Jim, Well said - for years now I have been trying to convince folks that there is a strong need for considering 2 'grounds' at a station. The first is the Safety Ground which should be a low impedance path to earth - large conductors, lots of heavy guage wire buried in the earth and ground rods, and this must also be connected to the utility ground. Properly implemented it should serve a a lightning protection ground.
The second is the RF Ground - and the Safety Ground may or may not suffice. Consider a good Safety Ground with an 8 foot connection from the antenna connection at the tuner - that combintion will likely produce a high impedance for RF at 10 meters, thus there will be no RF Ground at that frequency. In such conditions, the use of quarterwave counterpoises for each troublesome band is in order. 73, Don W3FPR -----Original Message----- So what? The significance of an RF ground is highly overemphasized. Park next the to end of the runway of your local airport and watch the 747's take off. Call me collect when you see one trailing a ground wire. Last I heard, the onboard electronics and radios work just fine without one. The earth is NOT a sump into which noise is dumped, nor will a connection to earth make a radio more stable. An earth connection has no beneficial effect on the operation of a radio transmitter, nor on the elimination of RF interference. In fact, a connection made to earth by a noise source or receiver will act as an antenna, radiating or receiving interference. A "ground system" for a long wire or vertical antenna is really a COUNTERPOISE for the antenna -- it provides the other half of the circuit for the transmitter (or receiver) as a load. This is why it is VERY important to bond the shield of the coax in a mobile antenna system to the body of the car at the base of the antenna. It isn't noise (although it might reduce noise), it's the other half of the antenna! The surface of the earth also serves as a reflector for the radio waves radiated by the antenna. That ground system will work better (be more efficient, have less IR loss) if it is has low impedance at the frequency where it is used. High moisture content results in very low resitivity and better reflectivity in the soil. It is the combination of the reflection(s) with the direct wave from the antenna that determine the vertical directivity of the antenna system. These two mechanisms are the significance of RF ground. Jim Brown K9YC http://audiosystemsgroup.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 -- No virus found in this incoming message. Checked by AVG Free Edition. Version: 7.1.392 / Virus Database: 268.6.1/344 - Release Date: 5/19/2006 -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.1.392 / Virus Database: 268.7.0/345 - Release Date: 5/22/2006 _______________________________________________ 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
