User's Manual

MDS 05-3627A01, Rev. D LEDR Series I/O Guide 11
Invisible place holder
Figure 7. Typical Grid Dish Antenna
Table 2 lists common grid dish antenna sizes and their approximate
gains. Note: Each antenna is designed to operate within only one fre-
quency band.
MDS can furnish antennas for use with your LEDR radio. Consult your
sales representative for details.
Feedlines
For maximum performance, a good quality feedline must be used to
connect the radio transceiver to the antenna. For short-range transmis-
sion, or where very short lengths of cable are used (up to 8 Meters/26
Feet), an inexpensive coax cable such as Type RG-213 may be accept-
able.
For longer cable runs, or for longer-range communication paths, we rec-
ommend using a low-loss cable suited for the frequency band of opera-
tion. Helical transmission lines, such as Andrew Heliax
™
or other
high-quality cable will provide the lowest loss and should be used in
systems where every dB counts. Whichever type of cable is used, it
should be kept as short as possible to minimize signal loss.
Remember that cable loss increases in direct proportion to the transmis-
sion frequency used. This means that a system operating at 900 MHz
will experience more cable loss than one operating at 400 MHz.
Table 2. Dish antenna size vs. approximate gain (dBi)
Antenna Size
Meters (feet)
400 MHz
Gain
700 MHz
Gain
900 MHz
Gain
1400 MHz
Gain
1.2 Meters
(4 feet)
13.1 dBi 15.85 dB 18.4 dBi 23.7 dBi
2.0 Meters
(6 feet)
16.3 dBi 19.05 dB 22.0 dBi 26.1 dBi
3.0 Meters
(10 feet)
19.6 dBi 22.35 dB 26.4 dBi 30.6 dBi
4.0 Meters
(12 feet)
22.2 dBi 24.95 dB 28.0 dBi 32.1 dBi