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Grounding systems -- need the help of some good elmers
Greetings,
To be honest, I'm a little embarrassed to even be posting this question. I've been a ham for over 10 years, but I've been out of the hobby for the past several and I'll freely admit that I'm one of those "memorize the multiple choice" people. Anyway, times have changed and I now own a house, and an HF rig, and have moved far from my roots. I want to get an HF station together, but I find the prospect of building/raising an antenna and putting together a grounding system a daunting task. So here's my question. Is it ok to have multiple shallow grounding rods versus one longer grounding rod? For example, what's the difference between 2 four foot rods versus 1 eight foot rod? Also, I'd like to describe my potential station set up, as I strongly suspect that it is not ideal, and I'd like any suggestions from the elmering crowd. It's on the 2nd floor of my home, over the garage. The power, cable, and phone connections are on the opposite side of the house, and there is no way to directly go under the house to get there (at least from outside the house). The home is nearly brand new (less than one year old). I should also mention that I have an unnatural fear of putting holes in the house, but I suppose I'll have to get over that in order to get on the air ;-). Thanks in advance and 73! Dan, W4XJF |
Grounding systems -- need the help of some good elmers
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Grounding systems -- need the help of some good elmers
On Sun, 29 Jul 2007 14:06:44 -0000, "
wrote: [snip So here's my question. Is it ok to have multiple shallow grounding rods versus one longer grounding rod? For example, what's the difference between 2 four foot rods versus 1 eight foot rod? [snip] Dan, W4XJF Dan, you didn't mention the type of ground you're seeking (safety, RF or lightining). If lightining, here's a good place to start. http://www.polyphaser.com/NR/rdonlyr...182/TD1016.pdf Danny, K6MHE |
Grounding systems -- need the help of some good elmers
On Jul 29, 1:09 pm, Ron in Radio Heaven
wrote: wrote: Dan, W4XJF Since you've moved I'll suggest that you do a change of address with the FCC, you're still listed as being in an apartment. W4XJF DANIEL F COATES 4619 Sunflower Rd. Apt 22 Knoxville TN 37909 73, Ron kc4yoy Good point... I'll definitely need to update that sooner than later. ;-). |
Grounding systems -- need the help of some good elmers
On Jul 29, 1:10 pm, Danny Richardson wrote:
On Sun, 29 Jul 2007 14:06:44 -0000, " wrote: [snip So here's my question. Is it ok to have multiple shallow grounding rods versus one longer grounding rod? For example, what's the difference between 2 four foot rods versus 1 eight foot rod? [snip] Dan, W4XJF Dan, you didn't mention the type of ground you're seeking (safety, RF or lightining). If lightining, here's a good place to start. http://www.polyphaser.com/NR/rdonlyr...C2-A98F-E88B80... Danny, K6MHE Sorry, I should have been somewhat more specific. I'm looking to create an RF ground. |
Grounding systems -- need the help of some good elmers
On Jul 29, 6:42 pm, " wrote:
On Jul 29, 1:10 pm, Danny Richardson wrote: On Sun, 29 Jul 2007 14:06:44 -0000, " wrote: [snip So here's my question. Is it ok to have multiple shallow grounding rods versus one longer grounding rod? For example, what's the difference between 2 four foot rods versus 1 eight foot rod? [snip] Dan, W4XJF Dan, you didn't mention the type of ground you're seeking (safety, RF or lightining). If lightining, here's a good place to start. http://www.polyphaser.com/NR/rdonlyr...C2-A98F-E88B80... Danny, K6MHE Sorry, I should have been somewhat more specific. I'm looking to create an RF ground. A couple of ground rods is not going to make much of an RF ground. Do you actually need an RF ground? Being you will be on the 2nd floor, I bet you would be better off without one. What will the antenna be? You would be better off to use a "complete" antenna, and that way you will not need an RF ground in the shack at all. An RF ground should always be under an antenna the way I see things. Trying to rig up an RF ground on the ground floor, and then rigging a wire from it, up to the 2nd floor, is a mistake, and will just act like part of the antenna. Myself, I would not even bother. Heck, I'm on the ground floor in this shack, and I don't use an RF ground to the shack. Haven't in nearly 15 years... MK |
Grounding systems -- need the help of some good elmers
" wrote in
ups.com: Greetings, To be honest, I'm a little embarrassed to even be posting this question. I've been a ham for over 10 years, but I've been out of the hobby for the past several and I'll freely admit that I'm one of those "memorize the multiple choice" people. Anyway, times have changed and I now own a house, and an HF rig, and have moved far from my roots. I want to get an HF station together, but I find the prospect of building/raising an antenna and putting together a grounding system a daunting task. So here's my question. Is it ok to have multiple shallow grounding rods versus one longer grounding rod? For example, what's the difference between 2 four foot rods versus 1 eight foot rod? Also, I'd like to describe my potential station set up, as I strongly suspect that it is not ideal, and I'd like any suggestions from the elmering crowd. It's on the 2nd floor of my home, over the garage. The power, cable, and phone connections are on the opposite side of the house, and there is no way to directly go under the house to get there (at least from outside the house). The home is nearly brand new (less than one year old). I should also mention that I have an unnatural fear of putting holes in the house, but I suppose I'll have to get over that in order to get on the air ;-). Thanks in advance and 73! Dan, W4XJF Hi Dan: I want to follow on what some of the other have said. First to only reason to have an RF ground in you shack is if you are going to use an antenna that brings part of the antenna that is supposed to radiate RF into the shack, as an example, a long wire antenna. Dipoles, beams and verticals that are feed with coax do not need RF grounds in the shack. Anyway making a RF ground in a second floor shack is a hard job. You do need a ground for lighting and static charge protection. For information on how to do that the Polyphaser web site is a good place to go. The basics are at least one 8’ ground rod as close to the shack as physically possible. More ground rods are better. Using shorter ground rods requires the use of more of them. In all cases more ground rods, properly installed the better. The ground rods should be connected together, if more than one is used, and to the shack with at least a #6 solid copper wire. You can bring it in to the shack anyway that is convent. Also national electrical code requires that all grounds to connect to the house ground (green wire ground) also. There is already a ground rod connecting your fuse panel to earth ground and your lighting protection ground must be connected to this ground via at least a #6 sold copper wire. The problem with RF ground and second story shacks is the length of wire will be too long the reach the earth and will act more as an antenna than a ground. Hope this helps. 73 John Passaneau W3JXP |
Grounding systems -- need the help of some good elmers
On Sun, 29 Jul 2007 23:42:52 -0000, "
wrote: On Jul 29, 1:10 pm, Danny Richardson wrote: On Sun, 29 Jul 2007 14:06:44 -0000, " wrote: [snip So here's my question. Is it ok to have multiple shallow grounding rods versus one longer grounding rod? For example, what's the difference between 2 four foot rods versus 1 eight foot rod? [snip] Dan, W4XJF Dan, you didn't mention the type of ground you're seeking (safety, RF or lightining). If lightining, here's a good place to start. http://www.polyphaser.com/NR/rdonlyr...C2-A98F-E88B80... Danny, K6MHE Sorry, I should have been somewhat more specific. I'm looking to create an RF ground. If it's an RF ground for an antenna, radials, buried or elevated, would be better than ground rod(s). bob k5qwg |
Grounding systems -- need the help of some good elmers
On Mon, 30 Jul 2007 13:40:27 +0000 (UTC), John Passaneau
wrote: I want to follow on what some of the other have said. First to only reason to have an RF ground in you shack is if you are going to use an antenna that brings part of the antenna that is supposed to radiate RF into the shack, as an example, a long wire antenna. Dipoles, beams and verticals that are feed with coax do not need RF grounds in the shack Not true. Feeding an antenna with coax does not remove the need for a station ground and here's why: http://k6mhe.com/sub/BlancedFeedLine.pdf Danny,K6MHE |
Grounding systems -- need the help of some good elmers
On Jul 30, 10:04 am, Danny Richardson wrote:
Not true. Feeding an antenna with coax does not remove the need for a station ground and here's why: http://k6mhe.com/sub/BlancedFeedLine.pdf Danny,K6MHE The coax has nothing to do with it. Whether or not the antenna is complete will be a much more deciding factor. But still, I see nothing in the pdf that would imply a ground is needed for feeding such an antenna, coax fed or not. Only decoupling of the feedline is needed. Not a shack ground. Why would one "need" a station ground in that case, assuming the feedline is decoupled? How would adding a station ground improve operation of a "complete" antenna that was not well decoupled? Myself, I would consider that a "bandaid" approach to the common mode problem. A ground can hide problems in some cases, but it never actually fixes anything. Common mode problems should never be "cured" by station "RF" grounding. MK |
Grounding systems -- need the help of some good elmers
Danny Richardson wrote in
: On Mon, 30 Jul 2007 13:40:27 +0000 (UTC), John Passaneau wrote: I want to follow on what some of the other have said. First to only reason to have an RF ground in you shack is if you are going to use an antenna that brings part of the antenna that is supposed to radiate RF into the shack, as an example, a long wire antenna. Dipoles, beams and verticals that are feed with coax do not need RF grounds in the shack Not true. Feeding an antenna with coax does not remove the need for a station ground and here's why: http://k6mhe.com/sub/BlancedFeedLine.pdf Danny,K6MHE Hi: Interesting web site, but what I meant to say and didn’t do well, is that if the antenna is installed properly and feed properly with coax and a balun or open wire line that is properly balanced, there will never be RF problems that an RF ground in the shack will solve. I had a problem with 80 meters at high power turning on my furnace. It was caused by the thermostat line being near resonate at 80 meters. All the RF grounds in the world would not have helped that, a clamp on ferrite choke did. It is very hard to get a RF ground in a second floor room. The idea that one or more ground rods or ground rods and radials outside with a length of wire running up to a second floor shack will be anything close to an RF ground at any Ham frequency is just plan wrong. How ever a lighting ground is a necessity and ground rods work quite well for that. John Passaneau W3JXP |
Grounding systems -- need the help of some good elmers
On Jul 30, 2:55 pm, Danny Richardson wrote:
May things you say are correct, but remember that a balun/choke does not totally choke off (eliminate) common mode current on the transmission line (particularly a multi-band antenna system) and a good station ground can provide additional reduction RFI problems. But again, it's really an antenna/feedline problem, rather than lack of ground. I'll agree.. Sometimes a ground can "bandaid" certain problems, but I consider it a last resort solution. For example here at my station where I have a half way decent single point RF grounding system. If I remove just my ground connection to my tuner - leaving everything else intact - and turn on my old CRT computer monitor I have over an S9 noise level. Reconnect the ground connection to the tuner the noise drops to less than S2. [BTW: I found that out quite by accident when I rearranged my station.] Sounds like that particular antenna system is not very well decoupled if you are having noise ingress problems of that level. I have a 21 inch CRT sitting right next to my ungrounded radio and have no noise problems at all. Station grounds can beneficial for several reasons. Well.. Dunno.. I guess for some people.. Myself, I have no need for one at all. Even running full legal limit power. I can say for sure, there ain't no way he is going to get a decent "RF" ground on the 2nd floor of that building by running a wire to it. So if I were him, I would forget all about it, and use better, more modern 21st century techniques to deal with any common mode problems that might or might not pop up. MK |
Grounding systems -- need the help of some good elmers
|
Grounding systems -- need the help of some good elmers
On Mon, 30 Jul 2007 19:46:26 +0000 (UTC), John Passaneau
wrote: Hi: Interesting web site, but what I meant to say and didn’t do well, is that if the antenna is installed properly and feed properly with coax and a balun or open wire line that is properly balanced, there will never be RF problems that an RF ground in the shack will solve. I had a problem with 80 meters at high power turning on my furnace. It was caused by the thermostat line being near resonate at 80 meters. All the RF grounds in the world would not have helped that, a clamp on ferrite choke did. It is very hard to get a RF ground in a second floor room. The idea that one or more ground rods or ground rods and radials outside with a length of wire running up to a second floor shack will be anything close to an RF ground at any Ham frequency is just plan wrong. How ever a lighting ground is a necessity and ground rods work quite well for that. John Passaneau W3JXP Agreed except the only properly built and installed antennas exist in text books and free space. For the antenna itself (forgetting for the moment the transmission line) it would have to be installed in a completely balance environment. Yard clutter such as buildings, trees, powerlines and etc. would have identical geometry in relation of your balanced antenna - something that does exist in the real world. Plus ground conditions under and near the antenna will vary. So there will be some unbalance. Next add the transmission line. Have you ever seen a ham station whose transmission line ran perfectly perpendicular from the antenna to the transmitter? In other words, there will be some unbalance the only question is how much, 73, Danny, K6MHE |
Grounding systems -- need the help of some good elmers
Agreed except the only properly built and installed antennas exist in text books and free space. For the antenna itself (forgetting for the moment the transmission line) it would have to be installed in a completely balance environment. Yard clutter such as buildings, trees, powerlines and etc. would have identical geometry in relation of your balanced antenna - something that does exist in the real world. Plus ground conditions under and near the antenna will vary. So there will be some unbalance. Next add the transmission line. Have you ever seen a ham station whose transmission line ran perfectly perpendicular from the antenna to the transmitter? In other words, there will be some unbalance the only question is how much, 73, Danny, K6MHE Hi Danny: You are of course correct, but with RF in the shack problems levels are important. If the level of RF is below some threshold it causes no harm. Almost all Ham stations operate just fine with low levels of unbalance and other defects in the antennas. Just for interest sake I ran some numbers on a model ground system. Let’s assume you have a perfect ground system and you connect to it from the shack on the second floor using 12' of #6 wire. And it runs in a straight line, no bends or curls. The self inductance of that wire is about 56.22uHy. So what will be the reactance of that wire at 3.5 MHz? Doing the math I get 1,235.7ohms. At the other extreme 28MHz, I get 9,886.52ohms. These are numbers that hardly make me confident that I have any kind of a RF ground. By the way at 60Hz the reactance is 0.021ohms that I think is a good ground. Please excuse me for harping on this, but I run the electronics shop in the Physics dept at Penn State University. I'm constantly seeing many meter long thin wires tied to some cold water pipe or something in a lab that is supposed to get rid of all the high frequency noise in some experiment and it has no chance of helping. If physics grad students have problems understanding grounding it's no wonder that Ham’s do too. John Passaneau W3JXP |
Grounding systems -- need the help of some good elmers
On Mon, 30 Jul 2007 18:47:13 -0500, JOHN PASSANEAU
wrote: Hi Danny: You are of course correct, but with RF in the shack problems levels are important. If the level of RF is below some threshold it causes no harm. Almost all Ham stations operate just fine with low levels of unbalance and other defects in the antennas. Just for interest sake I ran some numbers on a model ground system. Let’s assume you have a perfect ground system and you connect to it from the shack on the second floor using 12' of #6 wire. And it runs in a straight line, no bends or curls. The self inductance of that wire is about 56.22uHy. So what will be the reactance of that wire at 3.5 MHz? Doing the math I get 1,235.7ohms. At the other extreme 28MHz, I get 9,886.52ohms. These are numbers that hardly make me confident that I have any kind of a RF ground. By the way at 60Hz the reactance is 0.021ohms that I think is a good ground. Please excuse me for harping on this, but I run the electronics shop in the Physics dept at Penn State University. I'm constantly seeing many meter long thin wires tied to some cold water pipe or something in a lab that is supposed to get rid of all the high frequency noise in some experiment and it has no chance of helping. If physics grad students have problems understanding grounding it's no wonder that Ham’s do too. John Passaneau W3JXP John, You are absolutely correct. My error was I didn't address the second story issue. At that location all bets are off and your statements above are correct. Although using copper strapping with multiple runs of different lengths from the station to the ground system should work better. My station here is on ground level. The distance from the connection point of the outside ground system to the point inside were all equipment is connected is about three feet of 3/8" diameter copper tubing. My frequencies of interest is 80-10 meters. The ground system consists of eighteen #8 copper radial wires connected to a eight foot ground rod which serves as the anchor point. The radials are fanned out over about 210º arc varying in length from as short as about twenty feet up to seventy feet. It seems to work fairly well. Thanks for the input and addressing the original poster's question. I had taken off on a tangent based on the statement that a so called balanced antenna wouldn't benefit from using a station ground. Very 73, Danny, K6MHE |
Grounding systems -- need the help of some good elmers
Danny Richardson wrote:
On Mon, 30 Jul 2007 13:10:36 -0700, wrote: Sounds like that particular antenna system is not very well decoupled if you are having noise ingress problems of that level. I have a 21 inch CRT sitting right next to my ungrounded radio and have no noise problems at all. Not all common mode problems can be fixed by transmission line/antenna decoupling. Noise can be coupled to the transmission line or other station equipment (as in my example). It would have made no difference had I the world's best decoupling choke installed at the transmission line to antenna transition point the noise would still be there. Secondly I have never been able to find any broadband balun or choke (80-10 meters) that is effective on all bands. Indeed, I have measured the common mode impedance of some commercially made broadband baluns that have had as little as 100 ohms on some bands while very high on others. Common mode current will always be with you the only questions are what is the source and how much. It may be very little and no consequence while on other bands - particularly in a multi-band antenna system - it can be substantial. I have no doubt that your CRT monitor didn't give you any problems but, then again you weren't using mine. So you are not comparing apples to apples. Additionally, you can also have common mode problems via electrical wiring system. And no matter what you do to decouple the antenna will have any effect on that but, utilizing a good ground could reduce it substantially, although, additional filter may be required. It boils down that a good single point station RF ground system can't hurt - it can only help. It just an additional protective measure. One I would not be without. Danny, K6MHE See http://www.audiosystemsgroup.com/RFI-Ham.pdf from Jim Brown. K9YC An excellent discussion of RFI, interference, chokes, baluns, grounding with test data and recommendations. |
Grounding systems -- need the help of some good elmers
All
I now want to piggyback onto the earlier discussion as i face an even more difficult siting / grounding issue. I have just installed a 1/2 wave G5RV dipole at approx. 30 ft above ground. My shack is in the back of the house but on the second floor (effectively in the roof of the house) above the garden but due to the house design i think i would struggle to have a RF ground wire of less than 30-40 feet. Based on above discussions should I : 1) fit a ground rod and run this up to the shack even though its a long way up along various walls 2) buy an articial ground unit such as the MFJ-931 3) forget about it and make do without a ground. I am pretty thoroughly confused. Thanks Andy |
Grounding systems -- need the help of some good elmers
|
Grounding systems -- need the help of some good elmers
Bob Miller wrote:
The G5RV dipole is a balanced antenna and does not require a ground. So unless you want one for some other reason, option 3... bob k5qwg And they work GREAT. I've worked stations all over the world with one and a barefoot TS-520S. 73, Ron kc4yoy |
Grounding systems -- need the help of some good elmers
Bob Miller wrote:
The G5RV dipole is a balanced antenna and does not require a ground. So unless you want one for some other reason, option 3... The G5RV is a *symmetrical* antenna. Feedline radiation can still occur, and often does. In that case, the antenna isn't *balanced*, in the sense that the current on the two antenna halves isn't equal. See Figs. 2-4 in http://eznec.com/Amateur/Articles/Baluns.pdf. You need a truly balanced tuner in conjunction with the G5RV to assure balance. A good current balun, instead of a balanced tuner, might be adequate on bands where the input impedance is reasonable. Roy Lewallen, W7EL |
Grounding systems -- need the help of some good elmers
Thanks for swift responses - in which case do i just need a DC earth
up from the ground floor or can i get away with a radiator pipe etc. Andy |
Grounding systems -- need the help of some good elmers
John's observations are useful. A dramatic example happened to me many
years ago with a second story transmitter having a grounding wire that was as short as possible: with a change of frequency, the grounding wire became resonant and caused the transmitter to be very hot - I can still see the small scar tissue where I touched a knob. The short term cure was to run a longer grounding wire in parallel, which detuned the first wire. If you use a reasonably balanced antenna (dipole, yagi, log-periodic, .... ) it is unlikely that you will have a problem. If you are to use a doublet fed with open-wire and fairly low power, an old Johnson Matchbox will be an ideal way to keep your transmitter happy. Keep us posted. 73, Mac N8TT -- J. Mc Laughlin; Michigan U.S.A. Home: "JOHN PASSANEAU" wrote in message ... Hi Danny: You are of course correct, but with RF in the shack problems levels are important. If the level of RF is below some threshold it causes no harm. Almost all Ham stations operate just fine with low levels of unbalance and other defects in the antennas. Just for interest sake I ran some numbers on a model ground system. Let's assume you have a perfect ground system and you connect to it from the shack on the second floor using 12' of #6 wire. And it runs in a straight line, no bends or curls. The self inductance of that wire is about 56.22uHy. So what will be the reactance of that wire at 3.5 MHz? Doing the math I get 1,235.7ohms. At the other extreme 28MHz, I get 9,886.52ohms. These are numbers that hardly make me confident that I have any kind of a RF ground. By the way at 60Hz the reactance is 0.021ohms that I think is a good ground. Please excuse me for harping on this, but I run the electronics shop in the Physics dept at Penn State University. I'm constantly seeing many meter long thin wires tied to some cold water pipe or something in a lab that is supposed to get rid of all the high frequency noise in some experiment and it has no chance of helping. If physics grad students have problems understanding grounding it's no wonder that Ham's do too. John Passaneau W3JXP |
Grounding systems -- need the help of some good elmers
Thank you to everyone who replied to my initial e-mails. With a
little luck, I now have the information I need to build a shack (I've got the radio, just no antenna... or any other stuff done yet for that matter). Regards, Dan W4XJF |
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