[KYHAM] KEN TRAINING For Jan. 7, 2002: FM and Repeater Operation Facts and Fallacies

[Ron Dodson]

Hope everyone had a great holiday season!  As promised, we
are starting a series of "HOW TO" type articles.  This one
is from Tony, KC4JTV in Area 5. He is a 2-way radio tech for
KSP in his paid capacity.  Many newer amateurs will probably
really enjoy and benefit from this one.

BTW, I am always open to more "How To..." articles for
future weeks.  So far, we have 12v and Generator Power
Supplies, Command Post Design Considerations, Command Post
RFI Problems and Mobile Radio Installations. Got an idea or
field that might benefit our ARES members??? Write it out
and send it to me.

73,
Ron, KA4MAP
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A Basic Overview of FM and Repeater Operation: Facts and
Fallacies
By Tony Whobrey, KC4JTV

 Not too many years after Edwin H. Armstrong initially
tested FM modulation for broadcast use on June 9, 1934, FM
radios were used for military communications during World
War 2. Due to the success of this use, nearly all commercial
land-mobile users soon implemented FM. The ease of operation
and relative freedom from interference of the new FM radio,
as compared to the AM equipment previously available, was
considered a near miracle. Soon most public safety and
service vehicles were equipped with FM radios operating in
the 25-42MHz (now 30-50MHz) range, known as �low band�.
Two-way radios were considered cutting edge technology, and
many taxicabs, tow trucks and public utility vehicles
sported 6-foot whips and the now nostalgic words �radio
dispatched� on a door or fender.

 When low band became crowded, a new allocation of 150 to
174 MHz, just above the 2-meter amateur band, was unveiled
with the understandable name of �high band�. Subsequently, a
UHF band was also established, then covering 450 to 470 MHz.
Mobile to mobile simplex range on both high band and UHF
left much to be desired, and the eventual solution was the
�mobile relay� station; a.k.a. repeater. The now ubiquitous
repeater was an instant hit, with both commercial and
amateur radio users.

 The combination of FM and repeater operation is arguably
one of the best happenings in amateur radio�s recent past.
With the availability of surplus �high band� equipment in
the late 60�s, more 2-meter amateur repeaters began to
appear. Some 35 years later, nearly every community with a
population of more than a few thousand is within range of at
least one amateur repeater, with some larger communities
having several. For this reason, the first radio used by
many new licensees is often an FM transceiver on the 2-meter
band. You can make your operation via a repeater far more
enjoyable, with attention to a few often-overlooked
essentials of repeater operation;

The repeater doesn�t recognize that you are on a handheld
radio. - If you use a portable radio, you may soon discover
that you can hear the repeater much better than it can hear
you, unfortunately, this is a normal condition. Most modern
portables have excellent receivers that will hear a
repeater�s powerful transmitter at distances that their own
small transmitter can never equal. A good rule of thumb for
portable operation; If you hear any noise at all on a
repeater�s signal, it probably can�t hear you well, if at
all.

In FM operation, louder isn�t always better. -  If you are
asked to repeat a transmission, resist the urge to speak
loudly. This can be a hard habit to break, as it would seem
to defy logic. In fact, an FM signal will lose apparent
strength as the deviation increases, since its power will
spread out over a larger bandwidth. Speaking in a thunderous
voice will actually decrease your signal�s effectiveness in
most cases.

Limit background noise when possible. - With rare exception,
contemporary ham radio equipment will have more than enough
microphone gain. Newer transceivers tend to have very
sensitive microphones, which can pick up your CD player, air
conditioner blower or the conversation of anyone nearby as
readily as your own voice. This can make your signal
somewhat less intelligible than it should be, and thus can
mark you as a less experienced operator. If you consistently
get reports of �wind noise� in mobile operation, you have
far too much mike gain; a small piece of foam placed in
front of the microphone element will often eliminate such
problems.


Every repeater has its own personality. - A repeater will
reflect the philosophy of its keeper, to some extent. You
will, of course, have to determine the input frequency of
the repeater you wish to access; only a few are
non-standard. Some require that a specific sub-audible tone
(CTCSS tone) be transmitted to access the repeater, while
others don�t require one. Some repeaters will deny access to
anyone using a tone, while working fine for those who don�t
use a sub-audible tone. All repeaters in amateur service are
required to limit any single transmission�s continuous
access to a maximum of 3 minutes. The method of recovery
from such a timeout varies, some require that the repeater
transmitter be allowed to un-key, while others reset when
the receiver squelch closes. If you have questions about a
particular machine, don�t be afraid to ask the trustee or
one of the more experienced users.