Using the Wisconsin Network - Part 20
                 by Andy Nemec, KB9ALN

     In the last couple of years, packet operators have been
able to take advantage of higher speed packet operation at a
more reasonable cost than in the past. TNC manufacturers are
now accomodating the amateur radio market and have
pre-packaged high-speed TNC's available. Although they have
become much easier to set up than in the past, there are some
things that you should know before you take the plunge into
the magic land of 9600 baud operation and buy that new TNC.

     First of all, how much good will it really do you? Under
ideal conditions, 9600 baud data rates are 8 times faster than
the 1200 baud operation that we have become accustomed to. In
reality, a lot of factors affect data throughput and your
results may vary considerably from the ideal. No question
about it, 9600 baud packet operation is faster. In order to
see a substantial difference, there are important things you
have to deal with.

     Your radio is the first thing to look at. What kind of
radio do you plan on using? Most garden-variety FM Amateur
transceivers are not adequate for the purpose, even the ones
marked "9600 Baud Ready". Why? Modern radios use a method of
modulation that is incompatible with 9600 baud operation.  For
narrow-band voice signals, this works acceptably. For the
wide-band 9600 baud data signal, this modulation scheme will
cause serious distortion of the data signal, making it
impossible to decode. Not only that, a lot of these radios
have a significant frequency error right, brand new, "out of
the box".

     Another common affliction of these radios is the time it
takes a transmitter to "settle" on frequency, and the time a
receiver takes to recover from the transmit mode. These radios
are often slow on both counts, causing retries and lost data.
Even if your station can send data fast, receiving it is quite
another matter.

     What can be done? There are 3 alternatives. The first is
a multi-mode radio. Why? These radios rely on a different
modulation scheme, and they often have faster
transmit-to-receive "turnaround time". Therefore, they not
only transmit a cleaner data signal, the receiver recovers
quickly, and can hear a response from a sent packet. They also
feature a more precise tuning readout, which means that it is
easier to get them on the proper frequency. The drawback is
that these radios are often very expensive.

     Another alternative is to buy a radio expressly designed
for this purpose. Older Kantronics Data Radios are best
avoided - I have heard little good about these radios. One
radio that I hear consistently good reports about are the
radios made by Tekk.  There may be others as well. The
important thing to look for is a crystal-controlled radio, or
one that has a synthesizer optimized for 9600 baud operation.

    The third alternative is to obtain a surplus commercial
radio, such as a Motorola or G.E. We have had excellent
success with Motorola Mitrek radios, they are crystal
controlled, inexpensive on the used market, and very high
quality.

     The disadvatage with getting any second-hand radio is the
adjustment required to get it to operate correctly. it takes a
bit of technical skill and equipment to get everything set
right. Unless you know a qualified technician, this may not be
an option. Even some commercial equipment requires a small
amount of modification to get it "just right" for 9600 baud
operation.

     Now that we have talked about the RF end of things, there
is yet another thing to consider. Even if your station is 9600
baud ready, is your area ready for it? In other words, do you
have access to a 9600 baud end-user node?

     In their eagerness to utilize this mode, some operators
who do not have access to such a node rush out and buy a TNC,
and get it almost working with some kind of radio. They
neglect to find out if there is a 9600 baud end-user node and
find themselves on a 9600 baud backbone node frequency. I
can't stress this point enough to you - DON'T DO THIS!.

     Why? A lot of these radio/TNC combos are not optimized
for the backbone frequency. Remember, the purpose of the
backbone is to handle a high volume of packet traffic, and
these nodes are optimized for this purpose. They often have
very fast response times, and communicate with nodes quite a
distance away. This can disrupt the network in two ways.

     The first disruption occurs from retries between a poorly
set up end user and the local backbone node. The backbone node
answers the end user quicker than it can deal with, and a
packet has to be repeated very often. This slows data
throughput between the end user and the local backbone node,
as well as between the backbone nodes.

     The second problem occurs because of the "hidden
transmitter syndrome". Remember that backbone nodes may well
be a considerable distance away, and are often located in high
places with good paths to the remote node. The end-user
station may not be so well blessed; it may be using a marginal
antenna, or may not be in a good location. This means that it
cannot hear the remote node. Consequently, this end user will
transmit at the same time the remote node does. The local
backbone node hears both of them, and hears a "double".
Neither packet is decoded, and they have to be re-tried.
Enough of these can seriously disrupt a network conection, and
frustrate the end user. This will spoil it for everybody!

     All of this may sound quite discouraging. Actually, it is
intended as a guide to help you think carefully about your
impending purchase. No doubt, 9600 baud packet operation will
become the norm in a very few years. However, a lot of people
may get discouraged if they make the wrong choice.

     What to do? If you don't have a 9600 baud LAN end-user
node, thnk about what it would take to have one in your area.
It can be done for less than $500, and if enough interested
people in your area kick in a few bucks, that is not such a
big pile of cash to generate. Node Operators often have enough
cash stuck into their systems, and they often pull it out of
their own pockets. Making it a community effort will not only
make it a whole lot easier, it can help pull a radio club
together and give it a project.

     If you don't have a 9600 baud LAN frequency, contact
Steve, KE9LZ (KE9LZ@KB9ALN.#GRB.WI.USA.NA) and ask for one. He
can assign one that is compatible with the bandplan in effect
in your area.  If you can't put an end-user node on the air
quickly, at least you will have a place to park until you can.
And it will keep you from interfering with the backbone
operation.

     The bottom line in all of this is "do it right". Not only
will you get more enjoyment from this mode of operation, you
will be operating in concert with the rest of the Wisconsin
Network.

  ***End of Part 20***