Microair Avionics M760 Transceiver Installation & User Manual
760 install & user manual ver N Page 9 of 24 8
th
December 2003
4.4.1 Metal Skin Airframes
For metal skin aircraft a ¼ wave whip is the easiest antenna to fit. Ensure that the antenna base and the
coax shield are firmly grounded to the skin of the airframe, on the inside of the aircraft. Ensure that any
anti-corrosion product, which may be used to seal the exterior surface, does not isolate the antenna base
from the airframe. For best performance the whip should be straight and vertical, when mounted on the
airframe.
4.4.2 Non-Metal Skin Airframes
For non-metal airframes, a ¼ wave whip may still be used, but a ground plane must be installed, on the
inside face of the aircraft skin. The ground plane should ideally be circular, and have a diameter of half
the height of the whip. The ground plane should be fabricated from a lightweight metal, eg thin
aluminium sheet, or adhesive foil tape. For best performance the ground plane should be flat and
horizontal, when mounted on the airframe.
An alternative antenna for non-metal airframes is the Ground Plane independent dipole. This antenna is
physically similar to the ¼ wave whip, but has a small stubbie antenna pointing downwards from the
antenna base. The stubbie section of the antenna takes the place of the ground plane, and simplifies
installation.
Beware of fabric surfaces with silver dope finishes. The silver dope is a conductive surface, and with
screen antennas which are mounted internally.
4.5 Backlighting
The backlighting is activated, by taking input supply voltage to pin 8. This line can be individually
switched outside the DB15 connector to enable the backlighting to be turned off.
If the backlighting is wired but not switched, the backlighting will come on when the master switch is
turned on. The aircraft may be started with the radio off, but with the backlighting active, without the
possibility of injury to the radio.
The backlighting line from pin 8 may be taken to a dimmer. The backlighting consists of 4 LED’s behind
the LCD display which operate on 1-14 volts. The backlighting cannot be seen below 3 volts.
4.6 Power Savings
For installations, operating from a battery only, Microair recommends saving battery power by NOT
wiring the backlighting – do NOT wire pin 8. The backlighting will draw an additional 80mA of power.
This nearly doubles the standby power demand.
Not connecting the backlighting can effectively double the running time on your battery.
The operator should remember that the minimum operating voltage is 10 volts. This is the loaded voltage
(ie the voltage when the radio is transmitting). For battery operators, check the battery voltage level, then
press the PTT briefly to note the voltage drop. If the voltage dips by more than 0.5 volts, change the
battery before flying.
