Wet ground increases range
I knew moist loamy ground helped range, but we have had some what of a drought. After a few days of heavy rains, my range went up noticeably, about 4 times. Before the rain I estimate my strong Part 15 AM signal ~150 feet; further than that sound quality started to suffer. Usually a listenable signal was all but gone in another 150 ft before the rain. Now I can hear my signal (albeit scratchy) out to about 1/5th of a mile away, ~1000 ft. The sound isn't grand at this "fringe" distance, but I can hear it in my car two blocks away, where before I could not.
So there you have it, water your ground farm. Keep in mind this is just a 3 meter long wire antenna hanging out my 2nd floor window. 1000 feet is no record. I still consider the range to be that of a much stranger signal. To say I have 1/5th mile range is not accurate, when the signal sounds like a mouse farting in a wind storm, in my opinion. However this wet ground affect is pretty interesting. Obviously it's hard to control ground moisture. You have to use the earth/dirt you have, unless you know how to do a rain dance.
What a great example of the influence of ground conductivity on AM BCB signals. Beyond near field radiation from the antenna system (radiator+ground system), ground conductivity takes over for propagation of the "far field" signal. The higher the ground/soil conductivity the better the range and launch of the signal. The antenna system cannot propagate in the fair-field a signal that is diminished in the near-field. A good ground radial system determines the baseline/benchmark for the range of any AM BCB signal. Even with a perfect shortened wire radial ground system, ground conductivity is still "the rest of the story." Thanks for sharing your experience.
Admittedly, even while inwardly knowing the importance of good grounding, up until now I have put all effort into the antenna above the ground, trying to find arrangements that radiated as well as possible.
Finally the time is here to look down at the ground and begin planning the development of that part of the system.
Because the rear wall of the building is being rebuilt, as part of the design a heavy copper wire is being installed from inside to outdoors at the ground level so that an indoor transmitter has a route outdoors for grounding.
The ground wire, heavy copper, will run from the building uphill to the far back of the yard, where no antenna signal reaches because of a chronic problem trying to transmit uphill. The theory is that the one continuous ground wire will force the signal right up to the top.
Am I right?
I have the opposite problem. Woe when wet.
I'm on the roof tweaking the antenna when the weather is good. So, I would guess the tuning changes for the worse with wet conditions. I've seen this with our City TIS station.
I'm using a ground counterpoise of 6 radials each about 15 feet long on the roof.
My best coverage occurs between 10 AM and 4 PM on clear, dry days.
What I would do in your situation is keep your present transmitter/antenna system, BUT, build a second system in some way to better take advantage of other times of the day and other weather patterns.
Then, I would build a way of switching from one to the other when needed.
Kind of like big radio stations with day night antenna patterns.
What I think I may do is ground mount the antenna. Much easier to work on down here.
I figure an elevated ground plane, say about eight feet off the ground. I'll make the counterpoise look like a canopy with mosquito netting over it. That way, maybe the XYL will go along with it.
We could even put a cafe table and chairs under there...
Love the cafe table umbrella idea. The reception at the table will be astounding.
BUT, what if people sitting at the table messes with the antenna pattern? You may want to have an "off limits" cafe table, there for appearance only.
Part 15 AM experiments I did in the 1970s
showed an increased range when the ground
was soaked with water from a rain storm.
However, in the last AM set-up I had that
worked well - the range went down when it
was rainy and wet. It was best when it was
hot and sunny. I believe the rain was detuning
the antenna/ground system somehow. But
when the sun came out and dried everything
up, the station went farther again. This makes
sense because the outside set-up was slapped
together, and there were probably places where
water could get in.
I like the idea of the table and chairs around the
base of the antenna. That's pretty funny.
All of my Part 15 3 meter sticks have been ground
mounted.
As far as ground radials are concerned, first I
set up the transmitter and antenna outside on
the ground. The transmitter was fed by an
audio/power cable that was also buried under
the surface. (Argh, oof, back pain, etc.) Then
I put down 4 radials. That was easy. Then after
that - I put down another 4 to make 8 total. It
was getting harder then because of trees and
tree roots, a storage shed that was nearby, rocks
in the gtound, bushes, and a bunch of poison ivy -
you know that sort of
thing. Then, over the period of weeks, I just
kept adding radials in the places that were the
easiest - one at a time. I had 17, but one got
lost somehow, so as of now there are 16. Some
of the radials were 10 feet long and some were
20 feet long. I wanted to go to 32 radials, but
I lost track of where they were. (Although I'm
sure there are ways to solve that problem.)
The thing is, I think if you are doing things pretty much
right - the outside transmitter with just 4 radials
will go much farther than any kind of inside
set-up. (At least in my experience.) And if the
set-up isn't too far from your house, then you
don't have to bury a lot of power/audio cable.
Best Wishes,
Bruce, MICRO1690/1700
"Because the rear wall of the building is being rebuilt, as part of the design a heavy copper wire is being installed from inside to outdoors at the ground level so that an indoor transmitter has a route outdoors for grounding"
Other than a safety ground apart from your house ground, I don't see how that will help, certainly not a ground radial system, because the radials must go outward from the center of the vertical antenna, or else they don't act as a capacitive element for preventing ground loss, allowing the vertical antenna to be more efficient as the intentional radiator.
The ground mounted system with radials will always be more efficient than one with no capacitive element, but, indeed, can have an effect on system tuning, as would a capacitive hat, or even altitude of the ground where the system is located.
But, for the life of me, I can't see how wet ground would so radically detune the system that it would actually reduce range ... unless there is some piece of information missing, like water shorting the antenna to the ground.
Because my system is on a boat in sea water, occasionally I can detect the signal (just barely) on land in close proximity to the sea quite a long distance away. I think it follows the coastline, because it doesn't travel direct out across the water that far.
...I think it follows the coastline, because it doesn't travel direct out across the water that far.
Ken, I'm not sure what to think about that.. This makes me think about back when I had the Rangemaster on the pier.
While driving off the island the signal would fade to static about a mile down the highway.. and the entire distance is salt water swamp on both sides of the hwy.
Yet when on the next island over (about 10 miles away) I could turn the radio on at the dump or the ballpark and get a clear strong signal.
I'm sure this range was mostly due (as I've mentioned in the past) to being tied into the pavilions grounding system.,, which prob was not compliant.
But my point is that if it just followed the coastline then I would never have lost the signal enroute between the two islands at all.
Now as to why I would lose the signal completely shortly out, and then pick it up again strong 10 miles away.. well, I don't know, you tell me.
In the AM broadcast band, RF currents penetrate the earth a considerable distance. Rain typically just wets the topsoil. This is why such inconsistent results are obtained when reporting propagation before and after a rain. Maybe if a flood brings the water table above the surface, a definite difference will be seen. But then, you probably will not be bothering with radio experiments.
Your neck of the woods ... well, it hardly has any (woods, that is). It looks from pictures like the beach is mostly sand, which won't carry a signal.
If it makes contact on the other island (10 mi. is a heckuvva long ways away), maybe it's ground systems facing your island cause some sort of coupling.
This confirms what Ermi wrote. If you want your current setup to get distance, I recommend a very deep ground connection, deep as you can get it, and more than one if possible.
I don't work for them or have I ever bought anything from them, but DX engineering is aimed at the Ham Radio market. They have a nice ground system that may give you all some ideas. It is based around a square stainless steal plate with studs, to attach all the ground radials. It clamps to the mounting pole in the ground and is just above ground level. I like that, it's visible and easier maintenance. It's not all stealth, but it's heavy duty. They also sell ground radial kits. They have cool aluminum polls for verticals as well. Pricing out copper, the aluminum is a bargain, not including shipping. Here is the manual for grounding. It has all kind of info and ideas for grounding and mounting a vertical.
http://www.dxengineering.com/pdf/RADP-3-Rev0a.pdf
There vertical systems mount right off the ground. It has an interesting way to erect it with a hinged or slotted mounting plate. These instructions have lots of ideas that I can apply to a short 3 meter long MW antenna. I like the traps that could be made into loading coils.
http://www.dxengineering.com/pdf/BTV-INSTALL-GUIDE-Rev0a.pdf
Here is a owner installed antenna. Too bad we can't use 43 foot long mono poll.
http://www.dxengineering.com/pdf/KB8UUZ.pdf
They have hardware, utility boxes and goodies for antennas which you might find interesting for ideas.
http://www.dxengineering.com/default.asp
The idea of building a landscaped water feature with antenna grounding in mind has been hinted at, but I don't think it has been seriously considered.
What about building a swamp feature into an over-sized "swimming pool" filled with salt water and quagmire riddled with ground radials. Except for attracting alligators it could work. If the lining was water-proof, the water would remain mostly embedded and would replenish with every rain.
Probably some egrets and turtles would find it.
It has been my personal experience that water wicks into the connections of the antenna and ground radial systems. And where there is water and electricity, there is electrolysis which produces oxidation. Most metals produce some kind of oxidation, even gold and platinum. What this means is that connections that are outdoors or in moist environments must be brazed, welded, soldered, cad-welded or fused in some manner to make a solid metallic bond between conductors. Because RF travels on the outside of conductors (skin effect) any oxidation presents resistance to the signal. Add moisture and the resistance goes up, reducing current flowing in the system. This ultimately means a reduction in propagated signal.
Any joint not sealed or bonded should have a coating of clear silicone GREASE applied to it. Do not use Silastic sealer because some of it contains acetic acid (it smells sour) and will corrode the joints and conductors. If the silicone sealant does not have acetic acid, go ahead and use it.
And finally, my experience and study says that four elevated ground radials has the same effect on the antenna system as 60 or more buried radials of the same electrical length. I realize my experience is anecdotal at best, but the international DX contacts on ham radio don't lie. And, some of the contacts were QRP (4-5 watts).