Antenna earth stakes - a tricky one!
I am wanting to install an earth stake/rod for a new antenna system. The
problem I have is that the 'best' position for this falls somewhere near where our underground sewer pipes run. As accurate measurements that I can ascertain from the engineering drawings puts it somewhere within 3" (75mm) of this sewer pipe and I am not prepared to rely on the accuracy of the drawing and or the pipes installer and end up puncturing the sewer pipe! I could drill a hole in a concrete path and sink the earth stake/rod through the concrete path and this raises the question! Is this likely to be a good position to put an earth stake/rod seeing the ground under the concrete path would never get seasonal rain and in fact has not seen seasonal rain for some 30 years! Does this matter or is good old mother earth still going to provide a good earth for my antenna system? Sure would appreciate some advice regarding this. VK5JE - from way 'down under'! |
Antenna earth stakes - a tricky one!
JERD wrote:
Does this matter or is good old mother earth still going to provide a good earth for my antenna system? I think you should look at an alternative ground system. For example, a copper "matt" laid over the sewer pipes instead of between them. If you have a decent earthworm population, you can lay it down on the ground and in a few years it will be buried. I'm assuming that you want something for HF work, so the size of the "squares" can be fairly large, there is no reason to use screening. If you are looking for an electrical saftey ground, for example as lightening protection, then a horizontal ground rod will do. Bury it below the "frost line" and you should be ok. Geoff. -- Geoffrey S. Mendelson, Jerusalem, Israel N3OWJ/4X1GM IL Voice: (07)-7424-1667 U.S. Voice: 1-215-821-1838 Visit my 'blog at http://geoffstechno.livejournal.com/ |
Antenna earth stakes - a tricky one!
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Antenna earth stakes - a tricky one!
JERD wrote:
Does this matter or is good old mother earth still going to provide a good earth for my antenna system? What is the function of the earth stake? e.g. lightning protection? Counterpoise? Increased gain? -- 73, Cecil http://www.w5dxp.com |
Antenna earth stakes - a tricky one!
JERD wrote:
"Does it matter or is good old mother earth still going to provide a good earth for my antenna system?' According to B. Whitfield Griffith, Jr. in "Radio-Electronic Transmission Fundamentals" on page 351, a single ground rod introduces about 50 ohms to an antenna`s resistance. He says contact resistance to the soil may be very low but the loss will be in the large area of soil surrounding the rod. Radials are the answer to the low soil conductivity probl;em. A broadcast grounding system of 120 radials, each 1/4-wavelength long, may have a ground resistance of about one ohm, as shown in Fig. 43-2 on page 353. Best regards, Richard Harrison, KB5WZI |
Antenna earth stakes - a tricky one!
Cecil, W5DXP wrote:
"Increased gain?" That is correct when considering "power gain" of an antenna, which is, power into some reference antenna / power into the gain antenna in the same direction. "Directive gain" of an antenna has nothing to do with losses. Best regards, Richard Harrison, KB5WZI |
Antenna earth stakes - a tricky one!
"Cecil Moore" wrote in message . .. JERD wrote: Does this matter or is good old mother earth still going to provide a good earth for my antenna system? What is the function of the earth stake? e.g. lightning protection? Counterpoise? Increased gain? -- 73, Cecil http://www.w5dxp.com The function of the earth stake is to 'ground' my new HF ham rig and also the AT-4 automatic antenna tuner. JERD - (Original poster) VK5JE |
Antenna earth stakes - a tricky one!
"JERD" wrote in
: .... The function of the earth stake is to 'ground' my new HF ham rig and also the AT-4 automatic antenna tuner. .... Jerd, Nothing here stated AC protective ground (which comes from the earth pin in your three wire power socket) or lightning ground. You have identified that you want to attach the second output terminal of the AH4 to the electrode. The proposed electrode (whether or not it is throught the path) is likely to have a resistance that results in a low antenna system efficiency at frequencies where the radiation resistance of the antenna is relatively low. The article at http://www.vk1od.net/InvertedL/InvertedL.htm models a scenario that is probably quite similar to that which you are considering, and discusses points relevant to the design... could be worth a read. Now, there will be a body of opinion that it doesn't matter what you do, you will still get QSOs, that it therefore 'works'. It sounds from your question that you are more interested in that shallow level of engagements, so read around. I wrote another article on a minimal setup again with an AH4 and end fed wire, it is at http://www.vk1od.net/NaroomaEFW/NaroomaEFW.htm . By all means, drive an earth electrode as you have proposed principally for lightning protection (though I would use a 2.4m copper clad steel electrode), but run at least a couple of (untuned) shallow buried bare copper radial wires from the AH4. Locating the AH4 remotely from your shack and house if you can will reduce the RF intensity in those places and reduce EMC problems. Catch you on air sometime. Owen |
Antenna earth stakes - a tricky one!
JERD wrote:
The function of the earth stake is to 'ground' my new HF ham rig and also the AT-4 automatic antenna tuner. RF 'ground'? AC 'ground'? Lightning 'ground'? DC 'ground'? -- 73, Cecil http://www.w5dxp.com |
Antenna earth stakes - a tricky one!
"Stefan Wolfe" wrote in
: .... foot radial, counterpoise et al. A good, deep ground rod in reasonably moist soil will turn the ground terminal on your radio into a true zero voltage reference point and stop allowing your antenna and A simple proposition for sure... but if it was true, why does the rod need to be 8' long? The only way that the ground terminal is a 'true zero voltage reference point' wrt the larger ground mass at RF is that if the connection to the ground mass is of zero length, and that isn't true either above or below the ground. Owen |
Antenna earth stakes - a tricky one!
"Stefan Wolfe" wrote in
: .... With a radial system or mesh system, you are merely fabricating an artifical counterpoise loosely connected to earth that may give one the perception that true theoretical 'ground' is achieved, depending of course upon the frequency in question. A connection to earth mass with a rod that has copper copper cladding that reacts with the ph of the soil forms an oxide or hydroxide compound that makes the steel in the ground rod electrically homogeous with the surrounding soil, rendering the electrical potential of the steel in the rod at "zero" with respect to RF radiation potentials, lightening, the power generating generating station or conduction of electrons in any sense. Do you sell copper clad ground rods? With your creative explanation, you have missed your calling if you don't! Owen |
Antenna earth stakes - a tricky one!
In article ,
"Stefan Wolfe" wrote: I always thought that the grid grounds and radials were a waste of time. What can make a better ground than earth itself? What you have learned is that "Ground is NOT Ground, the World Around" an Old Radiomans adage from an earlier generation. Power Distribution Ground is not the same as RF Ground, and mostly the two are Mutually Exclusive. You ask what makes a better "RF" Ground than earth itself? That is very simple. Ocean Sal****er makes a much better RF Ground, than anything you have, or can build, on earth. Bruce in alaska an Old Radioman from the previous generation.... -- add path before @ |
Antenna earth stakes - a tricky one!
Bruce in Alaska wrote:
"Power Distribution Ground is not the same as RF Ground and mostly the two are Mutually Exclusive. Mostly Bruce is right. But, I`ve worked in many broadcast plants and can assure you that the radial grounding system is more than adequate as a power distribution ground except for code compliance which may require a ground rod and/or connection to a metallic water pipe. The radials are the best RF ground. Best regards, Richard Harrison, KB5WZI |
Antenna earth stakes - a tricky one!
Owen Duffy wrote in
: .... Now, there will be a body of opinion that it doesn't matter what you do, you will still get QSOs, that it therefore 'works'. It sounds from your question that you are more interested in that shallow level of engagements, so read around. That didn't come out right... it should have read: Now, there will be a body of opinion that it doesn't matter what you do, you will still get QSOs, that it therefore 'works'. It sounds from your question that you are more interested than that shallow level of engagements, so read around. Owen |
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