Magnum Dynalab MD-108 - Manual (Page 12)

12
RECEPTION TECHNIQUES
Antenna Cabling:
The lead-in cable from the antenna is often the weakest link in the FM system. Some time
spent on selection and matching will yield dramatic results when it comes to noise reduction in
weak signals.
A good grade of 75 ohm coaxial cable will provide very sufficient signal passage, along with
effective shielding against interference. Without effective shielding your coaxial cable can in fact
become an antenna in itself. There are different grades of 75 ohm cable, there is RG59/U
(Suitable for 50 feet and less) and RG 6. RG 6 is the better of the two and should be used in runs
of 50 feet or more. The RG 6 has quad shielding and 50 % less losses than RG 59/U.
A good type of RG 6 is Beldon 1189 A. Combine this cable with LRC connectors and you
will have an installation that will optimize the performance of your tuner.
The key to maximizing the efficiency of the system is insuring that all connections are clean
and tight, silicon grease on outdoor connections will insure good performance over a long period
of time. If you splice either cable, make sure that exactly the same type of cable is used.
Types of Antennas:
Multi-element Yagi - This is a unidirectional antenna capable of pulling in very distant stations
due to its high gain, the higher the gain the better. These types of antennas are very directional
and should be used with a rotor to get the maximum benefit of the antenna. The directional
feature helps eliminate multi-path problems by allowing only the signal from the direction that
the antenna is facing to be picked up by the antenna and not the signals that come from a
different direction.
Magnum Dynalab offers two Yagi antennae, the MD 6 FM or MD 10 FM
Vertical ½ Wave - This design offers ease of installation and operation. This type of antenna is
omni-directional, which means that it picks up stations coming from all directions. No rotor is
required to pull in stations from behind or the side. This design also gathers more of the FM
signal from the air, offering superior fidelity over that of a standard bi-directional antenna. It
also gives 2.5 dB gain to the signal strength over that of a standard dipole.
If multi-path is a reception problem try laying the antenna down in the horizontal plane rather
than the vertical plane. This type of antenna can be used indoors or outdoors, but regardless of
whether it is installed indoors or outdoors the higher that you can put it the better it will perform.
Magnum Dynalab offers the MD ST-2, an excellent vertical ½ wave antenna
Folded Di-Pole - This is the most common and simplest of all antennas, most people are familiar
with the 79 cent piece of wire you received with most electronics gear (generally provided with a
tuner or receiver). This piece of wire is bi-directional and the performance of it is affected by the
angle that the signal hits the piece of wire. There are quite a number of di-pole antenna designs;
they work well in areas of strong signal strength, such as local stations.
Magnum Dynalab offers the SR-100 as a good folded di-pole.
There are many styles of antennas but all of them are based on one of these types.