Yaesu FT-900 Operating Manual page 37

Operation
Before You Begin .....
The suggestions and descriptions concerning
packet TNC interconnection and operation are in-
tended to be general, and do not encompass all
aspects of the hardware, software and operating
techniques used in this highly popular mode.
There. is a wide range of TNC units available on the
market. Audio data wiring, plugs, connectors and
operation o ften varies between manufacturers,
and in some cases between models of the same
company. While in some cases "plug-in and play"
operation is as simple as that, m<:>st TNC intercon-
nections and digital operation requires familiarity
with your particular TNC and patience (you will
probably have to solder a few wires to make a
patch cable).
Before "diving in" to digital operation, we recom-
mend thoroughly reviewing the documentation
provided with your TNC and with the FT-900. Un-
derstanding the audio 1/0 data flowpath between
transceiver and TNC as well as the connector
pin-out wiring is important. This will save you from
much of the headaches and frustration associated
with "hit-and-miss" cable patching and "trial-and-
erro(' operating.
If you are uncertain, don't be afraid to ask lor
assistance before you begin! Although your dealer
may
not have connection data for every TNC on
the market, he can guide you to many amateur
clubs and user-groups that can be contacted for
assistance.
Transmitter Adjustment
Press the AGC button for fast AGC, and the SSB
mode button for LSB (normal shift). The display shows
the suppressed carrier frequency, so bear in mind that
your actual transmitted signal is offset below the dis-
play by the (audio) frequency of the AFSK tones gen-
erated by your T U.
Before transmitting the first time, preset the RF
PWR control to about 12 o'clock, and unplug the
microphone. Select ALC level on the meter display
and then key the transmitler from your keyboard. Ad·
just the MIC GAIN control if necessary, lor a level that
gives less than mid-scale indication on the meter. Now
you can adjust the RF PWR for the desired power
output.
Note that for AMTOR and F1 packet operation, you
must have the
vox
button off (- ) for fast trans-
mit/receive turn -around.
Frequency Display & Tuning
As mentioned above, the transceiver displays the
suppressed carrier frequency, from which you must
subtract the audio frequency of your TU's or TNC's
AFSK tones to find the actual operating frequency. For
example, if your TNC uses 1600- and 1800-Hz tones,
you can subtract the difference ( 1700 Hz) from the
display to find the actual center frequency of your
transmitted signal. Also, you want to center your re-
ceiver audio passband at ' 1 700 Hz, so you need to turn
the SHIFT control counterclockwise to about the 11·
o'clock position (the normal SSB passband is cen-
tered about 1500H z away from the carrier frequency).
Of course, if your TNC or TU uses higher-fre-
quency tones, you have to shift the passband fu rther.
Example: You want to have a packe t QSO with a
station who has told you they will be on 14.1013 MHz
(sometimes called the old ''14.103" according to the
Transmitter AF Input Relationships
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UP
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DOWN
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Modular Microphone Jack
Pin-Out Connections
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