My next D-Star project... another home-brew repeater

This project was born out of necessity.  I need to do some service work, mods and maintenance on the ID-RP4000V Icom D-Star hardware used at the VK5REX, but I can't bear to be without a D-Star repeater while it's on the bench... so I thought I would build a repeater to take its place.

Recently I've been playing around with some old Motorola MCS2000 UHF radios and found that they work very nicely with the various D-Star GMSK Node Adapter boards.  Interfacing the DV Node Adapter to the MCS2000 accessory connector is relatively straightforward. The programming took a little more time to get things "just right", but is all sorted out now.  

My only concern with the MCS2000 radios is that they get incredibly hot during extended transmit times. After all, the MCS2000 is designed to be a mobile radio, not a base station/repeater radio. They really can't handle a high duty cycle without some kind of external forced air cooling.

I've done preliminary tests with two MCS2000 radios connected to one of my original Satoshi DV Node Adapter boards using DVAR Hot Spot software in repeater mode.  This worked great and gave me the final confidence to go ahead with the home-brew repeater build using the MCS2000 as RF hardware.

I will be following the same basic plan that the home-brew VK5REX C repeater uses. The Satoshi DV Node Adapter board will connect to the VK5REX D-Star controller using one of my ID-RP2C Interface boards to allow it to function just like a genuine Icom D-Star repeater.  Most of the parts I will be using are junk-box parts... you know, those trinkets that you just can't bear to throw away because you'll use them "one day".

Two days into the build, I have the two MCS2000 radios mounted on the 4u rack shelf and fabricated some aluminium rods to increase the rigidity of the shelf when out of the rack.  I've also cut and drilled some 35mm aluminium angle extrusion to hold two N chassis RF connectors at the rear of the shelf.  



As the V01.01 Satoshi DV Node Adapter does not have any onboard 5V regulation, I'm using a surplus junk box Lind branded switch-mode 5V power supply.  Unlike the VK5REX C repeater I will not be able to fit the ID-RP2C interface board inside the DV Node Adapter box. It will be placed in a small diecast aluminium box mounted on top of the existing Hammond case that houses the DV Node Adapter.



Here is a photo of some of the other parts that will make up the finished repeater.


Failsafe fan cooling of the transmit MCS2000 radio is vitally important to ensure it doesn't start unsoldering components by itself.  My plan to safeguard against "thermal runaway" is to use a computer style fan that has a PWM/rotational output capability and use this in conjunction with a simple fan failure alarm to control a relay. This relay will then kill the power to the transmit radio if the cooling fan fails.  I found cheap fan failure alarm on eBay which activates a piezo buzzer.  I'll crack it open, hack it a little to make it control the relay. I'm also thinking about fitting a thermal circuit breaker to the heatsink of the transmit radio... just in case! 

Ivan VK5HS from Renmark is working on a duct system that fits between the MCS2000 body and mounting bracket to help direct air from the fan along the heatsink fins. I can't wait to see what he comes up with.

 Here are some close up photos of the various parts.  You can see more in the Photo Gallery.



Stay tuned for more updates very soon!


NW Digital Radio UDR56K-4 70cm 25W transceiver

A new product from NW Digital Radio has been announced at the Dayton Hamvention 2012.   I've been hearing rumours about this product from various sources... I can't wait to get my hands on one! 

I know D-Star experimenters are eager to work on a 4800bd Digital Data protocol that is compatible with existing D-Star repeater infrastructure.  This proposal would use the entire 4800bd D-Star stream for data. An Icom DV radio would ignore the data stream and remain silent.  I don't know the exact details of this protocol and how it will work with existing repeaters.  I would presume that the D-Star header would remain the same.  Bit 7 of Flag One in the D-Star header distinguishes between voice and data communications.   The UDR56K-4 is the perfect radio for those wishing to experiment with this proposed new low speed DD mode.

The UDR56K-4 is a flexible 70cm 25 Watt transceiver that is designed for digital radio.  Below is a press release from John Hays K7VE, Director of Marketing.


For Immediate Release

NorthWest Digital Radio Announces New Universal Digital Radio at Hamvention® 2012

Dayton, OH – NW Digital Radio introduced the UDR56K-4 Universal Digital Radio at the annual gathering of Amateur (Ham) Radio enthusiasts. The radio, which has been designed to support digital data and digital voice needs of both amateur radio emergency service teams and digital radio experimenters The radio will support data rates from 4800-56K+ bps with selectable modulation methods including GMSK, FSK, and 4FSK. The UDR56K will operate in the 70cm band (420-450 mHz.) at up to 25 watts.

Bryan Hoyer (KG6GEU), President of NW Digital Radio said, “The UDR56K is a radical departure from legacy commercial radio offerings and brings a new, open platform, to the Amateur Radio community by providing a stable, integrated, software managed radio for digital communications combined with a tightly integrated Linux based computing platform in a compact package.”

The radio, which measures 4×6 inches and is topped with an eye-catching red colored heat sink, has none of the usual switched, knobs, dials, buttons, or switches. It has one Ethernet jack, four host USB ports, power, and antenna connections. All radio functions are controlled by software, using either a web browser interface or custom application.

NW Digital Radio has already integrated the Radio Messaging System (RMS) and D-STARi gateway and controller software. They are also in talks with noted software developers to provide additional digital radio protocols and applications on the UDR56K platform. Common Linux applications are easily installed using package management tools or may be compiled for the radio. Some applications of interest to the amateur radio community have already been tested, such as AX.25 networking, gpsd, Xwindows, bluetooth integration, wireless 3G/4G broadband, USB sound, and others.

“As we have talked to amateur radio operators, who are interested in digital communication for emergency communication or the development of new protocols, vocoders, and networks, there has been universal excitement fot the UDR56K,” according to John Hays (K7VE), Director of Marketing. Mr. Hays further noted that “Many have said, ‘can we pay now, to be at the front of the line?’”

Mr. Hoyer added, “We think we have a winner in this design, and anticipate a series of new products from our company. We want to build on the resurgence of ‘do it yourself’ activity. We will put the Amateur back in Amateur Radio!”

This device is not offered for sale, pending certification and approval by the FCC.

The UDR56K-4 has an anticipated release in the 4th Quarter of this year, with a target MSRP of $395.


I would recommend heading to the NW Digital Radio website and subscribe to receive more information as it is released.



RE (Receive Enable) Logic Probe for D-Star repeater admins/owners

Following on from my previous blog post (April 22, 2012), I've come up with a simple design for a logic probe that can be used to see if your D-Star DV repeater is exhibiting the random triggering of the RE line.

Without the visual diagnostic feedback provided by something like the N5EBW LED Board it's not readily apparent if a D-Star repeater receive radio is showing symptoms... apart from the "missing transmission" syndrome that seems to accompany times the RE line falsely triggering.

I felt that D-Star repeater administrators and owners needed a simple diagnostic tool that they can build in minutes (literally) to monitor the RE (Receive Enable) line on the RJ45 connector on the back of their D-Star repeaters.

This design is nothing terribly revolutionary... consisting of a RJ45 plug, a LED, a 33 Ohm resistor, some wire & some small diameter heatshrink...  and you will also need access to a RJ45 crimping tool.

Of course here comes the obligatory warning... I take no responsibility if you damage your D-Star repeater hardware if you do something wrong when making this device.  That being said, the chances of causing damage even if you mis-wire the plug is remote...   but please take care.



The 0V/GND connection is on Pin 3 and the Receive Enable signal is on Pin 5.  You just need some wire of appropriate diameter to fit the RJ45 plug.  Some small heatshrink is used to insulate the 33 Ohm resistor that is soldered directly to the LED.  If you want, you can use some two part epoxy glue to pot the wires in the RJ45 to secure them.  I've not bothered to draw up a schematic... it's a VERY basic circuit. The cathode of the LED goes to Pin 3 of the RJ45 which is the 0V connection, the anode of the LED goes to pin 5 via the 33 Ohm resistor.




Here is a quick video clip showing the above pictured RE Logic Probe in action.



I've also written up a .pdf file that is available in the downloads section.

Gather the parts, warm up the soldering iron and get building.  You will then have a valuable diagnostic tool for visits to you D-Star repeater site.



Remote diagnostics and the Icom ID-RP4000V

One of the annoying things with the Icom D-Star repeater hardware is a distinct lack of both local (LED, displays, etc.) and remote diagnostics.   Apart from the green power LED, there is no other visible indication of anything.

In August 2008, after being an Icom D-Star repeater admin for only a few months, I found a mention on Brian NJ6N's webpage about something "interesting" that he came across at the 2008 Dayton Hamvention.

Designed and made by Eric N5EBW, it was a drop in replacement PCB for the Icom D-Star repeater hardware, replacing the existing back panel PCB (RJ45 & power distribution).   It included two transistors connected to the TE and RE lines going to/from the ID-RP2C controller.  These transistors switched two LED's to indicate activity on the RE and TE lines, in effect providing PTT and Receive indication!  A red LED for transmit, a green one for receive.  Finally... some basic diagnostic indications for the Icom D-Star repeater hardware.  Needless to say I contacted Eric and ordered a board!

Here is a picture of the N5EBW board installed in the VK5REX B D-Star repeater.



Now, not long after installing the N5EBW LED board, I started to notice something strange during site visits.  Every now and then I would see the green RE (RX) LED flashing/blinking randomly, and sometimes it would be locked on... even when the repeater wasn't being used.  By this stage I had become fully aware of the performance "issues" of the Icom D-Star repeater receiver and thought it was the receiver being affected by out of band RF activity or noise.  The repeater did seem to work, when I keyed up my Icom IC-91AD handheld radio while on site the repeater keyed up and seemed to function properly.  I had no answer as to why this was happening, not many other repeater owners had fitted the N5EBW board and without this there would have been no visible indication that the RE (receive enable) line was being activated in this random fashion. I did seem to remember a forum post somewhere that mentioned that the "squelch level" on the D-Star repeaters would "drift" after time and a power reset was needed to fix it.

I did find that a power reset of my ID-RP4000V seemed to "fix" this problem with the flashing green RE LED and it would stay fixed for months on end.  I made a point of checking this when I visited the repeater site to work on other equipment. If the green RE LED was flashing, I did a quick power reset.

For years I didn't really think a lot about this little annoyance... the repeater seemed to be functioning properly and with the duplexer RF hardware problems finally resolved last year all the lingering hardware based issues seemed to be behind me... or were they?  


From time to time I can remember odd occasions when the repeater failed to "hear" incoming RF transmissions. These were generally from locations where I knew RF coverage was good (when using a handheld radio) and even while mobile around town where there are NO RF black holes. Quite often I would notice it first thing in the morning, when the repeater had been idle (RX wise) for 6-8 hours.  I would key up with a Dplus command in the URCall field... and nothing would happen!  I re-key and my Dplus command would work.  I put this down to a glitch with either Dplus or the internet/network connection.  I started looking at the dplus.log file on a more regular basis and found that my missing transmissions were indeed missing, times I know I transmitted did not appear in the gateway logs!  Even more interesting was that it wasn't just Dplus that missed my transmissions,  the Icom G2 database was also not updated, and ircDDB did not "see" the missing transmissions either... it seemed to be a little more than a basic software issue.  I can recall many times during QSO's or nets where I would key up and transmit only to find that when I un-keyed, someone else would be talking and my transmission went nowhere!

Late last year I started to put two and two together and seemed to notice a correlation between times when the repeater did not "hear" me and when the RE LED was found to be "blinking"  I thought that maybe the ID-RP2C controller got "confused" with all the activity on the RE line and missed a vaild incoming call on RF.  The RE line is controlled directly by the main CPU in the ID-RP4000V receive radio and without knowing exactly how the firmware determines what is a valid D-Star transmission... it's all speculation.

I've posted details about this on the DStar-Gateway Yahoo group and found that others have indeed seen this... but no one has come up with a definite cause or a solution... other than to send the repeater back to Icom to get checked out.

I do have the "official" Icom ID-RP4000V adjustment .PDF document file that describes how to align/calibrate the ID-RP4000V repeater radios (receiver and transmit).  This document also describes how to activate the "/reserve" mode of the ID-RP4000V programming software.  This mode can be quite dangerous, there are NO factory default values in the RF hardware, each repeater is aligned at the factory from scratch.  If you change a value and don't write down the original... it's gone! There is no back button. 

One of the interesting things about the reserve mode is that when you are connected to the receive side of the repeater, you get a RSSI bargraph on the main screen! Finally some real diagnostics.   Indeed it is a true RSSI, totally independent of the D-Star GMSK modem side of the receiver, you key up in FM mode and you see the RSSI indication.   Now I can keep an eye on what the receiver is seeing.... if only I could do it remotely.

Well, as it turns out there is a way to connect to USB devices remotely.  I had previously purchased Win-Star USB Network Server.  I intended to use this to connect to a GMSK DV Node Adapter over a network connection... The DV Node Adapter could be seen and connected to over a TCP/IP network but the timing wasn't up to scratch and the TX data stream failed to reach the DV Node Adapter properly.  The client software connected to the USB Network Server using UPnP, there was no way to specify an IP address, it only worked within a subnet. This limited it's functionality a little bit. The Win-Star USB Network Server was put on the shelf.  

I had often wondered if I could use the USB Network Server to remotely connect to the USB sockets on the front of the ID-RP4000V repeater... so on Friday 20th April I did a quick trip to the repeater site and installed it, connecting to the on-site network switch and the ID-RP4000V receiver USB socket.  



The VK5REX network is an extension of my home network using Mikrotik 5.8GHz link equipment, I figured this would pass UPnP OK.  Back home I set up my laptop on the kitchen table. I already had the USB Network Server client software installed, I fired it up and was able to see the the "ID-RP4000V SERVICE R" usb device connected to the server. I clicked connect and confirmed that the ID-RP4000V USB device had appeared in the device manager.  I then started the ID-RP4000V setting software (in reserve mode) and it connected to the repeater hardware through the network link.... success!!!

I then keyed up my ID-31A handheld radio and was pleased to see the RSSI indication.

Now I can remotely monitor my D-Star repeaters receiver... when I notice the "missing transmission" symptom, I can check and see the receiver RSSI while at home. 

I don't know if I will ever determine the cause of the flashing green RE LED and if the random pulsing of the RE line causes the ID-RP2C controller to get confused and miss valid incoming D-Star calls... but this is a good first step in catching the problem as it happens!


I have also posted a YouTube video showing the USB Network Server installation and operation.







DV-RPTR :- add on boards are coming!

Early in February 2012 the development team behind the DV-RPTR GMSK modem board announced two add on boards that will plug into the DV-RPTR board. 

I quote from the email sent to the DV-RPTR Yahoo group :-

Starting in April 2012 we will have two additional boards which can be plugged
on the DV-RPTR board:

1) AMBE Speech Codec Board

This tiny board has connectors for Microphone and Speaker. Together with the
DV-RPTR and an FM transceiver you get a real DV transceiver.
This board has two modes:
* DV Transceiver to make QSOs via DV Repeaters or direct
* DV Dongle Mode to talk via Reflectors in the internet

2) FM Transceiver Board

a little add-on board to be plugged on the DV-RPTR. It has a simplex transceiver
based on the well known chipset which is also used in the UV-3R. It covers 2m
and 70cm HAM bands. The output power is 2 watts max.
It turns your DV-RPTR into a wireless hotspot.

Both boards can be connected to the DV-RPTR at the same time. Then you have a

real DV-Transceiver. In this configuration it does not fit into the little metal
box, you will need another box.

Please help us !

We need to know how many AMBE Chips and Transceiver Chip we have to buy. If you
are interested then please go to and register the quantity of
boards you need.
Thank you
Your DV Developer Group

This announcement has created a lot of interest... as you would expect.  There are many people out there (me included) who have a DVAP Dongle and can't use it with the new 70cm only ID-31A D-Star radio.  The transceiver board will turn the DV-RPTR board into a DVAP Dongle "on steroids" on both 2m and 70cm.  It might not be as compact as the DVAP Dongle, but I think I will be able to find space for it in my laptop bag!

The AMBE board is also a very interesting development.  You will be able to plug a speaker/microphone directly into the board and transmit/receive D-Star DV audio.  This board will also allow the DV-RPTR board to function like a DV Dongle, you will be able to decode D-Star digital audio direct off air AND via an internet connection as well.

All we need now is a way to control the DV-RPTR/AMBE Board combination without a PC and you will have a viable alternative to an Icom D-Star radio... it will then be a D-Star digital audio plug-and-play solution for any radio with a 9600bd packet/data 6-pin DIN socket.

With both boards plugged in to the DV-RPTR board you wouldn't need an external FM transceiver at all! You speak into a microphone and you transmit D-Star on either 2m or 70cm!

Below is a picture of the AMBE add on board. More images are in the DV-RPTR Photo Gallery.


I have placed a request with the DV-RPTR team for both add-on boards. I cannot wait until they are released!