174BARRETT 4050 HF SDR TRANSCEIVER - OPERATING AND INSTALLATION MANUALGround (Earth) SystemThe ground (earth) system is a key part of the overall antenna system and con-sequently the system operation. An inadequate ground system is the primarycause of poor performance and tuning problems. There is little point in install-ing the antenna unless a good ground system can be provided. In areas ofgood ground conductivity (i.e. ground always damp), an effective ground canbe made through a grounding rod. This should be approximately three metresin length and should be installed as close to the tuner as possible. Several rodsbonded together will improve the ground contact. In some cases metal waterpipes may be used as a ground providing:• The water pipe is close to the tuner and the water pipe enters the groundclose to the tuner.• There are no joints or couplings in the pipe that will increase the resist-ance path to ground.• The water pipe enters soil with good conductivity.• A low resistance joint is made with the water pipe.)UHTXHQWO\WKHJURXQGFRQGXFWLYLW\ZLOOQRWEHVXIÀFLHQWWRSURYLGHDVDWLVIDF-tory ground for the Barrett 911 tuner. This will almost certainly be the case inwell drained sandy soils or on rock. In these cases, a counterpoise must be usedas a ground system. This will also be the case in rooftop installations where noH[LVWLQJJURXQGSODWH VXFKDVPHWDOURRÀQJH[LVWV The number of radials required for an effective counterpoise depends on thesoil quality, dampness and other factors which affect the conductivity of thesoil. The more radials used, the better will be the performance of the antenna/ ATU combination especially at lower frequencies. This manual suggests aminimum of 20 radials, but optimum performance at low frequencies is notguaranteed.The radials of the counterpoise need only be of much thinner cable i.e.5.48mm 2 (#1 #2 SWG) preferably copper wire. RG58 Coaxial cable may beused. At the base of the antenna, the radials all couple together at a commonwell bonded antenna ground point. The radials should be buried into theground to a minimum of 200 mm depth.Note: To accomplish reliable ATU tunes at frequencies below 5 MHz, it is notuncommon, with poor conductive soil conditions, to require up to 120 radials eachof up to 70 m length, requiring thousands of metres of cable and a lot of trenching.This is impractical and is the reason we do NOT recommend Whip / ATU antennafor land based systems.
