Re: [Elecraft] Best way to secure RF ground from 2nd floor?
i believe the originator had said that he has a centerfed dipole with a balanced feedline. i think the first thing the lead wire should come to is a suitable matching device. i use an elecraft t1 which works well for my qrp activities. the coaxial input to my t1 has 10 inches of suitable ferrites on it to act as a common mode rf choke to keep rf off the exterior of the coax regardless of it's length. that ensures that whether the feedline is perfectly balanced or not all of the rf is properly contained inside the coax. the tuner itself is likely a bit hot but it is of no consequence. my next oft delayed project is to build up a simple insertion/extraction pair for a bit of dc onto the coax to remotely trigger the t1 tuning cycle. 73 jim ab3cv ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
RE: [Elecraft] Best way to secure RF ground from 2nd floor?
> > > Grounds can serve three purposes: lightning protection, power line > safety, or RF ground. These are three very different things, requiring > very different ground methods. > > ... > > Al N1AL > > True. But should we go a step further and avoid even using the phrase RF ground? Long ago I asked an old Zen master about the best way to RF ground my station. His answer was "What do you mean by ground?" This was the best possible answer because it made me think about the physics that's going on: You don't want to seek some elusive "ground" potential. What you want is to keep unbalanced feedline current out of your shack or at least as far from your equipment as possible. 73, Carl WS7L No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.516 / Virus Database: 269.20.9/1290 - Release Date: 2/20/2008 8:45 PM ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
RE: [Elecraft] Best way to secure RF ground from 2nd floor?
Grounds can serve three purposes: lightning protection, power line safety, or RF ground. These are three very different things, requiring very different ground methods. For an RF ground, forget about a wire to earth ground. It will almost always be too long to present a low impedance at RF. Even if you can tune out the reactance by adjusting the length to a multiple of 1/2 wavelength or by using a tuner, it will still have RF current flowing in it and so will still radiate RF. A better method is to use a counterpoise wire. This is like a single radial, 1/4 wavelength long, connected to the chassis of the antenna tuner. One counterpoise is needed for each band of interest. Al N1AL ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
RE: [Elecraft] Best way to secure RF ground from 2nd floor?
I ran a TR-3 with no gnd at all for 4 yrs from higher floor with no problems. The AC had a gnd pin. I say, if u have no problems with no gnd, forget it. Of course, my Thailand 230VAC is supplied with no separate 3rd wire gnd The guy who installed my water pump here ran the gnd wire from it to a plastic water pipe. The guy who installed my outside air cond condenser ran the gnd wire to a screw in the concrete wall. Then my dog chewed the wires in two. Buzz, zap.Charles Harpole [EMAIL PROTECTED] > From: [EMAIL PROTECTED]> To: elecraft@mailman.qth.net> Subject: RE: [Elecraft] Best way to secure RF ground from 2nd floor?> Date: Tue, 19 Feb 2008 20:44:34 -0800> > -Original Message-> > > Here is a solution from a very old QST,> > > > It's not from QST.> > > > and all I can say is it works> > > > > > for me. My shack is on the 2nd floor and I run several rigs w/ amps > > > . I> > > was having RF everywhere until I tried this:> > > - Run coax ( RG-8 or similar) from rig to a real good ground . Put a > > > .01 cap across the shield and center conductor at both ends. Cap needs > > > to be 2KV or better. You will be using the center conductor as your > > > connection to rig and the ground rod.You should also use an ATU as > > > mentioned in an earlier reply.> > If it is not from QST, do you know where it is from? Do you know where (or> how) I can get a reprint of it? My shack is on the second floor, too.> > And I believe that The Wireman used to sell a kit containing the capacitors!> > Dan Allen> KB4ZVM> K2 S/N 1757> > -> > Those capacitors look like "shorts" at RF. So the center conductor is tied> to the shield at RF, but not at D-C. Direct current isn't the problem. Tying> the shield to the center makes the impedance of the cable slightly less> because it's slightly bigger to the RF. > > Even so, at RF it's still just a wire from the second story to ground. > > If you force a wire to either a low impedance (grounded) or high impedance> (insulated) at one end, it will show at the opposite end the opposite> impedance if it's 1/4 wavelength long or an odd multiple of 1/4 wavelength> long, and it'll show at the opposite end the *same* impedance if it's 1/2> wave long or a multiple of 1/2 wavelength long. Everything in between will> be something "in between". > > Even a marginal RF ground will cure problems caused by no RF ground in some> situations. Even a hunk of coax. > > The things you can do to provide a low(er) impedance ground than a wire is> to make the wire larger, or parallel a lot of wires to ground, all> separated, such as running a large wide sheet of metal from the rig to the> ground. If you're on the second floor, that's seldom practical for those who> live in the same building with our "shacks" ;-) My shack is, fortunately, on> the ground floor about 3 feet from where the large metal conduit for the> underground utilities emerges from the earth. It's also where all the other> services - telephone, cable, etc. - are grounded along with the mains> ground. And my RF ground goes there. Since it's only a few feet away, I use> a 2-foot wide strip of copper attached to the wall from the rig to a point> on the wall opposite the mains conduit. Then a pair of ground wires makes> the run through the wall to the mains conduit. Each wire is about 12 inches> long. Two in parallel reduce the impedance of one. To RF, they look like on> FAT conductor. > > I didn't suggest that because, from the 2nd floor, it'd take very large> piece of metal to show low enough impedance.> > But all is not lost. You can operate free from RF when you aren't close to> ground. It's been done by everything from rigs in Zeppelins to Hams stuck in> the attic! > > The "trick" is to keep the impedance of all RF antenna circuits at the rig> low. > > A 50 ohm dummy load does that, but it's a lousy radiator. But it> demonstrates the concept: keep the impedance low.> > Feeding an antenna at a current loop (low-impedance) point will do that.> That's why Hams seldom have trouble with center-fed dipoles. The impedance> at the center of a dipole is low - typically not far from 50 ohms. Bringing> the feed point of the dipole directly to the rig or through a length of coax> that has a low SWR keeps the impedance at the rig low. The impedance is low> because each half of a dipole is 1/4 wavelength long. The far ends are> insulated, forcing their impedance high. So the ends at the rig are low>
RE: [Elecraft] Best way to secure RF ground from 2nd floor?
-Original Message- > > Here is a solution from a very old QST, > > It's not from QST. > > and all I can say is it works > > > > for me. My shack is on the 2nd floor and I run several rigs w/ amps > > . I > > was having RF everywhere until I tried this: > > - Run coax ( RG-8 or similar) from rig to a real good ground . Put a > > .01 cap across the shield and center conductor at both ends. Cap needs > > to be 2KV or better. You will be using the center conductor as your > > connection to rig and the ground rod.You should also use an ATU as > > mentioned in an earlier reply. If it is not from QST, do you know where it is from? Do you know where (or how) I can get a reprint of it? My shack is on the second floor, too. And I believe that The Wireman used to sell a kit containing the capacitors! Dan Allen KB4ZVM K2 S/N 1757 - Those capacitors look like "shorts" at RF. So the center conductor is tied to the shield at RF, but not at D-C. Direct current isn't the problem. Tying the shield to the center makes the impedance of the cable slightly less because it's slightly bigger to the RF. Even so, at RF it's still just a wire from the second story to ground. If you force a wire to either a low impedance (grounded) or high impedance (insulated) at one end, it will show at the opposite end the opposite impedance if it's 1/4 wavelength long or an odd multiple of 1/4 wavelength long, and it'll show at the opposite end the *same* impedance if it's 1/2 wave long or a multiple of 1/2 wavelength long. Everything in between will be something "in between". Even a marginal RF ground will cure problems caused by no RF ground in some situations. Even a hunk of coax. The things you can do to provide a low(er) impedance ground than a wire is to make the wire larger, or parallel a lot of wires to ground, all separated, such as running a large wide sheet of metal from the rig to the ground. If you're on the second floor, that's seldom practical for those who live in the same building with our "shacks" ;-) My shack is, fortunately, on the ground floor about 3 feet from where the large metal conduit for the underground utilities emerges from the earth. It's also where all the other services - telephone, cable, etc. - are grounded along with the mains ground. And my RF ground goes there. Since it's only a few feet away, I use a 2-foot wide strip of copper attached to the wall from the rig to a point on the wall opposite the mains conduit. Then a pair of ground wires makes the run through the wall to the mains conduit. Each wire is about 12 inches long. Two in parallel reduce the impedance of one. To RF, they look like on FAT conductor. I didn't suggest that because, from the 2nd floor, it'd take very large piece of metal to show low enough impedance. But all is not lost. You can operate free from RF when you aren't close to ground. It's been done by everything from rigs in Zeppelins to Hams stuck in the attic! The "trick" is to keep the impedance of all RF antenna circuits at the rig low. A 50 ohm dummy load does that, but it's a lousy radiator. But it demonstrates the concept: keep the impedance low. Feeding an antenna at a current loop (low-impedance) point will do that. That's why Hams seldom have trouble with center-fed dipoles. The impedance at the center of a dipole is low - typically not far from 50 ohms. Bringing the feed point of the dipole directly to the rig or through a length of coax that has a low SWR keeps the impedance at the rig low. The impedance is low because each half of a dipole is 1/4 wavelength long. The far ends are insulated, forcing their impedance high. So the ends at the rig are low impedance - typically 20 to 30 ohms. Two of them makes a 50 ohm load for the rig. The famous "Zeppelin" antennas did the same for a rig floating high in the sky held aloft by a bag of hydrogen. An open wire feed line, exactly 1/4 wavelength long, was connected to the rig. At the far end one side of the feeder was connected to nothing at all: it was well insulated. The other side of the feeder was connected to a 1/2 wavelength hunk of wire floating out behind the ship in the air stream. The 1/2 wavelength long wire showed a high impedance to the feeder at its end. The feed line, being 1/4 wave long matched that high impedance while showing a low impedance at the rig. The other side of the feed line, being insulated at the far end, also showed a low impedance at the rig in the airship. Low impedance at the rig meant no RF to cause sparks and burns which meant the airship didn't catch fire. If your not using a "Zepp"eline antenna you can do the same thing. Just hook a 1/4 wave long piece of wire to the chassis of your rig. Yes, that means you need one for each frequency you operate on. That's the bad news. The good news is that it's generally adequate to use only one for each Amateur band. As I mentioned above, you don't need a perfect ground. The "prob
Re: [Elecraft] Best way to secure RF ground from 2nd floor?
> > Here is a solution from a very old QST, > > It's not from QST. > > and all I can say is it works > > > > for me. My shack is on the 2nd floor and I run several rigs w/ amps . I > > was having RF everywhere until I tried this: > > - Run coax ( RG-8 or similar) from rig to a real good ground . Put a > > .01 cap across the shield and center conductor at both ends. Cap needs > > to be 2KV or better. You will be using the center conductor as your > > connection to rig and the ground rod.You should also use an ATU as > > mentioned in an earlier reply. If it is not from QST, do you know where it is from? Do you know where (or how) I can get a reprint of it? My shack is on the second floor, too. And I believe that The Wireman used to sell a kit containing the capacitors! Dan Allen KB4ZVM K2 S/N 1757 ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Best way to secure RF ground from 2nd floor?
In a message dated 2/19/08 8:50:41 PM Eastern Standard Time, [EMAIL PROTECTED] writes: > Here is a solution from a very old QST, It's not from QST. and all I can say is it works > > for me. My shack is on the 2nd floor and I run several rigs w/ amps . I > was having RF everywhere until I tried this: > - Run coax ( RG-8 or similar) from rig to a real good ground . Put a > .01 cap across the shield and center conductor at both ends. Cap needs > to be 2KV or better. You will be using the center conductor as your > connection to rig and the ground rod.You should also use an ATU as > mentioned in an earlier reply. Have you tried just using the coax as a ground conductor, without the capacitors, and the center conductor tied to the shield? 73 de Jim, N2EY ** Ideas to please picky eaters. Watch video on AOL Living. (http://living.aol.com/video/how-to-please-your-picky-eater/rachel-campos-duffy/ 2050827?NCID=aolcmp0030002598) ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Best way to secure RF ground from 2nd floor?
DOUGLAS ZWIEBEL wrote: HI all: I am re-doing all my 20 year old connections here in the shack, which is on the 2nd floor of my house. Can anyone point me to a resource for the "best way" to ensure a proper RF ground from the 2nd floor? I have lots of holes in the walls going outside (rotor cables, control lines, many coaxes, etc), so going through the wall is not an issue. If fact, maybe I can use the shield of a coax to help with an earth ground? I"m not looking for "resonant" inside radialsI want a genuine RF ground. Looking forward to your comments. Since I suspect this may a topic of wider interest, I'll ask you post your comments here (or you can always post to me directly if you disagree with "filling up the reflector"). Thanks so much! de Doug KR2Q ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com Here is a solution from a very old QST, and all I can say is it works for me. My shack is on the 2nd floor and I run several rigs w/ amps . I was having RF everywhere until I tried this: - Run coax ( RG-8 or similar) from rig to a real good ground . Put a .01 cap across the shield and center conductor at both ends. Cap needs to be 2KV or better. You will be using the center conductor as your connection to rig and the ground rod.You should also use an ATU as mentioned in an earlier reply. 73 Dale K5AJZ ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Best way to secure RF ground from 2nd floor?
On Mon, 18 Feb 2008 20:44:55 -0800, Ron AC7AC wrote: > >Another approach for an RF ground is to use your connection to the ground >rod, but tune out the reactance. MFJ made a small "tuner" for just that >purpose: a coil and capacitor in series that one adjusted as needed to >produce maximum ground current at the rig. That can be very effective, but >it is frequency-sensitive: it requires readjustment for every band. And, >because the circuit involves a capacitor in series with the coil, it is not >a d-c ground if that's what you are looking for. But it can produce a good >RF ground. > >Ron AC7AC An automatic ground tuner might be nice-- a GTU, i guess you would call it. 73, Drew AF2Z ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
RE: [Elecraft] Best way to secure RF ground from 2nd floor?
The problem you face is getting a non-reactive connection from the rig to the ground. Any conductor connected to the earth at the ground level will be grounded at that point and will be "above RF ground" at the other (rig) end. If you happened to have a 1/4 wavelength wire between your rig and the ground, you'll have the highest possible RF voltage on your rig! Anything other than 1/4 wave or an odd multiple thereof, will show more or less RF voltage. It won't be a "good RF ground". A 1/2 wave wire between your rig and a ground rod will show a good RF ground at the rig end: duplicating the impedance at the ground rod, but only at the frequency where it's a half wave or a multiple of 1/2 wave. Usually the best way to "ground" a rig for RF that isn't near real ground (less than, say .05 wavelengths at the highest frequencies you use or, on 10 meters, 0.8 feet maximum between the rig and the ground pipe, or 7 feet on 80 meters) its to use a 1/4 wave wire attached to the rig whose far end is well insulated from ground. With the far end insulated, it will be forced to be at a voltage loop or high impedance point. That puts the other end, at the rig, at a current loop or low impedance point. You can still use a wire to your ground rod in parallel with that if you like although most electrical codes frown on having a ground separate from the mains utility ground. Another approach for an RF ground is to use your connection to the ground rod, but tune out the reactance. MFJ made a small "tuner" for just that purpose: a coil and capacitor in series that one adjusted as needed to produce maximum ground current at the rig. That can be very effective, but it is frequency-sensitive: it requires readjustment for every band. And, because the circuit involves a capacitor in series with the coil, it is not a d-c ground if that's what you are looking for. But it can produce a good RF ground. Ron AC7AC -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of DOUGLAS ZWIEBEL Sent: Monday, February 18, 2008 4:23 PM To: elecraft@mailman.qth.net Subject: [Elecraft] Best way to secure RF ground from 2nd floor? HI all: I am re-doing all my 20 year old connections here in the shack, which is on the 2nd floor of my house. Can anyone point me to a resource for the "best way" to ensure a proper RF ground from the 2nd floor? I have lots of holes in the walls going outside (rotor cables, control lines, many coaxes, etc), so going through the wall is not an issue. If fact, maybe I can use the shield of a coax to help with an earth ground? I"m not looking for "resonant" inside radialsI want a genuine RF ground. Looking forward to your comments. Since I suspect this may a topic of wider interest, I'll ask you post your comments here (or you can always post to me directly if you disagree with "filling up the reflector"). Thanks so much! de Doug KR2Q ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
Re: [Elecraft] Best way to secure RF ground from 2nd floor?
I'm not on a 2nd floor, but I use 2" wide copper strap. It comes from a sheet metal shop, which cuts it with a sheer from the side of a 4' x 8' sheet. The strap is run along the back of my desk with brass 1/4 x 20 bolts soldered at 12" intervals. I use brass wing-nuts on the bolts. 73! Ken Kopp - K0PP [EMAIL PROTECTED] or [EMAIL PROTECTED] ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
[Elecraft] Best way to secure RF ground from 2nd floor?
HI all: I am re-doing all my 20 year old connections here in the shack, which is on the 2nd floor of my house. Can anyone point me to a resource for the "best way" to ensure a proper RF ground from the 2nd floor? I have lots of holes in the walls going outside (rotor cables, control lines, many coaxes, etc), so going through the wall is not an issue. If fact, maybe I can use the shield of a coax to help with an earth ground? I"m not looking for "resonant" inside radialsI want a genuine RF ground. Looking forward to your comments. Since I suspect this may a topic of wider interest, I'll ask you post your comments here (or you can always post to me directly if you disagree with "filling up the reflector"). Thanks so much! de Doug KR2Q ___ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
