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EI2GYB > PACKET 05.10.25 13:51l 170 Lines 11837 Bytes #57 (0) @ WW
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Subj: INTRODUCTION TO PACKET RADIO - PART 2
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INTRODUCTION TO PACKET RADIO - PART 2 - by Larry Kenney, WB9LOZ
In the first part of this series I told you, in general terms, what packet
radio was all about. Now I'm going to tell you how to get on the air,
make a QSO, and become familiar with your packet station. Whether you're
new to packet, have been involved for just a short time, or are one of the
"old timers", this series should help all of you. Even if you don't yet
have equipment to get on the air, you should keep this series of articles
handy for future use. I'll bet you'll be joining us soon!
The equipment that's needed to get on the air with packet is a transceiver,
a computer or terminal, and a TNC - a terminal node controller - the little
black box I talked about in part 1. Or, if you're using a computer, not
just a terminal, you can use special software and a small packet modem
instead of a TNC. You need a special modem, though, not one that's used
to connect your computer to the telephone line. The tones used for packet
are different than those used on the phone.
I highly recommend that you start with a 2 meter transceiver. There is
packet activity on 220, 440 and HF, but 2 meters is where most of the
action is and that's the best place to start.
When you buy a TNC or packet modem and take it out of the box, you'll find
a cable supplied for connecting it to the radio, but you'll have to attach
the appropriate mic and speaker jack connectors for the radio you're going
to use. You'll have to furnish the cable that connects the TNC to your
computer or terminal. In most cases, the TNC or modem is connected to the
standard RS-232 communications port of the computer. On a PC this port is
called a serial or COM port. On other systems it may be referred to as a
telecommunications port or telephone port. You can make up the cable that
goes between the TNC and computer yourself, or you can purchase it at a
local computer store. As an option, you may be able to purchase one or
both of the needed cables from the manufacturer of your TNC with the
appropriate connectors factory installed for your particular radio and
computer. The operating manuals that are supplied with TNCs and modems
have a good description of the cabling needed for the various computers.
Please read the introduction and set up procedures for your particular TNC
or packet modem very carefully. Most companies have supplied excellent
manuals, and you shouldn't have any trouble figuring out your particular
set up from the information supplied in the manual.
Once you have everything connected as described above, you've completed
the hardware phase of the installation. Now you need to turn your
attention to software. If you're using a TNC, you'll need a terminal or
communications program for your computer. Any software used for a
telephone modem, such as Procomm or the Windows Terminal program, will
work well for packet. There are also many special programs that have been
developed specifically for packet radio use, such as PC PACRATT, MFJCOM,
PAKET, PacketGold, TPK, etc. If you're using the small modem instead of
a TNC, you'll need to use the special packet software written for the
modem, such as Baycom. Read the instructions carefully for setting up the
program on your computer.
No matter what software you use, you'll have to specify the communications
port you'll be using and set the baud rate (data rate) and data parameters
for that port. (Note: There are two baud rates associated with your packet
station: 1-the baud rate between your computer and TNC and 2-the baud rate
of the packets on the air. Here I am discussing the first of these baud
rates. The second will be discussed in part 3 of this series.) Refer to
the manual or help information for the specific program you've chosen, to
set the baud rate and data parameters. The baud rate of your computer must
match the baud rate of your TNC. Some TNCs will automatically set their
baud rate to match the computer. Other TNCs have software commands or
switches for setting the baud rate. Again, you'll need to refer to your
manual for specific instructions. When setting the data parameters, 8-N-1
is normally used: 8 data bits, no parity, 1 stop bit. But like the baud
rate, the computer and TNC parameters must match.
Now I need to point out the various levels of communicating you can do from
the keyboard. First, you can communicate with your computer for setting up
your software program; second, you can communicate with the TNC or packet
software; and third, you can send data over the radio. It's very important
that you know which level you're in when working packet. You need to know
where your keystrokes are going! If you're not using a TNC, you will have
to figure out the difference between software set up and software usage.
This is explained in the program instructions.
Once you have your communications program or packet software up and running,
you can move on to the next step. If you're using a TNC, you now need to
set it up. First, turn it on. You should get a "greeting" or sign on
message from the TNC on your screen showing the manufacturer's name, the
software version, a date, etc. If you see a bunch of gibberish, such as
&tf$d.h#sxn, it means that the parameters of the TNC and computer don't
agree and you'll have to make adjustments. If you don't see a "greeting"
or the gibberish, check your cables and connections. Make sure that you
have everything connected properly, that the right wires are on the right
pins, and so on.
Next, do a "control C" (press the CNTL and the letter C simultaneously);
this puts the TNC in COMMAND mode, the level where you communicate directly
with the TNC from the keyboard. You should see "cmd:" on your screen.
Enter: MYCALL - - - - with your callsign in place of the dashed lines
(such as: MYCALL WB9LOZ) followed by a carriage return <CR>. (The carriage
return key is labelled "Enter" or "Return" on most keyboards.) All commands
must be followed by a <CR>. This sets into the TNC memory the call that
you're going to use on the air. Now if you type MYCALL <CR>, it should
respond with your callsign. If it does, you've proven that the computer
to TNC link is working fine. If you do not see anything on the screen
when you type, blindly enter the following: ECHO ON <CR>. If you see two
of everything that you type, such as MMYYCCAALLLL, enter ECHO OFF <CR>.
Now enter the following commands: MONITOR ON <CR> MRPT ON <CR>
For those using packet software and a modem instead of a TNC, you should
have already entered your callsign in the configuration file during the
set up procedure. If you have not, refer to the software instructions
for preparing the configuration file for your station. Also note that
with this software, you don't enter Control C to go into command mode.
You simply use the ESC (Escape) key prior to entering each command.
You're now ready to go on the air! Turn on your radio, make sure the
volume is turned up about a third of a turn (about the "10 or 11 o'clock"
position) and make sure the squelch is set. It should be at the point where
the background noise disappears, just as it would be set for a voice QSO.
Tune the receiver to any odd numbered frequency between 144.91 and 145.09
or 145.61 and 145.79 MHz and set the rig for simplex operation. You might
have to tune around for a frequency with activity in your area. Watch your
screen. You should soon be seeing the packets that are being sent over the
air by other stations.
Let's look at what you might see. You should see something similar to this:
WB9LOZ > W6PW-3: The meeting will be held at 8:00 pm.
This shows a packet being sent by WB9LOZ to W6PW-3. Watch for callsigns
with asterisks next to them in packets that look like this:
WB9LOZ > W6PW-3,W6PW-1*: The meeting will be held at 8:00 pm.
The asterisk indicates that you're receiving the packet from W6PW-1, not the
originating station, WB9LOZ. The packets are being digitally repeated, or
digipeated, by W6PW-1. The station that's doing the digipeating is called
a digipeater. You'll also note that some stations are using names or a
series of letters rather than callsigns. You might see something like SFW,
BERKLY, or BLUE. These are packet stations set up to operate as nodes.
The stations are usually located in higher locations, and they're installed
to make connections to other stations easier. They often use a name or
letters, called an alias, that identify their location. They send both their
alias and callsign at 10 minute intervals to identify themselves and to be
legal. (Both digipeaters and nodes will be discussed in detail in a later
part of this series.)
You'll also notice that some callsigns have a trailing number attached to
them. On packet you can have up to 16 different stations on the air at the
same time using the same callsign. That's where the numbers at the end of
the callsign come into play. The calls W6PW, W6PW-1, W6PW-2, W6PW-3, W6PW-4
and W6PW-5 are all individual stations operating under the same station
license. A callsign without a number is the same as -0. These numbers are
called Secondary Station IDs or SSIDs, and are used to differentiate between
the various stations. There should never be more than one station using the
same callsign and SSID on the air at the same time.
Now that you're familiar with what you might see on packet, you're ready to
make your first packet QSO! If you're using a TNC, make sure it's still in
command mode. (Remember, it's Control-C.) Watch for a familiar call on the
screen or note calls you see frequently. Be sure to note whether or not a
digipeater is being used. When the station you want to contact is finished
with his QSO, enter the command: C - - - - or C - - - - V - - - -
(depending on whether or not a digipeater is needed) follow(depending on whether or
not a digipeater is needed) followed by <CR>.
Replace the dashed lines after the "C" with the call of the station you want
to contact and the dashed lines after the "V" with the digipeater call, if
needed. Don't forget the SSID if the call has one. The C means CONNECT and
the V means VIA. C WB9LOZ V W6PW-1 means connect to WB9LOZ via W6PW-1. If
you're successful, you should soon see "*** CONNECTED TO (callsign)" on your
screen and your first packet QSO is underway!
You have now entered the third level of communications, called CONVERSE
mode, and this is where you communicate from the keyboard to the radio.
Anything you type on the keyboard will be transmitted over the air as a
packet every time you hit a <CR> and it will appear on the other station's
screen. Anything sent by the other station will be transmitted to you and
will appear on your screen.
When you're finished with your QSO, be sure to do a CONTROL C to get back
into command mode on your TNC, or hit the ESC key if into command mode on your TNC,
or hit the ESC key if using the packet
software, then enter D to disconnect from the other station. You'll
see "DISCONNECTED" on the screen. If you get connected to a station but
you don't receive a response, you might have reached an unattended station
or a node. Don't despair, disconnect and try someone else.
You're on the way now to lots of packet fun and adventure! If you are
still having problems at this point, contact a friend that has some
experience on packet and ask for help. The initial set up of the computer,
TNC, software and radio is probably the biggest stumbling block in packet.
Any experienced packet operator will be happy to help you get through this
process to get you on the air.- - - -
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