|
2nd Floor grounding
After reading the archive regarding 2nd floor grounding, a couple of
questions. Outside of sufficiently thick gauge wire and proper depth to grounding rod. Are there any ELECTRICAL (nonRF) issues left to resolve for a 2nd floor ground? Several articles referred to long grounding lines being close to 1/4 wavelength as being a problem. Is this eliminated with balanced feedline? Thanks, john |
2nd Floor grounding
ORIGINAL MESSAGE: On Sat, 31 Dec 2005 10:16:19 -0500, jawod wrote: Several articles referred to long grounding lines being close to 1/4 wavelength as being a problem. Is this eliminated with balanced feedline? Thanks, john ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ No. You can not "ground" your station for RF, at least not in the sense of running a wire to ground. Don't bother because it isn't necessary anyway. You do need two kinds of ground, one for the AC mains for safety, and one for lightning. RF energy is expensive to generate. Don't waste it by running part of it into a lossy "ground". Keep it up in the air where it belongs. Baluns are your friend. 73, Bill W6WRT |
2nd Floor grounding
jawod wrote:
After reading the archive regarding 2nd floor grounding, a couple of questions. Outside of sufficiently thick gauge wire and proper depth to grounding rod. Are there any ELECTRICAL (nonRF) issues left to resolve for a 2nd floor ground? Several articles referred to long grounding lines being close to 1/4 wavelength as being a problem. Is this eliminated with balanced feedline? SNIPPED NO NO NO !!! |
2nd Floor grounding
jawod wrote:
After reading the archive regarding 2nd floor grounding, a couple of questions. Outside of sufficiently thick gauge wire and proper depth to grounding rod. Are there any ELECTRICAL (nonRF) issues left to resolve for a 2nd floor ground? Several articles referred to long grounding lines being close to 1/4 wavelength as being a problem. Is this eliminated with balanced feedline? Thanks, john 1) Make sure you have a good connection from equipment cases to AC Power main ground/earth. I use a 1/2 inch copper pipe on the table where my station is mounted. Each piece of equipment on the table, transceivers, amplifiers, power supplies, computer, are individually bonded to this copper pipe. This 1/2 inch copper pipe is then connected to earth ground by a #6 AWG wire run directly to the electrical service panel where it is connected to the earth connection. 2) If you use a 1/4 wavelength, or equivalent, vertical antenna you need a counterpoise, often called 'ground', at the base of the antenna. 3) A balanced feedline is used for a balanced antenna, e.g. dipole etc., to minimize RF coupling to the transmission line. The balanced line needs to run away from the antenna for a minimum of 1/4 wavelength at right angles to be effective. A dipole fed with coax cable needs a balun to produce a balanced signal to the antenna. The coax should also run away from the antenna at right angles for 1/4 wavelength to be effective in minimizin current on the coax. If you need to run from the antenna at less than 1/4 wavelength then a series of chokes or ferrites should be used to keep RF out of the house. These chokes/ferrites should be mounted at least 1/4 wavelength from the antenna. |
2nd Floor grounding
Amos Keag wrote:
. . . 3) A balanced feedline is used for a balanced antenna, e.g. dipole etc., to minimize RF coupling to the transmission line. The balanced line needs to run away from the antenna for a minimum of 1/4 wavelength at right angles to be effective. A dipole fed with coax cable needs a balun to produce a balanced signal to the antenna. The coax should also run away from the antenna at right angles for 1/4 wavelength to be effective in minimizin current on the coax. If you need to run from the antenna at less than 1/4 wavelength then a series of chokes or ferrites should be used to keep RF out of the house. These chokes/ferrites should be mounted at least 1/4 wavelength from the antenna. A symmetrical feedline is no guarantee of balance. Balance is achieved only when the two conductors carry equal and opposite currents, and that can be achieved with either coax or symmetrical feedline. Likewise, imbalance can occur with either type of feedline. You can learn more about the issue at http://eznec.com/Amateur/Articles/Baluns.pdf. That article doesn't mention imbalance caused by coupling to the antenna, which can occur if a dipole isn't symmetrical or if either type of feedline is asymmetrically placed relative to the antenna. Roy Lewallen, W7EL |
2nd Floor grounding
ORIGINAL MESSAGE: On Sat, 31 Dec 2005 12:14:38 -0500, Amos Keag wrote: The balanced line needs to run away from the antenna for a minimum of 1/4 wavelength at right angles to be effective. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Nonsense. An unbalanced antenna and/or feedline can be VERY effective. Hams have used them since the days of spark. All the unbalance does is change the antenna pattern, not the effectiveness. It will be better in some directions, worse in others. 73, Bill W6WRT |
2nd Floor grounding
ORIGINAL MESSAGE: On Sat, 31 Dec 2005 12:14:38 -0500, Amos Keag wrote: 1) Make sure you have a good connection from equipment cases to AC Power main ground/earth. I use a 1/2 inch copper pipe on the table where my station is mounted. Each piece of equipment on the table, transceivers, amplifiers, power supplies, computer, are individually bonded to this copper pipe. This 1/2 inch copper pipe is then connected to earth ground by a #6 AWG wire run directly to the electrical service panel where it is connected to the earth connection. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Why? 73, Bill W6WRT |
2nd Floor grounding
"Bill Turner" wrote in message ... ORIGINAL MESSAGE: On Sat, 31 Dec 2005 10:16:19 -0500, jawod wrote: Several articles referred to long grounding lines being close to 1/4 wavelength as being a problem. Is this eliminated with balanced feedline? Thanks, john ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ No. You can not "ground" your station for RF, at least not in the sense of running a wire to ground. Don't bother because it isn't necessary anyway. You do need two kinds of ground, one for the AC mains for safety, and one for lightning. RF energy is expensive to generate. Don't waste it by running part of it into a lossy "ground". Keep it up in the air where it belongs. Baluns are your friend. 73, Bill W6WRT Bill, I like your answer but it leaves me to want a bit more. Would you mind expanding on your 2 paragraphs? Thanks. west AF4GC |
2nd Floor grounding
ORIGINAL MESSAGE: On Sun, 01 Jan 2006 20:10:08 GMT, "west" wrote: "Bill Turner" wrote in message .. . ORIGINAL MESSAGE: On Sat, 31 Dec 2005 10:16:19 -0500, jawod wrote: Several articles referred to long grounding lines being close to 1/4 wavelength as being a problem. Is this eliminated with balanced feedline? Thanks, john ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ No. You can not "ground" your station for RF, at least not in the sense of running a wire to ground. Don't bother because it isn't necessary anyway. You do need two kinds of ground, one for the AC mains for safety, and one for lightning. RF energy is expensive to generate. Don't waste it by running part of it into a lossy "ground". Keep it up in the air where it belongs. Baluns are your friend. 73, Bill W6WRT Bill, I like your answer but it leaves me to want a bit more. Would you mind expanding on your 2 paragraphs? Thanks. west AF4GC ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ OK. 1. Running a wire from your rig to ground will not do what you think it will. Any wire is a significant portion of a wavelength at HF and may be many wavelengths at VHF and UHF. On ten meters, for example, eight feet is almost exactly 1/4 wavelegth. If you recall your basic transmission line theory, whatever condition is present at one end of a 1/4 wave line has just the opposite at the other end. If you really do have a good ground connection at the grounded end of the wire, the other is an open circuit. Not very effective for grounding, is it? The effect becomes less as you lower the frequency, but never completely disappears. It is possible to tune out this effect with a suitable coil and capacitor combination, but it really isn't needed anyway. MFJ makes a "ground tuner" or whatever they call it, and I suppose it does work, but think about this: If getting a good RF ground actually improves your signal, you have a SERIOUS problem in your antenna. More on this in the next paragraph. 2. RF does no good flowing through the earth. None at all. Dirt is a poor conductor at any ham frequency and you should do your best to keep your RF out of it. I suspect the idea that "ground" helps your signal came from the very early days of radio when frequencies were very low and wavelenghts were very long... miles long in fact. At those frequencies there are two factors which might make use of ground desireable: The earth is much more conductive at very low frequencies, and miles of wire for an antenna is not easily done. Under those circumstances, working a long wire against ground might actually be a good idea. None of that applies to ham frequencies, of course. At ham frequencies, RF works best when it's up in the air, all of it. Not in the ground, not in your shack, up in the air. Keep that in mind and you can't go wrong. 73, Bill W6WRT |
2nd Floor grounding
jawod wrote:
After reading the archive regarding 2nd floor grounding, a couple of questions. Outside of sufficiently thick gauge wire and proper depth to grounding rod. Are there any ELECTRICAL (nonRF) issues left to resolve for a 2nd floor ground? Several articles referred to long grounding lines being close to 1/4 wavelength as being a problem. Is this eliminated with balanced feedline? Thanks, john Forget about balun's and other widgetry! Get a virtual earth! They are easy to build for all ham bands! It's basically a phasing unit for the earth connection which can null the voltage on the earth at the RF Rig! If you don't want to build one, MFJ sells one! Cheers M0DFI |
2nd Floor grounding
ORIGINAL MESSAGE: On Mon, 02 Jan 2006 00:17:00 +0000, Dan Andersson wrote: Forget about balun's and other widgetry! Get a virtual earth! They are easy to build for all ham bands! It's basically a phasing unit for the earth connection which can null the voltage on the earth at the RF Rig! If you don't want to build one, MFJ sells one! Cheers M0DFI ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ They're great if you like your antenna two feet above ground. The way you "null out the voltage" is by making that wire resonant and resonant wires love to radiate. Nobody would intentionally install an antenna below knee level, but that's what you're doing. Busted any pileups lately? :-) 73, Bill W6WRT |
2nd Floor grounding
Bill Turner wrote:
They're great if you like your antenna two feet above ground. The way you "null out the voltage" is by making that wire resonant and resonant wires love to radiate. Nobody would intentionally install an antenna below knee level, but that's what you're doing. . . . I don't agree entirely with some of the recent short postings. And making a wire resonant doesn't make it radiate any better or worse than a non-resonant one. But if you have an unbalanced feedline (and by this I don't mean a symmetrical feedline like ladder line, but one of any construction with imbalanced currents) and consequential current from your rig to ground, that conductive path to ground will radiate just like an antenna -- any current flowing on a conductor causes radiation, regardless of whether we consider it to be an "antenna", a "ground wire", or a "transmission line". And as Bill points out, the location of a ground wire isn't usually what you'd choose for an antenna. Other consequential effects are that an unbalanced feedline has a net (common mode) current and so it radiates, too. The feedline and ground wire are also part of the antenna when receiving, so they'll be good at receiving noise that's generated in the house or radiating from mains wiring. All in all, it's not an ideal situation, although quite a number of people manage to get away with it. Roy Lewallen, W7EL |
2nd Floor grounding
ORIGINAL MESSAGE: On Sun, 01 Jan 2006 18:45:57 -0800, Roy Lewallen wrote: I don't agree entirely with some of the recent short postings. And making a wire resonant doesn't make it radiate any better or worse than a non-resonant one. ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ You are correct of course. I should have said a resonant antenna (or ground wire) is easier to couple energy into, and in that sense, it radiates better. 73, Bill W6WRT |
2nd Floor grounding
Forget about balun's and other widgetry!
And replace it with snake oil? Why? Get a virtual earth! They are easy to build for all ham bands! He's probably fairly young , has his health, etc. The last thing he needs is a "virtual earth" on the 2nd floor. It's basically a phasing unit for the earth connection which can null the voltage on the earth at the RF Rig! It's basically a bandaid device to cure problems from using poorly designed antenna systems. . If you don't want to build one, MFJ sells one! I don't doubt that. They sell about everything else... Seriously, if someone is on a 2nd floor, or even a ground floor, there is no need for rf grounding in the shack at all. All he needs to do is run complete antennas and there is *no* need for any rf grounding. Sure, he needs safety grounding for some gear, but that is taken care of by a grounded electrical cord. RF grounding should always be under an antenna that requires it. Not at a shack, unless the antenna is fed from the shack. And that is a bad way to live in general. All he needs to do is run any complete antenna, such as a coax fed dipole, or ladder line fed dipole, or a vertical that has it's own rf ground under it. Adding a shack ground to any of these scenarios is a waste of time. It also usually causes more problems, than it hopes to cure... If he's feeding any of those antennas with coax, which I recommend for ease of use in any location, a balun is his best friend, not widgetry. I'm on the ground floor, and I use no RF ground in the shack. Have no need for one. Grounding has enough "wives tales" , etc, attached to it, to add more snake oil, or bandaid solutions. Lightning grounding is a whole nother story, but it also belongs outside, and not in the shack so doesn't really apply to his case of being on a 2nd floor and worrying about a rf ground. MK |
2nd Floor grounding
"Dan Andersson" wrote in message ... jawod wrote: After reading the archive regarding 2nd floor grounding, a couple of questions. Outside of sufficiently thick gauge wire and proper depth to grounding rod. Are there any ELECTRICAL (nonRF) issues left to resolve for a 2nd floor ground? Several articles referred to long grounding lines being close to 1/4 wavelength as being a problem. Is this eliminated with balanced feedline? Thanks, john Forget about balun's and other widgetry! Get a virtual earth! They are easy to build for all ham bands! It's basically a phasing unit for the earth connection which can null the voltage on the earth at the RF Rig! If you don't want to build one, MFJ sells one! Cheers M0DFI Ok Dan, How about a follow up and give us a link or a schematic to build one? west |
2nd Floor grounding
"Bill Turner" wrote in message ... ORIGINAL MESSAGE: On Sun, 01 Jan 2006 20:10:08 GMT, "west" wrote: "Bill Turner" wrote in message .. . ORIGINAL MESSAGE: On Sat, 31 Dec 2005 10:16:19 -0500, jawod wrote: Several articles referred to long grounding lines being close to 1/4 wavelength as being a problem. Is this eliminated with balanced feedline? Thanks, john ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ No. You can not "ground" your station for RF, at least not in the sense of running a wire to ground. Don't bother because it isn't necessary anyway. You do need two kinds of ground, one for the AC mains for safety, and one for lightning. RF energy is expensive to generate. Don't waste it by running part of it into a lossy "ground". Keep it up in the air where it belongs. Baluns are your friend. 73, Bill W6WRT Bill, I like your answer but it leaves me to want a bit more. Would you mind expanding on your 2 paragraphs? Thanks. west AF4GC ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ OK. 1. Running a wire from your rig to ground will not do what you think it will. Any wire is a significant portion of a wavelength at HF and may be many wavelengths at VHF and UHF. On ten meters, for example, eight feet is almost exactly 1/4 wavelegth. If you recall your basic transmission line theory, whatever condition is present at one end of a 1/4 wave line has just the opposite at the other end. If you really do have a good ground connection at the grounded end of the wire, the other is an open circuit. Not very effective for grounding, is it? The effect becomes less as you lower the frequency, but never completely disappears. It is possible to tune out this effect with a suitable coil and capacitor combination, but it really isn't needed anyway. MFJ makes a "ground tuner" or whatever they call it, and I suppose it does work, but think about this: If getting a good RF ground actually improves your signal, you have a SERIOUS problem in your antenna. More on this in the next paragraph. 2. RF does no good flowing through the earth. None at all. Dirt is a poor conductor at any ham frequency and you should do your best to keep your RF out of it. I suspect the idea that "ground" helps your signal came from the very early days of radio when frequencies were very low and wavelenghts were very long... miles long in fact. At those frequencies there are two factors which might make use of ground desireable: The earth is much more conductive at very low frequencies, and miles of wire for an antenna is not easily done. Under those circumstances, working a long wire against ground might actually be a good idea. None of that applies to ham frequencies, of course. At ham frequencies, RF works best when it's up in the air, all of it. Not in the ground, not in your shack, up in the air. Keep that in mind and you can't go wrong. 73, Bill W6WRT That makes a lot of sense, Bill. It takes talent to take a rather technical concept and put it into an easy to understand explanation. This post is going in my Ham archive. Thanks again. Cordially, west AF4GC |
2nd Floor grounding
There are grounds and there are are grounds.
Lightning ground House wiring safety ground Antenna counterpoise (ground) Ham shack common RF bus ground If you live in an apartment building or if you use soundcard modes you will soon find out that using the building's electrical safety ground as your antenna's counterpoise is a bad thing. Dont try to use an endfed wire antenna in an apartment. You will be unhappy if you try to use your TV and soundcard speakers as your antenna counterpoise. I came to the conclusion that balanced antennas are the answer. Put up a dipole or, better yet, a loop antenna. Balanced antennas have their "ground" as part of the antenna itself. I personally have never used a balun at the antenna but have used choke baluns near the rig and have used 4:1 baluns at the tuner. I often use an antenna tuner and ladder line so am not so sure that a balun at the antenna is a good thing under those conditions. I have experimented with "artificial grounds" They are just a series L-C circuit that you insert between your station common RF bus and your counterpoise system. Series LC circuits act like a short when tuned so the idea is that when your station counterpoise system is tuned with the series LC circuit, your station bussbar ground will have the highest current path to counterpoise system ground You can make an RF current meter with a diode a toroid a little magnet wire and a volt meter. MFJ artificial grounds or tuned counterpoise tuners have you tune for max current through the series LC circuit. I have found that max current through the series LC circuit is not always the best setting for getting minimum rf in the shack. I use my soundcard speaker amp as my canary - tune the counterpoise for least audio out of the speakers. KL7R PS, I live in a rain forest. I dont know a thing about lightning grounds. |
2nd Floor grounding
"kl7r" wrote Dont try to use an endfed wire antenna in an apartment. ======================================== If the domestic plumbing system, hot and cold pipes, central heating system and mains wiring are connected together, then the impedance to true ground, as a whole, will be very low. The RF potential difference between 'ground' and true ground at the lower HF frequencies will be small. In principle it could be measured - IF you could find a real ground. The actual distance in wavelengths between 'ground' and true ground, wherever that may be, is indeterminate and inconsequential. In the extreme case the elevated ground system can be considered as a sort of Faraday cage with no more than normal interference between the electrical equipments in the vicinity. By not using low-feedpoint-impedance anrtennas, such as exactly 1/4-wavelength or 3/4-wavelength in length, things can very often continue as normal. It is, in any case, undesirable to use very low impedance antennas even in good ground circumstances. And antennas crudely 1/2-wavelength in length work just as well with either good or very poor ground systems. Appartment and flat dwellers should not be discouraged from simple endfed antennas. In all probability they will be successful. Very often they are unable to erect anything else. My own experience extends from successful working with end-fed wires from bedrooms to a 13th storey in an appartment block. The appartment block antenna was a 0.3 wavelength sloping wire on the 160m band, open circuit at the bottom end fed at the top. Ground was an aligator-clip connection to the nearest hot water radiator pipe in the domestic central heating system. But I could just have well used the cold water pipe to the flush-tank in the toilet had it been nearer. Appartment dwellers - carry on as normal! ---- Reg, G4FGQ. |
| All times are GMT +1. The time now is 11:52 PM. |
Powered by vBulletin® Copyright ©2000 - 2025, Jelsoft Enterprises Ltd.
RadioBanter.com