New Ham's Second Floor Station Ground
I am new to HF installing a shack on the second floor of my house (unavoidable). I have read several recommended sites on grounding and lightening protection, but I am still a newbie, so any advice and remarks are appreciated :-) The way I plan to ground the shack is:
1. Inside the shack is a Yaesu FT-950, a Samlex Power supply and an antenna tuner (probably will be a Palstar AT2K). Each DC ground will be connected to a length of 1 in. (25mm) copper pipe by a short length of .5 in (12mm) braid.
2. The copper pipe will be connected to 3 in (75mm) thin copper foil and heavy 8 AWG copper wire to my house's existing electrical ground rod, 8 ft ( 3m ) below and 8 ft (3m) laterally from my shack. So all of the grounds will be tied together at this point.
3. Antennas will be connected via coax bulkhead feed-throughs to the tuner. All of the feed-throughs pass through a wooden board in my window which has two metal plates, one on each side. The feed-throughs ground to these plates which are also connected to the heavy copper wire DC ground and RF foil ground,
4. On the outside each SO-239 feed-through bulkhead will have a lightening arrester also wired to the copper DC ground.
5. There will be a total of four antennas; a 2m 70cm j-pole, a G5RV Jr and 2 dipoles.
After all the reading about ground loops, AC hum feedback etc. I am confused, so if anyone sees something amiss (or missing!) please let me know!
Thanks for the input and 73's,
The feedlines should all go down to ground level, the shields grounded there, then go into your house.
Provided that everything that comes into the house is grounded outside the house, and all ground rods are bonded together and with your AC ground where it enters the house, and antennas are either balanced (G5RV, dipoles) or have appropriate radials or counterpoise, then with modern equipment there's really no need for all that braid and pipes and stuff. AC safety is taken care of by the grounded plug of your power supply. No other ground in your shack is needed.
I have managed to be hit three times by lightning. All logic aside, lightning, when it strikes, finds a path, of course, it is supposed to be the least resistive to ground.... In reality, the lightning Gods have a creative mind-set, and the 'least resistive' path may not seem as such to the mere mortal human. The comment about the ground plugs on modern gear is correct, of course, but in no way can that come close to 'insuring' a safe station.' Your precautions sound over and above the usual grounding efforts, and would make most of us sleep well during a storm. Bottom line there is no guarantee of any safe, lightning proof set-up, however.
My preference has always been to disconnect all antennas and the rotor cable plug when I am away from the station. Having a central ground point is a very good first step. basicly creating an area where the lightning has NO chance of entry is best. However in the final analysis, lightning, for the most part, ignores ham antennas and towers. I think that is because we have so much crap in the air, we confuse the streamers that preceed a strike, and wind up dissipating the energy before it forms a focus.
In any case, your more likely problems from being on a second floor relate to creating an effective RF ground. That may(or may not) require some efforts and detective work.
However, you are off to a great start, and welcome to the hobby!!
"Clear intent is the best predictor of experience"
You can't have a "ground" or an earth that high above the ground, if you have a wire at the back of your tranceiver it might cause more noise than not having it there. An earth is supposed to be short, less than 6 ft. If you have an earth pin on your power socket that is quite sufficient. I've been operating for 23 years without an earth, never had problems
This makes sense. What is the best way to ground the coax shields to the outside ground rod. Is it necessary to use lossy connectors? Is it OK to strip the insulation and connect the shield to ground via a strap? Sorry for the dumb question !
I've never had anything "grounded" and never had a problem even when I ran a KW amplifier
lucky I guess
3 types of grounds:
1 - AC safety ground (covered by your third prong an properly wired AC outlets)
2 - lightning ground - covered by bonding all house grounds at the entry point, and grounding all feeds entering the house.
3 - RF ground - if you are using a system that is in balance, the RF currents go on the feed line in equal and opposite directions canceling each other - aka differential currents - this is true for coax (center wire and inside shield) and for balanced lines. This is why radiating coax or balanced line should not be an issue. In such a perfect situation there is no need for an RF Ground in the shack. The problem occurs dealing with common mode current, which is a "third" current that flows on feeds that are not in balance and does radiate. The best fix is to solve the problem through the use of a choke/balun, etc. You can deal with it through a good RF ground, but that's nearly impossible to achieve in your situation. Better to use good antenna systems that don't force you into requiring it.
Don't confuse the three types of grounds.
A long ground wire from the second story forms much too high an impedance for an RF ground.
Quality connectors are not lossy. Yes, you should use them. Some people take the coax jacket off and ground the shield directly. I never wanted to do that, but if you do make sure you waterproof it throroughly. MFJ makes a ready-made window panel you can use for grounding.
The most important thing for lightning safety is to tie all the grounds together - particularly the AC service ground and any other grounding you do outside the shack. There should be no difference in electrical potential between any ground in the house - otherwise you run the risk of currents flowing between them. (e.g. AC hits power lines and sees a lower impedance path to ground that goes right through your shack). Lightning behaves like RF, not like DC. So you need very short, very low impedance connections to handle it effectively. Long wires more than a few feet, and thin gauge wires won't work.
Most people dealing with lightning grounds are dealing with a few feet at most, and use copper strap, copper flashing, and or very large gauge wire as in 0,4,6 gauge.
Last edited by AE2CS; 03-18-2011 at 02:04 PM.
Forgive me for not remembering the source, but I recall years ago reading that a suitable 'RF' grounding method for 2nd floor and higher installations, was to construct a 'shielded' ground.
Using coax cable (the bigger the center conductor the better), the center conductor and the shield are bonded to a ground rod. The station end of the shield is left open, and the center conductor is your ground point.
My shack is on the second floor and all 7 dipole antennas are in the attic and drop through the ceiling to my shack. Not the best situation, but what I could do. I have no ground to my radio other than the 3rd wire ground on my 12 volt switching power supply. As said earlier, disconnecting everything would be the safe thing to do. I don't and never have in 36 years here and other houses. I don't have any noise problems or RFI problems in the house except for external speakers on two computers and 4 ferrite beads on each fixed both. I do have a ferrite bead coaxial isolator between the antenna switch and my rig. I operate 160M through 2m from this shack. If I had outside antennas I would run the the coax in next to the fuse box and ground to the earth ground rod.
I would say a ground to earth from the second floor is really more like a short lightning rod. If it's your time, it's your time. Uncorrelated data, there has been two homes hit by lightning in our area over the past 10 years. This is out of about 20,000 houses so it happens but the odds are pretty rare.
Be sure to listen for my beacon on 28.278.8 MHz
Hey! Everyone's input is appreciated here. The grounding plan is getting simpler (or perhaps I'm getting simpler, but no matter):
I am dealing with three separate grounds for my shack.
First is the AC power ground. I have a modern three-wire house ground with a green neutral 12 AWG wire that runs all the way back through the house wiring to the house's earth ground. Also, the SO-239 connectors on my transceiver and antenna tuner are grounded to the chassis and the heavy coax braid to the SO-239s at the SPG end will be grounded to the NEMA box and to the house earth ground rod. So why do I need all of that braid and copper path to earth ground mentioned in the manuals and on-line forums ?? I think it is redundant and I'm even worried that it might provide a shorter path into my shack. I have done some research and have not been able to find a clear reason for this anywhere, other than that it may be a holdover from the days when houses had two-conductor electrical wiring.
Second, is lightning protection. The most likely problem is heavy induced EMP currents. These are RF, NOT DC like I assumed. I think I can put a metal NEMA box about 12 inches from my house ground rod and strap it to that same ground rod. Then I can bring all of my antennas into the box to SO-239's grounded to the box. From there I can lead coax out of the box again, up the outside wall and 8 ft over to my shack. I can use feed-throughs (or not) to bring the coax into my antenna tuner. Less likely is a direct lightning strike; it seems to be that I may have done all that I can. If zillions of amps arcing through a mile of ionized air hit my house, there is some possibility that I may not be able to control its path at that point with a piece of wire ;-) I'm still trying to find out if there is need of a lightning arrester or static discharge device at that point to take care of a charge that builds up on the antenna and center conductor of the coax.
Third is the RF ground. I don't think I need the copper foil path to ground. There is NO RF on the transceiver or tuner chassis that I can find. If it occurs, it must be reflected from OUTSIDE down my coax and the solution then is probably to use a balun or something to match my antenna correctly ... not to "ground out" the RF that I am doing all this to transmit! I must be crazy!
I researched the requirement for an RF foil ground and found that a big part of it goes back to Gordon West's FCC Exam books. I followed up with a company that manufactures it and they sent me a sample and a "complete explanation" from Gordon West. The explanation was complete alright --- it was a very good explanation for using the copper foil to provide a saltwater ground for a SSB rig on a yacht! When I trade my 1998 Jeep Wrangler for a yacht I will immediately order a roll of this foil ... for the moment, I will wait and see if I need it :-)
The big lesson I m learning is not that I have it all figured out, but that there is a lot of "iffy" information and "common practice" out there. It's worth the time and effort to try to sort it all out and understand it myself and then correct my understanding as problems occur.
Thanks again to everyone who has taken so much time to share what you know with me.
Any addition thoughts, information, criticism or humor is always appreciated.