From the living room to the world: your hotspot and digital networking

The quiet change of the VHF repeater

It has become quiet on the VHF repeater, very quiet. One reason for this is the migration to digital operating modes such as DMR, D-Star, C4FM and others. Of course, on the one hand, the new, the play instinct, is tempting, but so is real technical progress. In addition to voice, data such as GPS position can also be transmitted. Or the name and call sign and short messages. On the other hand, digital modulation is often more efficient in the use of the available bandwidth. And the big advantage - the national and international networking of the relays with each other. This has made long-range radio connections possible with the simplest of means.

Hotspot

Digital relays on the advance and the incompatibility problem

In recent years, a large number of so-called DV (Digital Voice) repeaters have been established at many locations alongside FM repeaters. Sometimes they have also replaced FM technology. This is also encouraged by the fact that manufacturers offer hardware for repeater stations that is more or less ready for operation. However, this also highlights a problem, namely the large number of incompatible DV modes. A radio that “speaks” D-Star, for example, cannot communicate via a DMR or C4FM repeater. And what do I do if there is no DV repeater available in my area? In that case, the latest technology is of no use to me in amateur radio. Or is it?

Digital relays and the emergence of hotspots

New technical possibilities stimulate the play instinct of radio amateurs. Although the networking of relay radio stations is not fundamentally new, it is something that previously could only be set up with a lot of effort and manual work. With digital relays, however, networking is the basic principle and therefore quite easy to set up. And what is to prevent us radio amateurs from building micro-relays with the lowest power, setting them up right in my home and networking them? Voilá - the 'hotspot' is born.

The new era of cross-system wireless networks

A hotspot is therefore an extremely small radio system that is designed for digital languages and uses an internet connection to connect to the existing network. And for which DV system? For all of them, of course! High-performance hotspots 'speak' all common digital modulations. And cross-system from DMR to C4FM? That works too!

Hotspot
Hotspot

That was very fast. Let's take it slowly again, step by step

A hotspot has an extremely small radio, usually just a board barely the size of a thumb with a transmitting power of a few milliwatts. But that's enough to cover an apartment, a mobile home or the field day area. These small radio modules are available for VHF (2 m) and UHF (70 cm), a few can also do both bands. The circuit board with the radio module also houses the so-called modem, which comes in two variants: the DVMega or the MMDVM - the Multi Mode Digital Voice Modem. More about this later.

The second side of the hotspot consists of the connection to the Internet. A small computer is used here, for example the popular Raspberry Pi or similar so-called single-board computers (SBC). The wireless circuit board is usually plugged directly into this small computer, so that the whole thing is hardly larger than two matchboxes. Of course, the whole thing still needs to be supplied with power, so the power supply for the Raspberry Pi, i.e. 5 volts and 1 to 2 amps, is used for this. The hotspot connects to the local network either via an Ethernet cable or via WLAN.

So much for the hardware, but what about the software?

Of course, nothing works on this computer without the appropriate software. A world of its own has developed here over many years. It all started with the so-called MMDVMHost, the software that talks to the modem (DDVmega or MMDVM) and brings the data from there to the Internet and vice versa. MMDVMhost was developed by Jonathan Naylor, G4KLX. The program is in use in practically all hotspots today.

To make the whole thing operable, the need to provide a more convenient interface quickly arose. This is how the so-called Dashboard was developed, first by Hans, DL5DI and Kim, DG9VH. Andy, MW0MWZ later developed today's dashboard on this basis. It is essentially a website that allows for the entire configuration, control and monitoring of the hotspot.

Hotspot

And the last step was to make all these programs available on a memory card together with the operating system. Linux is actually always used as the operating system, but it is hidden under the convenient user interface. The concept is: create SD card, insert card into hotspot, start and off you go. Andy, MW0MWZ, has also implemented this idea, resulting in the “Pi-Star Digital Voice Software”. Today, it is one of the most frequently used complete solutions for amateur radio hotspots in the digital voice area. It is available as a ready-to-use “image” for various hardware solutions.

WPSD: The new progress in amateur radio

And since progress always occurs when someone is not satisfied with the existing solution, another similar project has been around for several years. This is how WPSD came about as a modification (a so-called 'fork', a branch) of Pi-Star. This software is also available free of charge as a ready-to-use image for Raspberry-Pi, Odroid, nano-Pi and many other single board computers.

In a nutshell

A typical hotspot consists of

  • Radio module with modem (DVmega or MMDVM, VHF, UHF or both, half or full duplex)
  • SBC like Raspberry-Pi or Odroid
  • Software like Pi-Star or WPSD

Of course, an antenna, power supply and possibly cables are also needed.

Hotspot

Hotspots take amateur radio everywhere

With the very small hotspot, you can now use it at home or on the go. The data volumes are low enough that you can use your cell phone as a WiFi router to access the internet. Some OMs even use their hotspot in the car, with the internet connection coming from a smartphone or a special router.

Compatible digital radios

What is ultimately still needed is a DV-capable radio. And regardless of whether it is one for DMR, D-Star or Yaesu Fusion (C4FM) - the hotspot can do it all. There is plenty of choice, for example at WiMo:

Of course, the market offers many more suitable radios.

Revolutionary ready-to-use hotspots

And ready-to-use hotspots? WiMo offers products from the Dutch company DVmega, from Guus, PE1PLM. The best-known product is the DVmega Euronode Hotspot. MMDVM hotspots are offered as open source projects on a variety of platforms.

What about FM?

A number of radio amateurs thought the same thing and created the “FM radio network”. Here, too, relays are networked with each other, and here, too, hotspots are available for private use at home. The main difference is the modulation, normal FM is used. This means that there are no options for data transmission (signaling, location, short messages), but on the other hand, the voice quality is usually significantly better than with Digital Voice. The best-known open source hotspot for FM is probably the “Shari Hotspot” on AliExpress.

Independence and networking for everyone

All in all, hotspots, whether for Digital Voice or FM, offer an enormous enrichment for amateur radio. Anyone can use the normal devices to participate in a wide variety of networks, even if no repeater is available at the location. Especially when on vacation, hotspots offer a great opportunity to stay in touch with friends at home via amateur radio. Completely independent of relays or other facilities in the vacation country. The relatively low price and sophisticated software make operation affordable and accessible to everyone. Today, amateur radio is no longer imaginable without hotspots.

Ekkehard 'Ekki' Plicht, DF4OR

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