|
A Guide to FM Reception
(cont.)
by Dave
Downing
What
is FM Radio | FM's Strengths |
FM's Weaknesses | Why
Reception Quality Varies | Multipath
Distortion | Interference |
Receiver Overloading | Docket 80-90
| Antennas for FM Reception
A good test for receiver overload is to tune up
and down the dial looking for signals that shouldn't be there. A station on
106.7 should not show up on, say, 96.4. Also, look for "stations"
that seem to be playing multiple programs on top of one another. These are
sure signs of an overloaded receiver.
You may find that some radios overload where
others do not. One receiver's dynamic range may be different than another;
the greater its dynamic range, the less prone a receiver will be to
overloading. Now I'm not talking about audio dynamic range here;
I mean radio frequency dynamic range; this is
not something the average hi-fi store salesman is likely to know anything
about. In a perfect world, receiver manufacturers would advertise their
products' RF dynamic ranges and you could shop for a radio that
best meets your needs. Unfortunately, however,
no one advertises such a specification, nor do consumer product testing
organizations test for it.
The FCC rulemaking I mentioned, however, is
another matter. It is called Docket 80-90, and it came about when the
Federal Communications Commission decided in the early eighties to authorize
the construction of more than a thousand new FM stations across the United
States. If it weren?t for this FCC ruling WLNZ would not be on the air.
This ruling opened up a place where our frequency could be used in Lansing
where before it was not possible. However, the ruling allows for increased
interference levels for all stations on the air, including WLNZ. So the
further you get away from the transmitter location in downtown Lansing, the
more likely you will get interference from signals of other stations.
In most cases the best antenna is an outdoor,
roof-mounted directional antenna called a Yagi-Uda after its Japanese
inventors, or "Yagi" for short. These are available at Radio
Shack, among other places, and their advantage lies in the fact that they
are particularly sensitive only in a single direction, which means you can
point a Yagi in the direction of an especially strong signal and the antenna
will discriminate against other signals or reflections arriving from
different directions. This antenna is a powerful weapon against multipath
problems and interference. It is the universal choice of professionals in
the background music industry who often use FM radio stations to distribute
music to stores and businesses. We have heard from many listeners that have
used the small FM antennas available from such electronic stores like Radio
Shack at their homes which have helped in reception of WLNZ on their home
stereos. These listeners live in communities such as Mason, St. Johns, and
as far away as Laingsburg.
Many listeners cannot use outdoor antennas, and
the most common indoor antenna for high-fidelity receivers is the folded
dipole, which is a piece of insulated wire shaped like the letter T. These
antennas are directional in that they most efficiently receive signals
approaching their broadsides. Signals approaching from the direction of
either end of the T are normally discriminated against; however, if this
type of antenna is used indoors, human bodies or metallic objects nearby
will largely negate this property.
Dipole antennas are most effective in
wood-frame buildings; if they are used in concrete and steel buildings,
which tend to block radio waves, the antennas should be mounted as close as
possible to a window.
Whip antennas such as those on many portable
radios behave much like dipoles; like them, they perform best outdoors or in
wood-frame buildings away from human bodies or other electrical conductors.
Some radios use their AC power cords as
antennas, and most Walkman-style receivers use the cords of their
headphones. These antennas cannot always be placed optimally, so they are
not as desirable.
WLNZ is limited by the FCC in the output power
of the transmitter. Some of these suggestions might help your reception, but
in the outlying areas surrounding Lansing there just might nothing that can
help. There is on-going research to determine the possibility of increasing
our power, but for the foreseeable future, the current situation will
remain. On the "plus" side WLNZ has one of the strongest signals
in the downtown Lansing area. Also, remember, before WLNZ there was a void
when it came to jazz, blues and the diverse weekend programs now heard on
89.7FM. With listener support we have come a very long way in the first five
years of being on the air?and we look forward for the next five years to
be just as rewarding.
What
is FM Radio | FM's Strengths |
FM's Weaknesses | Why
Reception Quality Varies | Multipath
Distortion | Interference |
Receiver Overloading | Docket 80-90
| Antennas for FM Reception
Make
WLNZ your start page
|
LISTEN
LIVE!
