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DIGISONDE-4D
SYSTEM MANUAL
VERSION 1.2.11
SECTION 2 - INSTALLATION, SETTING UP AND FIELD VALIDATION 2-5
struction. Other antennas or masts, such as GPS antennas, which do not have significant horizontal extent,
are probably not an issue as long as they are not inside the above described cone.
2:15. The receive antennas must be as far as possible from high voltage power transmission lines. It is diffi-
cult to be specific since the noise radiated from such lines varies tremendously. Certainly an antenna should
be at least 10 meters away from even the lowest voltage overhead power lines.
2:16.
It is likely that Arc Discharge lights, particularly those used for street lights, will generate considerable elec-
trical noise picked up by the Digisonde receive antennas. Arc discharge lights include sodium vapor, high
pressure sodium vapor, mercury vapor, metal halide, high intensity discharge technologies. It is difficult to
be definitive, but arc discharge lights beyond 150 meters will probably be ok. If there is significant interfer-
ence, LDI recommends removing such lighting. There is a trend among utilities to replace arc discharge
lights with more efficient , longer life, LED lights. According to the FCC all US manufacturers of such
lighting are supposed to meet FCC 15.107 and 15.109 standards, but such standards do not apply worldwide.
It is also possible that lights generating the electrical noise picked up by the Digisonde may be malfunction-
ing, and so may be operating outside of typical behavior. In any case, without acquiring further data LDI
can only recommend that any lights within 50 meters of the receive antenna field be incandescent or quartz
halogen. Further away LED lights may be reasonable. The best way to evaluate noise present at any poten-
tial installation site is to temporarily field the Digisonde without transmit antenna and observe the noise in
the data collected.
Antennas not on level terrain
2:17. Ideally, the area where the transmit and receive antennas will be installed should be flat and level. This
is more critical for the transmit antenna where one will encounter physical or mechanical problems if the
center of the antenna and the four corners differ more than a meter or so in height. The transmit antennas’
concrete foundation must be laid on level ground.
2:18. However the receiving antenna field may have a uniform gradient of up to 10. If the site is not level,
do not attempt to “flatten” the array by raising individual antennas (i.e., by extending the legs.) The receive
loop antennas should be installed at roughly (within 1/2 meter) the same height above the ground since the
performance of the antennas is somewhat dependent on the antennas height above the ground. After instal-
lation LDI will add "correction cables" to the higher antennas to electrically put the antennas in a horizontal
plane. To do this the measured relative heights of the antennas to 0.2 meters or so must be known. Then ca-
bles can be fabricated to be added the higher antennas of length 2/3 (assuming a cable velocity factor or 0.66
for RG213) the height difference between the higher antenna and the lowest antenna. Alternatively, the
short RG-58 cables between the lightening suppressors and the back of the DPS4D box can be shortened by
2/3 the height difference between the highest antenna and the lower antennas.
Lightning Protection
2:19. Surge protectors are fitted on all external cables (two Tx antennas, four Rx antennas, and GPS receiver)
in order to reduce the effects of lightning surge upon the sounder and ancillary items.
2:20. It is recommended the customer provide surge protection for all external connections, including power
and network interfaces.
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