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Hi. Just found this forum yesterday and spent several hours reading past threads.
Hi. Just found this forum yesterday and spent several hours reading past threads.
Not much of a techie (any math will be lost on me), but I have been wanting to “play radio” for a long time. Have decided on Part 15 AM as the way to go, probably with a Procaster or a Rangemaster for an all-in-one package.
Hope it’s OK to throw out some real newbie questions here …
I live in a neighborhood of 100 houses. I think if I could achieve a good signal out to 1/2 mile (at least), I could reach everyone. And if I did that, I would put up a flyer to let my neighbors know about me. Therefore I want to be reasonably sure I am FCC compliant (doesn’t sound like it’s possible to be 100% sure!). So no long ground leads for one thing, I guess.
First question: How seriously will trees interfere with a signal?
When they built my neighborhood, they didn’t clear lots. Instead, they cut as few trees as possible and built up among them. We literally live in a forest. Except for my immediate next-door neighbor, there would be hundreds to thousands of quite large trees between my transmitter and any other house I wanted to reach. This is not something that can be avoided, no matter where I locate my transmitter.
I have other questions regarding transmitter location, and grounding. Will save those for later.
Steve Smith
Chatham County, North Carolina (outside Chapel Hill)
Total posts : 45366Hello Stephen Smith and welcome to the enjoyable world of Part 15.
It sounds like you’re catching on fast, if you already know that “ground lead” is something to question.
For fun I will submit a first answer about trees, which will be a guess, then other members will step in who actually know the facts.
I think trees can block signal, but AM may do much better than FM since AM is conducted along the ground and may pass under the foliage part of the tree, depending on species. Trees without leaves probably cause small ripples, whereas leaves probably block much more, especially if wet.
Unless the moisture actually carries the signal through a tree, as wet ground sometimes improves a signal.
Now we know exactly as little as before.
Total posts : 45366Depends on the density of the forest, but AM radio at broadcast band frequencies travels along the ground, more or less following the terrain during the day, which is why it generally goes further than FM.
The AM signal should find its way out through the trees OK. It suffers much more from powerline booster transformers, atmospheric disturbances, florescent lighting systems, electric motors, and the like, than organic materials. The homes themselves will have more tendency to block signals than trees.
If your place of transmission, say your house, is in the somewhere in the middle of the compound, it should work OK.
Otherwise, you may very well want to consider leaky cable or carrier current broadcasting system.
Total posts : 45366Live trees are slightly conductive because of the electrolyte in the sap. The conductivity of trees even allows them to be used as antennas. It is possible that a lot of foliage in an area can have a shielding or attenuating effect on radio waves.
Total posts : 45366The AM signal should find its way out through the trees OK…
Live trees are slightly conductive because of the electrolyte in the sap. The conductivity of trees even allows them to be used as antennas.
I’m surprised to hear you answering these questions this way.. It’s always been my understanding that trees has a tendancy to “soak up” (as it were) the radio waves.
My first install ever was with a Rangemaster in Ellabell GA and there were a lot of tall trees everywhere in the area.. even with the transmitter on top the mobile home with chicken wire ground plane and a long ground to an 8 foot deep ground rod I was only able to accomplish about a 1/2 mile usuable signal… I always blamed it on the large amount of tall trees.
I’ve never heard that a tree could be used as an attenna before..
Ermi, in the second part of your comment, are you saying the tree itself can be good for your signal, but the foliage is bad?
It is possible that a lot of foliage in an area can have a shielding or attenuating effect on radio waves.
Total posts : 45366Because trees are conductive, they (and foliage) can absorb radio waves.
It is rare for an electrical scientist and inventor to achieve high military rank, but the discoverer of the utility of trees as antennas was Major General George Owen Squier, Chief Signal Officer of the Signal Corps during WWI. General Squier was credited with numerous radio-related discoveries and inventions.
A grateful nation honored the General by naming a transport ship, the “General G. O. Squier” after him. Indeed, 30 nearly identical ships were in the “General G. O. Squier Class” of transport ships.
Coincidentally, the picture I use for my posts in this forum is of the “General M. B. Stewart,” the eleventh of the class of 30 Squier ships.
Total posts : 45366Ermi.. seriously.. like WOW!
That’s got to be the most fascinating thing I’ve heard in a long time! Never heard about it before..
A real quick search resulted with this about General Squire and his talking trees..
I’m copy and pasting several key points from the full article at: http://www.rexresearch.com/squier/squier.htm
I suspect this will wet the appetite of curiosity for others, like myself, who have never heard of such a thing..=========================================================
George O. SQUIER
Tree AntennasIt is not a joke nor a scientific curiosity, this strange discovery of Gen. George O. Squire, Chief Signal Officer, that trees — all trees, of all kinds and all heights, growing anywhere — are nature’s own wireless towers and antenna combined. The matter first came to his attention in 1904, through the use of trees as grounds for Army buzzer and telegraph and telephone sets, which, in perfectly dry ground and in a dry season, functioned poorly or not at all with ordinary grounds. Right then he began experiments with a view to seeing what possibilities, if any, the tree had as an aerial.
With the remarkably sensitive amplifiers now available, it was not only possible to receive signals from all the principle European stations through a tree, but it has developed beyond a theory and to a fact that a tree is as good as any man-made aerial, regardless of the size or extent of the latter, and better in the respect that it brings to the operator’s ears far less static interference.
It will puzzle the amateur as it has puzzled the experts, how a tree, which is certainly well grounded, can also be an insulated aerial. The method of getting the disturbances in potential from treetop to instrument is so simple as to be almost laughable. One climbs a tree to two-thirds of its height, drives a nail a couple of inches into the tree, hangs a wire therefrom, and attaches the wire to the receiving apparatus as if it were a regular lead-in from a lofty copper or aluminum aerial. Apparently some of the etheric disturbances passing from treetop to ground through the tree are diverted through the wire — and the thermionic tube most efficiently does the rest.
It is interesting to learn that the tree behaves very much like any other aerial; it receives better in dry clear weather than in muggy, damp weather. It plucks messages from the ether more clearly at night than in the day. It is affected very little by rain. It is affected not at all by the presence of other trees; so far as has yet been ascertained it makes little difference whether one drives his nail in a tree in the forest or a lone tree on the plain.
A dead tree will not do, and a tree not in leaf is not so sensitive as one in full foliage. It makes much difference where the nail is driven. General Squier calls the proper place the optimum point, and experimentally it has been determined that two-thirds of the distance from ground to top is the best place.
One nail is sufficient, and it may be any kind of nail; but copper is preferred as not rusting.
Some skeptics have expressed the belief that it was not the tree, but the wire leading to the nail in the tree which was the real aerial….
but to set any doubt at rest, the wire to the tree has been hung to the nail by means of an insulator, when the signals immediately cease, only to come in as strong as ever just as soon as the connection is again established.Just what this development of the art of radio telegraphy may mean has not yet been worked out. It is the history of most discoveries that their potentialities are hardly dreamed of when they are first made
If, as indicated in these experiments, the earth’s surface is already generously provided with efficient antennae, which we have but to utilize for such communication, even over short distances, it is a fascinating thought to dwell upon in connection with the future development of the transmission of intelligence.
The amateur wireless world will unquestionably take an intense interest in the tree radio work.
Total posts : 45366A couple of things come to mind after I read it..
1. This could kind of explain an interesting documentary I once saw – or possibly read about, that referred to evidence, that when trees in one area are being attacked by some fungus, moth, caterpillars, or whatever.. then other trees in neighboring and presently unaffected areas will began producing certain chemicals specifically geared to combat the force attacking the other trees..
Interesting to me. But back on the subject of Part15..
Now, call me crazy, but after reading the SQUIRE article, I wonder if a copper nail driven 20 – 30ft up in a tree could also function as an effective ground?
It can’t be any crazier than a tree serving as an antenna!
Total posts : 45366As I indicated in my first reply, the density of the forest is a factor.
1/2 mi. range with one ground connection is actually pretty good for a Part 15 installation, especially with trees. Obviously, trees affect the signal (fascinating story from Ermi), but I can get my signal going across fields and through large stands of trees nearly a mile away, but yet buildings and cars in town, much closer, can both block the signal in some cases, and cause severe noise in others.
Total posts : 45366Thanks for the replies and the interesting discussion. On balance, it sounds as though trees might not be a huge problem — and if I give ’em enough hugs they might even help relay my signal across the neighborhood! 🙂
It also seems, though, that I would be better off placing my antenna at some height rather than on the ground, especially with the presence of many trees around. At least that’s how I’m reading it.
Thanks also for the friendly welcome to this newbie and wannabe Part 15 broadcaster. I have a few other noob questions that I’ll be posting soon.
Steve
Total posts : 45366Squier coupled to the tree with a nail, but more sophisticated coupling methods have been invented and patented over the years. Squier emphasized the use of trees as receiving antennas, but they can be used as transmitting antennas as well.
It should be emphasized that the ionic conductivity produced by electrolytes (like tree sap) is much lower than the electron conductivity of metals. So, tree antennas are not going to be particularly efficient, but they will at least work. A tree antenna would also be difficult to spot by the enemy.
Rich also included a non-radio related article about obtaining low-level battery power from trees that can be used to power sensors and monitors without having to ever replace batteries. This works on the same principle as the popular children’s science fair project demonstrating getting electicity from electodes poked into a potato.
To understand why a Major General (Squier) would be a noted electrical scientist, it should be appreciated that he got practically all of his education in the Army. He never went to high school. He learned his math and science at West Point. Computing artillery trajectories, and designing fortifications, for example, require a good understanding of mathematics and engineering, and it is not surprising that he studied scientific subjects as a cadet. After West Point, Squier went on to obtain a Ph.D.
By the way, “Squier” is prononced like “squirrel.” but without the “l” at the end.
What about tree antennas for Part 15? I guess the tree should be no more than 3 meters high (or should I say “hi,” […. ..]?).
Total posts : 45366It was stated in a post on another site that trees don’t significantly interfere with a signal if they are much shorter than a wavelength. Here is how trees in the near field can interfere with a signal even if they are short compared to wavelength.:
The near field extends to up to about a half wavelength from a vertical monopole over ground. In the near field, the signal does not propagate, but produces standing waves. The RF current goes up the monopole from the hot side of the RF source, and returns to the cold side of the source by dispacement current through the air and ohmic conduction in the ground plane. There are RF losses in the ground plane.
If there are trees in the near field, some of the displacement current is intercepted by the trees, and conductive current flows down the trees to the ground plane. The conductive current in the trees causes additional ground loss. More importantly, the RF current flowing down the trees is 180 degrees out of phase with the RF current in the monopole, causing partial cancellation of the fields generated by the monopole. This reduces the power generated by the monopole.
The higher the tree density, the higher the power loss due to the trees.
Total posts : 45366I would guess, based on hunch rather than exact knowledge, that the moisture content of the tree and the trees outer wetness would also strongly affect the influence of trees on a radio signal.
Total posts : 45366Another hunch-(not on interference, but on propagation).
Jumping back…
In reference to the SQUIRE story previously in this thread, I reprise the ponderation of an elevated installation using a copper nail driven 20 – 30ft up in a tree as a ground..It may sound silly (and maybe it is), but if a tree can indeed be used as an effective antenna, then it seems just as plausible that the same type method could ground your transmitter.
If so, it doesn’t seem an inspection would classify a live tree trunk as a radiating ground!
Total posts : 45366“It may sound silly (and maybe it is), but if a tree can indeed be used as an effective antenna, then it seems just as plausible that the same type method could ground your transmitter.”
If you read Ermi’s last post, you should see the folly in that assumption. IMO, if the tree, or any ground conductor in the antenna system (the trees will likely be several orders of magnitude in height above anything else), being in the ground, they will short-circuit before propagation takes place, canceling most if not all of the signal.
If you had enough property, say with Ponderosa Pines spread far apart, as opposed to Douglas Fir or Lodgepole Pine … which notably grow in densely crowded stands … a longwire antenna strung between the Ponderosas (illegal for Part 15 of course) could get out pretty well.
Or, you might try a large diameter cage monopole or the same with a helical as we’ve been discussing of late.
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