RDT RM96xx Installationsanleitung PDF herunterladen (Seite 3)

Site Survey

It is advisable to carry out a survey to establish a good radio path prior to installation. This

will help with the positioning of the equipment and choice of antenna. Your distributor

should be able to assist with information and may be able to provide a Survey Kit and

antennas.

Before commencing a survey, measure or estimate from a map, the straight-line distance

between the two sites. From the tables on page 9

, check which type of antenna would be

needed to cover the required distance. Visit the sites to see if there is a suitable location

for equipment and the antennas, normally on the roof of the building. It should also be

possible to see if there is a reasonable line-of-sight between the two locations or if there are

any significant obstructions (see Technical Notes). A pair of field glasses may be useful if

the sites are some distance apart.

Make a temporary installation of a camera and transmitter. Note: battery-operated

equipment is available for this purpose. Position the antenna and leave the equipment

running. At the receive site, set up the receiver and monitor. Position the antenna and

adjust its position to get the best picture quality. If the picture quality is not good, try

moving the antenna to other locations. Performance will be affected by obstructions or

metal objects nearby. Even the antenna mounting pole can cause a problem if the antenna

is not correctly mounted clear of the pole. For longer distances, it may be necessary to use

a high gain antenna on the receiver site.

Note: High gain antennas are directional and must be aimed at the transmission site and

then adjusted by rotating until maximum signal strength is achieved. The POLARISATION

of both antennas must match. For example, if the transmitting antenna is vertical then the

receiving antenna must also be vertical.

If the signal strength is too low it may be increased by raising the height of the transmit

antenna, receive antenna or both. Care must be taken, however, because there will be a

loss of signal in the cable and connectors. For the actual installation, a good quality low-

loss cable should be used between the antenna and the VideoWave units (i.e.LMR400).

Alternatively, the VideoWave unit can be housed in a weatherproof enclosure and mounted

on the pole near the antenna.

If the picture quality is poor, even with reasonable signal strength, this may be due to

interference. Remember that this is a license free band and other users could be

transmitting in the area. If interference is suspected, try turning off the transmitter and

checking the LED on the receiver. This should be RED and not GREEN or flickering

RED/GREEN. Also look at the monitor, which should just show a clean screen with no

patterning. If there is interference, try moving the antennas.

Figure 3

Figure 3 shows the most common connection diagram for setting up a simple wireless

video link using the VideoWave system.

Installation

For this section, it is assumed that the equipment has been bench tested, is working

correctly and that a site survey has been completed. If not, carry out these tests before

beginning the installation.

Transmitter

Start by installing the transmitter in the required location. The transmitter can either be

located inside or outside, if it is housed in a suitable weatherproof enclosure. (See page

11)

Connect the antenna. For short-range operation the standard Patch or ½ Wave whip

antenna can be used, fitted directly to the transmitter. For greater distances a Dipole or

12dB patch should be selected. These will require external mounting on a suitable pole

(see page 7).

Note: 1/2 Wave Whip antennas are not weatherproof and therefore not really

recommended for external use.

Generally, the higher the antenna, the better the radio performance. It should be noted

however that there will be a significant loss of signal in the antenna cable if it is too long.

The recommended cable is LMR400, which has a loss of approximately 0.2dB per metre.

There will also be a small loss of approximately 0.2dB for each connector.

Using these figures as a guide, the recommended maximum length of antenna cable is

about 5 metres, which equates to a loss of about 1dB. This will reduce the effective

radiated power, but will have little effect on the actual distance achieved. Raising the

antenna height has a much greater effect than changing the radiated power.

If it is necessary to mount the antenna even higher, to clear a building for example, then a

higher gain antenna can be used to compensate for the loss in the cable. If possible, it may

be better to house the transmitter in a weatherproof enclosure and mount the unit close to

the antenna.

Install the camera in the required position and connect to the transmitter using a 75 ohm

coax cable. Connect the power to both units.

Before leaving the transmitter site, if possible, check that the unit is working correctly using

the receiver unit connected to a monitor. It may be necessary to adjust the camera view or

lens iris to obtain the clearest picture.

To 12V DC

Adaptor

To 12V DC

Adaptor

Video Camera

Video Monitor

Transmitter

Receiver

1 2 3 4 5 6 7 8

VideoWave 1.4GHz 1

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