Hello all,
I just posted this queston over on a group at Facebook and wanted to ask it here as well.
I have a question about moist ground and ground elements for AM antennas. I am about to put up a part 15 AM with the 3 Meter (10 ft.) antenna mounted a few inches above the ground and ground radials made of copper wire, not sure what gauge yet. I have a some what moist yard most of the time but if it rains you'd better get your boots on and be prepared to slosh around in a few inches of grass and water.
How much could that water help or hinder the signal aside from the copper turning green? I am sure there will be some change in the inductance depending on the moisture content of the ground.
What are your thoghts?
I think I know something of an answer.
Lucky for you, there are smarter members here who might come along and give even better opinions.
I think moist soil improves the conductivity with your radials, lowers the impedance of the match, and results in much better transmission range.
Very dry soil loses conductivity and the impedance goes way up and the range decreases.
As far as green copper, I am not sure if the color changes the result or not.
"The "skin effect" pushes the electron flow towards the surface of the conducting material. If you have an insulating material on the surface, regardless of whether this is a completely different material such as a plastic coating or a chemical reaction product such as copper oxide (any oxidation state will do), the skin effect is pushing the electron flow towards that surface. But, it doesn't push it onto the surface. Therefore, the only effect the insulating material will have is on the dissipation of the heat build-up due to the I2R losses. This will indirectly affect the current flow because of a change in resistance as the conductor temperature changes.
Now, when you are terminating the conductor, the current flow must not only get onto the surface of the conductor, but leave it where the surface is intimately attached to another conducting material. In this location the oxide coating is definitely harmful."
The previous tech info from John WDCX is marked by quote symbols but is not attributed to a quoter. Who is being channeled?
Is oxide green?
Would you even need radials if your soil is that moist? I was researching radials for an amateur radio antenna project over the weekend, and came across a comment that with exceptionally conductive soil, a ground stake driven into it could be sufficient.
Hi Rock: I have a question about moist ground and ground elements for AM antennas.
Here is my answer on your question. NOTE: ( I have tested about 8 transmitters with and without ground systems. )
Moist ground does make a difference on the am transmitter and helps it's range out !
1) If you have a septic drain field, use that as your ground.
2) Using a water drip system on top of the ground. Example Old water hose with pin holes and the end of the hose cap off laying on top of your complete ground systems.
3) Cat litter will work as well do to it will hold moisture. ( have not tested and don't know how long it will last.)
4) Clay would be another ground do to holding moisture ( have not tested and don't know how long it will last or preform.)
5) Salt water is another great ground.
6) I found that using heavier awg wire is better for a ground .
Here is a site where you can get a ground set up.
Write up is here.
http://www.theradiosource.com/articles/techtalk-groundplanes.htm
Picture and write up is here.
http://www.issinfosite.com/articles-techtalk-powerplane.htm
I hope this helps Jeff
I think for most people - moisture will
increase range.
For a different reason - it was the opposite for
me.
Because for limitations I had - my installation
was not competely sealed up from moisture.
During rain, the water detuned my system and
the range went down. It came back up on dry
sunny days.
I still would put ground radials down if you can - in any
case.
Bruce
All good answers in this thread and i should add what keeps my yard so wet is the run off from the ridge behind me. There had been some work done with a bulldozer that didn't quite have the results the person using the bulldozer expected.
So whether it rains or we have heavy fog here in the mountains the water will run off the property above me on the ridge, follow a path down a steep slope and eventually make it's way into my yard.
Though i have a ditch line at the bottom of that slope to catch some of the run off from the ridge above, it does reach a limit and over flow into my yard.
I don't mind it so much because it doesn't flood the whole yard and becuase it got me thinking what kind of range would that wet ground offer a low powered Am station?
Then i also thought of Tybee Tiny Radio, though in that situation the water is salt water (right?) which offers more bounce per ounce. Not that my landlord would mind, but i think i'll refrain from sprinkling salt on the lawn and save it for my french fries.
Flooding is a problem even at higher elevations, although i keep getting conflicting numbers from different websites and devices. One say's i am 980 feet and another says 1,398 feet.
But regardless of my elevation, it floods here because of poor planning from the roads dept, the state of kentucky and mother nature. I thought it would be helpful to have a station here that knows what is going on and in the neighborhood and pass that information on down the line using radio.
Am would be the best way to do just that, Fm just wouldn't cut it since the 200 foot limit is what i gauge my coverage by. Even if we were allowed 1 watt on part 15 Fm the extreme hills would just toss that signal around like a rag doll.
Am is near and dear to my heart, i cut my teeth on radio listening to an old AM car radio in a chevy station wagon when my mom was driving us late at night to god knows where. Later i aquired an AM/FM GE Clock Radio. The kind that was black and white with the vertical dial, a tuning knob, volume knob, am/fm switch and a large clock to the left. The speaker i believe was on the bottom facing the table it sat on.
In short, fm has been my choice for ease of installation but am offers a challenge.
Once you find that sweet spot in the tuning then all is well in the world of radio.
I should get my transmitter this coming Monday and then the fun begins.
This is the first radio i ever owned and it only had AM.
https://www.etsy.com/listing/73822893/general-electric-am-fm-clock-radio
A couple of years ago I did an experiment where I monitored the relative field strength of my outdoor ground mounted above radials transmitter signal for a year. The observations were for wet/dry, hot/cold, etc. for four seasons.
The thread is here: http://www.part15.us/blogs/radio8z/weather-effects-antenna-performance
It is a long read but maybe it will be useful.
Neil
This experience is worth reporting.
2 years ago we had a 3 or 4 month drought that made the ground crack, bushes and trees died.
At that time I was deep into carrier current which depends on a ground rod I put 8-feet down, and as it got drier and drier the reception on auto radio along the several blocks of powerline got lower and lower.
So I added a trickle hose at the ground rod and ran it for probably several days.
The signal field strength went up and up and was like the best days before the drought.
The moisture mattered.