HFPacket the PDF version of the Quick Start guide to distribute to your ham radio club!
Getting into VHF packet was actually very easy for me. I purchased a rig that had a built-in TNC, so the only thing I had to do was learn the commands and get it hooked up to my computer. This was very simple for me. I was also fortunate to have one of the local packet gurus in my area lead me through the basic packet protocols. He sent me an email as he noticed I was on the air, gave me the commands to connect to his node, and we had a nice QSO detailing how to access and navigate the BBS, chat with other packet users and so forth. Thanks Jerry, KG0GG.
Diving into HF packet wasn’t as easy, but I was able to get on the air and make a contact! Essentially, that meant I had done everything right!
While there is a lot of information on HF packet on the Internet, it’s not contained to one site. The objective of this post is to get you at least up and running on HF packet while giving you a basic understanding of how all of it works.
I have a hardware TNC, so this will be a little bit different than if you were to use a soundcard-based packet program. The theory is pretty much the same, however the commands may be different.
If you’re not sure you’ll enjoy HF packet, here are a few things to think about:
If you’ve operated on VHF packet, you’ll notice that HF packet is quite a bit slower than VHF packet. Why? For starters, on VHF packet you generally operate at 1200 baud (9600 baud is possible on 70 cm), while on HF it’s only 300 baud. Propagation also plays a factor on how well the signals are sent and received on either end.
If you think VHF packet is boring, HF packet is a lot more fun! Despite what the gloom-and-doomers say, there is plenty of packet activity to be had, especially on 20 meters.
An HF packet modem doesn’t have to cost a lot of money. TNCs can be had on eBay for under $100. I picked up a used AEA PK-88 for $70, and that included shipping. You can find them cheaper if you do a little more searching and are patient. Recently, I saw an AEA PK-232 MBX go for $31.00 on eBay. You may have to build the interface cable that goes between the TNC and your radio. I chose to build one, and it was very easy for me — a person who has some visual problems — to build. You can also buy the cables online for a fair price. Note that when looking for a cheap TNC, make sure it doesn’t require anything more than a “dumb” terminal program (WinPack or Hyper Terminal in Windows, and Terminal or iTerm for Mac OS X) to operate it. There are some “computer patches” out there that will require special software to operate it. Steer clear of those unless you want to run DOS and can find the associated software for it. Make sure the TNC will operate HF packet (The PK-88 operates on HF and VHF packet), and don’t expect it to operate more than packet. If you want to do MORE than packet, like AMTOR or PACTOR, look for a TNC that will handle those modes. A perfect example of one would be the AEA PK-232 MBX.
Now that we have that out of the way, let’s begin! You have your hardware TNC. Now what? First, make an inventory of what you’ll need. You’ll need an RS-232C (DB-25) male to RS-232 (DB-9) female computer cable. if you have an older external modem laying around, chances are good that you’ll have one of these. If not, you can find them online or possibly at an electronics store or ham fest. If your computer doesn’t have the DB-9 male serial port on it, not to worry! You CAN use the USB-serial adaptors with a hardware TNC. I have three TNCs in my shack, and all of them work perfectly fine with the USB-serial interface. The only thing I would caution you against when it comes to the USB-Serial adaptors is to NOT buy the cheap ones! Get the ones that have the chip in it and that require a driver. Most are Mac and PC compatible. Trust me, it’ll save you a lot of frustration. This is the one I purchased off of Amazon.com.
If you don’t have it, you also might need an audio cable to get the audio from your rig to the TNC. You can get a 1/8″ male to 1/8″ male cable at Radio Shack for fairly cheap. You can either feed the audio from the headphone jack, or use the rear audio jack, get a Y-adapter so you can feed the audio to an external speaker, which will allow you to hear the signals, and then take the audio cable and feed it into the TNC. It doesn’t need to be a long run … just enough to stretch from the TNC to the radio. If you choose to use the headphone jack, you’ll need a 1/4″ adaptor.
If you need to build the interface cable, you can use network cable (preferably shielded but unshielded will work). If you plan on using the microphone jack of your HF rig to connect to the TNC, you’ll want to get these little guys. They can be had at Radio Shack for under $5. This is the way I interfaced the two devices together, and I haven’t had a problem since. If you would rather NOT build a cable, you can find the appropriate cable on the Buxcomm website. I’ve dealt with these guys and customer service is outstanding! You’ll get your cable rather quickly.
Just a note: I’m not intentionally trying to endorse Radio Shack. It’s just that most of what you need can be found at Radio Shack and most people have a Radio Shack near them. You can find these components online for a lot cheaper, but keep in mind, the shipping may offset the price. I love to order stuff from allelectronics.com, but I generally don’t order from there unless I need to buy in bulk.
Now that I have that out of the way, make sure you have the TNC manual handy. Yes, it’s thick and it looks intimidating. Be assured that you won’t have to read the whole thing. Keep it around though, because it will serve to be a valuable tool. if you don’t have the physical manual, you should be able to find it online.
After you get your TNC and radio hooked up, you’ll need to get it set up. Walk through the setup instructions in the manual. You’ll need to input your callsign, set the baud rate to 300 for HF packet (this might be the HBAUD command for your TNC), and you may need to set the tones, or bell number as well. More on that in a moment. You’ll also need to calibrate the TNC and the radio. The manual should walk you through how to do this. It’s not really difficult, but do be prepared for it to be a little time consuming.
Before you calibrate the rig, you may want to see what the default “tone” settings are. You’ll need to know this in order to operate on HF packet. My AEA PK-88 has four different tone or bell options. For HF packet, I set mine to 1075/1275, which is tone 0, or bell 103 originate. Some use the 1600/1800 tone pair which is more common. If your TNC goes higher than that, fine, but I would stay at or below 2100/2300. Why? More on this a little later. But for now, just make sure you select a good tone pair. Note that the numbers will ALWAYS be a difference of 200. I’ll explain what all of these numbers mean in a bit.
You can calibrate your TNC with your rig in two different ways: Using the ALC meter, which is somewhat difficult, or using the power meter, which is much easier. In addition to using the mic gain control on your rig, you may also want to use the “trim pot” on the back or inside of the TNC to adjust the audio level as well. A rule of thumb is not to be transmitting more than 50% of your rig’s rated output power since packet puts a 100% load on your transmitter … even in SSB. In other words, if you’re rig can push out 100 watts, you wouldn’t want to output more than 50 watts when operating packet. If you’re a little above 50 watts, that’s fine. Pushing 60 watts won’t hurt your rig, but you really shouldn’t intentionally try to go above 50 watts, unless of course your transmitter can push out more than 100 watts.
Now that you have your rig calibrated, you need to change a couple of more settings in your TNC. Don’t worry, it’s really easy. This is specific to HF. Note that if you are using a KAM you should not need to take all of these steps as the KAM uses the 1600/1800 tone pair. If you’re just exploring HF packet, it’s not likely that you’ll have a KAM, unless you have a very generous friend who happens to be a ham they lend you their KAM.
Set the FRACK (Frame Acknowledgement) to 5. This may be the “FRACK” command for your TNC, but you should consult your manual. The frame acknowledgement is basically the amount of time your TNC will wait (generally in seconds, but check your manual) before acknowledging the last sent protocol or “packet” before retrying to resend acknowledgement.
Set the DWAIT to 0. DWAIT basically helps avoid collisions with digipeated packets.
Set PACLEN to 60. This basically tells the TNC how many bytes to send in each packet.
Set MAXFRAME to 1. This command does two things: It sets the maximum amount of contiguous packets in a transmission, and it also sets a maximum number of unacknowledged packets that the TNC will permit on a link between a station at any time.
Until you get the feel for HF packet, it’s probably a good idea NOT to digipeat packets, so make sure you turn OFF the digipeating function on your TNC. Most TNCs have it ON by default. You would turn this off by typing in “DIGIPEAT OFF” command in your TNC. Consult your manual to be sure.
In layman’s term, digipeating is actually repeating a packet that is received. Think of it as a repeater of sorts. If someone wants to connect to a packet station and they are unable to do so directly, they can establish a connection to that station through you. it works very well on VHF and it is okay to use on HF, but it will be quite a bit slower.
If you’re still hanging in there, GREAT! Now we get to the fun stuff. For our first packet encounter, we’ll use “Network 105.” You can find Network 105 at 14.105, which is on 20 meters. The reason for this is because there is a LOT of activity on this network, and you’re pretty much guaranteed to connect to someone. Now, connecting to a packet station on HF isn’t as simple as turning the dial to the desired frequency and connecting with someone. There is a little math involved.
For HF packet, there are two different frequencies we are concerned with: The mark frequency and the space frequency. This is where the tones come in. If your TNC uses the 1600/1800 tone pair, you can set your rig to 14.105 in LSB mode. it doesn’t matter what sideband you use, but for consistency sake, everyone on ’105 uses LSB, and you should too.
If your TNC uses a different tone pair like mine, then a little math is involved.
The “mark” frequency for Network 105 is 14.103.4. The “space” frequency is 14.103.2. So, if you take 14.105 and subtract 1.600 (1600 Hz) from it, you’ll get the mark frequency of 14.103.4. The same holds true if you subtract 1.800 (1800 Hz) from 14.105, you’ll get the space frequency of 14.103.2. This is all fine and good, but what if your TNC doesn’t use the 1600/1800 tone pair? This is where the fun begins.
Unless your TNC has a “tuning eye,” like the PK-232 MBX, you’ll need to figure out the dial frequency. It’s not that hard, though. We’ll start simple. Network 14.105 operators and users put their rigs in LSB. This is not required, but it’ll make our life easier for the time being.
Let’s use the example of my TNC. It uses the tone pairs of 1075/1275. We know the mark and space frequencies, and now we need to figure out what the dial frequency is. In LSB mode, we would take the mark frequency, which is 14103.4 and ADD 1.075. We get a frequency of 14.104.475. Now we take the space frequency of 14.103.2 and ADD 1.275 to that. We also come up with a frequency of 14.104.475. The frequency, 14.104.475 will be our DIAL frequency in LSB mode.
You would do the same thing if your tone pairs were 2100/2300. Remember that the smaller number (2100) is the MARK tone, and the larger number (2300) is in the SPACE tone.
Now that you’ve determined what the appropriate frequency for you should be, Set your radio to that frequency and listen. If you have everything set up correctly, you should start hearing some packet squawks and seeing some text come across your terminal screen. Depending on the time of day, it might take a bit for you to see and hear packets. You’ll probably have better luck during the day and during the weekend.
Connecting to an HF packet station is the same as on VHF. You type C followed by the station you want to connect to. You can chat with the person on the other end if they respond, and it’s likely they will. If they don’t, you will be able to leave a “message.” Once you leave a message or are done chatting, simply type D, and you’ll be disconnected. All other commands are the same as VHF/UHF packet. If you need more information on how to get started on VHF packet, check this website out. it’s quite dated, but the information can still be applied today.
There are other packet frequencies to play on besides 14.105. My first contact was actually on 40 meters with a station up in Canada. Here are just a few of the main frequencies that you can use. There are others, but these are the ones where you will likely find the most activity.
3.598 = LSB
7.086.50 = USB
7.086.515 = USB
10.149 = LSB
You would figure out the “dial” frequency on these frequencies as demonstrated above.
Now, you’re probably asking “How do I figure out the dial frequency for USB?” Excellent question! it’s basically the same with a couple of differences. You would still find the mark and space frequencies using the 1600/1800 tone pairs. So, instead of SUBTRACTING the tone pairs like we did in the first example to figure out/verify the mark and space frequencies, we will now ADD the frequencies. Let’s use 7086.50 as an example.
7.086.50+1.600 = 7.088.10, which is the “mark” frequency.
7.086.50+1.800 = 7.088.30, which is the “space” frequency.
Now that we know that, we can continue to figure out what our tone pairs will be according to the tone pairs that we use. For instance, for the PK-88 I would use the following equations:
7.088.10-1.075 = 7.087.025
7.088.30-1.275 = 7.087.025. 7.087.025 will be our dial frequency.
You can also use this equation if you would rather operate on Network 105 in USB, but you’ll need to use THEIR current mark and space frequencies. I won’t go into detail on how to do this here to save you the information overload!
let me touch on one other thing. Remember earlier in the primer I had said not to use tone pairs higher than 2100/2300? The reason why you DON’T want to use tone pairs any higher than that on HF is because some rigs have SSB filters in them that are quite narrow. If you use a higher tone pair, it may fall outside of the filter’s receiving range at the receiving station.
Some of you are probably wondering what programs you can use for HF packet. On Windows you can use Hyper Terminal, which may or may not be installed on your machine. If it’s not, you can fetch it off of your Windows XP install disc. I’m not sure if Windows Vista or Windows 7 has Hyper Terminal or not. Another great option is to use WinPack (the latest version is 6.80). It’s a pretty robust program and has a lot of nice features. It’s also really easy to set up. Make sure you go through the program settings and set the baud rate, stop bits and parity. These settings MUST match those in the communications port settings in the hardware profile. The USB-serial cable will show up in one of the communications ports.
On Mac OS X you can use the standard terminal program. You could also use iTerm, which should allow you to bookmark the terminal command to connect to your TNC once you selected it. So, how do you access your TNC in the terminal on Mac OS X? Easy! First you’ll need to know the name of your USB-serial device name in the Mac. Make sure your drivers are installed, open up a terminal window, then enter
ls -l /dev/tty.*
This will give you a list of all the attached tty devices. See which one matches to your USB-serial cable. It should be fairly obvious. For instance, my device name is “usbserial.” So, to access my TNC via the terminal, I would simply type in
screen /dev/tty.usbserial 9600
Let me break this down for you. “Screen” is the command that allows you to “see and control” the TNC via the terminal. “/dev/tty.usbserial” is the path and name of the device, where “tty.NameOfUSB-SerialDevice” is telling the terminal to access your USB-serial cable. “9600″ is the baud rate that allows your computer and TNC to communicate with each other.
You can also use the above steps to access your TNC if you plan on doing VHF/UHF packet as well, or if you have a multimode TNC.
This primer may seem very overwhelming! Keep referring back to it as often as you like! I’m sure you’ll get it. And, as always, if you need help or clarification, please feel free to post a comment and I’ll answer your comment/question as quickly and clearly as I can!
Enjoy operating HF packet! I hope to catch you on the air!