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7
ANTENNA INSTALLATION
7.1
MOBILE ANTENNA INSTALLATION
7.1.1
Install the Mobile Antenna
Table 4-4 (page 25) lists the mobile antenna available for M5300 and M7300 mobile radio motorcycle
installations. This antenna is a voltage/end-fed high-impedance antenna that provides the proper VSWR
and radiation pattern without the use of a ground plane. Typical antenna gain without a ground plane is 0
dBd.
The following mobile antenna installation procedure is recommended:
1. Review the information presented in Section 1.2 (page 6), taking note of the Recommended
Minimum Safe Lateral Distance for Controlled Environments presented in Table 1-1 (page 8).
2. Verify the antenna's mounting location on the triangular-shaped end of the Case/Antenna Bracket
places the motorcycle operator outside of the Minimum Safe Lateral Distance for Controlled
Environments. If it does not, the bracket(s) must be repositioned on the motorcycle. If necessary,
contact the Technical Assistance Center. See page 19 for TAC contact information.
3. Mount the antenna in accordance with the instructions supplied with it.
4. Calculate the required antenna coax cable length using the information presented in the following
section.
7.1.2
Calculating the Antenna Cable Length
Typically, an antenna coax cable length of at least 32 inches will be required to reach from the base of the
antenna to the TNC RF antenna connector at the rear of the radio. This length includes appropriately 6
inches for a service loop inside the case. To calculate the proper antenna coax cable length, proceed as
follows:
1. Determine the center frequency of the majority of programmed transmit channel frequencies.
2. Use the following formula to calculate the ¼-wavelength, in inches:
Example: Assume the customer has a radio with all transmit frequencies between 816 and 821 MHz.
Therefore, the center frequency is 818.5 MHz. Applying the above formula results in:
3. Calculate the ½-wavelength by multiplying the ¼-wavelength by 2:
Since the antenna is a high-impedance, voltage/end-fed antenna, the length of the
coaxial cable from the base of the antenna to the radio's TNC antenna connector
is critical. It cannot be an arbitrary length. To prevent possible extraneous radiation,
high VSWR, RFI feedback from the antenna to the radio, or antenna ground currents,
select an antenna coaxial cable length that is close to a multiple of an odd quarter-
wavelength. Refer to the following information for details on calculating the correct
cable length.
¼
in
inches
¼
in
inches
Example: = 3.43 x 2 = 6.86 inches
2805
Frequency
in
MHz
2805
= 3.43 inches
818
5 .
MM-015371-001, Rev. C
37
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