Reprinted from Mike Candy's, KI7FX, article

Published in the RTTY Digital Journal, April 1994

Greetings once again to all RDJ readers. Another month has come and gone and there are a lot of projects stacking up here. There is never a shortage of new stuff to review, or innovative ideas to check out. Remember, a lot of my articles are based directly on your comments and suggestions, so keep 'em coming!

This month I would like to extend a special hello to the Dayton Hamvention readers. If you are not a member of the ADRS, you are missing out on a wonderful opportunity to become involved in the cutting edge of digital technology. Unfortunately, it looks like I won't be able to make Dayton this year - After spending 20 years in the Air Force, it's time to prepare for a career change, so look for me next year! If this is your first time checking out the HARDWARE column, keep reading! I review and evaluate everything from the latest high tech goodies to the best of the old reliable Terminal Units - if it dies digital, you'll read about it here.

Last month, I discussed some of the latest innovations in high speed VHF/UHF Packet. I received a few letters of interest, and I have come to the conclusion that there are two types of packet operators - those who "know" about the secrets of 9600 baud and those who don't have a clue. Up until the last few weeks, I was in the second category. With a little research and with the help of the great tech-help from AEA, I think I finally have a grasp of the basics of 9600 baud VHF packet. First of all, I hate 1200 baud packet. It is slow and clunky, and on a busy multi-user system, throughput is slower than 45 baud RTTY! In defense of 1200 baud, we all know it's easy to install- just plug it in and your are ready. On the other hand, 9600 baud packet is not a matter of plugging in and getting on the air. 9600 baud requires a little knowledge of what is happening with the transmit and receive signal, and how it is processed in your radio. There is some information available on the Packet BBS' or Internet to help you get started, but after you have done it, you will agree: 9600 baud packet is an incredible mode, and it is a lot easier than you think. You will probably never have a chance again to learn so much, with so little effort.

AEA's PK-96
Advanced Electronic Applications (AEA) has just released the latest in their line of high quality products for Radio Amateur - The Pk-96, high speed 1200/9600 baud packet controller. This controller has standard AX.25 level 1 & 2, 1200/9600 baud operation in the Command, Host and KISS modes. My PK-96 just arrived in the mail a few weeks ago and I have spent quite a bit of time getting familiar with it. My first impression of the PK-96 is that it is another high quality, nice looking product from AEA. Measuring in at 6 inches wide, 1 1/4" high and 7: deep, and has connectors on the back for RADIO (5 pin DIN), COMPUTER (DB-25), RX AUDIO, and POWER (13 VDC). To top off the good news, the PK-96 has an external RESET switch in the back and two TX LEVEL adjustments (one for 1200 and one for 9600). Finally, someone putting the RESET and AFSK adjustments on the back of the controller where the operator can reach them! The separate 1200 and 9600 adjustments are a great idea. The two modes are so different from each other and I appreciate the ability to set each level independently. The nice dark gray/light gray color scheme is also a pleasant surprise and looks good in the shack sitting on top of my ICOM 275/475 twins. The front panel contains a power switch and a green LED along with red LEDs for XMT, DCD, CON, STA, and Mail. Nothing earth shattering here, but necessary stuff. The Pk-96 runs on 12-16 VDC @ 400 mA max. The PK-96 comes standard with an 18K mailbox and is upgradeable to a 100K mailbox from AEA.

It seems lately, the worst part of getting a new piece of equipment up and running is opening the manual and wading through pages and pages of information until I find what I need. Well, I was in for a surprise this time. I opened the manual and snooped around - I called AEA on the phone and asked "Who wrote this manual?" It is the best written, most informative, and most useful manual I have seen in a long time. This manual not only covers the usual installation and command features, but goes into detail and gives examples of what is needed to get on the air with 9600 baud packet. If you remember from last months article, I told you that you can not simply plug a 9600 baud TNC into your radio's microphone/speaker jacks. The manual discusses connecting the TNC to these ports, but don't let that fool you, that is for 1200 baud connections ONLY. When you get to the part about 9600 baud, the rules change fast. Radio connections for 9600 baud are different, much different. Most VHF/UHF FM transceivers are primarily designed for voice operation and require special connections for high speed data use. With one or two exceptions, you can't connect the transmit section directly to the microphone jack, nor the receive section to the speaker output. Don't even bother trying, I can save you the trouble because it won't work (just ask me). The transmit audio (TXA) output signal from your TNC must be directly connected to the modulator stage of the FM transmitter, and the receive section must be connected to the discriminator of the FM receiver.

Presently, most FM transceiver don't have these connections for high speed controllers, but this is starting to change and radio manufacturers are beginning to make these connections available. What is needed is a connecting point on the back of the radio - usually a DIN connector for DATA. In particular, the TEKK KS-900, and the (newer model) Yaesu FT-5100 are 9600 baud connectable, right out of the box. Although identified as a 9600 baud radio, I have heard the Alinco DR-1200/H is not quite up to speed yet. The rule is don't always believe what you read. According to my ICOM 275 and 475 manual, the back port connectors tap into the receive detector stage. I am here to say it isn't so. Check and double check carefully before you decide to buy a new radio for this purpose. Don't worry if your don't have one of the new radios though, as "mods" are very easy to do.

Fortunately, it's not difficult to locate the connection needed for 9600 baud operation in most modern FM transceivers. The PK-96 manual included a pretty thorough list of radios that are "known" to work at 9600 baud with a little work. AEA says it's embarrassing to call them "mods" - since you're only bringing out terminations of existing signals in the radio. I can personally attest to the fact. Bringing out the TX and RX signals of the radio is a very easy procedure so you might as well get with the times - 9600 baud is here to stay! AEA includes an excellent section on connections or modifications to most radios - getting wired up is an easy process with the help of this manual.

For new packet users, don't be afraid of the PK-96's high tech, high speed abilities! This is the perfect TNC for new users as well as old timers. The manual includes a section on "Packet Protocol Basics" which explains (in understandable terms) the meaning of all those strange commands like FRACK, RETRY, and MAXFRAME, etc. The pK-96's commands are explained well, and again for new users, the EXPERT command will shield you from too many cryptic commands until you are ready for them. As a replacement for your existing Packet controller or for your first Packet controller, the PK-96 is right on target.

Unfortunately for me, there are no other 9600 baud systems running in the Spokane, Washington area, so I had to rely on a little help from my friends. I shipped my AEA DSP-2232 (which has the 9600 baud G3RUH compatible modem) over to Jay's (WS7I) house and convinced him to open up his Yaesu FT-736R and tap into the necessary points. He agreed, the mod is an easy one, and nothing for most users to be afraid of. After making all the necessary connections on his end and me connecting the PK-96 to my external data port, we could not make a 9600 baud connect. For that matter, we failed to make a 1200 baud connect - it appears the 8 miles or so between us is a pretty poor path for VHF - We couldn't even work FM simplex. I guess it's understandable, since I am shooting directly over the "noisy" Fairchild Air Force Base. I opted for a different path / direction to work from. After some successful tests on FM and SSB with Mike (N3CEV) 10 miles directly south (and NOT over the base), I decided to ship the DSP-2232 over to his place. With strong S-7 signals, we figured there would be no problem connection. I got home and called Mike - we were ready for the big test! 1200 baud connects worked fine, but no luck at 9600. We checked and re-checked the parameters and everything else I could thin of, but no luck. After a couple of hours of trying, I got Mike to admit it - he connected the input / output of the TNC to his microphone connector! I guess it was my fault, I didn't stress the importance of direct connections at high speed, although I did leave him with clear and easy instructions on wiring up the Yaesu. Initially, he seemed a bit concerned about taking the cover off his shiny new Yaesu FT-735R and I can't blame him. It may seem a bit intimidating, but take my word for it, AEA has covered a lot of radio connections in their manual, and I (and Mike) can attest that once the change is done, it's better (where have I heard this before).

A test is a test, and we can't stop now! Mike called me up the next day and said the wiring was complete and it only took about 20 minutes. We were ready to try again and Mike was feeling better already. After more frustration and 1200 baud connects, we had to stop and think about it some more - something was not right and this thing wasn't going to work. The only link in the puzzle that was not "known" was my ICOM VHF and UHF rigs. Although this combination is not mentioned in the manual (how come guys?) I did have some conflicting information on setting them up for 9600 baud packet. I decided to open the case and give it a shot. From start to finish, the whole procedure took about 30 minutes and that was including trying to read the confusing and conflicting instructions I accumulated over the last 6 months or so. I should have done this in the first place, because as soon as I issued a connect to Mike this time, the radios came to life - 9600 baud - connected to N3CEV! This stuff is amazing! Although I am certainly not new to high speed data, running 9600 baud packet is a thrill that everyone should experience. Monitoring the audio while we were testing, all you would hear is a fast (and I mean fast) Pssst, Pssst signal from the radio. No more of this BRRRRAAAAPPP stuff here! Great sound effects, 'eh? We had the Pk-96 and the DSP-2232 transferring files so fast, I never would have believed it was possible over the air. It reminded me of a fast (less than one second per packet) AMTOR signal. Working 9600 baud packet is a BLAST!

A few things we learned along the way relating to 9600 baud packet, thanks to Glen (WB6W via Packet Radio) and our experience (we are experts now - grin):

  1. 9600 baud is VERY sensitive to carrier frequency. If possible, use a multimode rig with 1 KHz steps. Being 1 KHz off makes for a very erratic 9600 baud link. Being 2 KHz off results in a system that just doesn't work.
  2. 9600 baud operation is sensitive to multipath propagation. Use directional antennas to reduce the multipath. Horizontally or Circularly polarization works best. We used circular polarization and found excellent results.
  3. The optimum parameters for 9600 are different than they are for 1200. Not that 1200 baud parameters won't work, but you won't get the throughput that 9600 is capable of - reduce the TXD settings to the minimum. I set my TXD to 10 mS and made the connection just scream!

With all this information laid out, and 1200 baud as an alternative, it is clear that 9600 is the way to go. It is easy, fast, and incredibly efficient. You can move a lot of data at 9600. I suspect that 9600 baud modes will start showing up in a lot more places over the next year. Hopefully, we will have a 9600 baud node here in the Spokane area in the next few months. Check with your local packet group - 9600 baud is here to stay, and AEA has made the PK-96 within easy reach of all hams. If you don't have other 9600 baud users or a 9600 baud node in your area, use it at 1200 for now. Listen on the common packet frequencies for the familiar Pssst, Pssst sound. When 9600 baud hits your area, you will be ready! Weighing in at less than $200.00, the PK-96 is an excellent bargain. In the dollar/feature ratio, the PK-96 is outstanding. Stay tuned and I will let you know how it works on satellite.