Thank you very much. Hello. Good afternoon. Hope you're all well. Not cooking up too much
in this room. My name is Manuel, so I'm a radio amateur. I renewed Nerd if you prefer. I like
experimenting with new or older equipment, see what we can do with it, or use existing
software or hardware and deploy it as widespread as possible. If possible, within the amateur
radio community and keeping things open source whenever I can as well. So today I'm about
to talk about cutting-edge technology straight from the 1990s, pagers. So if you've seen
those things, well, it might bring you back some memories because they were heavily used
in the 80s and the 90s. It was used by mostly doctors, drug dealers, or businessmen, sometimes
the three at the same time. So basically they were everywhere in the 90s and started to disappear
later on when GSMs made their operation. But this was something really common. In those times,
you can still see it in TV shows, medical TV shows, getting paged, the doctor's getting paged
because there's a code blue, whatever that means in room 204. Now, I'd like to explore this thing
because behind this hallmark from before, they're extremely simple communication systems. And I
think it's worth exploring them a bit more and see what you can do with it today in the open
source community and the amateur radio community. So today we'll be looking at what is paging in
itself, what does that mean, how does it work, generally speaking. We'll go a bit into the
technical part of it. So how it works, the modulation types, how you can make a pagering,
and then we'll bring that into the amateur radio context. We'll talk about the DapNet project,
which has been around for a few years now, what you can do with it, how you can get started,
and then I'll be open for questions if you have them. So coming back into the techniques,
let's talk about paging in simpler terms. Paging is basically sending a message,
making a small device ring one way or another, very often to small, low-powering, compact
receivers. Most of them use a standard which is called PoxSag, which was developed in the 1980s,
but much older standards exist and are almost not used anymore. So PoxSag is one of them that
remains. The other one being developed by Motorola and proprietary, but we don't talk about that here.
The topology is always the same. You've got one big transmitter, high power, and then you've got
your receivers around that receive the messages whenever there's one. So the frequencies, you
have them starting in 8-chef, I should have put that. So you've got pagers on 27 MHz and then all
the way up. Here in Belgium, the national services use 160 MHz. In other countries, you will see them
in 460 MHz and sometimes even higher in the US, they're all up to 900 MHz, if I'm not mistaken.
So you see them on a lot of different frequencies, and you also see that compared to a classic two-way
radio, the antenna is built into the device, which is itself a challenge because it means that your
signal needs to be higher in intensity to be received by those antennas because they perform a bit
less than the standard WIP antenna. Use cases in the commercial world, you'll find them, for instance,
for one single hospital to be able to call doctors or industrial scale systems or sometimes a bit
bigger. National scale being one of them. Here in Belgium, we have one single frequency for a
distributed system of transmitters operated by Astrid, which is used by firefighters, ambulance
services and others, so it's still being used today. You will see them also in foot trucks or in order
to take away food courts such as if you've been to the wolf two days ago, you'll receive a little
pager that would have rang, sorry, whenever your food was ready. So this is also a pager in itself.
How does that work? As I said, it's using one single frequency, a specific carrier that we modulate
in FSK, so simple frequency shift keying. You send a zero by shifting one way, the other way is a zero,
so just by shifting one from one to another, you send one zeroes and then format it into very
simple packets. So very often, please mute your radio, just saw it. If you want to send a packet
usually, you send a preamble that wakes the receiver up because those receivers usually
sleep for long periods of time and wake up from time to time to see if there's not a preamble for
them there. And once it wakes up, it will start decoding the signal and then it sends an address
and the linked message. And if the address doesn't match the pager's address, it will just shut down,
go back in sleep mode, so that makes for very power efficient receivers. So this thing can last up
to one month on one single AA battery. So yeah, that's pretty much the idea. Again, if you want your
pager to receive a message, you put the address into it, basically. So if you want, for instance,
to program this message, which is aimed at the pager with the address 101, you put the address
101 in the pager. If it receives it, it displays a message and rings. Otherwise, it will just stay
asleep because this is, for instance, a message for 102, not aimed at the pager itself, it stops ringing.
Now, you can also make group alerts that way. So it's quite simple. You just put the same address,
recall the RIC. You put the same RIC across all pagers and if they receive it, they will just
ring altogether at the same time, displaying the message. So that means that for individual or
group calls, you basically address one individual ID to a single pager and then you put one common
group ID across all pagers. So you can select if you want to address one person or a specific group
and you can organize your system this way. So it makes for a very simple type of receiver and then
you can see yourself when you're building the network how you're addressing each pager or
each group of pagers. Poxa-Agonamator Radio is not new. It's been done since the 1980s. I think it
appeared at the same time as paging itself, so we started filling with that a long time ago. We use
the TNCs connected to old VHF systems and yeah, the thing is you had to modify the pagers themselves
very often by changing quarts and retuning the receiver loops to make sure that it felt between
the amateur radio frequency allocations. But very often those were individual stations
used for bulletin board systems at the time, for weather alerts or that kind of messages.
So it kind of disappeared when packet radio really folded after the 90s. So right now the only thing
we know on packet radio is mostly APRS or the more widespread you use is IPRS. So BBS, you don't see
them anymore and the technology got lost in the ages. But now we have easier ways to interconnect
stations together using HandNet for instance. So you now have IP links that can be made on
amateur radio frequencies quite easily with modified Wi-Fi equipment or others. And there's a team from
the Akan University of German Radio Amateurs that developed a network of internet-connected
Poxa-Agonamators using free and open-source software and that is the DapNet project.
So DapNet stands for Decentralized Amateur Paging Network. The idea is to have
various core servers that are geographically separated, interconnected via HandNet,
that exchange the messages through multiple nodes. So if you have one, fails, the others will take over.
Now of course if you're outside of that HandNet link, you can always get a bridge through
internet and this is what I'm doing here because I don't have an HandNet link here. We still haven't
brought the HandNet links from Germany up here until unto Brussels. But you can go either way.
The frequency is almost universal. Depending on your regulations we try to stay on the same
frequency everywhere which is 439.9875 megahertz. That's a mouthful but that's the one we try to
use everywhere. The only exception right now I see is the Netherlands because they don't have the
access to this frequency so they're using a frequency on 432 if I'm not mistaken. But I mean
from with this pager I can use it basically in Belgium, in Germany, in Switzerland. There are
some transmitters in France as well so it's growing little by little. Now for addressing transmitters
they have to be synchronized one way or another otherwise you have several transmitters
that start keying up at the same time and then we'd interfere with on another. So they split up in
time slots so if you have two overlapping transmitters you'll put one that transmits on one time slot
and the other one that will transmit on another time slot. Just make sure they don't transmit at the
same time. So what happens is you send a message on the DapNet infrastructure and as I said this
only records basic numbers so there's no call sign you can encode in there. So there's a database
on the DapNet infrastructure that links your call sign to an identifier. Very often we put the DMR
ID because this is a way to identify hands with numbers and then it matches to this specific
rig, this specific address, sends it to the transmitters that are linked to the area we
selected so you can key up all transmitters or regionalize your calls. So you can say that if
you know that the person that you're trying to reach is in Belgium you put Oscar November dash
all. If you want to reach an area in a specific province well you can narrow it down and try
not to use the network as extensively and just try to reduce the load if you know where your
person is. Same for Germany, the Netherlands, Luxembourg, France there's this same kind of
geographical way of cutting the transmitters. You can also make group calls so there are
we call them rubrics and you have some for weather alerts, DX clusters etc etc. I'll come back to this
in a moment. So what can we do with that? Well pretty much whatever you want.
You can send messages manually to a specific pager via the handpager.de website. There's an
Android app, I think there's even an iOS app but I don't know what's the status on that.
Via the DMR infrastructure from Brandmeister, from APRS, from Tetra, so basically sending a text
message from your radio will make it land on the DapNet infrastructure and then it will relay it to
to your person you want to call. Then there's an API you can use to send weather alerts. There are
automated messages for urgent alerts which will make all the pagers ring for example.
DX clusters as I said or status on space solar flux conditions etc. That is something that
also is also sent every four hours on the platform. You could also build something for a repeater
telemetry or any IoT advice that you want but again keep in mind this is a network aimed at
amateurs, for amateurs non-commercial and please keep in mind that is maintained by volunteers
that do it on the free time with servers they have access to so don't start bombarding the network
with telemetry that sends every second to the status of your fridge because that would be kind of a
problem. So say reasonable but this is the kind of thing you can do as long as it's non-commercial.
Now how can you get started? As long as you radio amateur with a call sign you can register right
now there's a website to submit the tickets and we'll create your account. So once you do that
you have access to the platform you can send messages if you want to receive them you'll have
to buy, modify or build your own pager for the 439 megahertz frequency. That's one thing but then
you need a transmitter somewhere. If you're lucky enough to have one within your living area you're
good to go, enjoy. Otherwise well you can go your own way and install a hotspot at home or you can
make it a nice project for your local radio club and build a wide range transmitter for everyone
to enjoy. So there are two ways you can go. Speaking of specifics, acquiring a usable pager is
relatively easy today so as I said before that you had to buy second hand pagers, replace a
quart, retune the receiver chain but today we have more frequency agile receivers that have
PLLs instead of the quarts that can be directly retuned or directly bought to work on those frequencies.
So one of them is the AlphaPok 602R which I thought I had, yeah I have it on loan but here it is.
So this one costs about, I think it was 90 euros when we checked on the AlphaPok website directly
from Germany. You can buy it on Aliexpress but your mileage may vary. So that's a way to get quickly
into it. You could go higher range and buy those commercial ones which are a bit more expensive
but work as well or you can go the DIY and free open source routes and build your own using open
source software like a project I've been working on which is the ESP32 pager which Bastia also
improved a bit on the UI side because that's suck at UI but basically using a ESP32 Lora
deathboards you can make it a Poxhack pager and have a receiver for quite cheap. I think those
deathboards are about 15 euros on Aliexpress as well right now. So it's built on on radio
lib so also freely modifiable so have a look if you're interested. As for transmitters you have
two options right now for hotspots you can use if you already have an MMDVM hotspot well you're
all set you just need to register it on the DapNet and activate the transmitter so that's one way
if you want to build a wide range transmitter things can be extremely simple because you just
need a small single board computer such as a Raspberry Pi, an FM transceiver you fit it directly
into the audio unfiltered path of your transmitter and then well you're good to go so basically it
requires four components the transmitter the Pi a transistor and one capacitor so you can get
on the air quite quickly. All our transmitters are being worked on again Bastia is working on a
ESP32 transmitter to make a small hotspot even cheaper if possible so again quite easily
reachable. So where does that leave us? For me it's quite an elegant solution to receive text
messages on our own independent networks having fun in the way learning how to use basic systems
implement them and deploy networks that everyone can enjoy and it has its uses for telemetry or others
you can do weather reports emergency messages text your friends via pager send silly jokes and the
challenge of having it to fit within 80 characters so there are ways to make snappy jokes and
intelligence ones at that but I think that thanks to the DapNet network the arrival of audio cars
that can act as TNCs instead of using an external module it really made the thing much more accessible
so if I'm able to SSH into my hotspots I can make you a quick demo of how that works
so give me a quick second
who's got a pager here? One? Nice? Nice? Nice? Very nice that's already one
depending on what you registered in it I don't know if I'll be able to make a drink but
so basically here you have my personal pager this is one from a friend I just borrowed and
this one which just died on me which is not a problem in itself I'll just make this presentation
shorter oh no it's alive there you go so those all have their own individual addresses so this
one is 2069009 206500 sorry this one I don't remember this one is address 100 so I can make
this one ring specifically I just key the transceiver up say I want to make the trans the
pager number 100 ring please work don't make me look silly
there you go so right now you have only this one ringing so I just made an individual call to this
one now let's imagine I want to send a group alert for I don't know some weather storm weather coming
up or a rare DX spot happening right now on on 18 meters 18 megahertz sorry so then I can make
everything ring at the same time 1040 and then everything rings and it's just a nightmare
and I need to confirm that otherwise it will ring again so there you go quite simply using
basic addressing basic open source software this is just the hotspots just an MMDVM here running
in the background and I can directly key the transmitter up if you have access to the DapNet
system right now I think at least two or three of yous have access make you can make an individual
call to myself there you go he just sent me a message on my on my pager and what did he just say
how does a SQL expert get it how does a SQL expert get a date
okay nice very nice nice so there you have it if you have any questions oh yeah there's another
open source project that is just coming up with it where is alexander hello didn't see you yet
if I'm not mistaken you worked on a pox hack decoder which is getting finished up as we speak for
sdr plus plus so yeah I think it's important to report that as well sorry I didn't get the time
to fit it into the the slides but again if you have any questions I'm I'm just Jesus Christ
thank you for your attention and yeah I'm only yours
all right I hear a question do we have a microphone or
I'll repeat the question so I live quite close to an old school pager site
yep they transmit very high power on vhf they do
what causes interference a lot of other stuff whoo okay so you know in practice how much power do
the transmitters in this network need to be useful and what happens when the pager misses a message
is there a transmit or do you go to get one shot um well very often in professional network I'll
start from the I'll repeat the question first so you have problems there's an interfering
pager transmitter next to you because it's using high power so how much power we're using and
second question sorry short term memory is what happens when the pager misses a message
if you what happens when you miss a miss a message so the first one being yeah for commercial
systems very often they who use 200 300 watts for transmitters because it needs to reach inside of
parkings and the antennas are lousy at best so you need high power to get through for amateur radio
systems it's less of a god now everyone is trolling me now in um yeah for amateur radio systems very
often we don't go to that imperative of being able to reach everyone to through parking lots so very
often the transmitters are 25 watts to 50 watts I mean higher up would cause problems such as what
you're talking about but yeah usually we keep it low and we just add more transmitters here in
Belgium is a problem because every time you add a transmitter you need to pay for an extra license
so I mean we're still limited a bit legally speaking but it's not a problem in Germany or
other countries where they don't pay repeater licenses or they're much cheaper speaking about
missed messages there are two mitigation measures well actually just one is repeating message if
it's lost it's lost if you don't get it that's it because there is no way to send an ack so
either you receive it or you don't and that links to the first problem that's why the commercial
systems use high power so there is no store and forward system in paging so yeah that's a small
small limit other questions yes you don't need a call sign to receive
signals specifically on radio amateur bands so you could perfectly use an sdr or I don't know buy
a pager and put some public public messages but to be able to receive individual to you
or to be able to transmit or you know at least access the platform you would need an amateur radio
call sign but I mean radio amateur is much more than paging and I think it's worth looking into it
if you don't have a license yet I'm not going to start into my big talk about about that because
I've done it for about 25 times today but yeah there's a lot to discover and that hobby and
might be worth looking into it if you have the time to access that hobby other questions
yes yes it does it does you can change the ringtone you make it make it go beep the blue
whatever you can even compose your own ringtones on some of them yes p32 pager actually has a
provision for you there are different tones and you just compose a music you want so
if you wanted to make play Tetris go ahead there was one question here and then you
no question here okay what's the frequency range of the receiver the receiver so the receiver itself
could be tuned pretty much anywhere on the UHF band so 43440 but the problem is it's using an antenna
loop so a loop antenna so it has a very high q so you need to tune it yeah it's 70 centimeters
yep yep there is one there is one I would need you have internet you're connected to the
custom network here yeah if you're looking to hand pager dot de you should be able to
at least get the address book so yeah my time is up thank you