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Article reprinted from Buck Rogers', K4ABT, article Published in CQ Magazine
9600 Baud From the User's Point of View
We've
covered the topic of 9600 baud several times in this column, but mostly at the
9600 baud network node level. In the case of 9600 baud networks and backbones,
we have performed our job well.
In looking over our packet columns we discovered that we are long past due covering 9600 baud with respect to user-level transceivers and terminal node controllers (TNCs). Most of our efforts with 9600 baud applications have meant that we chop, channel, and modify our transceiver audio modulation and demodulation circuits to accommodate the use of 9600 baud.
The high-speed data pair described in this month's column will fill the user-level void with flying colors.
Corny Communications
Ever hear the old
cliché "Sooner or later, every ole hawg comes across a good ear of
corn?" I picked this one up from Ed, WB4MUL, one morning as he was
describing his good fortune of having found a "good deal" on a radio
purchase at the Columbus Georgia hamfest. Hopefully, after you read this month's
column you will have the same feeling.
There is no question that we have now gained the attention of transceiver manufacturers. What used to be a chore that we didn't care to undertake has now been addressed at the OEM level. In this case, it has been handled very efficiently by Kenwood.
Not so long ago we had to chop and modify a transceiver to mold it into one capable of passing a 9600 baud data signal through its modulator circuits without sending the data through the phase-distorting elements of the microphone circuit. The other side of the data path had to have enough room for the 9600 baud data to pass through the receiver IF without rolling off the data to such a degree that it was not recoverable at the discriminator.
Although I've written many articles about modifying transceivers for 9600 baud operation (May 1990 and May 1992 CQ, and several of my books), I've never been enthusiastic about the idea of modifying and possibly damaging the circuitry of my transceivers.
The Kenwood TM-251A
With the addition of
the new Kenwood TM-251A, the chop and channel job has gone away. Here is a 50
watt transceiver that has the capability for 9600 baud data without sacrificing
the voice element or quality of phone operation.
Another one of our plights was centered around the installation of the 9600 baud modem. Most TNC manufacturers of course had built their TNCs with the provision to add an additional modem by way of the TNC modem disconnect header. This header was usually in the form of a 20-pin header that was configured to accept these proprietary devices.
After the James Miller, G3RUH, 9600 baud FSK modem set a clear standard, we then had a target for other systems to follow. This standard is now considered the FSK amateur standard for 9600 baud.
A few months ago I looked over the many new TNCs that were being offered to the amateur digital market. I wanted to see who had taken the plunge to build a truly 9600 baud TNC that would target the end user. The idea was to find a TNC that was being manufactured purposely for 9600 baud.
Enter the AEA PK-96
The AEA Pk-96 has
been engineered around a different CPU, and it has the features that are not
found in other commercial, off-the-shelf (COTS) TNCs. In addition, there is the
user full featured mailbox, which we will discuss later in this column.
The AEA PK-96 terminal baud rates will vary according to the kind of computer you use and the associated terminal software. When operating the PK-96 at the radio baud rate of 9600 baud, the terminal speed should be set for a speed greater than 9600 baud. I use wither 19,200 baud, or with the late-model PCs 38,400 baud. The latter is used only when the terminal program (software) will support this rate
Some of the more popular PK-96 to terminal interface examples are provided in the unit's well-documented manual. I'll have more comments about the PK-96 manual later. AEA offers several terminal (software) programs for the IBM and compatibles. AEA also has a software package for the Macintosh called MacRatt.
The Pk-96 interface to the Kenwood TM-251A dataport is shown in figure 1. Although I've included the wire colors associated with the Pk-96 signals, it is always best to verify the final connector wiring. All hardware level controls and interface connections are made at the rear of the AEA PK-96. In figure 2 I've drawn a rear view of the PK-96.
Having interfaced the Pk-96 and the Kenwood TM-215A, the next step was to determine the optimum timing setup for the PK-96 and the TM251A. Setting timing parameters in a 1200 baud station is more or less straightforward and in many TNCs the default parameters will suffice. In the case of this AEA and Kenwood combination I found that using TNC parameters similar to the following provided optimum performance at 9600 baud.
TXDelay = 15 to 17 (not the usual 30 or 35)
Dwait = 5 (not the usual 16
to 33)
Frack = 2 (not the default of 5)
MAXFrame = 7 (let it all hang out!)
As we become further acquainted with our 9600 baud system we may try fine-tuning our 9600 baud station even further. For now though, I am pleased with its performance.
Intermediate and Advanced Commands
If
you are new to packet radio, the PK-96 has a measure of support for the
beginner. Use of all the packet commands is not employed at the intermediate or
beginner level. As you progress and become more proficient in the use of packet,
you can activate the "advanced" command level within the firmware of
the Pk-96. The advanced level commands allow the user to fine-tune the Pk-96 for
much better performance, especially when moving into the higher speed of the AEA
PK-96.
To make the shift, or advance to the "expert" level, use the EXPert command. At the cmd: prompt type: EXP ON This activates a much larger command list within the firmware of the Pk-96. The user should spend a few minutes looking over the command list in the AEA PK-96 user's manual.
The AEA PK-96 can operate at either 1200 or 9600 radio port baud rates. To switch from 1200 baud (default to 9600 baud, at the command (cmd:) prompt type: HB 9600 <enter>
To return to the radio data rate of 1200 baud the command is similar: cmd: HB <enter>
And The Fun Is Just Beginning
In many
ways the AEA PK-96 offers features not found in all TNCs. In this case, the term
node is reinforced by truly supporting a node within the Pk-96 firmware. This
node is similar in some ways to the network nodes. It allows other station users
to connect to it, and from it, to other stations or nodes that are within its
range, frequency, and baud rate.
The AEA Pk-96 node has additional features that are displayed after the user connects to the Pk-96 node. The node name or callsign is entered using the MYGATE command entry. One of the features allows us to connect and issue the L, or listen, command. The L command can be toggled on and off while the user is connected into the Pk-96 MYGATE callsign.
To activate the MYGATE (node) in the PK-96, the PK-96 owner must set the MYGATE callsign. To illustrate, I'll use the MYGATE callsign K4ABT-7. In addition to the MYGATE callsign, the node SYSOP (Owner) must also set the number of gate users that will be allowed to use the node. This is done by setting the GUSER command to three (3). With the GUSER set to three, you have enabled three pairs or up to six stations to be connected through your PK-96 node. At the command (cmd:) prompt I set the MYGATE call as follows: cmd: MYGATE K4ABT-7 <enter>
When first connecting to the MYGATE call, the user received the following reply:
***CONNECTED to K4ABT-7
***K4ABT-7 Gateway, Type ? for help.
de K4ABT-7 (B, C, D, J, L, N, S, ?)>
After connecting to my Pk-96 node the user types and enters the ? The node user will receive the following help menu:
B(ye) - Log off gateway
C(onnect) n - Connect to station "n"
C n Stay - Stay connected to gateway when "n" disconnects
D(isconnect)
- Cancel a connect attempt
J(heard) - Display stations heard
L(isten) - Toggle monitoring
N(Nodes) - Displays nodes heard (up to 10 TheNet type nodes)
S(end) - Broadcast unproto (CQ, UI, etc.de K4ABT-7 - (B, C, D, J, L, N, S,
?)
Having connected to your AEA PK-96 gateway the user may then issue a connect request to another station or another node that is on the same frequency, at the same baud rate and in range of the PK-96 node.
"Listen" To My Favorite Feature
I've
already settled on my favorite feature of the Pk-96 node. The listen feature
allows the user to connect to the MYGATE callsign and issue the L, or listen,
command. This toggles the listen feature on, and while the user is connected to
the PK-96 node, the node will deliver the call or station received information
to the connected (listening( station that issued the L command.
There is just one minor irritant that I find with the listen feature. It happens when I connect to the PK-96 GATE.NODE CALL from another node. As soon as I toggle the listen feature on, the listen feature of the PK-96 sees the second node. As soon as I toggle the listen feature on, the listen feature of the PK-96 sees the second node sending the Heard text to me and it duplicates the same text again. This can turn into a round-robin that becomes a tiring exercise. To stop it I had to do a hard disconnect (Control C, then D <enter>) from the gateway.
When connecting to the PK-96 node/gate direct, you can have lots of fun watching QSOs by stations on the far side of the hill that you would not otherwise see. When you are finished with the listen feature, simply issue another "L" to toggle the Pk-96 listen feature off.
After the listen feature is off, you may connect to a station callsign that was seen while in the listen mode, or execute another command that is displayed when you view the PK-96 gateway feature menu.
If you have no other command to execute, you may issue B for the bye command and exit the node/gateway.
The MailDrop
No, you don't have to leave
your computer on while your mailbox is in. I think this is the most often asked
question I hear from new packeteers at my forums and packet seminars.
The AEA PK-96 MailDrop enables the users to take the computer off-line to perform other functions such as word-processing, letter writing, games, cadd, etc. The MailDrop also has the capability of forwarding to other MailDrops or to a properly configured bulletin board system (BBS). It will also receive forwards from the large BBSes. Within the firmware of the PK-96 is a means of setting the KILLONFWD command on. This enables automatic detection of messages after they have been forwarded to another BBS.
The PK-96 comes with a large mailbox that can hold over 15 1000 byte messages. However, should the PK-96 owner wish to enlarge the PK-96 MailDrop capacity, additional RAM can be ordered from AEA. I like the idea of having more RAM available, since I learned the hard way what it means to limit my mailbox space by forgetting to turn off the additional GUSERs I had enabled.
Case in Point
Bruce Dean, WB4OLD, in
Warner Robins, Georgia, connected to my mailbox in Lynchburg, Virginia. He began
the usual setup to leave a message. After only one sentence sent to my mailbox,
he received "OUT OF MEMORY" from my mailbox. I had forgotten to
release some memory by setting GUSERs to a lower number. Setting GUSERs (number
of PK-96 node-user pairs) too high will consume a "bunch" of memory
(RAM) fast. It did! Unfortunately, all I received from Bruce's message was the
callsign and a blinking "Mail Waiting" LED.
Keep IT Simple
The MailDrop allows the
user to model some of the built-in options by customizing the MailDrop connect
text messages. MailDrop configuration in the PK-96 can be as simple as you like,
or as the owner quickly discovers, the PK-96 MailDrop con become the community
electronic post office. A full chapter of the PK-96 manual is dedicated to
application and multiple configurations of the AEA PK-96 MailDrop.
What Happened to the Manual?
I made it a
special point to call Kevin Cox at AEA and wage my complaint that the manual for
the Pk-96 is too much for me to handle, as it doesn't follow the normal manual
pattern. This manual is so well written and so organized that I plan to make it
a part of my reference library!
You will find that the Pk-96 manual alone will become a true asset to you as a 9600 baud user. In addition to providing an easy to follow setup and operation procedure for the PK-96, the manual also references many other sources of 9600 baud reference material. I suppose the only thing I find a bit disappointing is that it doesn't reference any of my writings about 9600 baud radio modifications and use. But what the heck; I already have those articles and books anyway.
After you've finished reading the manual text, you reach the addendum section. Here you find almost every interface illustration that I've ever put into the "Packet Users Notebook" in almost 10 years of writing for CQ magazine.
Clear, easy-to-follow schematic drawings of the PK-96 circuitry, pictorials of the parts placement on the PC board, and more is included in the manual. AEA, you have done a true favor by developing this documentation.