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 ```I have put significant amounts of blood, sweat, and tears into vertical arrays for 160, over the years... As a result I have definite opinions in this area of antenna practice... >Since the sides of the square are 35 feet, the >radials extending inside the square would intersect. The theory is that this >can cause undesirable cancellation of currents in the radials, so the >standard procedure is to bind all the radials inside the square to a pair of >bus wires that cross in the middle of the square First, I have a problem with the concept that radials crossing each other cause undesireable cancellation of the currents... And with the concept that connecting everything to a central buss bar cancels this cancellation.... The first thing a common buss does is to concentrate the currents into a smaller area raising the I^2R ground losses, especially for an on the ground system ... The whole idea of an extensive radial field is to spread the currents over a larger area thereby decreasing the current per square meter (or what ever units you prefer) ... And, I have a definite bias against rolling out a length of bare wire on the ground and thinking that it has some specific electrical length.... the electrical length of that wire is unknown and unmeasureable... Dirt is a slurry of ionized salts, water, metals,and carbon, impregnated through a dough of nonconductive material - forming a partially conductive plane... With the addition of bare radials all you have is dirt with a high concentration of metal in long strips.... The RF current, initially finding metal strips to have a lower surge impedence than the adjacent dirt near the antenna, will preferentially flow along the wire, but current will be leaking laterally (shorting) into the ground between the radials as it goes... At the same time the dirt is shorting the bare wire back towards zero volts of RF, thus destroying any resonance the installer might have been counting on... This whole scenario is why I do not use bare wire for radials... I do not have any chance at all of establishing resonance in this half of the antenna system... All you can do is add more radials hoping to increase the percentage of metal in your dirt... Certainly, 4X8 sheets of pure copper covering the ground for a few hundred feet will do even better, but is impractical... This should be a wake up call.... A single tapering, quarter wave , vertical element is not going to be that broad... When I tried the input impedance measurement, I found that the point of lowest impedance was 25 ohms at about 7.300! When I checked the impedance at 7.150, it was 37 ohms. A 50 ohm coax is only flat when terminated in a 50 ohm load... A random length of coax when terminated in non 50 ohm load is going to act as a voltage and phase transformer, and give you problems at the feed end... Your antenna/ground-system is resonant at 7.300 (the point of lowest impedence is the resonant frequency, when measured at the antenna terminals)... Now, you need to trim the antenna until it is resonant where you want it... Then you need to measure the impedence, and with this information you can design the matching device... I prefer a wound transformer / tapped coil / etc., over quarter wave lengths of coax, but they all work when properly designed... The way I prefer to tune a vertical is to first hang two 1/4 wave elevated radials - 3 or 4 feet high is fine for 40 meters - fold them to fit the space, if needed..(shorter radials are ok, just load them until they are resonant)... Then using the RF-1 drive the two radials at the center as a dipole antenna, and adjust their length until they are resonant at your chosen frequency (yes, the impedence at resonance will be a few ohms... Not to worry)... Now reattach them as radials and drive the vertical element against the (now) tuned radials... Adjust the vertical length until is is resonant where you want it... voila, you are done except for the matching network - and I guarantee it won't be flat across the entire 40 meter band... You HAVE to detune (or take down) all 40 meter vertical antennas within 2 or 3 wavelengths of the one you are working on, or they will couple and you will go mad trying to get the system to behave (actually it can't be done if the element you are adjusting is resonance coupled to another antenna because you have coupled tuned circuits and they will exhibit pulling of the frequency depending on which direction you are tuning as you approach one {or more} of the resonance points).. When I tuned my 4 element array it required many trips back and forth to isolate the feed points for other 3 elements, especially with three iterations around the circle... I do not use ferrite beads over the coax... I prefer a wound choke balun on the end of the coax to choke the common mode current.... Cheers ... Denny -- FAQ on WWW: http://www.contesting.com/towertalkfaq.html Submissions: towertalk@contesting.com Administrative requests: towertalk-REQUEST@contesting.com Problems: owner-towertalk@contesting.com Search: http://www.contesting.com/km9p/search ```