Tuners Part 2: How to
Purchase an FM Tuner
Last month we looked at some of
the reasons why you might want to add a tuner to your system. This time out, let’s
take a closer look at some points to consider when you purchase a tuner. Prices for FM
tuners can range from a few hundred dollars for simple but good-sounding components, up to
a few thousand dollars for very high-quality units.
Cambridge Audio’s high-value T500 tuner
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Some discriminating listeners consider
analog tuners superior to digital or frequency-synthesized tuners, since they offer finer
adjustment of the frequency. Certainly, many of the costliest tuners are analog, while
most budget tuners use digital frequency synthesis. Don't be misled by the word
"digital" in this context: Conventional AM and FM radio signals are
analog, it is just that the tuning is done digitally by synthesized tuners in discrete
steps. These tuners also have the advantage of offering such features as scan, seek, and
station presets. And you should be aware that you can't always tell whether a tuner is
analog or digital by how the station information is displayed -- many analog tuners have
digital readouts, presumably because they are easier to read.
There are several measures of a tuner’s performance
that will determine its overall quality and its suitability for your use. Signal-to-noise
ratio is the measure of the difference between background noise and the maximum signal
strength. Poor signal-to-noise ratio will result in audible hissing and unwanted noise --
always present, of course, but most noticeable during quiet passages.
Sensitivity refers to a tuner’s ability to pull
in weaker stations. If you live in a rural area away from the transmitters of most radio
stations, the sensitivity of a tuner will be of great importance.
However, if you live in an urban area where the airwaves
are crowded with the transmissions of many radio stations, a tuner’s selectivity
will be of greater importance to you. There are two kinds of selectivity: adjacent channel
and alternate channel. Adjacent channel selectivity refers to a tuner’s
ability to reject interference from the channels directly adjacent to the one being tuned
while alternate channel selectivity refers to the ability to reject interference
from stations two channels away.
Almost every tuner will have a signal strength meter
and a stereo/mono switch that can be set to mono to reduce noise when
receiving very weak stations. Better tuners will have an intermediate frequency (IF)
bandwidth control that can be set to either wide or narrow. Setting the IF bandwidth
to narrow will improve the audio quality, but will decrease both the sensitivity and
selectivity. This setting is used for the best possible sound quality when a strong signal
is present with very little interference from other stations.
Good tuners will also have a multipath indicator.
Multipath is the condition that exists when a tuner receives, in addition to a signal,
delayed reflections of the same signal from mountains, large buildings, or other
obstructions, which will degrade the sound quality. A multipath level meter can be used to
orient your antenna to minimize the amount of multipath that your tuner encounters.
A final consideration when planning a tuner purchase is
that you will need a good antenna. Hooking up the coaxial antenna input of your tuner to
the cable system will not allow you to realize the full potential of your tuner, since
most cable companies compress FM radio signals on their systems. Also take note that a
directional antenna is required to compensate for multipath problems. Good-quality
antennas can be purchased for as little as $20 or $30, while much better, more directional
antennas can cost as much as several hundred dollars.
We asked Vince Stables of Magnum Dynalab, a
well-respected manufacturer of FM tuners, a few questions to get his expert opinion.
GS: What is the most important aspect
of (FM) tuner performance for most buyers?
VS: An FM tuner is not like any other
component in your system. It must grab signals from the air that are being broadcast from,
sometimes, great distances. Then, it must filter out the noise from the true FM signal.
Also, it must filter the station next to the station that you are listening or tuned to.
Adjacent channel rejection is often a specification that is no longer published, yet it is
one of the most crucial of them all. A tuner’s ability to hone in on a signal and
reject the neighboring stations requires extreme precision, especially for those who live
in a large metropolis, such as New York or Los Angeles, where the airwaves are extremely
polluted with RF information. Another problem is posed by high-rise apartments, where you
might lock onto -- let’s say -- 91.1 FM NY, yet your antenna may also be picking up
information from 91.1 from Connecticut. You can see where problems can arise.
Magnum Dynalab’s MD 90 analog FM tuner
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Many tuners will compress or limit their
bandwidth, which increases selectivity and sensitivity, which gives the appearance of a
cleaner signal. However, you lose bass extension, as well as high-frequency extension.
GS: Does good tuner sound depend on
where the buyer lives or is it a combination of other factors?
VS: I think the geography is very
important. The customer needs to understand what is happening in his or her particular
environment. What is the signal strength coming in to their tuner? Is there multipath
present? Is there a humungously powered teeny-bopper station broadcasting at 15 trillion
watts right next to your favorite college jazz station?
You must understand your geography with a tuner so that you
can make a very important decision about the type of antenna system you will use with it.
This is extremely important, since the antenna is your first point of contact, much like a
turntable cartridge.
GS: Why should someone invest in a
quality tuner?
VS: FM is a wonderful medium that gives
you free access to extremely good music that you wouldn’t necessarily be exposed to.
Also, FM, done properly, can quite easily rival the sound quality of a decent CD player.
However, most people’s exposure to decent FM reproduction is limited. Most tuners are
an afterthought -- something that simply completes a package of electronics. The purchase
of ANY component must be made because it is better! My most important piece of advice to
anyone purchasing any component, not just a tuner, is to make a serious attempt to take
that piece home and try it in their own system. This is the only way to understand what is
occurring with the match of electronics, as well as with the environment.
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