ing the need for re-tuning or use of the SHIFT control
One of four standard tone pairs can be chosen for
operation from menu selection 6-5 , as desired. The menu
display shows the center frequency of the selected tone
pair (see the table below for actual mark/space tone
combinations). Set the Packet Tone Pair to match the
tones generated by your TNC (these are usually set
via terminal software or DIP switches - check in your
Important Note! - if changing packet tone pair to
other than 2025/2225 Hz, be sure to re-calibrate the
tuning meter as outlined on page 85. The calibration
routine is simple, and ensures your center tuning indi-
cation matches the tone pair.
Packet Frequency Display Offset - You can dis-
play the center frequency of the two transmitted carri-
ers, (that is, the packet tone pair used), without any
offset, instead of the actual carrier frequency. Recall
menu selection 6-4 and turn the main knob to select the
offset (±3.000 kHz).
Note - The default display offset is -2.125 kHz (to
match the default tone pair* in 6-5 above, and assum-
ing LSB operation). Ideally, the display offset should
match the default tone pair, which in turn should match
those used by your TNC. If you would rather have the
actual carrier frequency (without offset) displayed, set
the display offset to 0.000 kHz.
Select the NAR 2 (500-Hz or 250-Hz) filter for 300-
baud packet, and press the [ PKT ] mode button on the
front panel once or twice, so that the green LSB LED
indicator lights along with the red PKT LED.
Transmitter adjustment is similar to SSB:
r Preset the RF PWR control counterclockwise, and
set the METER selector to "ALC."
r Now set your TNC to its "calibrate" mode, prefer-
ably with both tones alternating, and adjust the MIC
control so that the meter deflects to mid-scale. Your
TNC's "TX Audio" output may also be capable of
adjustment via a potentiometer inside the TNC.
r Switch the METER selector to "PO" and advance
the RF PWR control for the desired power output.
TNC Tone Pair
ø indicates default setting (used by normal convention)
Tone Center Frequency
When tuning, be aware that some common HF
packet channels, such as "14.103" MHz, were origi-
nally determined to correspond with an actual IF cen-
ter frequency 1700 Hz lower (in accordance with an
old TAPR convention). Therefore, if you have the
Packet Frequency Display Offset ( menu selection 6-4 )
set to match your TNC's actual tones, the display shows
14.101.30 when tuned to the above frequency - which
is the actual center of your receiver passband, and the
frequency mid-way between the two FSK carriers you
Initially, you may need to adjust the receiver IF shift
slightly right or left to get the 500-Hz IF filters perfectly
centered over incoming signals. Start with the SHIFT
control centered, and try to establish a connection with
a moderately strong signal on a clear channel. If the
connection is poor (many repeats), move the SHIFT
control slightly right, and see if the repeats decline.
Continue in this manner until you find the best SHIFT
setting (with minimal repeats), and use this same set-
ting for all future HF packet operation.
1200-Baud FM Packet
The equipment setup for 1200-baud FM packet
(above 29 MHz) is the same as for 300-baud packet,
except that you may want to connect the squelch line
of the TNC to pin 5 of the PACKET jack if you plan to
use the squelch. Press the [ PKT ] mode switch until
both it and the green LED on the FM mode button are
lit. Tuning is much less critical in this mode, requiring
no special adjustments. Also, the FM MIC GAIN con-
trol in the top access panel has been preset at the fac-
tory for proper deviation with typical signal levels, so
you should not need to readjust it (you should adjust
the Tx audio output level of your TNC, though, if your
signal sounds distorted in the monitor).
To set up the transmitter for FM packet:
r Start with the RF PWR control counterclockwise.
r Switch the METER selector to "PO" and set the RF
PWR control for the desired power output.
MARK-V FT-1000MP Operating Manual