Friday, February 3, 2017

February Radio Club Presentation

Last night, February 2, WB8RCR gave a presentation on the new D-STAR repeater to the Midland Amateur Radio Club. The slides are presented below.


Although a discussion of the repeater was promised, most of this presentation will be about D-STAR, how does it work, how do you use it. Knowing that, the repeater makes more sense.
You all know D-STAR is a digital voice technology.  What that means is that when you speak into the microphone, your voice is digitized, data is added to the packet, and the data is then transmitted over the air.

When the packet is received, the data is sent to the screen on the radio, and the voice to the speaker.

D-STAR repeaters are almost always linked. One thing that differentiates D-STAR from other technologies like DMR is that with D-STAR, the user determines the linking, rather than the repeater owner.  If you want to link the Midland repeater to the Battle Creek repeater, or the Glasgow repeater, or the Brisbane repeater, fine.

To understand why D-STAR works the way it does, it helps to understand the stack of modules that make up a D-STAR repeater. To be useful, a D-STAR repeater has to have at least a radio module and a gateway module.  Many D-STAR repeaters have multiple radio modules.  The slide shows the naming convention for the modules.  A 'B' module will be a 440 repeater, 'C' will be 2 meters, and 'G' will be a gateway.

Most of the Michigan D-STAR repeaters have both 2 meter and 440 modules. There are a few that also have 23 cm voice and 23 cm high speed data.  D-STAR voice modules can also carry data, but they are much slower than the 23 cm 'D' module.

To give you control over the repeater, each D-STAR data packet includes 4 'call signs', each with a specific purpose. MYCALL is obvious, it should be the call sign of the person holding the microphone.

RPT1 is the call of the repeater module you are connecting with. You can think of this one as like PL on an analog repeater.  If you transmit on the Midland repeater's frequency with RPT1 set to the call of Battle Creek, the Midland repeater will ignore you, since it knows you aren't talking to it, but to some other repeater.

RPT2 is perhaps the most confusing.  This is almost always the gateway module for the repeater in RPT1. If you leave RPT2 blank, you can still be heard on the local repeater, but you will not be heard on any linked repeater. You will, however, still hear calls made through the linked repeater.

URCALL almost always contains CQCQCQ, meaning you will be heard by anyone. As we will see later, this field can also issue commands to the repeater.

The first 6 characters of a call sign field are the call sign, as you would expect.  The seventh character is the module letter.  In the URCALL field, the eighth character is the command. If the call you are referencing has less than six characters, you need to leave enough spaces for the module letter to appear in position 7 and the command in 8.

In addition to your call in the MYCALL field, you may also program a message to be sent along with your call.  People frequently put their name, location, and sometimes the kind of radio they are using in this message.  When they key the mike, you will see this scroll across your screen.

To program your radio for the Midland repeater, set the frequency to 444.350, duplex, offset 5 MHz (standard for 440), no PL.  PL has no meaning in D-STAR.  Set RPT1 to KC8ARJ B, module B being the 440 module. RPT2 set to KC8ARJ G, the gateway, and URCALL to CQCQCQ.

This basically says that you will talk to anyone on the repeater, like a normal repeater, but you will also talk to anyone on a repeater or reflector linked to the repeater.

The URCALL field is where stuff happens; particularly the eighth position of URCALL.  If this is an I, the repeater will tell you about itself, an E will cause your transmission to be echoed, an L links the repeater to something else, and a U unlinks.

To use the commands, you set the eighth character, key the mike for a second, then go back to CQCQCQ to use whatever you have set up. In the case of E, Echo, you speak for a few seconds.  On most radios you can make this change from the front panel, but depending on the radio it might be a bit of a pain.  If you only use a few D-STAR repeaters, you might program channels for the common commands.

So for example, set an I in position 8, key the mike for a second, and 'Linked to REF024 C' might scroll across the screen and the repeater speaks 'Linked to R E F 0 2 4 charlie'.  During the meeting we demonstrated this with an HT.  Put an E in position 8, key the mike and speak for a few seconds, and the repeater repeats your transmission back to you.  This is a great way to tell how well you are making the repeater.

To link to a reflector, you need to put the name of the reflector in URCALL before the L in position 8. Key the mike for a second, the repeater responds as it does for 'I'. Return to CQCQCQ to talk over the reflector. A reflector is kind of like a chat room for repeaters.  It is a place that a number of repeaters may link.

To unlink, simply send a U in position 8 and the repeater will be unlinked from whatever it is linked to, and respond with 'Not Linked'.

You can link to a repeater, just like to a reflector.  Reflector names are always 7 characters, but repeaters might be less, to you may need blanks to move the module letter to position 7 and the link command to position 8.  For example, W 8 D F blank blank C L to link to the 2 meter module of the Battle Creek repeater, or W X 8 G R R B L for the 440 module at Grand Rapids.

Some newer radios have a DR mode.  You download a repeater list from the Internet and read it into the radio.  The list can include both D-STAR and analog repeaters.  You can then see a list of repeaters and simply touch the repeater on the screen to setup frequency, offset and PL for analog repeaters, calls for D-STAR repeaters.

Since these radios have a GPS, you can see the list of repeaters sorted by distance from you.  You can even scan nearby repeaters, and the list will update as you drive.  In this mode, there are on-screen choices to linking, info, echo, etc.

Pressing the DR button on the radio brings up two boxes. Tapping the lower 'From' box gives you a choice or a repeater list, a nearby repeater list, or a list of repeaters to which you have recently transmitted.

Tapping the top box, gives you the menu of linking, unlinking, info and echo.

WD8BPT brought his ID-5100, and antenna and power supply into the meeting so we could demonstrate how simple it is to load the repeater list and get on the air. It took less than two minutes, even in demo mode, to load all the Michigan repeaters and many from adjoining states into Denny's 5100.

There are a LOT of reflectors.  Some of the common ones are
  • REF024C an open reflector commonly used around Michigan.  Repeaters in Midland, Owosso, Stutsmanville, Howell and Traverse City are often linked to this reflector.
  • REF024A the Michigan ARES reflector. This reflector is used by ARES groups, including the SEOC, when there is an activation. There is an ARES net on this reflector every Monday evening.
  • REF001C is sometimes called the Megarepeater. A couple dozen repeaters around the world are commonly linked, as well as a lot of hotspots, mostly in English-speaking countries. This tends to be a favorite of British, Irish and Scottish operators but is open to anyone.
  • REF004C is often used by folks meeting on REF001C but moving off for a rag chew to free up the very busy REF001C
  • REF030C is a lot like REF001C except that mostly it links U.S. repeaters

Since the radios typically have GPS, you can configure your radio to transmit your location as part of the packet.  Then the receiving station can get a display of your location.  In this screenshot, Dave, G7HJX was in his car transmitting from Burntwood Staff's, which is apparently 3631 miles northeast of WB8RCR.

Most of the reflectors have Internet dashboards. Here you can see the repeaters linked in, any hotspots linked, as well as the recently heard stations.  If the station's call is shown in orange, clicking on it will show you the location on Google Maps.

So finally we get to talking about the repeater itself.  It is the same Yaesu DR-1X Fusion repeater that has been there about a year, but we have added a Raspberry Pi and an NW Digital UDRC, which allows D-STAR to be added to the previous Fusion and analog capabilities.  We also added a power controller which allows for the repeater power to be cycled remotely.

Here are some of the more common radios.  The Icom ID-5100 is a dual band mobile, very feature-rich. Even if you are not interested in D-STAR, the capabilities of this radio make it a great choice if you want a high-end mobile.  The main downside is that the control head is huge to accommodate the large touch screen.  However, the format of the head is a lot like a GPS, so windshield mounts intended for a GPS work well.

The ID-51A+ is kind of the handheld sister of the ID-5100.  The ID-51A+2 add a Bluetooth hotspot, so you can tether the HT to your phone, and continue your conversation on a reflector even when you aren't in repeater range.

The ID-880H is a current D-STAR radio, but the small display makes working with D-STAR challenging.

The Kenwood TH-D74A is interesting in that it is a three band D-STAR radio, in addition to 2 meters and 440 it adds 220 capability. If does not, however, support DPRS.

The Icom IC-7100 is a D-STAR radio that also does HF. There are, in fact, HF D-STAR nets. This radio also has DR mode, but it isn't quite as polished as the 5100.

There are a number of ways to access the D-STAR reflectors when you are not within range of a repeater.

The old standard is the DV Dongle.  This lets you connect to D-STAR using your computer's speaker and microphone, no radio required.  The DVAP is like your private, D-STAR repeater.  Like the DV Dongle, it connects to your PC, but it requires a D-STAR radio.  The DV4mini adds DMR capabilities, but otherwise is similar to the DVAP.  The DV-Mega sits on a Raspberry Pi, providing similar features to the DV4mini without typing up your computer.

If you have questions, post them in the comments below.

Some useful links:


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