Mobile antenna
A distinction is made between tuned and tuneable antennas. Tuned
antennas should only be mounted on a great metallic surface, as
for example on the roof of the vehicle or the trunk lid, assuring a
short connection to ground. For an antenna which must be fixed
by drilling a hole into the car body, the body sheet must be tho-
roughly smoothed in order to assure a reliable positioning of the
fixing screws and the sealing washer! Be careful not to bend the
coaxial cable or to damage it otherwise by positioning it on sharp
edges (for avoiding the risk of short-circuits!).
Antenna for stationary radio sets
When using a stationary antenna, the maximum range of your
radio set is achieved. For outside antennas, the relevant regulations
of the German VDE (Association of German Electrotechnical
Engineers) (with regard to lightning protection!), of constructural
statics and of the building code have to be considered by all means!
In this case, we recommend you to have the antenna system
installed by an expert!
Please refer to the stabo accessories for a comprehensive range
of stationary antennas.
Adjusting the antenna
You should not transmit without antenna under any circ-
umstances, since this can result in a destruction of the radio set.
Adjusting the antenna means that your antenna is adjusted to the
output resistance of the transmitter, i.e. to 50 ohms.
The actual characteristic antenna impedance depends on its length
and on its environment of installation. For this reason, the manu-
facturer can only provide you with a roughly tuned antenna. Nor-
mally it is designed such that there is always enough scope left
for adjusting it to the given conditions. In practical operation, this
means that a new antenna is usually too long.
For adjusting the antenna, a VSWR bridge (e.g. President TOS-
1, article no. 50004) is connected into the circuit between the stabo
xm 5003 and the antenna and the antenna is shortened or elon-
gated according to the manufacturers information such that the
VSWR on your preferred channel or one of the median channels
is as small as possible. For this, set the radio set to FM modulation
to work always with a constant transmitting power when measuring.
In any case, a value of < 1:2 should be achieved. For mobile
operation,it does not make much sense to adjust a value of 1:1
by all means, since this value can always be modified again due
to different environments, cable modifications etc. However, we
recommend you to check the adjustment regularly, because an
unfavourable value points to connector and cable problems.
Power supply
A direct voltage of 13.2 volts max. is supplied to your radio set
which is equipped with a reverse voltage protection.
However,
before switching it on, check the device for correct polarity!
The nominal supply voltage amounts to 13.2 V and must not exceed
15 V in any case.
24
