Author Topic: Advice for grounding 2nd story HF station  (Read 7041 times)

Offline iam4liberty

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Advice for grounding 2nd story HF station
« on: June 05, 2017, 05:53:12 PM »
Does anyone have advice for properly grounding an HF station on the 2nd story of a house? It will be 13 feet up. 

Offline Tanasi

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Re: Advice for grounding 2nd story HF station
« Reply #1 on: June 06, 2017, 07:52:23 AM »
I asked a while ago on a local repeater and the folks there indicated running a heavy ground cable or braid to your earthen ground is fine. Do you have any different information? I will be doing this soon as well, so would like to know the correct way, and if I should run the ground completely around the house or under house to get to exisitng electrical ground for the meter or is it ok to drive a new ground below my shack. If nothing else, go by the ARRL recommendations I would think you would be good.

Tanasi in TN

Offline Skispcs

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Re: Advice for grounding 2nd story HF station
« Reply #2 on: June 06, 2017, 08:01:53 AM »
Never run braid, braided copper, etc outdoors or where it is exposed to corrosion. Corrosion can hide inside of the braid and you will never see it even if you were to perform periodic inspections.

There are many books and articles online that do a better job of telling you how to do it correctly than I could in this post.
http://www.arrl.org/grounding
https://www.amazon.com/gp/product/1625950659/ref=oh_aui_search_detailpage?ie=UTF8&psc=1


Offline Tanasi

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Re: Advice for grounding 2nd story HF station
« Reply #3 on: June 06, 2017, 08:16:03 AM »
Good info Skipcs, I think you are right about not using braid. I followed up one of your links and found thislink which may help the OP:     http://www.arrl.org/files/file/Technology/tis/info/pdf/49680.pdf

Offline Carl

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Re: Advice for grounding 2nd story HF station
« Reply #4 on: June 06, 2017, 09:08:32 AM »
  I need more detail,like what kind of antenna and power supply etc,but in general ,there are TWO KINDS OF GROUND...Lightening and RF ground.
 With a balanced antenna like a dipole or inverted "V" (balanced as in both sides match in length) you don't need a ground for RF and often the third wird on the cord for the power supply is adequate for lightening ,until you get a direct hit ...and you really can't defend enough to eliminate problems then...just minimise damage.

  With an unbalanced antenna,say a multi-band vertical or zeppelin , your RF needs a place to go and a counterpoise wire of 17 or 34 or 70m feet attached to the ground lug of the radio or tuner should give RF a path and eliminate RF  interference to most devices in home and provide better effectiveness of your antenna.I can suggest better when I know more about your station as a long path to ground does little to protect from lightening.


And before someone says that Ham radio must kave a ground...explain how you ground a mobile station.....

Offline Skispcs

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Re: Advice for grounding 2nd story HF station
« Reply #5 on: June 06, 2017, 09:28:59 AM »
  you don't need a ground for RF and often the third wird on the cord for the power supply is adequate for lightening

Using the electrical ground for anything else other than electrical safety is against NEC Code.
"250.6 of the NEC specifies that objectionable current is not to flow on grounding and bonding paths"

Believe me, you do not want the energy from a lighting strike to come into your house. All paths for Lightning should go straight to ground and stay outside of the structure.
The path for Lightning needs to be much more robust than most anything in your house for electrical safety.

Offline Ken325

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Re: Advice for grounding 2nd story HF station
« Reply #6 on: June 06, 2017, 09:43:13 AM »
I had this same question.  I decided to open the wall in my garage and drill a hole through the slab with a hammer drill inside the wall.  The wall is a inside wall, but I am ok with doing dry wall work to patch the hole.Then I will run braid in the wall to my upstairs office.  This way I can do a direct run that is about 15 feet long.  I do know you need to keep the ground as short as possible.

I haven't done this yet because I am currently focused on keeping my gear portable.  I just wanted to comment so I could see future replies to this question.

Offline Carl

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Re: Advice for grounding 2nd story HF station
« Reply #7 on: June 06, 2017, 10:05:00 AM »
I had this same question.  I decided to open the wall in my garage and drill a hole through the slab with a hammer drill inside the wall.  The wall is a inside wall, but I am ok with doing dry wall work to patch the hole.Then I will run braid in the wall to my upstairs office.  This way I can do a direct run that is about 15 feet long.  I do know you need to keep the ground as short as possible.

I haven't done this yet because I am currently focused on keeping my gear portable.  I just wanted to comment so I could see future replies to this question.

Your 15 or so feet will help with static buildup and eliminate some problems with static and nearby lightening ,but after 'arcing' 1/2 mile or more with hundreds to thousands of AMPS ...most any wire you use will vaporize. So it does some good ,but unless you use a really large antenna and there are no trees/power lines, or tall buildings around (they get hit first) then the homes electrical ground will protect you quite well.

  The most important ground is for RF as in to balance the output of the transmitter and earth ground is not so great for this as HALF or your RF goes to dirt and dirt does not really conduct so well.

Others may not have my opinion.

Offline Smurf Hunter

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Re: Advice for grounding 2nd story HF station
« Reply #8 on: June 06, 2017, 10:43:34 AM »
I'm still a rookie on this subject, but there are 3 grounds in amateur radio:

electrical safety ground (lightning)
electrical ground (e.g. multiple power supplies connected to a common "bus")
RF ground (as Carl described. usually the "other" half of an antenna).

To me, there seems a possible overlap between the two electrical grounds.

Suppose I hammered a big 8 foot copper rod into the dirt.  It seems that could serve as an antenna ground in case of lightning strike, or a common ground for all shack devices like this:


Though it seems inappropriate for a given ground rod to do both.  Would that direct a lightning strike right at your power supplies and radios?

For a ground setup like the attached image, what's the downside/harm/risk of sending that to your home's electrical ground?

Offline Carl

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Re: Advice for grounding 2nd story HF station
« Reply #9 on: June 06, 2017, 11:11:20 AM »
SMURF...Isn't lighting seeking a path to ground? It can be confusing as I loose 2 "S" units of noise when NOT powered off my homes AC,but from my battery /solar and ONLY my tower is grounded for lightening as I would prefer not to give a path to ground for lighting THROUGH MY RADIO GEAR.
I may be wrong ,but this has worked with radio ,for me, for the last 45 years. Here is a text from the GROUNDING folder of my HF ANTENNAS folder that I offered for download FREE.  I checked and the link works ,but feel free to download any you want to keep as I may remove these files to offer something else soon.

Link: https://drive.google.com/drive/folders/0B5ZIZLZV4AwIM2pBeWxBVk5VQmM?usp=sharing


This guy's an MIT expert!
Grounding is key to good reception
From: jpd@space.mit.edu (John Doty)
Newsgroups: rec.radio.shortwave
Date: 16 Feb 1995 16:36:40 GMT
In article <825_9502140342@tor250.org> Larry.Picard@odxabbs.tor250.org (Larry Picard) writes:


In your recent post you advised that coax should be grounded at two sites, first at the antenna and then just before entering the house. Is there an advantage in grounding at more than these sites?
With grounds the most common experience is "the more the merrier". As you add more, however, you usually reach a diminishing returns (no pun intended) situation where there is no *observable* improvement: that's usually a good place to stop. There are also exceptional circumstances where grounding increases noise problems, but these, in my experience, are much rarer than the pundits who preach against "ground loops" seem to think.
Even a semi-quantitative theoretical treatment of grounding in oversimplified situations requires heavy math at RF. Experimentation is thus required even if one has done elaborate calculations. It's often easier to use the theory as a guide to what to try, and then experiment.
I would also assume that the antenna is grounded when it is connected to the receiver as the outer braid of the coax is in continuity with the receiver chassis.
What's ground? If I connect the shield of my coax (which is grounded outside) to the antenna input of my R8, I hear lots of junk, indicating that there is an RF voltage difference between the coax shield and the R8 chassis. Last night this measured about S5.5, which is about -93 dBm (preamp off, 6KHz bandwidth). That's a lot of noise: it was 18 dB above my antenna's "noise floor", and 26 dB above the receiver's noise floor.
This sort of disagreement about ground potential is characteristic of electrically noisy environments. The receiver will, of course, respond to any voltage input that differs from its chassis ground. The antenna, on the other hand, is in a very different environment, and will have its own idea of what ground potential is. If you want to avoid noise pickup, you need to deliver a signal, referenced at the antenna to whatever its ground potential is, in such a way that when it arrives at the receiver, the reference potential is now the receiver's chassis potential.
Coaxial cable represents one way to do this. Coax has two key properties:
1. The voltage between the inner conductor and the shield depends only on the state of the electromagnetic field within the shield.
2. The shield prevents the external electromagnetic field from influencing the internal electromagnetic field (but watch out at the ends of the cable!).
So, it's easy, right? Run coax from the antenna to the receiver. Ground at the antenna end will be whatever the antenna thinks it is, while ground at the receiver end will be whatever the receiver thinks it is. The antenna will produce the appropriate voltage difference at the input side, and the receiver will see that voltage difference uncontaminated by external fields, according to the properties given above.
Unfortunately, it doesn't quite work that way. It's all true as far as it goes, but it neglects the fact that the coax can also guide noise from your house to your antenna, where it can couple back into the cable and into your receiver. To see how this works, let me first describe how this noise gets around.
The noise I'm talking about here is more properly called "broadband electromagnetic interference" (EMI). It's made by computers, lamp dimmers, televisions, motors and other modern gadgets. I have all these things. In many cases, I can't get them turned off, because it would provoke intrafamilal rebellion. However, even when I turn them off, the noise in the house doesn't go down very much, because my neighbors all have them too. In any case, one of the worst offenders is my computer, which is such a handy radio companion I'm not about to turn *it* off.
Some of this noise is radiated, but the more troublesome component of this is conducted noise that follows utility wires. Any sort of cable supports a "common mode" of electromagnetic energy transport in which all of the conductors in the cable are at the some potential, but that potential differs from the potential of other nearby conductors ("ground"). The noise sources of concern generate common mode waves on power, telephone, and CATV cables which then distribute these waves around your neighborhood. They also generate "differential" mode waves, but simple filters can block these so they aren't normally a problem.
So, let's say you have a longwire antenna attached to a coaxial cable through an MLB ("Magnetic Longwire Balun" [sic]). Suppose your next door neighbor turns on a dimmer switch. The resulting RF interference travels out his power lines, in through yours, through your receiver's power cord to its chassis, and out your coaxial cable to your MLB. Now on coax, a common mode wave is associated with a current on the shield only, while the mode we want the signal to be in, the "differential" mode, has equal but opposite currents flowing on shield and inner conductor. The MLB works by coupling energy from a current flowing between the antenna wire and the coax shield into into the differential mode. But wait a second: the current from the antenna flows on the coax shield just like the common mode current does. Does this mean that the antenna mode is contaminated with the noise from your neighbor's dimmer?
The answer is a resounding (and unpleasant) yes! The way wire receiving antennas work is by first moving energy from free space into a common mode moving along the antenna wire, and then picking some of that off and coupling it into a mode on the feedline. In this case, the common mode current moving along the antenna wire flows into the common mode of the coax, and vice versa. The coax is not just feedline: it's an intimate part of the antenna! Furthermore, as we've seen, it's connected back through your electrical wiring to your neighbor's dimmer switch. You have a circuitous but electrically direct connection to this infernal noise source. No wonder it's such a nuisance!
The solution is to somehow isolate the antenna from the common mode currents on the feedline. One common way to do this is with a balanced "dipole" antenna. Instead of connecting the feedline to the wire at the end, connect it to the middle. Now the antenna current can flow from one side of the antenna to the other, without having to involve the coax shield. Unfortunately, removing the necessity of having the coax be part of the antenna doesn't automatically isolate it: a coax-fed dipole is often only slightly quieter than an end-fed longwire. A "balun", a device which blocks common mode currents from the feedline, is often employed. This can improve the situation considerably. Note that this is not the same device as the miscalled "Magnetic Longwire Balun".
Another way is to ground the coaxial shield, "short circuiting" the common mode. Antenna currents flow into such a ground freely, in principle not interacting with noise currents. The best ground for such a purpose will be a earth ground near the antenna and far from utility lines.
Still another way is to block common mode waves by burying the cable. Soil is a very effective absorber of RF energy at close range.
Unfortunately, none of these methods is generally adequate by itself in the toughest cases. Baluns are not perfectly effective at blocking common mode currents. Even the best balun can be partially defeated if there's any other unsymmetrical coupling between the antenna and feedline. Such coupling can occur if the feedline doesn't come away from the antenna at a right angle. Grounds are not perfect either. Cable burial generally lets some energy leak through. A combination of methods is usually required, both encouraging the common mode currents to take harmless paths (grounding) and blocking them from the harmful paths (baluns and/or burial).
The required isolation to reach the true reception potential of the site can be large. According to the measurements I quoted above, for my site the antenna noise floor is 18 dB below the conducted noise level at 10 MHz. 18 dB of isolation would thus make the levels equal, but we want to do better than that: we want the pickup of common mode EMI to be insignificant, at least 5 dB down from the antenna's floor. In my location the situation gets worse at higher frequencies as the natural noise level drops and therefore I become more sensitive: even 30 dB of isolation isn't enough to completely silence the common mode noise (but 36 dB *is* enough, except at my computer's CPU clock frequency of 25 MHz).
Getting rid of the conducted noise can make a huge difference in the number and kinds of stations you can pick up: the 18 dB difference between the conducted and natural noise levels in the case above corresponds to the power difference between a 300 kW major world broadcaster and a modest 5 kW regional station. The method I use is to ground the cable shield at two ground stakes and bury the cable in between. The scheme of alternating blocking methods with grounds will generally be the most effective. The ground stake near the house provides a place for the common mode noise current to go, far from the antenna where it cannot couple significantly. The ground stake at the base of my inverted-L antenna provides a place for the antenna current to flow, at a true ground potential relative to the antenna potential. The buried coax between these two points blocks noise currents.
There has been some discussion of grounding problems on this and related echos. I believe it has been mentioned that electrical codes require that all grounds be tied together with heavy guage wire.
I'm no expert on electrical codes, and codes differ in different countries. However, I believe that any such requirement must refer only to grounds used for safety in an electric power distribution system: I do not believe this applies to RF grounds.
Remember that proper grounding practice for electrical wiring has very little to do with RF grounding. The purpose of an electrical ground is to be at a safe potential (a few volts) relative to non-electrical grounded objects like plumbing. At an operating frequency of 50/60 Hz, it needs to have a low enough impedance (a fraction of an ohm) that in case of a short circuit a fuse or breaker will blow immediately.
At RF such low impedances are essentially impossible: even a few centimeters of thick wire is likely to exhibit an inductive impedance in the ohm range at 10 MHz (depends sensitively on the locations and connections of nearby conductors). Actual ground connections to real soil may exhibit resistive impedances in the tens of ohms. Despite this, a quiet RF ground needs to be within a fraction of a microvolt of the potential of the surrounding soil. This is difficult, and that's why a single ground is often not enough.
A little experimentation with my radio showed that the chassis was directly connected to the third (grounding) prong of the wall plug. I am concerned that by connecting my receiver to an outside ground I am creating a ground loop that involves my house wiring. Can you comment on this?
Yes, you have a "ground loop". It's harmless. In case of a nearby lightning strike it may actually save your receiver. My R8 isn't grounded like that, so I had to take steps to prevent the coax ground potential from getting wildly out of kilter with the line potential and arcing through the power supply. I'm using a surge supressor designed to protect video equipment: it has both AC outlets and feedthroughs with varistor or gas tube clamps to keep the various relative voltages in check. Of course the best lightning protection is to disconnect the receiver, but I'm a bit absent minded so I need a backup.
This may seem like a trivial point but I recently discovered that the main ground from the electrical service panel in my house was attached to a water pipe which had been painted over. I stripped the paint from the pipe and re-attached the grounding clamp and I noticed a reduction in noise from my receiver.
Not trivial. Not only did you improve reception, but your wiring is safer for having a good ground.
I suspect part of the reason I see so much noise from neighbors' appliances on my electric lines may be that my house's main ground wire is quite long. The electrical service comes in at the south corner of the house (which is where the breaker box is), while the water (to which the ground wire is clamped) enters at the east corner. All perfectly up to code and okay at 60 Hz, but lousy at RF: if it was shorter, presumably more of the noise current would want to go that way, and stay away from my receiver.
I am also a little confused by what constitues an adequate ground. I have read that a conducting stake driven into the ground will divert lightning and provides for electrical safety but that RF grounding systems have to be a lot more complex with multiple radials with lengths related to the frequencies of interest. Is this true?
Depends on what you're doing. If you're trying to get maximum signal transfer with a short loaded (resonant) vertical antenna with a radiation resistance of, say, 10 ohms, 20 ohms of ground resistance is going to be a big deal. If you're transmitting 50 kW, your ground resistance had better be *really* tiny or things are going to smoke, melt or arc.
On the other hand, a ground with a resistance of 20 ohms is going to be fairly effective at grounding a cable with a common mode characteristic impedance of a few hundred ohms (the characteristic impedance printed on the cable is for the differential mode; the common mode characteristic impedance depends somewhat on the distance of the cable from other conductors, but is usually in the range of hundreds of ohms). Of course, if it was lower a single ground might do the whole job (but watch out for mutual inductance coupling separate conductors as they approach your single ground).
In addition, a ground with a resistance of 20 ohms is fine for an unbalanced antenna fed with a high impedance transformer to supress resonance. Such a nonresonant antenna isn't particularly efficient, but high efficiency is not required for good reception at HF and below (not true for VHF and especially microwave frequencies).
Much antenna lore comes from folks with transmitters who, armed with the "reciprocity" principle, assume that reception is the same problem. The reciprocity principle says that an antenna's transmission and reception properties are closely related: it's good physics, but it ignores the fact that the virtues required of a transmitting and receiving antenna are somewhat different. Inefficiency in a transmitting antenna has a direct, proportional effect on the received signal to noise ratio. On the other hand, moderate inefficiency in an HF receiving antenna usually has a negligible effect on the final result. A few picowatts of excess noise on a transmitting antenna has no effect on its function, but is a big deal if you're receiving (of course, one might not want to have transmitter power going out via unintended paths like utility lines: this is indeed the "reciprocal" of the conducted noise problem, and has similar solutions).
Appendix: Absolute RF measurements with an R8.
Although the Drake R8's signal strength meter is marked with silly "S" units, the alignment procedure in the service manual actually sets up the meter to an absolute standard, at least sort of. A 60% modulated signal with a carrier level of -73 dBm (which is really closer to -72 dBm in total power including sidebands) is S9. One S unit is 5 dB. This is with 6 kHz bandwidth and with neither the RF preamp or attenuator engaged. I assume this is what they do at the factory.
Now, I don't really know how accurately this calibration is performed, and it certainly can't be more accurate than the flatness of the input passband filters (spec'd at <2 dB p-p). There are also problems because the measurement is actually being made by a peak-responding AGC system rather than an RMS meter. Based on experience with other peak sensing systems, I estimate that the meter probably reads noise power too high by about 3 dB, relative to the carrier power in the test waveform. Therefore, for noise, S9 is about -76 dBm.
On my R8, the linearity of the S-meter calibration is poor at the very low end: S1 is much less than 10 dB below S3. Therefore, for measurements below S3 I do relative measurements and refer them to stronger signals. I have on my NeXT computer an old demo application that gives the RMS amplitude of a signal on the audio input jack. With the R8's AGC turned off and the RF gain set low enough to insure good linearity, this may be used to make quite accurate relative power measurements. You could, of course, use an ordinary AC voltmeter to do this if you have one sensitive enough to read the level of the Drake's audio output (I don't have one).
Considering all of the uncertainties, the numbers hold together remarkably well, better than the likely accuracies in this case (just dumb luck). For the measurements quoted in my previous message, the receiver's noise floor is -119 dBm. Drake's specs imply that for a 6 kHz bandwidth the noise floor should be below -118 dBm with the preamp off.
According to "Reference Data for Radio Engineers" (Sams, 1975), the wintertime level of natural noise in my area at 10 MHz should be about 32 dB above the thermal reference level: this would produce a noise floor of -104 dBm in this bandwidth with a perfectly efficient antenna. A calculation for a 17 m vertical antenna feeding a high impedance transformer predicts a loss due to mismatch/lack of resonance of 4.5 dB at 10 MHz. My antenna is not a vertical but an inverted L which I presume is slightly less efficient (difficult to calculate). There are also presumably some modest losses in the transformer, the grounds, the cables and the connectors. I wouldn't be surprised if these added up to 3 dB or so. With a total antenna system inefficiency of 7 dB, I'd therefore expect to see an antenna noise floor of -111 dBm, which is, in fact, just what I measure.

Are we confused yet?  Good luck...Carl

Offline iam4liberty

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Re: Advice for grounding 2nd story HF station
« Reply #10 on: June 06, 2017, 06:13:17 PM »
Thanks everyone for the feedback.

Good info Skipcs, I think you are right about not using braid. I followed up one of your links and found thislink which may help the OP:     http://www.arrl.org/files/file/Technology/tis/info/pdf/49680.pdf

thanks!  I missed that one. 

  I need more detail,like what kind of antenna and power supply etc,but in general ,there are TWO KINDS OF GROUND...Lightening and RF ground.

Antenna is a ~110 foot end-fed wire of the "QSO King" variety.  Transceiver wattage will be in the 300 Watt range.  Bands are 20 meter, 40 meter, and 80 meter.  Original plan was for both lightning and RF grounded to the same 10' rod.  Antenna has a lightning arrester in design. 

The issue I am facing is that all the articles are clearcut for underground/one story and three story+. 

For underground/one story the current recommendation is to have house ground, RF ground, and lightning ground all tied together.  General rule is just have as short ground leads as possible.

For three story+ the recommendation is two use a coiled wire artificial ground (similar in theory to a counterpoise on an antenna) for RF and flashing for lightning to a rod.

For two stories it is all over the place.  Some say use 6 to 8 inch copper or 12 inch aluminum flashing and set it up just like one story. Others say instead of flashing use a more typical wire but use a ground tuner (like MFJ-931) or use a coax cable (!) with capacitor like this to reduce the 'apparent' length of the wire:



Still others suggest using the artificial ground approach like for a taller structure.  And a lot of are still recommending tying RF ground to copper plumbing but ARRL reference warns against doing this. 

Net, there appears to be no consistent recommendation.  Which maybe the answer is that all these approaches are viable if implemented well.  I think I am leaning towards the 8" copper flashing approach as I understand how that works best.  But I am definitely still open to suggestions!
« Last Edit: June 06, 2017, 06:23:31 PM by iam4liberty »

Offline iam4liberty

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Re: Advice for grounding 2nd story HF station
« Reply #11 on: June 06, 2017, 08:31:16 PM »
And of course there is the the argument for no RF ground too (with appropriate antenna type choice): https://www.eham.net/articles/8951

Offline Carl

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Re: Advice for grounding 2nd story HF station
« Reply #12 on: June 07, 2017, 04:24:53 AM »
  In this case the RF ground would be to serve as the other half of the antenna so as to balance the system better with 1/4 'counterpoise than lossy soil getting half of the RF power from the radio and amplifier and also counters having 'HOT' devices within the shack and home.

Offline Alan Georges

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Re: Advice for grounding 2nd story HF station
« Reply #13 on: June 07, 2017, 05:35:50 AM »
And of course there is the the argument for no RF ground too (with appropriate antenna type choice): https://www.eham.net/articles/8951.
:clap:  This guy gets it right.

Offline iam4liberty

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Re: Advice for grounding 2nd story HF station
« Reply #14 on: June 07, 2017, 08:53:47 AM »
:clap:  This guy gets it right.

Yeah, it is hard to argue that much of the recommendations for grounding are to bandaid issues that should have been dealt with by other means.

  In this case the RF ground would be to serve as the other half of the antenna so as to balance the system better with 1/4 'counterpoise than lossy soil getting half of the RF power from the radio and amplifier and also counters having 'HOT' devices within the shack and home.

Then in the spirit of the above logic, maybe i shouldn't ground shield of coax or station.  Rather couldnt i use a long enough length of coax so it acts as counterpoise and then use an isolator/choke at end of run to counter hot devices?

NET:

1. Run suitable wire from lightning arrester to ground rod for lightning safety.
2. Do not RF ground station.  Of course it will still have household electric neutral for safety.
3. Do not ground shield of coax.  Let it act as a counterpoise.  But install choke/isolator to stop current from entering equipment.

Am i off my rocker or would this work?  Well, I guess it could be both!  :)




Offline Smurf Hunter

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Re: Advice for grounding 2nd story HF station
« Reply #15 on: June 07, 2017, 09:20:00 AM »

Then in the spirit of the above logic, maybe i shouldn't ground shield of coax or station.

Let's unpack this for sanity sake.

Assume a balanced dipole antenna with no need for RF ground. 
Further lets assume a portable station at a public park running off a battery on a dry sunny day (no lightning risk).

In that happy scenario, there's no need for any kind of ground, RF or otherwise.

For lighting protection you want your home and your home station to always be at the same electrical potential - everything bonded to everything else and the house ground. This is to ensure that if it is struck by lightning, everything will be at the same potential. It's when you have a potential difference that you have a problem.

I recommend the mission should be to create the same electrical potential across all your station equipment. I'm not an expert at how to best achieve this, but whatever proposed solution should solve that specific problem of creating equal potential.

Offline Carl

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Re: Advice for grounding 2nd story HF station
« Reply #16 on: June 07, 2017, 11:05:30 AM »
[quote author=iam4liberty link=topic=60507.msg718487#msg718487 date=149684722

 couldnt i use a long enough length of coax so it acts as counterpoise and then use an isolator/choke at end of run to counter hot devices?
Am i off my rocker or would this work?  Well, I guess it could be both!  :)
[/quote]

Coaxial cable might not radiate RF (it is designed not to) and so it may not be an effective counterpoise...though some antennas get by with it.
I look forward to a report.

Offline iam4liberty

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Re: Advice for grounding 2nd story HF station
« Reply #17 on: June 10, 2017, 09:00:50 AM »
Let's unpack this for sanity sake.

Sounds like a good course of attack.

For lighting protection you want your home and your home station to always be at the same electrical potential - everything bonded to everything else and the house ground. This is to ensure that if it is struck by lightning, everything will be at the same potential. It's when you have a potential difference that you have a problem.

Agreed.  The logic is that a 'modern' ham station generally has three grounding points: house electrical safety, at the station, and at the antenna (e.g. mast/tower).  If these are not tied together effectively than when lightening strikes electricity can flow through the house/station.  If lightning hits the power lines, most of the electricity will flow through the house electrical safety but some will flow through the house electrical wiring, through the station into its ground, and through the antenna lead into its ground.  If lightning strikes the antenna/tower most will flow into that ground but some will flow through the antenna wire to the station into its ground and through the house wiring to the house ground.  By connecting all three of these together it minimizes (never eliminates) the electricity from the strike moving through the station/house wiring to the various grounds.

I recommend the mission should be to create the same electrical potential across all your station equipment. I'm not an expert at how to best achieve this, but whatever proposed solution should solve that specific problem of creating equal potential.

If we are using multiple grounds than that is definitely the best course of action.  The problem we have is that with a second story station it is very hard for the station ground to be at the same potential because of the length of the ground wire.  Even using wide flashing to maximize the surface area it is iffy but may be sufficient.

So the alternative is to go back to a design like the early ham stations.  Back then the stations weren't grounded themselves and they were not tied into the household ground wiring.  And the mast/tower was grounded but not tied to the house ground.  And best practice was to always unplug the antenna from the station.  So, if lightning hit the power lines, current didn't flow through the station (since it was not grounded).  And if lightning hit the tower, current flowed directly to its ground and not through station/house since those were not connected.

The first approach (three grounding points all tied together) is what is currently recommended for one story houses and it is probably the optimal configuration.  The second approach is what is recommended for stations 3+ stories high (with an artificial ground used for dealing with  RF issue).  For two story houses it seems to be able to go either way hence the quest for more information.

Coaxial cable might not radiate RF (it is designed not to) and so it may not be an effective counterpoise...though some antennas get by with it.
I look forward to a report.

I have been reading some of reviews of the commercial QSO-King antenna.  It is basically all 4.9 - 5.0  out of 5.0 on eham.net.  Most are apparently running it without a ground but with a line isolator and 50+ feet of coax as recommended.  That 50 feet of coax is recommended suggests to me that it is acting as a counterpoise to some degree. 

I appreciate everyone's help while I try to noodle through this.
« Last Edit: June 10, 2017, 09:08:29 AM by iam4liberty »

Offline Carl

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Re: Advice for grounding 2nd story HF station
« Reply #18 on: June 10, 2017, 09:54:10 AM »
But they are trying to SELL an antenna with little balance and poor effectiveness...yes ,it will work but even my portable setup verticals are way less effective with 4 radials/counterpoises than a dipole or inverted "V".A typical mobile on 40/80 meters is rare that gets %5 of it's rf out the antenna due to antenna inefficiency and poor 'ground' (through the capacitance of car to ground)...Bottom line...most any antenna will work but I refuse to put half of my transmitted power into heating the earth. If you don't know what GOOD is ,you would be happy with what you paid good money for.

Feel free to use one as they are easy ,but read again all of the reviews and see how many say SWR is 'perfect' and judge that a perfect vertical is 31 ohms and very narrow area of frequence (it should measure no less that 1.5 to one SWR and REQUIRE a tuner were it not for losses)

As to station grounding...It is best to ground tower,radio equipment,and electrical and a tower mounted (also grounded to tower) like POLY PHASER

http://www.polyphaser.com/?gclid=CKa4t-3Qs9QCFQkQaQodpHQFYA

Might give one a better chance of surviving a nearby strike...but there really are no guarantees. A small gap will certainly stop a 5000 foot long arc with a millions volts and thousand amps or so  :sarcasm: but the more grounded you are ,the better your chances.

Offline LodeRunner

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Re: Advice for grounding 2nd story HF station
« Reply #19 on: November 04, 2017, 06:16:55 PM »
  In this case the RF ground would be to serve as the other half of the antenna so as to balance the system better with 1/4 'counterpoise than lossy soil getting half of the RF power from the radio and amplifier and also counters having 'HOT' devices within the shack and home.

Lets talk first about "RF Ground" -
When transmitting, you want a good, low impedance from your radio equipment to RF ground. The helps prevent "Hot Mic" issues, Transmit audio distortion, and spurs being transmitted outside the [audio] passband of the transmitter which would interfere with other stations. 
When using a balanced antenna such as a dipole, this is usually easy to achieve.  But with unbalanced antennas you definitely need to provide a solid, reliable ground (or return path, a.k.a. counterpoise). 

The best place for this "Transmitting ground" is at the antenna end of the coax.  Period.  Ideally, this will consist of a ground rod, plus 4 to 12 buried radials of at least 25 feet (for HF operation).  The best results I've had, I used four 75' radials and another four 33' radials, all tied to a pair of 8' ground rods placed about five feet apart. The antenna(s) should be DC grounded to this ground to prevent static charge build-up, and to no other ground so as not to bring a lightening surge into your shack.  This requires "Galvanic Isolation", or in other words a good 1:1 UNUN at the feed point.  A "Choke Balun" made of ferite beads over the coax feeder is the second best choice, if you can't get/build a 1:1 UNUN that has DC isolation between windings.

Sometimes multiple antennas can share a "Transmitting Ground" and sometimes not.  You should be able to share this ground without issues assuming you use a good, "ground breaking" antenna selector relay box.  You'll have to build one of those relay boxes, though, because I'm not aware of any commercial vendor selling them to the ham community, and those sold for broadcast and GOV/MIL use are insanely expensive (although you might find such a unit used at a hamfest for a decent price. - if you do, GRAB IT, it's worth it's weight in gold for multi-antenna environments).
The less costly, but sometimes less successful solution, is to run multiple feedlines -one for each antenna- and simply share the ground (on the antenna side of the UNUNs).  The bad news is that, where two (or more) antennas both have resonances in the same band, your ability to match one or more of the antennas on that band may be compromised, and/or the efficiency of the matched antenna may be very poor as a result of the parasitic coupling between the antenna you are trying to use, and the other one which exhibits resonance in that band.
Further, you may not *think* that another antenna has a resonance in the band in question... but when it is loading across the capacitance of an arbitrary length of coax, an antenna can exhibit resonance at frequencies far from those it is designed for.  So, sharing an antenna ground without a ground-breaking antenna relay can prove to be a challenge. 

Grounding Receive-Only Antennas - this is probably the simplest answer of all.  Each and every Receive Antenna should have it's own dedicated ground rod(s) to which nothing else is connected (with one exception).  If you're not going to bother with dedicated grounds for your receive antennas, then you should probably focus on "ground independent" receive antennas (and hope for the best).  At best, sharing grounds will probably distort the patterns of your receive antennas.  At worst, you'll end up inviting noise into the system which will defeat the point of the receive antenna all together.  The exception is this - if you have a "star layout" of Beverage antennas, and have a relay-switched directional controller at the centralized feedpoint, then the feedpoint where the Beverages come together can share a single Ground, and you should do your very best to make sure that ground is totally bomber (as the Australians say).

The "Station RF Ground".  This is one (or more) ground rods set as close to the station equipment as possible, and connected to the station equipment by a wide, flat conductor such as heavy copper flashing.  Don't use bare copper braid outside - it will corrode and loose its utility quickly.  If you can't use copper flashing, then the second best alternative is to use one or more sections of RG8 or RG213 coax.  Tie the shield and center-conductor together at both ends, route as necessary, and then terminate the inside end with a PL259.  Connect this to one position of your antenna switch.  Now take a hose clamp, and clamp the end of a section of copper braid to the shell of the PL259, routing the other end to your (main) antenna tuner, so the antenna tuner is well grounded.  If you have multiple antenna tuners, then run individual braids from each back to your PL259 'central grounding point'.  DO NOT DAISY-CHAIN STATION GROUNDS - ALWAYS USE A 'STAR' CONFIGURATION
Radios get their ground through their antenna tuner via the coax jumper - NOT the other way around.  If there is to be any current on a Station Ground lead, you want it to be the radio that put it there, and not any other piece of equipment.  That is why the radio must be at "the end of the line", not in the middle.  EVER.
Depending on your station power supply, you may have to use a power isolator - essentially a 1:1 transformer for AC power - that breaks the ground connection between the radio and the NEC safety ground  through the power supply wiring.  Old, heavy power supplies rarely require this, but the new, compact switching supplies often tie the Neutral and Ground connections together, essentially connecting the negative lead of the power supply directly to both the Neutral and Ground of the branch circuit in the house.  This is a total fail.  Test your power supply(ies) for this with an ohm meter and fix or sell any that are wired this way.  It's more than a problem, it's a potential fire hazard (lots of current can flow between Neutral and Ground if something else in the house faults, and the lowest resistance path to (any) ground is though your power supply or other station accessory which is thus wired.  That's why NEC prohibits tying Neut. and Gnd. together anywhere but at a Service Panel)

Do NOT connect any other equipment to the Station RF Ground.  Not computers, nor power supplies, not ANYTHING. 

Why not to connect anything else?
1. Surge/Static.  You want to isolate your radios to the greatest extent possible from any source of electrical surge or static (lightening) discharge which might do them damage.  To do this, they must have a ground of their own, which no other piece of equipment can 'load' or saturate.  The moment you connect other equipment to the Station Ground, you have violated the principle of isolation.  Worse, you don't know what the resistance of the "utility ground" is at the outlets in your shack, but it is almost assuredly higher than the resistance of your well-provisioned Station Ground - because of this, if you connect other equipment to the Station Ground, that equipment *will* use your station ground as its NEC Safety Ground, including running current through it.  (Yes, I know it's against NEC code for any appliance or device to run current through the Safety Ground, but it happens more often than you might think -- see my comments above about some switching PSes grounding their neutral lead.  Cheap Chinese computer and laptop power supplies are notorious for this, BTW.)

2. RF Noise incursion.  The second benefit from isolating your station ground from *everything* except your radios, is to keep electrical noise from making its way into your receiver and causing interference.  But it only takes one break in that isolation to spoil your work in this regard.  You can easily eliminate 2 to 6 S-units of noise (sometimes much more) from your receiver just by using a proper Transmitting Ground and properly isolating your Station Ground.


Cheers