FT-920 Operating Manual
56
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For Packet operation, you may leave Menu #
U-46 in its default
2125-U (pseudo-USB
mode), or set it to
1700-U or some other value
as required by the configuration of your TNC.
See the documentation provided with your
TNC’s communication software for details re-
garding defining the transmitted tones.
The packet frequency display (offset) may also be
modified via Menu # U-45, allowing you to have the
radio’s display indicate either Mark or Space fre-
quency, or the center frequency of the two tones.
At this point, you are ready to utilize your TNC’s
software to begin operation. After loading the soft-
ware, tune in an RTTY station so that it is properly
decoded on your computer screen. When solid
copy is obtained, you may press the appropriate
key on your computer’s keyboard to activate the
transmitter, and begin typing. See your TNC’s in-
struction manual for further details regarding ac-
tual operation.
The DSP High- and Low-Cut filter are particularly
beneficial in reducing interference in RTTY pile-
up situations. A typical setting of the H
IGH
C
UT
con-
trol is at approximately 1 o’clock, while the L
OW
C
UT
control may be set approximately to 11 o’clock.
The CW Narrow filter may also be used for AFSK
operation. Just press the [N
ARROW
] switch, then
rotate the S
HIFT
control to peak the signal in the
narrowed IF passband.
Via Menu # U-10, the Enhanced Tuning Scale may
be engaged so as to allow a visual representation
of precise tuning pursuant to the tone frequency
selected via Menu # U-46. However, since your
TNC may also have such a facility, and because
the TNC is ultimately in control of the tone gen-
eration and decoding, you may wish to rely on the
TNC’s tuning indicator, and use the Enhanced
Tuning Scale of your FT-920 for other purposes.
For 1200 bps FM packet, press the D
ATA
key until
D
ATA
and FM appear on the display.
FSK RTTY Operation
This mode utilizes the tone generator in the FT-920
for production of the required Mark and Space tones
used for RTTY operation.
Follow the interconnection guidelines on page 17
for details on how to hook up your terminal equip-
ment to the transceiver. Be certain to set the
AFSK-FSK switch on the rear panel of the trans-
ceiver to FSK. In this mode of operation, closing
Pin 1 of the D
ATA
jack to ground causes the car-
rier to shift; the magnitude of the shift (170/425/
850 Hz) is set via Menu # U-43, while the carrier’s
offset from zero beat and its sideband (USB/LSB)
can be set via Menu # U-42. Do not connect Pin 1
of the D
ATA
jack to any TNC/TU line which carries
“M
IC
A
UDIO
” or “T
X
A
UDIO
” as these lines are used
for AFSK operation (see previous section).
Press the front panel [D
ATA
] key to select the [D
ATA
]
[LSB] mode, which corresponds to “FSK” opera-
tion (remember, “D
ATA
USB” is used for “AFSK”
operation).
At this point, you are ready to utilize your TNC/
TU’s software to begin operation. After loading the
software, tune in an RTTY station so that it is prop-
erly decoded on your computer screen or TU dis-
play. When solid copy is obtained, you may press
the appropriate key on your computer’s keyboard
to activate the transmitter, and begin typing. See
your TNC/TU instruction manual for further de-
tails regarding actual operation.
As with AFSK operation, the CW filter may be
engaged in the FSK mode by pressing the [N
AR
-
ROW
] key, and the DSP filters may also be used to
reduce interference in crowded digital operating
situations.
Operating Tips
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If you are hearing and decoding stations success-
fully in an AFSK environment, but stations cannot
understand you, check to be certain that your
TNC’s software has not set a shift other than 170
Hz, and be sure that the tones have not been “in-
verted” in the software configuration.
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If you are getting no shift (only a steady carrier) in
RTTY FSK operation, be sure that you have not
connected Pin 1 of the D
ATA
jack to an AFSK out-
put line from your TNC (use only the “FSK” line
provided by your TNC). If the FSK line has been
properly connected, check to be sure that you have
the “FSK” mode properly enabled on your TNC, if
the software requires you to do so.
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If you are having trouble decoding HF packet sta-
tions, be sure that you have set Menu # U-46 to
one of the settings which ends with “
U” (instead
of “
L”), and that you have chosen a tone frequency
compatible with the tones for which your TNC is
configured.
p
Summary of Contents for FT-920
Page 7: ...FT 920 Operating Manual 5...
Page 9: ...FT 920 Operating Manual 7...
