D-Star with an Icom ID-4100

Posted by Fred C (W6BSD) on Dec 30 2019

A couple of weeks ago I got a new D-Star mobile radio. The radio is an Icom ID-4100, VHF/UHV. According to Icom, this rig is a D-Star1 entry-level radio. The ID-4100 has the same features as the ID-5100, with a smaller screen and only one VFO.

ID-4100 head
Clear display

What I like

Icom's menu system is consistent across products. If you are familiar with any of their radios, you will have no difficulty quickly setting up this rig.

The screen is clear and easy to read. You can choose from 4 background colors. You can even set a background tone for day time and another one for night time.

The setup of this radio is even more straightforward if you go to dstarinfo.com and download the repeater list for the ID-4100. Install the list on an SD card and load it onto your ID-4100. With the GPS (included), you can select the Near Repeater option, and the radio will display a list of D-Star or FM repeaters close to you. By using a digital repeater, you can access any of the REF, XRF, DCS, and XLX reflectors. Just select Link to Reflector in the menu, enter the number of the reflector to which you want to connect. You are now ready to talk to the world.

The optional Bluetooth module lets you pair the radio with your Android or iPhone to send texts, files, and images.

What I don't like

The radio doesn't come with a mounting bracket. To install the transceiver in your car, you have to spend roughly $35 for just a piece of U shaped metal. You might also have to add a few dozen dollars for the extension cable and the bracket to install the head on the dashboard.

I am planning to use the ID-4100 in my shack and the fan is too loud. When the rig is installed under the car seat or in the trunk, a noisy fan is not an issue. For desktop use, having a loud fan next to you is annoying. Fortunately, the control head can be detached. I have installed the control head on my desk and the body of the radio far away.


D-Star is a digital voice and data protocol developed by the JARL2 and uses MFK3 as its standard. D-Star was the first digital mode explicitly designed for amateur radio.

With this rig, I am discovering the D-Star world. I am impressed by the audio quality compared to DMR. I rarely hear R2D2 voices. When I do, they often come from cross mode gateways. These gateways decode one mode and re-encode in the second mode. The decoding re-encoding degrades the quality of the audio.

If you use the repeater list provided by dstarinfo.com, you have everything you need to start having QSOs with the world. However, it is always a good idea to know how your radio works. The next section focuses on how D-Star works, and how to program a DV4 repeater in your radio.


Note in some of the D-Star fields, the spaces are essential. Everywhere space is needed, I will use the following character: •

In D-Star, the radio needs to know your call-sign. To do anything on digital with D-Star, you need to find My Station on the menu. Then select My Call Sign and enter your call sign. The field for the call sign has two parts. Before / enter the call. After it, you have 4 characters to enter anything you want. Originally these 4 characters were for the travelers to enter the country of operation. For example, W6BSD /VE, if I am traveling in Canada. Now people use it to put their initials or the model of the radio they are using.

Call signs

D-Star, uses call-signs for routing of traffic. All the call-sign fields have 8 characters. The 7 characters at the beginning are for the call sign, and 1 character at the end of the field is used for command.

The commands are:

G  Gateway
E - Echo Test
I  Identification
L  Link Repeater
U  Unlink Repeater

The last character can also indicate the band the repeater is operating on:

A - 1.2 GHz Voice
B - 440 MHz Voice
C - 144 MHz Voice

Switching to digital

To work D-Star, you need to put your radio in digital mode; it is called DR mode. In this mode, the screen will show 2 main fields: From: and To:.


The From: contain the pieces of information about the repeater you want to use. Here are all the fields for programming a DR5 repeater

Field name: Value Field name: Value
TYPE: DV Repeater FREQUENCY: 444.075.00
NAME: San Jose DUP: DUP+
GROUP: 23 USA West LONGITUDE: 122º 06.00'W

You are familiar with FM repeaters so I am not going to explain what offset and frequency are. I am going to focus on the critical fields.

In the field TYPE:, you can select DV Repeater or FM.

The fields CALL SIGN and GW CALL SIGN are also called RPT1 and RPT2 in older literature or on some internet pages.

CALL SIGN or RPT1 is the call sign of your repeater. The last letter in the field B means that the repeater is in the 440 MHz band.

GW CALL SIGN is the call sign of the gateway. A gateway is a machine running software responsible for routing the traffic to the internet.

The position (latitude/longitude) of the repeater is optional. I recommend setting these fields because the radio uses this information to determine which repeater is closest to where you are.

I have quickly described the information necessary for the From: field.


The To: contains the call sign you want to call. This call sign can either be a person, a gateway, a repeater, or a reflector. For example, suppose I am in California and I want to talk to people in Boston. I enter the call sign of a D-Star repeater in the To: field. My call is then automatically routed through the internet to the repeater in Boston. If the Boston repeater has a 440 and a 2-meter repeater, I need to end the call sign with the letter B or C depending on which repeater I want to access. The To: field is called UR or Your Call Sign.

ID-4100 screen
From: and To: fields

One of the cool features of D-Star is the option of calling someone. If in the field To: I enter the call sign of my friend in Orange county. The system knows what repeater my friend checked last. My call will automatically be routed to that repeater.

To make a general call not addressed to a particular person or repeater, enter CQCQCQ in the To:.

For the To: field, the IC-4100 has a menu with all sorts of shortcuts for a local call, someone, repeaters, or reflectors.

To summarize

Field Value Comment
My Call (MY) W6BSD My call sign followed by 4 free form characters.
RPT1 W6CX•••B My 70cm repeater (B)
RPT2 W6CX•••G Gateway (G)
UR (Your Call Sign) KE6YGM•• The call sign of the person you are trying to contact.


The best way to understand how things work is to look at a few examples. Pay attention to the UR field and especially the last character.

Keep in mind that in all these examples the first line is your call sign. It is in the general setting of the radio. The RPT1 and RPT2 lines are in the repeater memory. The last line is the To: field.

Local call on a repeater

  MY - W6BSD
RPT1 - W6CX•••B
RPT2 -

Echo function of your repeater

  MY - W6BSD
RPT1 -
RPT2 -
  UR - •••••••E

Linking to 14 Charly reflector

  MY - W6BSD
RPT1 - W6CX•••B
RPT2 - W6CX•••G
  UR - REF014CL


  MY - W6BSD
RPT1 - W6CX•••B
RPT2 - W6CX•••G
  UR - •••••••U

L and U are for linking and unlinking. You don't need to specify the name of the reflector you want to unlink. Putting REF014CU in the UR field also works.

Calling a person on a different repeater

  MY - W6BSD
RPT1 - W6CX•••B
RPT2 - W6CX•••G
  UR - KE6YGM••

No matter where your friend is. D-Star will locate the latest repeater used by your friend and route the call to that repeater.

Calling a repeater (link to another repeater)

  MY - W6BSD
RPT1 - W6CX•••B
RPT2 - W6CX•••G
  UR - /W8DF••C

W8DF in Battle Creek, Mi has two repeaters. One on 2 meters, the second is on 440. The C at the end of the call sign indicates we are contacting the 2 meters repeater. Also, notice the / at the beginning of the call sign.

I didn't explain step by step how to program your radio. I have tried to provide you with the background knowledge to help you understand how D-Star and your radio work.

  1. Digital Smart Technology for Amateur Radio 

  2. Japan Amateur Radio League 

  3. Gaussian minimum-shift keying with forward error correction 

  4. Digital Voice 

  5. Digital Repeater 

 D-Star      Digital Radio