Frequently Asked Questions (FAQs)
Q: Can I put this array near a fence?
A: Well, maybe. If the fence is a woven type with lots of places where the wire touches the ground you likely can get away with the array within about 5 feet of the fence. If the fence is an insulated wire type and possibly resonant, it is NOT recommended. Some have mounted their elements on the top of a short woven fence with great success. However all elements must have the same mounting above the fence.
Any resonant wires or objects within a minimum of 200 feet will have severe impact on the array performance.
Q: Will the array work better if I add more ground rods?
A: Generally No. In most ground conditions simple ground rods at each element of 2 to 3 feet in length and one half inch plus in diameter will realize all the performance of the array. Adding an extra rod in really poor soil is some added insurance, however more added rods has not shown any improvements.
Q: How do I clean the F connectors during maintenance.
A: First, use compressed air or an automotive electrical cleaner to dislodge any dirt or foreign matter in the cable connectors. Next take an ordinary #2 lead pencil with a pink eraser and press the eraser firmly into the end of the cable connector and twist vigorously. This does an adequate job of removing the copper oxide from the center conductor. Generally cleaning the chassis F connector is limited to using air or the automotive electrical cleaner on the outside threads. The internal connection is cleaned by the wiping action of the center conductor when the connector is mated.
Q: Is lightning protection required on the feed line and control cables to the shack?
A: Absolutely, Any connection leading into your house or radio shack should be protected. These arrays are no exception and should use suitable protection at the wiring entrance panel. There are many manufacturers of protection devices including ICE.
Q: Can I use a fiberglass pole element with a wire inside or taped to the outside?
A: Yes, by all means. The actual diameter of the element or wire conductor has very little affect on the signals received by the elements. It is important that the actual wire length used with a fiberglass element is the same for all elements in the array.
Q: Can I put the array near trees and brush?
A: Yes if the brush remains at least 5 feet away from the elements. Really tall trees will have a capacitive loading on the elements and may affect the array more. It is nearly impossible to simulate all the conditions. Tall trees should be at least 10 feet away from an element.
Q: Will the array overload my transceivers receiving antenna input?
A: There have been some cases of transceivers acting up as a result of the high levels of RF feeding back into the receiver while transmitting. This has been rare and specific to some 700 series transceivers. Lots of information is available about these transceivers with problems on the internet. The "front end saver" by KD9SV totally solved one problem and another was solved simply by a relay removing array power during transceiver keying. A third was solved with the ICE limiter product. The array output is internal circuitry limited at about S-9 plus 60 dB.
Q: Can the elements be elevated with a longer ground connection?
A: Extra length on the ground connecting wire is not recommended. It is best to keep the Hi-Z amplifier ground rod connection within 6 inches of the actual ground. The only exception that seems to work is if the array is mounted atop a woven fence where the fence wire itself becomes the real ground under each element.
Q: Can I use elevated radials around the elements.
A: Simple answer, NO! Oh and did I say NO? A sure way to mess an array up!
Q: Do the elements have to be exactly 20 feet long?
A: No, any length between 15 and 25 feet will work very well. The shorter elements will provide less signal on 160 meters but the patterns will remain the same. Longer elements may tend to overload the amplifiers with too much higher frequency signals. All elements must be the same length.
Q: Can I put a static discharge inductor on the elements?
A: No, this will totally disturb the phasing and impedance levels of the Hi-Z amp input. If you must use something, use a 10 Megohm 1/4 or 1/2 watt resistor on each Hi-Z amp input connection.
Q: Can I put this array next to my house?
A: Well maybe, It depends on if you can maintain at least 5 feet distance from non metallic siding. An array around a metal building will suffer some degradation. That being said, Dan, W5XZ has his array surrounding his brick type house in TX and has been very successful. Again, maybe it will work.
Q: Do I have to buy expensive connecting coaxial cable?
A: No, The only critical things about the cable is to use the element connecting cables all from the same spool and of the same length, and the delay cables must be measured accurately. If your location is exceptionally humid or you have a lot of rainfall you may want to use flooded cable to prevent moisture ingress which can damage the cable. For very long term installations it may make sense to use the flooded cable.
Q: Is this system waterproof?
A: No, you are on your own to cover or protect the controller and amplifiers from the weather. 1 Liter soda bottles work really well inverted over the Hi-Z amps and the local house wares dealer will have plastic enclosures. Using a controller container large enough to contain the phasing cables and the controller will insure that the cables will have a longer life.
Q: Will the system be improved by adding ground radials?
A: No, not in any case I am aware of. In the worst ground conditions I have recommended 6ea. 20 foot radials spaced evenly around the elements. Do not do this unless you have the worst rocky soil ever. Radials can cause unwanted phase shifts in the received signal deteriorating the performance of the array.
Q: Can I use cat5 cable for powering and switching the array directions?
A: Yes, up to about 200 feet distance between the power supply and the controller. The voltage must be maintained at the controller so that the system IMD performance will not deteriorate. Low voltage has been the cause of some broadcast interference in some arrays. Longer runs of cable can use 17 gauge sprinkler cable effectively. Array current draw is about 150 ma. An added preamp at the controller is about 50 more ma. for 200 ma total. Just remember that cat5 cable is designed for indoor use and will likely not survive long outdoors in the sun.
Q: What is the lowest voltage measured at the controller for proper operation.
A: I recommend no lower than +12.5 VDC with +13.8 VDC being ideal.
Q: Will I need any signal filtering in this system?
A: Maybe, It depends on a lot of factors. Most all arrays will need a preamp following the controller for use on 160 meters. If you have any close in A.M. broadcast systems you may see some receiver or preamp overload and a Hi-pass or band pass filter may be needed right after the controller. Higher IMD spec receivers may not need a filter. As the array has by nature, a greater output on 80 meters, some have noticed a bit less intermodulation during contests with a high pass filter installed. Hi-Z Antennas (tm) has both, Hi-Pass and a Band-Pass receiving only filters available and there are many others available such as the W2NQN series of designs.
Q: Will the array be influenced by my transmitting antenna?
A: Yes, it will. It is only a matter of degree. If your transmitting array is at least 200 feet away from any array elements the interaction will be mostly not noticeable. Only to the purists. Any closer and it will affect the front to back ratio drastically. Some form of transmitting antenna detuning during receiving can be very effective. Remember, this antenna is multi-band and what detunes on one band may make another band worse.
Q: Can the controller be mounted away from the center of the array?
A: Yes, The length of the element to controller cables is not critical and can be be purposefully made longer to facilitate moving the controller. All 4 connecting cables need only to remain the same physical length and from the same spool of cable so the delays are the same.
Q: Can I make the array smaller like 40 feet on a side?
A: Yes, but the 160 meter performance will suffer some. The need for dimensional accuracy gets greater and the phasing cables will become more critical in measurement. Also, the output signal level of the array will drop dramatically as the side dimension is reduced. 80 feet side remains the best compromise with a bit better 40-meter performance with a reduction to 60 feet. Increasing the side dimension to 100 feet will increase the array 160 meter output level but the 40-meter performance will suffer dramatically. Any close objects to a small spaced array will have a greater interaction than the wider spaced arrays.
Q: Will sloping ground affect the array?
A: From what I have been able to determine the pattern simply follows the slope of the ground. If the ground slopes up, the take-off angle slopes up, and vice versa. I think that ground level differences greater than 3 to 4 feet might not be the best, but I am not sure how one would measure this to know for sure. Sloping ground or not, the arrays still provide receiving improvement over a transmit antenna.
Q: Do I need to add common mode isolation protection to the array?
A: The Hi-Z amps have common mode isolation built into the circuitry. The controller is not generally grounded and so as of this time no one has seen any improvement as a result of adding common mode improvements.
Q: Do I need to switch the input grounding relays on the Hi-Z amps when transmitting?
A: To the best of my knowledge there has never been a case where this has been needed. The Hi-Z amp design is very robust and has been tested within 25 feet of a 160 meter transmitting antenna being fed with 2200 watts. There was no damage. It is my belief that the grounding relays are a good idea as the array has all the elements grounded when switched off. Just a little more static discharge protection during off periods.
Q: The array output specification is for 75 ohms. Do I need to transform my 50 ohm receiver to 75 ohms?
A; The array has been designed with an isolation amplifier that keeps any load discrepancies from affecting the array pattern. Generally, there has not been any problems reported, however one must realize that the array may see anywhere from 25 to 200 ohms as a result of the coax cable transforming the 50 ohms. If there were any IMD problems observed with the array one should consider making sure that the load impedance on the controller was at the 75 ohm level for the best performance. Hi-Z Antennas (tm) makes a 50 to 75 ohm transformer which will insure your array has its optimum performance potential.