ETH005 – VHF/UHF Packet

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Hello everybody and welcome back to the Everything Ham Radio Podcast! Over the past few episode, I have noticed something that I thought was pretty much dead. The last couple Amateur Radio Club Spotlights that I have done, I have noticed that they have an active packet radio network with their club. It really surprised me because when I got my license back in about 1995, packet radio was pretty big and there were things like Rosenet, Texnet and several other networks that had a big span to them. People had packet bulletin boards, and keyboard to keyboard chatting was fairly common.

Suddenly, things just started dying, it seemed. Systems we not being maintained and going offline and the systems that I used quite a while just stopped working. Maybe it was just here locally that it died, I don’t know. Then with APRS getting more and more popular, people were finding other uses for their TNC’s and the BBS’s and the digipeaters were being used for APRS. Since I have done the last couple episodes, it makes me wonder, just how much packet is used now-a-days. So I thought that I would do an episode about Packet, since it follows along with my whole digital ham radio theme for this quarter.

What is Packet Radio?

First off let’s talk a little bit about what Packet radio is exactly. The basic explanation of packet radio is the amateur radio version of texting but with more features. It is like texting because you can do keyboard to keyboard communications with it, much like an instant messenger or an IRC on a computer. It also has other features though, because it can be like email as well or an FTP server, or a forum.

Packet radio uses a computer or dumb terminal, some kind of translator device that changes the digital signal into audio that can then be transmitted by the antenna and visa versa.

Packet Station Setup

So let’s break this down a little bit. Let’s start with the computer. This doesn’t have to be a top of line computer with all the bells and whistles, It can be, but it doesn’t have to be. Most of the time, the only thing that you will use the computer for in this setup is an interface between what is being sent and received and what you see with your eyes. It doesn’t have to be fancy, it can be an old computer that you have laying around in your attic or garage, it could be a dumb terminal that doesn’t have anything except for a keyboard and screen. It doesn’t really matter what you use. The only requirements is that it have a screen, a keyboard and some way to hook it to the next component in your system.

The next part of the packet home station is your translator, or to be specific your Terminal Node Controller(TNC). The TNC takes the signal from your computer over a wire and translates into an audio signal that can be transmitted over the air and received by another station.

On the receiving side of things, a station will receive the signal through the antenna, then the TNC will translate it into a digital signal that the computer or dumb terminal can handle and then send it onto the computer/dumb terminal where it will be stored on the screen for the ham to read.

All the above is done in about a second or less if you are talking directly to each other. There are some things to consider with this whole situation though. Everybody that is in your area that is using packet, use the same frequency. That means that if more than one set of hams is talking at once, then there could be a delay because the TNC’s are smart enough to listen to the frequency to make sure that nothing is being received before it transmits its own signal.

So what happens if you are too far away from someone that you want to talk to, are you out of luck? No! Not only do TNCs allow you to directly use it to communicate someone while you are sitting there, but it can also be used by other both when you are using it and when you are not. You can actually connect to someone else through a third, fourth or fifth or even more person to make a contact. Now, the more “people” that you use, the slower the conversation will be. What happens is, let’s say you have two “people” between you and the person that you are trying to talk to. You transmit your message the the first station, they check it and make sure that it received it correctly, then it transmits it to the next station and it checks it and then finally sends it to the person you are talking to.

There is a limit however, to how many stations that you can connect through if memory serves, but I don’t remember how much that is, I can I find find anywhere that says it. I think that it has something to do with the packet length though. There is a way around that though. If you were to use a large network, like RoseNet or Texnet or something like that, you could go several hundred miles in one of two jumps because the network is connected through a dedicated TCP/IP or HF link.

Network Schemes

So let’s talk a little bit about the different types of networks that are out there, or at least use to be out there. I don’t know first hand how much of a network there is left since like I said at the beginning of this article, I had thought that Packet had died out, but it seems like it is making a comeback, at the very least in some geographical areas it is anyway.

The section below is an excerpt of the different network type as written on the Tucson Amateur Packet Radio Cop(TAPR) website that can be found at http://www.tapr.org

Digipeaters

The first networking scheme with packet radio was Digipeaters. Digipeaters would simply look at a packet, and if its call was in the digipeater field, would resend the packet. Digipeaters allow the extension of range of a transmitter by retransmitting any packets addressed to the digipeater. This scheme worked well when only a few people were on the radio channel. However, as packet became more popular, digipeaters soon were clogging up the airwaves with traffic being repeated over long distances. Also, if a packet got lost by one of the digipeaters, the originator station would have to retransmit the entire packet again, forcing even more congestion.

KA-Nodes

Kantronics improved on the digipeater slightly and created KA-Nodes. As with digipeaters, KA-Nodes simply repeat AX.25 frames. However, a KA-Node acknowledges every transmission at each link (node) instead of over the entire route. Therefore, instead of an end-to-end acknowledgment, KA-Nodes allow for more reliable connections with fewer timeouts, because acknowledgments are only carried on one link. KA-Nodes therefore are more reliable than digipeaters, but are not a true network. It is similar to having to wire your own telephone network to make a phone call.

NET/ROM

NET/ROM was one of the first networking schemes to try to address the problems with digipeaters. A user connects to a NET/ROM station as if connecting to any other packet station. From there, he can issue commands to instruct the station to connect to another user locally or connect to another NET/ROM station. This connect, then connect again, means that to a user’s TNC, you are connected to a local station only and its transmissions do not have to be digipeated over the entire network and risk losing packets. This local connection proved to be more reliable.

NET/ROM doesn’t use all of the AX.25 protocol. Instead, it uses special AX.25 packets called Unnumbered Information (UI) packets and then puts its own special protocol on top of AX.25. This is again used to increase efficiency of its transmissions. NET/ROM nodes, at regular intervals, transmit to other nodes their current list of known nodes. This is good because as new nodes come on-line, they are automatically integrated in the network. However, if band conditions such as ducting occur, ordinarily unreachable nodes can be entered into node lists. This causes the NET/ROM routing software to choose routes to distant nodes that are impossible. This problem requires users to develop a route to a distant node manually defining each hop instead of using the automatic routing feature.

NET/ROM is a commercial firmware (software put on a chip) program that is used as a replacement ROM in TAPR type TNCs. Other programs are available to emulate NET/ROM. Among them are TheNet, G8BPQ node switch, MSYS, and some versions of NET.

G8BPQ

In the early 1980s John Wiseman, G8BPQ, wrote a Personal Computer (PC) to NET/ROM multi-TNC gateway to support W0RLI, F6FBB, PRMPS and other BBS. The self-named G8BPQ code could interact with a network of TNCs and act as a driver for the BBS application program.

As of 2015 John still adds to and supports that program and it is now available for most MSWindows, MacOSX, and Linux (including one for the Raspberry Pi) distributions in pre-compiled and source file downloads.

It became sufficient and even advanced in that it now serves as a TCP/IP gateway, stand-alone packet radio network node, HF multi-protocol system, and a framework to support many different kinds of fully emulated TNCs.

The TARPN organization, dedicated to Amateur Radio VHF/UHF packet, uses, and documents the use of G8BPQ on the Raspberry PI embedded platform for a purely ham-radio slow-speed network.

ROSE

ROSE is another networking protocol derived from X.25. Each ROSE node has a static list of the nodes it can reach. For a user to use a ROSE switch, he issues a connect with the destination station and in the digipeater field places the call of the local ROSE switch and the distant ROSE switch the destination station can hear. Other than that, the network is completely transparent to the user.

ROSE’s use of static routing tables ensures that ROSE nodes don’t attempt to route packets through links that aren’t reliably reachable, as NET/ROM nodes often do. However, ROSE suffers from the inability to automatically update its routing tables as new nodes come on-line. The operators must manually update the routing tables, which is why ROSE networks require more maintenance.

TCP/IP

TCP/IP stands for Transmission Control Protocol/Internet Protocol. TCP/IP is commonly used over the Internet wired computer network. The TCP/IP suite contains different transmission facilities such as FTP (File Transfer Protocol), SMTP (Simple Mail Transport Protocol), Telnet (Remote terminal protocol), and NNTP (Net News Transfer Protocol) The KA9Q NOS program (also called NET) is the most commonly used version of TCP/IP in packet radio. NOS originally was written for the PC compatible. However, NOS has been ported to many different computers such as the Amiga, Macintosh, Unix, and others. Smaller computers like the Commodore 64 and the Timex-Sinclar do not currently have versions of NOS available. TCP/IP based amateur networks are becoming more common each day.

TexNet

TexNet is a 3-port switch designed to create a 9600 baud backbone with 2 local access channels. The TexNet network provides transparent network access to the user. The user simply accesses his/her local TexNet node and then either connects to a user at another node or accesses various system services. TexNet provides the stability of fixed routing, while allowing new nodes to be automatically brought into the network.

BULLETIN BOARDS

Another feature that packet radio has is Bulletin Boards. This could be an area wide bulletin board or a personal bulletin board. Some areas that have a packet system in place will have one station that serves as a bulletin board for the entire area. You can connect to this station and leave a message for someone else, or a club can leave a message for all of it’s members, or even traffic passed through the National Traffic System.

Another functionality of packet is a personal bulletin board. I think that Kantronics brand tnc’s were the only ones that had this feature, but I’m not 100% sure on that. If someone connected to your station while you were away, they could leave you a message and a little light would come on the front of your TNC that would show that you had a message waiting for you. Kind of like sending an email to your friend or something.

CONCLUSION

Now that we have talked about what Packet is, and some other features and uses of it, the only thing we have left to discuss is, is it still a feasible system to use. In some ways I could see that packet could still be a viable option to emergency communications, however, I’m not sure that the supporting backbone structure is still around to make it feasible. I see it’s main purpose really being as an emergency communication system and even then it’s iffy. With technology going the way that it is going, I see other things taking it’s place in the features that it has going for it.

Let’s take the internet out of the equation all together. If the networks that we talked about before are still operational, how many of those nodes use the internet as a connection median. Will those connections still be operational in the event of an emergency? If the links are over HF, then it could still be operational but would be dependant on band conditions.

Getting passed the distance factor and let’s focus on just smallish scale, like city wide or something. What options do you have with packet, basically text messaging only. You can’t send pictures, you can’t use voice. So you are severely limited, but that may be ok. If you have other avenues for voice comms, then great, you can use packet.

I honestly don’t see packet making a comeback. There is so much more out that that we as hams have access to, like Hamnet mesh networking for example. With hamnet, nodes are self discovering and self connecting so you don’t have to manually connect somewhere to do what you need to do. You can do voice communications, picture and/or file transferring, keyboard-to-keyboard communications, video, and so much more. All this being said, it does have a downside over packet in that it transmits on 2.4 or 5GHz so it has less of a range so you will need more “nodes” in the network to cover the same geographical area, but I think it is a small price to pay.

I personally think that Packet is a dying system and really the only reason it is still around is because APRS uses packet protocols. If you are reading this and you live in an area where packet is still alive and kicking, please leave a comment below and let us know how it is used in your area.


Amateur Radio Club Spotlight

Motorola Amateur Radio Club of Arizona (MARCA)

Website: http://www.w7mot.org

  • Some of our activities include maintaining & operating about 2 dozen repeaters located on Arizona mountain tops and the Phoenix area; expanding our experiences into new types of repeaters, such as Dstar & Fusion; Participating in ARRL Field Day typically held in the mountains near Forest Lakes, Az. (this is a very active activity) ; ARRL FMT contests; and Antenna construction, including mountain top tower climbing. Many members are, individually or in groups, active in HF activities such as Voice, Digital, CW, DXing, Digital HF modes, MESH, and EOC operations around the valley, including contesting,.
  • Meeting are held the 3rd Tuesday of each Month. Meetings start at 6:30pm and are typically 2 hours duration. The agenda typically is a business meeting, lasting about an hour, followed by a Presentation of interest by a guest speaker or club member.Meetings are held at the Denny’s on Broadway, south side of street, just east of Priest Rd., in Tempe. Denny’s, 1343 W. Broadway Rd., Tempe, Az. 85282. Next meeting is the day this podcast releases, Feb 16, 2016 at 6:30pm at the above location.
  • List of repeaters: http://www.w7mot.org/index.php/repeaters/repeater-list
  • Map of Repeater Locations: http://www.w7mot.org/index.php/repeaters/repeater-map
  • On their website you can find a very extensive file depository of a variety of information. While looking through their site, and actually one of the reasons that I chose this club to do the spotlight on this episode was their hammet mesh network presentation. Hamnet is something that I am extremely interested in and have been trying to learn more about it since I first did a post about it a few months ago. Those posts can be found here and here. The experiment that they documented in this presentation makes me hopeful that I can do what I am wanting to try and do here locally.
  • The have presentations on things from hamnet to APRS to NTS to Software Defined Radios. The also have a very active newsletter which appears to be a combined newsletter with a bunch of other ham clubs in the area.

That brings us to the end of this post. I hope that you enjoyed this blog post as well as the accompanying podcast episode. Please leave a comment below and let me know what you thought about this episode. Also, please head on over to ITunes and give me an honest star rating and review. This will really help me in the rankings of my podcast and help other people find it.

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