UDR56K-4 from NW Digital Radio... pre-orders are open!

A lot of people have been eagerly awaiting news from the team at NW Digital Radio about the UDR56K-4 70cm digital radio.

This innovative radio was first showcased at the 2012 Dayton Hamvention.

North West Digital radio announced on 31st March 2013 that pre-orders were being accepted with shipping of hardware expected to begin in Q3 2013.

More information on the UDR56K-4 can be found at the Universal Digital Radio Yahoo Group.

I can't wait to get one!!



Important information for DVAP Dongle and G4KLX software users!

During the PapaSys Thursday night D-Star Round Table on 31st January 2013 (REF012 C), I heard something that immediately grabbed my attention.  

Sean KK6BEB (and at least one other person during the evening) mentioned a post by Robin Cutshaw AA4RC on the DVAP Dongle Yahoo group.

As several people have experienced, there is a flaw in the 3rd party software
for the Raspberry Pi. The software wipes out the calibration data that is
programmed into the DVAP at the factory.

If you use the software, you will have to recalibrate using the DVAP Utility
software. It probably won't get you as close as factory settings but can bring
it back to usable.


I found this mesage very interesting due to my recent experimentation with the DVAP Dongle and the G4KLX ircDDB Gateway & DVAP Node software.  Personally I had not experienced any problems with my Raspberry Pi/DVAP Dongle/G4KLX Software combination.  I have used both the Windows versions of Jonathan's software, and more recently the Linux versions.  Hans DL5DI has made it very easy for amateurs to get the G4KLX software running on different Linux platforms.  My Portable D-Star HotSpot works very well.

I had also recently had an email exchange with Jonathan KK7PW about getting the G4KLX software working on the Raspberry Pi and some strange "R2D2" that he has been experienced with his DVAP Dongle but only with his IC-91AD radio... maybe this was related??

I sent Robin an email about his message asking for more information and then started to look more into this.  I downloaded the DVAP Dongle Technical Reference PDF, sat down and started to have a good read.

On page 28, (section I started to put the pieces together... DVAP Frequency Calibration

Purpose: Sets the reference frequency calibration of the DVAP.

Control Item Code: 0x0400

Control Item Parameter Format:

The first 4 parameter bytes are a 16 bit frequency offset value in little endian format.

The nominal crystal reference frequency is 19.6608MHz and this offset value is added to the nominal

reference crystal value when calculating the PLL output frequency.

The adjustment range is +/-2000Hz or about +-100ppm.

Example: Set the DVAP crystal reference frequency offset to -230Hz (0xFF1A):

The host sends:

[06][00] [00][04] [1A] [FF]

The Target responds with:

[06][00] [00][04] [1A] [FF]



This frequency calibration value is added to the reference crystal value to allow for component variations and to align the "dial" frequency with the actual transceiver frequency in the DVAP Dongle.  This is not unusual, virtually all radios have a method of adjusting the reference crystal frequency.  Adjustment can be done by various methods including a trimmer capacitor in series with the crystal & varicap diodes under manual or software control.

This DVAP Frequency Calibration value is set in "the factory" and should not need touching again.  While I have only one DVAP Dongle, I would assume that this value is fairly unique for each unit.


I then started to look at the G4KLX DVAP Node software and configuration file.  I recalled a setting in the dvapnode_1 config file called dvapOffset...and in my file this was set to 0 (zero).  I never really paid attention to the this parameter or the value... as mentioned before I had not experienced any problems at all.  I then started to think that setting this value to zero might be a problem.

I took my Portable D-Star HotSpot to work on the following Monday morning to do some further tests and observations on my IFR 500A AM/FM test set.

I downloaded Robin's dvaputil.exe software from the website :-

When I started it up and pressed the "Connect" button, the first thing I noticed was that the Freq Calibration value was zero!   

I connected the DVAP Dongle SMA antenna socket to my radio test set and checked the TX On box in DVAP Util.  I was instantly able to see how off frequency my DVAP Dongle was with an offset value of zero!


My IFR 500A was on the 3K scale when the above photo was taken.  The DVAP Dongle was around 1.35 kHz low with the DVAP Frequency Calibration value set to zero.

I found that the value needed to be around the -125 to -175 region to bring it back on frequency.  I also noticed that the frequency seemed to drift a little the longer it transmitted.  When the DVAP Dongle was "cold" a value of -125 was almost spot on, but after a minute or so of transmit the value needed to be decreased.

Having access to a radio test set or accurate frequency counter is essential to work out what Frequency Calibration value your DVAP Dongle requires.  

If you don't have ready access to test equipment, in the short term I would recommend setting it in the -125 to -175 range and see how you go.  

Also make sure you update your G4KLX Repeater software to version 20130203 (or later) or you will be undoing your recalibration work.  Jonathan G4KLX has removed the dvapOffset "feature" from the DVAP Node software from this version.   Both Windows and Linux versions are affected and need to be upgraded.   

Through emails I have received from others, the ID-31A and ID-51A seemed to be affected more than older radios.  I knew that amateurs using GMSK HotSpots with the newer radios needed to tweak the transmit deviation, too much deviation is bad!  The receiver passband of the ID-31A and ID-51A is narrower than older radios.  It's quite possible that if a DVAP Dongle is off frequency then the newer radios might have trouble decoding the transmissions.

If you aren't using a DVAP Dongle with the G4KLX software then there is no immediate need to update.


The Portable D-Star HotSpot is ready for action!

This project took around two months from concept to reality.

It looks amazingly similar to what I saw in my mind when I thought that I should build the DVAP Dongle and Raspberry Pi into a portable system.  Some ideas did change during the layout and construction phase. Originally I was going to put the DVAP/s in the lid of the Pelican case.  It turned out that the cable management system needed to keep everything connected, safe and secure was going to be too messy. I also wanted to keep the number of holes drilled in the Pelican case to a minimum.

As it happened, with careful planning, every component fitted in the base of the Pelican case with room to spare.  I have a location ready for a 70cm DVAP Dongle and even some space left over for fitting a small Li-Ion battery pack in the future with the move of the USB hub from the base plate to under the mount for the DVAP Dongles.

The picture below shows everything in place with support power supply and DC cables packed as well. The Diamond SRH36 antenna simply rotates down on the SMA elbow adapter and is flexible enough to fold around inside the case.

The powder coated aluminium base plate that everything is mounted on can be removed very easily. Most of the cabling can be accessed with the base plate installed in the Pelican case.

The G4KLX ircDDB Gateway and Repeater software running on the Raspberry Pi is fantastic!  I was worried that it (and/or the Linux operating system) would not survive being turned off by "pulling the plug".   The software has proven itself to be most robust in this regard.

The Routerboard RB751U router runs Mikrotik RouterOS.  This combined with my Huawei 3G USB stick gives me internet access wherever I have 3G cellphone coverage.  My ISP uses the Optus 3G network and there is very good coverage in my area.

When I am at home I plug the Raspberry Pi directly into my home network rather than use the 3G connection.   When I am out and about other devices can use the 3G internet connection... either by plugging an Ethernet cable into the RB751U or by using it's built in WiFi access point.  The Raspberry Pi uses DHCP to get it's IP address so I don't need to change any of the network config when swapping between internet connections.

The small Cosel switch-mode 5V 1600mA regulator has been fitted with extra LC filtering and the DC wires go through ferrite cores.  Power input is via an Anderson PowerPole connector.




Playing with DMR, one of D-Star's professional cousins

I am in the process of commissioning a VHF Hytera DMR repeater system for one of my clients.   It's been quite interesting experimenting with DMR in a repeater application before the system is handed over to the client.  I've installed both DMR and P25 encrypted simplex systems for secure communications between fishing vessels, but this is the first DMR repeater I have installed.  One of the features that the client wanted was for the handheld radios to have a "man down" alarm... it's been programmed, but I bet they will get real tired of having to make sure the radio is vertical all the time!  GPS polling & messaging is enabled, as is private calls and emergency button functionality.

The Hytera DMR radios are quite robustly built... my main gripe is that the mobile radio does not have a remote or removable front panel option.  This will make installing these radios in modern vehicles somewhat challenging.  Maybe the cars are bigger in China?

I'm quite impressed with the audio quality of the Hytera radios, received audio is clear and punchy.  The display & keypad version handheld radio is quite loud considering the speaker audio emanates from two slots between the green and red buttons and the numeric keypad.  One strange quirk with the mobile radio that I picked up on when installing into fishing boats is that you can't have an external speaker AND internal speaker active at the same time.  The external speaker option is enabled with a logic line held to GND, this then disables the internal speaker.  All external connections are made through a high density DA26 connector.

The programming software is relatively straightforward, some of the terminology that is used is unfamiliar.  I am quite thankful that my equipment supplier helped with the initial programming of the radios and repeater!

Here is a photo of a Hytera PD782G DMR handheld radio next to my Icom ID-31A D-Star radio.



AIS receiver installed at VK5REX

Working in the marine/fishing electronics industry, I have been aware of AIS (Automatic Identification System) for quite some time now.  AIS is like APRS for ships!

AIS is not a mandatory fit on many of the fishing vessels I work on, but it has been fitted voluntarily to a few of the tuna fishing vessels, mainly the vessels involved with towing live tuna caught in "the wild" back to the tuna pens closer to Port Lincoln.  While they are a lot smaller than a large open-ocean going ships, they are a lot less manoeuvrable and quite often travel at 1 knot or less while under full throttle.   AIS allows these tow vessels to be seen by the larger ships and allow them to see other ships, their name, callsign, MMSI, size, etc.  

There is a great website called where people can feed AIS data received from their location into a worldwide database, overlaying shipping movement on Google maps.  The website allows the public access to this pool of worldwide AIS information.

The guys at are always looking for people who can help them expand the coverage area of their service.  The VK5REX D-Star repeater site is perfect for an AIS receiver... elevated, internet access, overlooking a major shipping port and shipping lanes... and access to a spare VHF antenna!

I clicked on the "Cover Your Area" section of the website and sent in my details.  A simple form was emailed to me, filled out and returned.   About a month later I received a Comar SLR200N network AIS receiver, already configured... ready to go.  

Because there are quite a few existing VHF repeater system at the VK5REX repeater site (plus a 2kW FM broadcast transmitter), I also tuned and installed a VHF cavity filter to help the AIS receiver cope with the extra RF noise.

I installed the Comar AIS receiver next to the Motorola IRLP radio and plugged it into the same 5.8 GHz wireless network link that brings the internet to the site for the VK5REX D-Star gateway and IRLP node.