Hammarlund FM50A - Installation and Cable Connections

NOTE: In lieu of the use of a 10.7 MC signal, L10S may be adjusted in the center of the
range over which quieting sensitivity falls off. It is extremely important when making
this adjustment that the incoming signal be on frequency.
9. (b) Perform step 6(a) above.
CABLE INSTALLATION
Certain precautions must be observed when installing the FM-50-A. It is very important
that polarity be observed on vehicle installations. Using the power cable chart, at the rear of
the manual, first, determine which cable is to be used. In most installations, you will find that
modern vehicles employ a 12 volt negative ground system, therefore, be sure to use the cable
required for 12 volt negative ground installations. If the vehicle is a positive ground system be
sure to use the 12 volt positive ground cable, etc.
New vehicles will generally be no problem so far as polarity is concerned. On older
vehicles, the best policy is to use a volt meter and check the battery voltage and polarity before
proceeding with the installation. Experience will generally tell you what the voltage and polarity
of the various make and typ;! vehicles in the field are.
It is extremely important that polarity and voltage be observed because if the polarity is
accidentally reversed, you will, almost without exception, burn out at least one of the power
transistors. TO PREVENT BURNING OUT POWER TRANSISTORS, OBSERVE VOLTAGE AND
POLARITY.
Once the proper cable has been installed in a vehicle, the FM-50-A receiver-transmitter
unit may be exchanged or inter-changed throughout the fleet with no modification or switch
selection required.
COMMUNICATIONS UNIT INSTALLATION
There are generally three or four different ways that the unit may be mounted in the cab
or in area that is accessible to the driver. In most business and industrial applications, it will
be found that it is most desirable to locate the receiver-transmitter somewhere in the cab of
the truck or the front seat area of the vehicle. This has the advantage of short battery cables
with less voltage drop and less chance of abrasion and wear.
Floor Mount: Using the FM-50-A receiver-transmitter as a pattern, place it on the floor of
the vehicle and various locations until the most convenient location is found. The best location
will be one where the driver can tell at a glance whether his set is on or off and where he can
reach the controls on the front panel. When setting up this location, be sure to give considera-
tion to the length of the battery cable. Mter the location is found, secure the universal mount-
ing bracket, Hammarlund Part No. PL26610-Gl. When drilling through the floor of a vehicle,
or through any other panel or part of it, use every precaution to avoid drilling through a gas
line or electrical wiring, etc. Wherever it is not possible to use nuts and bolts, drill with a
proper size drill for self tapping screws and, using a good long screw driver, drive the steel
screws firmly into place. Always fasten parts securely to the vehicle to avoid noise from
"shaky" installation.
Under-Dash Mount: Using the radio as a template, find the best location under the dash of the
vehicle. Take into consideration, special handles found on dump trucks and controls found on
various types of vehicles in the field. Mter a practical location is found, secure the universal
mounting bracket in place with the proper hardware. Use every precaution to make the battery
cable as short as possible and route it in such a way that it will not interfere with the various
-9-
FREE DOWNLOAD COURTESY OF N9SOR WWW.HAMMARLUND.ORG