Timewave DSP-232, Operating Manual

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Chapter 5 Packet Operation
Perhaps the most difficult thing about HF packet operation is making sure the station you’re talking to is tuned
properly and stays tuned. Since HF packet uses 200 Hz Frequency Shift Keying to send data (2110/2310 Hz),
tuning accuracy is very important. Being off-frequency by only 20 Hz makes a noticeable difference in the DSP’s
ability to copy. Once you are tuned in, the superior filtering ability of the DSP-232 improves HF packet
performance. Follow the tuning procedure below carefully for the best results in tuning in HF packet stations.
1) Make certain your HF receiver is either in LSB or FSK, depending on your DSP’ set-up.
2) Turn any IF-Shift and Passband-Tuning controls to the Center or off position.
3) Tune your receiver to 14.103 MHz (or another frequency where you know there’s HF packet activity) and
listen to the packets.
4) Slowly vary the tuning knob on your receiver and look for a display on the DSP tuning indicator like the
one shown below:
Frequency too low Tuned in! Frequency too high
5) Adjust the DSP’s THRESHOLD so that the DCD light glows when a properly tuned packet is being
received. (You must also make certain that the DCD light goes out when no packet signals are present on
the frequency.)
After you have a packet station tuned in, you should start seeing HF packet stations on your display.
Transmitter Adjustments
Make sure your DSP is adjusted for your SSB transmitter as described in Chapter 3, SSB Transceiver Final
Adjustments . These are very critical adjustments. If your DSP’s AFSK level and transmitter microphone gain are not
adjusted properly, other stations will not be able to copy your packets. Check your plate or collector current or the
power output of your rig before going on the air.
Going On-the-Air
On HF there are two ways you can go about talking to another station:
♦
Monitor the frequency for packet traffic (or check your
MHEARD
list) for calls you can hear well and
choose one of them to connect to;
♦
You can also “Call CQ” by entering the Converse mode and pressing (
RETURN
).
Either way you decide to go on-the-air, remember that things happen much more slowly on HF packet than they do
on VHF and UHF packet. HF packet requires patience and careful tuning in order to be used successfully.
If you’re having problems connecting to other HF packet stations, try working with an experienced HF packet
operator in your area and listen to each other’s signals. See if you can copy each other’s packet signals. If he can’t
copy you, have him listen to your signal while you’re in the
CALIBRATE
mode to make sure you’re transmitting a
pure tone. As mentioned earlier, any distortion caused by overmodulation or RF feedback will make your signal
difficult or impossible to copy.
Packet Meteor Scatter Extension
A new packet protocol extension has been added for meteor scatter work that allows a Master/Slave packet
connection to be established. This is done to reduce the possibility of simultaneous transmissions by both sides of a
packet connection over a long meteor scatter path.
This experimental protocol is activated by turning
UBIT 18 ON ; the packet station that initiates a packet connect
will become the master station and the station that acknowledges the connect becomes the slave.
After a meteor scatter connection has been established, the master station will continually send either information
frames (I-frames) or polling frames and await an acknowledgment from the slave. The Master station therefore
sends packets constantly, even if all its I-frames have been acknowledged. The slave station sends nothing, not even
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