
		  Using the Wisconsin Network - Part 13
			  by Andy Nemec, KB9ALN

     In the last edition of "Using the Wisconsin Network", we
started  looking at the network from it's beginnings, your
station. We discussed, in basic terms, just how these pieces
work together. In this installment, we will continue this
discussion and look at setting up your radio and TNC so that
your station becomes more "friendly" toward the network, and to
other stations operating on your LAN frequency.

     And we will start in that order, with the radio. Many people
forget that packet radio is radio. The computer and associated
boxes you have may all be working just fine, but useless if your
radio is not properly set up. Remember that your data ultimately
gets transmitted and received as audio tones, so  the first place
you have to look at packet performance is at your radio.

     First, let's look at transmitting. Your transmitter has to
be on frequency, have the proper amount of deviation, and has to
have clean audio. No Buzzes, no P.L. tones, and no RF getting
into the microphone audio circuitry.

     Frequency error is often overlooked when people are trying
to diagnose a bad packet connection. If you have any doubt, try
checking it with a frequency counter. You will need absoloutely
NO audio into the mike circuitry when you do this, and don't
forget to turn off your P.L.

     Assuming that you find your radio on frequency, you can go
on to the next step, checking out your transmitter deviation.
Your audio level from your TNC directly effects this, so you will
need to hook your TNC back up and send some packets. To
accurately measure deviation, you need to look at the signal on a
Service Monitor. This handy test gear is out of the range of most
Amateurs, but ocassionally you will find someone who has one. If
you have access to one of these, your peak deviation should be
approximately 4 KHz. If you are like most of us and don't have
access to one, you can come close with an oscilloscope and
another radio to listen on. If you don't have a 'scope, then your
ears will have to do.

     The trick to these two methods is to have a reliable
reference to compare your signal to. This would probably be the
local node for most people. You adjust your transmit audio level
(On the TNC) so that it matches the volume level of the station
you are using for a reference. That is why you will need to
listen on another radio. It is easier and more accurate if you
use an oscilloscope hooked to the speaker terminals of the other
radio. It is even more accurate if you hook it to the
discriminator of the other radio, and have it calibrated. This is
not usually the case with most people, so you will probably be
hooking it up to the speaker.

     Once you have your transmit audio level set, you may wish to
look at the cabling to the TNC. Use high-quality shielded cable
for your connections to the microphone circuit (or Data
connector, if your radio has one).

     There is also one final part of the transmit system you
should pay attention to. That is what kind of antenna you are
using, and where you have placed it in relation to your computer
and TNC. First, using a rubber-duck antenna is not a preferred
setup for packet. Not only does it not work very well when
receiving or transmitting, but it also hears stuff you don't want
it to hear. Keeping a rubber duck in close proximity to the
computer and the TNC will insure the reception of computer hash
from both of them. It also has the nasty property of radiating a
signal into your electronics, which can distort your transmit
audio and possibly cause damage to your system. Best to have an
antenna on the roof, or at least a good distance away from the
rest of the equipment.

     Now on to the receiver. There are 2 simple adjustments here.
You don't need too much volume to get the TNC to decode properly,
so setting the volume at 10 to 11 O'Clock is generally quite
enough. More is not better here!

     The squelch may require a bit of tinkering with. Generally
speaking, the squelch should be set about 1/8th turn past the
threshold of quiet. Sometimes lower noise levels will open up
your squelch. This is not good, because in most cases this will
cause your DCD light on your TNC to come on, and will prevent
your station from transmitting (it thinks someone else is
transmitting). Don't overlook this if your station does not want
to transmit!

     Now that we have looked at the radio end of your station, we
will move on to the TNC. As was said earlier, this is important
as it affects the way that your station interacts with others
using the network and the LAN.

     The North East Digital Association (NEDA) has set up
guidelines for the real world of packet radio that make sense in
today's packet radio environment. They make a great deal of sense
when you look at it, and we will use their guidelines as a basis
for setting up our TNC's. Below is a list of the more important
parameters, what they do, and what is a realistic setting for
them. Remember, most factory defaults were set in a day when
packet radio was not as well populated as today, so it makes
sense to change them to match today's packet radio world.

     BEACON = 0  Turn off your beacon. There is no need to have a
beacon unless you have important information to disemminate. Your
idea of a good joke of a clever saying is not a good reason. If
people need to know that you are out there, they can look at
their "Heard" list. "Mail For" and ID broadcasts are legitimate
beacons. Every Amateur radio publication relating to Packet Radio
tells us that Beacons are a waste of spectrum. Let's end this
practice!

     DIGIPEAT = OFF   Turn off your digipeat feature, unless you
have no node in the area, or it is absoloutely necessary for some
reason. Nodes do a much better job of repeating your packets, and
keeping the Digi on will often override other features of your
TNC that govern timing.
     
     FRACK = 6 to 12 (seconds). This is the "FRame
ACKnowlegement" timer. It  governs how long your TNC waits for an
acknowlegement from the other station you are connected to. In
croded areas like Milwaukee, for instance, you may want to use 10
to 12.

     MAXFRAME = 1. This governs how many Data frames are sent
with each transmission. Too many frames will keep your
transmitter up too long, and not allow others to share the
channel. Also note that the more frames sent, the longer the
packet. The longer the packet, the more chance of errors, and
this means poor throughput of data.   

     PPERSIST = ON. This allows the TNC to wait a random amount
of time before transmitting. You MUST have the Digipeater turned
off for this to function. This gives other stations a chance to
transmit, too. 

     PERSIST = 64. This generates a random number to be used in
conjunction with SLOTTIME to calculate the time it waits before
transmitting. The lower the PERSIST, the longer it waits. Though
64 is suggested, you may use 128 if yours is not a busy packet
LAN frequency.

     SLOTTIME = 20 (in ms). This is used with the PERSIST setting
and again, governs the time the TNC delays before transmitting a
data packet to the  receiving station. Note: MFJ calls this
"deadtime".

     RESPTIME = 10 to 15. This is a timing parameter that
controls how long the TNC waits to acknowlege a received packet.
This differs from the above PERSIST in the PERSIST is involved in
sending a data packet. RESPTIME is only effective in the
acknowlegement of a received packet.
      
     RETRY = 10. This is the maximum number of retries allowed
before a station sends a disconnect. You may also consider
setting this to 6 or so. If you can't get to somebody in 6 tries,
you, or the other station, has a problem!

     Note that some TNC manufacturers may use slightly different
command names than we have used here (especially Multi-Mode
controllers). Take a good look at the TNC manual and see if any
of the commands have a similar description.

     While this all may seem to be more trouble than it is worth,
it will make a pronounced difference in throughput if you take
the time to change a few settings. And anytime you can improve
efficiency and channel usage, it is certainly worth the time. And
if everyone on a LAN can cooperate and use the same settings,
life will be easier for everyone.

     And if life is easier on the LAN, then it will be easier on
the network. And that will help you use the network more
effectively.

 *End of Part 13*
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