Don, I concur with what you are saying. At one installation the equipment was quite a distance from the ground rod. I installed a good DC ground. But there was still RF floating around. What I did was parallel insulated wires between the amp and the ground rod. Each wire was longer than the next. If I remember each of the insulated wires was a quarter wave on 15, 20 and 40M. RF problems disappeared. 73, N2TK, Tony
PS - K2 #3481 is ready to take back to WP2Z the end of February for ARRL SSB Test. -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Don Wilhelm Sent: Monday, January 22, 2007 10:27 PM To: JIMMY D HARRIS; [email protected] Subject: RE: [Elecraft] In Shack Radials and Ground Jim, Sorry to disagree - consider what happens on a quarterwave wire: It has a low impedance at one end and a high impedance at the other end. Think about what will happen if you connect the far end of a quarter wave wire to a good ground (low impedance) - the other (near) end will have a high impedance at that frequency, and will not serve as an RF ground at all (in fact quite the opposite). A halfwave wire however can have a low impedance at each end, so grounding the far end of a half wave wire will make the near end at a similarly low impedance. A grounded radial and a counterpoise wire are two different things - the counterpoise wire creates a low impedance (about 35 ohms) by nature of having the far end ungrounded, whereas a grounded (or buried) radial forms a screen or reflector - yes, the counterpoise will radiate because it becomes a part of the antenna system. The counterpoise controls the radiation instead of having it wander willy-nilly around the shack and other places where it should not be present. I do understand that this is not intuitive - we have to think in terms of antenna theory when dealing with RF grounds - what works fine at DC and low frequency AC does not necessarily work at RF. Ground rods can be a good RF ground, but the wire connecting the ground rod to the shack may not behave as expected - a 16 foot connection to the ground rod will present a high impedance to 14 MHz RF at the shack end - but should be a good RF ground for 10 meters since it is a halfwavelength away from the low impedance ground rod. 73, Don W3FPR > -----Original Message----- > > There was mention about ground rods not being a good RF ground. For the > most part I agree with that. However, the wiring to the ground rod is in > fact a radial that is some part of a wavelength long. As we know quarter > wavelength radials can tune out RF. By the same token other fraction of > wavelength ground runs (radials) can create RF in the shack when used in > conjunction with a poorly designed antenna system. Stay away from ground > runs that are halfwave wavelength (or near) or multiples thereof of > frequencies your antenna system is designed for. > > 'nough said...... > > Jim, AB0UK > K2/100 S/N 4787 > -- No virus found in this outgoing message. Checked by AVG Free Edition. Version: 7.5.432 / Virus Database: 268.17.4/644 - Release Date: 1/22/2007 7:30 AM _______________________________________________ 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
