KD0TLS: Intro to -IS only operation

 Perhaps decades ago, the distinction between RF and internet-based operators was stronger. But nowadays, most people move seamlessly between RF and -IS (Internet Service) operation without a thought. There are extremes on both ends, but little of the existential angst you might find between, say, analogue FM and digital FM operators. 

Operators that use the internet exclusively often do so because they don't want to install a mobile rig in their car, or can't set up a home RF station. In other cases, people have specific objectives that don't need RF-based operation, such as weather station reporting, telemetry, maintaining objects, etc. The CWOP (Civilian Weather Observer Program) has servers in amateur IP space, although most stations aren't run by amateur radio operators. 

 

Even operating exclusively on -IS, there's a lot of cross-over. For example, if you set up APRSDroid to run on your wi-fi, you'll be able to see the raw packet data and watch RF traffic being gated in real-time. So, you're not completely insulated from the RF world. Certainly other software does the exact same thing. Once you understand how to read the raw packet data, you'll start to see the ebb and flow (as well as the huge reach) of our local APRS network. 

 

Some people operate on -IS to conserve our resources. Keep in mind that 144.39 MHz is a shared simplex channel. It's highly doubtful that this single frequency could accommodate all of the metro APRS traffic. If you intend to broadcast your home location every three minutes (as some do), then maybe APRS-IS would be a considerate alternative that wouldn't consume vast amount of limited RF resources. This is also why objects (e.g. repeater locations/info) are run on the -IS, and OpenSpot stations maintain an APRS presence without creating congestion for RF-based operators. 

 

You may also find your APRS-IS station information being broadcast over RF. For whatever reason, the Faribault gateway (N0QVC-1) takes a lot of internet-based traffic and transmits it over RF as a STATUS packet -- which means it won't be re-gated, thankfully. I'm not sure what the radius is on this "service", but I've seen -IS stations as far from Faribault as Hugo being re-transmitted. With this "service", RF-only operators over a wide area can be made aware of the existence of your station, provided they are watching real-time raw packet data... because it's just packaged as STATUS packets from N0QVC-1. 

 

I've never heard any -IS only operators make disparaging remarks about RF-only operation, though that's a favour that is often not reciprocated by RF-only operators. A lot of it has to do with EmComm, and the false idea that the internet is unreliable in emergencies. Whatever disaster that wipes out the metro internet would be quite likely to take out a lot of the RF-based network as well. In fact, the RF-based network would most useful in such a case to connect to internet-based traffic outside the affected area -- so the two work hand-in-hand. 

 

All of this is just to emphasise that you should never feel apologetic about being limited to an -IS only APRS station. For years, I kept an -IS station active so that I could receive messages. If more of our local operators did that, APRS messaging would be much more compelling. 

 

KD0TLS: metro infrastructure status 10/30/21

 Here's a shot of the current metro gateway/digipeater arrangement: 

METRO APRS 10/30/21

All of these coverage maps can be enlarged by clicking on them.

There are a few familiar faces missing from this picture that those who follow the local APRS may be aware of:

• K0YTH-13 digipeater in Robbinsdale
• N9MEC gateway in Apple Valley 
• KB0HQD-10 RX-only gateway in Lake Elmo  

A new entrant to the field is N0KGK (Jim), a relatively new Tech running a digipeater out of his home QTH in Burnsville. It's a little unusual that this station doesn't broadcast the software it's using, but it seems to be a digi with decent coverage in a part of the metro where coverage seems to be declining. Even better, it's a using an alternating 10/30 minute interval between its ID packets. This makes it a very considerate user of the limited simplex space on 144.39 MHz 

N0KGK digi coverage 10/30/21

 I would rather have seen a TX gateway in this spot than a digipeater. We could really use even a modest TX-gateway station south of the freeway loop to expand messaging coverage. An RX-only gateway would also have been an effective addition, increasing redundancy in the Burnsville, MN area. Still, the addition of an RX-only gateway in Lakeville, Rosemount, or Farmington could very well leverage that N0KGK digi coverage to use metro TX capability to reach messaging stations serviced by south metro RX infrastructure. Conversely, an RX-only gateway Uptown or in Linden Hills would consolidate a lot of south metro suburban coverage gaps that N0KGK fails to reach.

 The loss of N9MEC seems more ephemeral, hopefully. This gateway has seen declining coverage for years. At one point, it used to reliably gate packets into Downtown Minneapolis. Now, it struggles to receive any stations south of the River. For some reason, it's had a very nice signal path to N0HOY-10 in Arden Hills, allowing a lot of local traffic to be funneled to N9MEC. It's primary strength has been its reliability, but now it's disconnecting from APRS-IS -- which makes it impossible to be an RX-only gateway. 

 KB0HQD has maintained an RX-only gateway in the east metro for years, adding reliable coverage for marathons and western WI digipeaters. Sadly, it dropped off the map back in July 2022. The K0JDD gateway in Woodbury does a fairly good job of covering that area, but we could still use another RX-only gateway in the Hudson/Stillwater/Lake Elmo area. Our border gateways handle an inordinate amount of Wisconsin digipeater traffic, and having some additional gateway capacity in that east metro fringe adds crucial redundancy. 

 I have mixed feelings about the disappearance of the K0YTH-13 digipeater in Robbinsdale. While it's presence benefits my station's coverage considerably, I have doubts as to whether adding a "dumb" digi (i.e. not connected to the internet) just adds RF noise or increases low-power stations' access to big gateways. K0YTH-13 has become less reliable over the past several years, and the metro could use an unreliable RX-only gateway more than it could use an unreliable "dumb" digi. 

K0JDD gateway coverage 10/2021

 While being located outside of the freeway loop, K0JDD-10 reaches into St. Paul quite nicely to provide direct gating coverage. It also holds down the SE portion of the metro's coverage, while providing messaging services into Wisconsin. 

K9MLS gateway coverage 10/2021

 It's nice that K9MLS has become more stable. I still question why we need another digipeater six miles away from N0HOY-10 and K0LAV-8, though. Yet, K9MLS operates on a respectful 20-minute beacon interval, and seems to be a "smart" digipeater (while also operating as a gateway, of course). This means that it's less likely to contribute "noise" to our local simplex channel. 

K0GV-10 gateway coverage

 K0GV-10 is back on the scene after being down for a few weeks. It's a two-way gateway, so it provides messaging service to the west metro area. Aside from covering I-494 quite nicely, it also provides fill-in coverage across the metro. If the western exurbs were ever to get improved digipeater coverage, K0GV-10 would be the gating element of that equation.

 Bear in mind that these coverage maps are really worst-case scenarios due to the way that aprs.fi handles the server data. Packets sent using WIDE2-1, for example, are considered suspicious by aprs.fi and are excluded. 

W0YC-5 gateway coverage

 The two big gateway/digi stations, W0YC-5 and W0PZT-1, provide an excellent baseline coverage across the metro. They also reach far outside the metro, connecting us to other parts of Minnesota and adjoining states. But, since APRS is a network, we need additional stations to provide a finer level of coverage and add redundancy to the network. 

 

 For several years, the metro APRS coverage operated on a fringe model: traffic from outside the freeway loop was funneled into the core gateway (W0YC-5) by digipeaters on the fringe of the metro. These digipeaters on the fringe would then re-broadcast metro traffic to the more far-flung exurban/rural areas. 

 

 To some extent, that's still the case. But the addition of W0PZT-1 (then known as N0AGI-1) created a second focal point that linked the metro much more tightly with digipeaters across the state to create a fairly robust RF-linked network. While there are still several parts of the state with poor coverage, there have been notable expansions that have made some rural areas "self-sufficient" in terms of APRS coverage and infrastructure. 

 

But, if you look at the digipeated (rather than directly-heard) coverage of even modest metro gateways, you will see that the metro still handles an out-sized share of traffic from rural areas of Minnesota and Wisconsin. This is less than ideal, and almost certainly can only be solved by adding additional rural gateways. 

 

N0ALE: My Entrance into the World of APRS

 

    Hello my name is James and I've been a licensed operator since February 2015. After getting my license, my exploration began into the various niches of Amateur Radio and once of those niches I wish to give my account on is APRS. I had always heard people talk about using APRS and setting up I-Gates etc. At that time I hadn't really given any thought into APRS as a whole and I didn't know what this all entailed. To me setting up an I-Gate sounded like a rather complicated process. As a result of doing some research I finally decided to take the plunge into the world of APRS and purchased my first modem. The modem itself was made by Mobilinkd and connected directly to my HT via a cable.

    This particular modem also had Bluetooth so I could Bluetooth it to my phone or tablet. After getting everything set up I took it for a spin on the air and was excited to see the RF packets I was receiving come across my screen. I was now officially on the APRS network. Aside from beaconing I could message stations, send one way emails and send SMS messages. I played around with these different aspects of APRS and after a while I decided that I would help contribute to the integrity of the APRS network as a way of giving back. At this point in time I had researched deep enough to now know what an I-Gate was so I went to work setting one up. I went with an I-Gate because there were plenty of digipeaters in the Metro at the time and I didn't want to add to the congestion on the RF side.

    My first I-Gate was rather primitive and also unstable. I used that same Mobilinkd modem linked to a spare radio and some APRS software running on an extra computer I had around. However because of the stability issues I knew eventually I wanted to get a standalone device that I could deploy quickly and not have to have a dedicated computer running 24/7. Finally after a few months I decided on a device made by Microsat in Poland. It was their WX3in1 Plus 2.0 model which had a built-in digipeater and I-Gate. The only downside is for the network connection it was ethernet only which I did not have readily accessible. Being someone with a network engineering degree I created a dedicated 5 GHz bridge link to the router downstairs so the device had internet access for gating packets.

    This particular I-Gate runs at my home under the callsign N0ALE-10. I configured it as a bidirectional system with a simple distance filter for gating packets from the internet to RF. With the new I-Gate system online I also decided to upgrade the DC power system that powered the host radio and other equipment. I had existing wiring in place but wanted something cleaner and more organized (both for safety and quicker diagnostics). My current wiring scheme puts my older wiring schemes to shame. Every circuit has a dedicated DC breaker with a push button reset. The DC power supply that powers everything is hooked up to surge protection to help protect the system from any unexpected surges that may arise. As of today the system has been running great with very little downtime and continues to gate packets from mobile stations across the East Metro.

    I should also mention the antenna for this whole system is indoors and always has been since I was first licensed. I take pride in just how well it can hear and transmit given where the antenna is located. My hope is to keep the system up and running as long as I can. One thing I know is this experience has taught me a great deal about the inter-workings of APRS both from the perspective of being a user and now a contributor.

KD0TLS: The passcode obstacle

 A whole lot of hams never got on to APRS because of a simple barrier: the  passcode. 

APRSDROID asks you to enter a passcode

 Most apps require a passcode to install or operate on the internet (APRS-IS) side. How to get this magical passcode has been something that has never been explained well. Back when I first was exploring this, the official League advice was "Ask someone running an I-Gate". In other cases, app developers will tell people to send an email to some address that becomes unattended. 

 Basically, APRS needs a way to ensure that you are a licensed amateur radio operator, much like EchoLink does. The APRS passcode, however, is far from some highly secure system. It's nothing more than a "hash" of the callsign in question. 

 The best way to get your passcode is to Google "APRS passcode generator", which will provide you with several. Any of these will do, and they tend to come and go. One such generator is this, by N5DUX. If you enter your callsign, the generator will give you the 5-digit number derived from your sign.

 It should become obvious immediately that you could enter ANY callsign on that page, and it will generate a passcode for it. Anyone can impersonate anyone, and non-hams can literally make up a non-existent callsign and use that. It's almost ironic that this system has become such a common obstacle to legitimate users. 

 If you decide to send an email to someone asking for your passcode, that person is extremely likely to use a generator similar to the several others out there. Waiting for a busy developer to do that is kind of pointless. Just do it yourself. The convention is that the software developer is supposed to provide the passcode to their users, but that's an obsolete notion to my mind. Especially with so much old and unsupported software out there, we should really just tell people to do it themselves.

 I've always thought that a club should provide you with your APRS passcode as soon as you become a member. It's a simple, free service that could help someone get on APRS easier. I have no idea why so many continue to push the idea that there's some secret method or some special people you need to convince before you can get on APRS. 

 Last, if you get a vanity callsign, don't forget to get the new passcode to go with that sign. You might be surprised at how many people get angry over their software suddenly not working, or some faceless APRS authority doubting their license status, when the problem is just that they didn't update their passcode.

Todd KD0TLS

KD0TLS: Getting in to it

  I had a relatively hard time getting into APRS. While that was only nine years ago, much has changed in the local infrastructure, hardware available, and resources to help solve issues. In a way, the obstacles I faced made me more excited to participate in APRS when I figured things out. 

 Even before I was licensed, I saw a video where two operators sent text back and forth during a hurricane. The noise from the storm was so loud that it would've drowned out their voices, so they connected a computer to a radio and passed information without the internet via text. This fascinated me. I had no idea these two people were using APRS, or even what APRS was. The idea of connecting computers to radios seemed really cool, but I had no idea at all how to do it. 

 When I got my license, I tried to find out about what this kind of operation was and how I could do it. Eventually, people mentioned terms like "packet" and "APRS" while providing no more information than that. I googled "APRS" and found enough information to understand that this was what I had wanted to do years earlier. Finding out how to do it myself was not so easy. Over and over again, I came across ancient and cheesy websites from the '90s that tried and failed to provide any useful information. Virtually all of the hardware mentioned was discontinued. Everything seemed to be written at the level of someone who already was well-versed in the subject, so it was impossible to gain any practical knowledge from these "resources".

  These instructions telling me to "put my TNC into UNPROTO" were basically useless to anyone who didn't already understand packet operation. What's a TNC? How do I put it into UNPROTO? What the hell is UNPROTO? The more I explored online 'mentoring', and the more I was exposed to 'help' from my Esteemed Elders, the more I came to understand that this phenomenon was typical in amateur radio. The entire point of "Elmers" was, apparently, to express the idea that they were smarter than you. If your problem got solved with this approach, it was a sheer coincidence.

 After explaining that I'd looked at dozens of web pages and had not found out how to get on APRS, my Esteemed Elders 'helped' me with the following responses:

• "Do a Google search"
• "You can do that on HF, so get your General"
• "Nobody does packet any more. Get your General"
• "I tried that once and it didn't work. Don't waste your time"
• "You're not gonna get Worked All States on APRS! HaHaHa!"

 It really convinced me that none of these Big Experts had any idea how to get on APRS, or even what it really was. Rather than admit that, they just tossed out inane 'solutions' and doubled down on them. 

 What changed for me is when I came across a post on an amateur blog describing the (new, at that point) Mobilinkd TNC. As I dug into this more and more, I saw stories of people using an HT, a smart-phone, and the Mobilinkd device to get on APRS! It looked easy, and I didn't need to buy a $500 mobile rig with native APRS to try this out. I already had an HT and a smart-phone, so I ordered the Mobilinkd TNC. I expected it to be very complicated, but I thought I could probably find specific help for the device instead of general help for APRS itself.

 With a toe-hold to work with, I quickly found out about the (new) APRSDroid app and I installed it on my Android phone. Wow! I could get on APRS without a radio while I was waiting for my TNC to arrive. It was exciting, mysterious, and satisfying at the same time. I had beaten the odds and out-smarted the 'mentors' to find my way into APRS. And getting my radio connected to it was a personal triumph. I could send packets across the metro, even further with digipeaters. I could see who heard me and how far my beacon signals went. I could see all of the metro traffic at once, and read the packets to understand what was happening. The Mobilinkd TNC was actually pretty simple to configure, and it made everything else so much easier to do.

 It was a whole new world, and I didn't even know about messaging, gateways, bulletins, objects, and telemetry at that point. 

 In future posts, I'm going to describe ways for you to get on APRS -- whether using RF or the internet -- and make it as easy as possible. Your entry may very well be completely different than mine. You may use a Raspberry Pi HAT, or a dedicated self-contained tracker. You might use an app on your IPhone, or an old Chromebook running Linux and DireWolf. You might use an expensive Kenwood mobile with APRS built in, or an old analogue scanner plugged in to an old Win98 box. 

 You can get into APRS pretty cheaply and still participate. You don't need towers with beams or $300 TNCs. You'll be surprised what an HT can do when it's plugged in to a 1/4-wave ground-plane or a roll-up J-pole hanging off the eaves of your garage. I set an HT with a stock duck in my window sill and plug it in to a Mobilinkd TNC to get in on the action across the metro. 

 And when you find your way, maybe you can write about it and get it posted here to help other people in the community experiment with this aspect of the hobby.

 

Todd KD0TLS

My APRS Digipeater Overview

Todd has built me up as an extra-class ham that might know something. I hope that I can live up to everyone's expectations. Thank you to Todd for the invitation to contribute.

Here is a brief description of my APRS gateway/digipeater station configuration:

I will start away from the radio-frequency side, the Internet connection. I use a DSL connection to the internet. Since bandwith requirements are very low, your family can still stream movies and surf the internet with your APRS gateway operating. Bandwidth requirements are so low that you could run an APRS gateway on an AREDN network connection or a D-Star data connection (both topics for another article) with plenty of bandwidth to spare. If you wanted to spend money on modems and copper telephone lines (remember them?) you could easily support an APRS gateway on a very low bandwidth 33.6kbps dial-up connection to the Internet. (Does any ISP support dial-up internet today?)

The computer I am using is an over a decade old quad-core computer that was given to me. It is running Ubuntu Linux, 64 bit Desktop version 21.10. This is much more computing power than what is required; a dual-core machine would be more than enough computing power for the task, and with modern operating systems is the minimum hardware required. Use whatever hardware and operating system you have; the software I am using will run on Windows just as well as it does on Ubuntu Linux. In fact, I have successfully run my station on an old RasberryPi, so if you have an old computer laying around chances are it will work for this application perfectly. The computer decodes and encodes packet audio using a software package called DireWolf. The software I use to actually digipeat and process packets to the APRS-IS network and also display stations on a map is YAAC. DireWolf has been rock-solid, and YAAC is very well supported by the user community and the developer, Andrew Pavlin KA2DDO. If you decide to use this software I would be happy to assist you.

 A Screen capture of my Digipeater/Gateway in operation. The large gray window is YAAC showing other stations in the area. This is covering part of the window with the white background; this window is DireWolf and shows packets going to and from the radio.

Many people use fancy and expensive interfaces between their computers and radios. I use a very simple homebrew computer to radio interface. Transmitter keying is accomplished via a serial port on a USB to serial adapter. The DTR line in the serial port switches a transistor on to transmit. Audio from the speaker output on the computer to the microphone input on the radio is reduced by a simple resistor attenuator.

Computer to Radio interface and schematic.

 

 

The radio is a Yaesu FT-50 handheld; transmit power is set on high, which is about 5 watts. It is powered by the 12 volt output of the computer power supply. In the event of some sort of malfunction I can log into the computer remotely, shut down the computer and radio will also be shut down since it is powered from the computer. The radio is connected to a second hand Cushcraft 2 meter Ringo that is missing the lower set of radials. It is at about 20 feet up in the air on a PVC pipe that is attached to my deck with large hose clamps. The radio is connected to the antenna with about 40 feet of RG-8 coaxial cable.

Second-hand antenna on PVC pipe mast.

 

How everything is configured and how audio levels are set along with other details will be covered in future articles. I will also provide details about my mobile station at a later date.

--Dan Meyer / n0kfb

Your APRS community, contributors

 Unlike many aspects of amateur radio, APRS is one that seldom operates in isolation. APRS, by its very nature, is part of a network or community, and is grounded in another group's efforts determining the measure of success your entry into that aspect will be. 

 Without a gateway or digipeater involved, your signals on the RF side of APRS will be limited. Even your internet-based interactions with the APRS servers involves you accessing IP space only available to hams running servers for other hams to communicate with amateur radio operators around the world. You become, whether you like it or not, part of a community in which your interests are entwined with other operators' interests and actions. 

 At this juncture, we have an Extra Class operator who has agreed to write on a regular basis. This would be Dan N0KFB, who has operated both mobile and base APRS stations for over a decade. The amateur community also benefits from the insights of a new entrant to APRS, Robert KA0RXU. This General Class ham has placed himself on the air using Apple software and an HT connected to an external antenna. One of the giants in the local APRS world, Matt N0YNT, is an Extra Class source of hands-on wisdom. He will contribute a few articles every year. And Stephen KF0AED will tell us of his entry into APRS, and how you can do what he does every day. 

 I, myself, Todd KD0TLS have operated on APRS for several years using a Mobilinkd TNC as a modem and various HTs (plus a few mobiles) as the RF end of my participation. I've run a TX APRS gateway from my condo in Plymouth for several years, and I frequently gate/transmit APRS messages. Even though I'm just a Technician, I've found a way to connect with the worldwide fun using a mag-mount antenna on my balcony, and a 10W HT in my car.

returning

  This blog will be returning to active status by the end of the year.

The topic will be limited to APRS for a few weeks, and then GMRS might be added. 

If the harassment starts up again, I will post the emails and callsigns here and I will suspend the blog once again. I would suggest that these Esteemed Elders simply "spin the dial" and find another blog that suits their tastes and parrots the hobby's group-think. 

 If you would like to contribute content to the new incarnation of the blog, contact me at kd0tls@amsat.org 

 

EDIT: At least two local hams have agreed to provide additional APRS content by becoming regular contributors. Maybe you have a story to tell involving APRS, or a vision of what it could be, or an explanation of how you got involved in APRS. Maybe you're just getting in to APRS, and you want to inform the amateur community of ways they could benefit from this aspect of the hobby. You don't need to be a skilled writer; sincerity goes pretty far in this kind of thing. Talk about what you know, what you've done, and what you think -- and you can't go wrong.