seawater ground.
With the capacitive ground it would take as much as a couple of seconds to recycle through the different Land C combinations.
But when we switched between the three seawater grounds, the tuner would immediately start and stop tuning, staying with the same settings through the three seawater connections.
Further tests on other days with big submerged copper-screen panels, copperpipes, and large copper-printed circuit board sheets showed signal reports that were comparable to those achieved with just a small bronze underwater through- hull.
Conclusions
If you are installing your own marine SSB or ham radio system and are looking for an easy way to ground it, start by grounding to a convenient underwater bronze through-hull near where the tuner is mounted in the lazarette. Just clamp the foil to the through-hull, being sure to first clean up the contact area on the fitting with a wire brush. Its a good idea to fold the foil under the clamp several times to insure the connection won't break down easily: Keep the foil (which has sharp cutting edges) clear of any hose attached to the through-hull and keep it away from any sloshing bilge water.
I also recommend grounding to a single through-hull. There is no need to run foil all over the bilge tying in additional through-hulls, tanks, rudderposts, and whatnot, as this will not appreciably raise the antenna current output or your signal strength to a distant station.
The best through-hull to use will be plumbed with non-conducting rubber hose and, of course, should stay in the water at all angles of heel. --((Me: here I don't quite grasp what he means)
True, a large ground plate is a better choice than a corroded through-hull fitting. Big bronze
ground plates have gold-plated studs for a good foil connection, and they also have more surface area than a small through-hull. There is no question that increased surface contact with the water helps lower onboard noise sources, and getting noises out of your radio system can be just as important as pumping out every last milliamp of antenna current. But my tests have confirmed that the porosity of ground plates does not effectively improve contact with the water, and I have found that a single plate the length and width of a common brick is all that is needed to develop a substantial amount of antenna current.
The longest distance between your antenna coupler and your seawater ground, be it a throughhull or a ground plate, should not exceed 15 feet. The shorter the run, the less the likelihood of developing inductive reactance.
And never use wire to make the connection; always be sure to use copper foil, as this offers the least resistance to radio-wave AC currents.
I have found the largest noisemakers are electronic tachometers, shore side battery chargers, solar-panel voltage regulators, water-purification systems, refrigerators, radiated energy from battery monitors, and any microprocessor clock circuit.
Connecting instruments to a good seawater ground will minimize all this errant noise radiation.
Capacitive grounding may only reradiate these interfering signals somewhere else aboard the boat. In fact, short capacitive-ground systems may actually invert the antenna/ground signals, radiating more signals below deck than through the antenna above deck.
Finally, it is best to develop an entirely separate grounding system for lightning protection.
Remember, when it comes to you high-frequency radio, your best ground is the element you're floating in, plain old seawater. If you aren't taking advantage of it, you may be losing valuable antenna current.
Run a low-reactive copper-foil ground to seawater, and your transmit and receive signals will dramatically intensify over long and short signal paths.
http://sfbaysss.org/resource/doc/SeawaterGroundingFor_HF_Radios_byGordonWest.pdf
Thanks for sharing "Gordo's Link."
I take it you must know Gordo?
He has shaken my grimy mitt from time to time.