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: [email protected] 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 radials....I 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: [email protected] 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: [email protected] 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
