VK6ROX B

Homebrew DStar Repeater

Description

How it works (roughly!)

The repeater is a conventional layout and can be used as an FM analogue or DStar machine by simply running a different control software.

The receiver audio is picked up right at the discriminator before any hardware filtering is done.  This discriminator audio is digitized in the MIC input of the Laptop's sound card (or USB sound FOB if preferred).  The SoundCardRepeater software implements a GMSK decoder and logic to disassemble and reassemble the digital data string which contains header, FEC (forward error correction), routing information as well as the undecoded AMBE digital voice data and separate user 1200baud digital data that is simultaneously sent with the voice information.

Transmit audio similar to the received digital string (with modified routing information and added auxiliary information such as BERI) is modulated and injected into the exciter just before the limiter.  Again it needs to be transmitted "as is" with no hardware filtering prior to FM modulation.

The DStar magic is all taken care of by the brilliant software called SoundCardRepeater and ircDDBGateway written by Jonathan Naylor G4KLX

Use DTMF Tone to Link Reflectors

VK6ROX B is on line - please feel free to call CQ or link up to REF, XREF or DCS series reflectors.  Try DTMF tones *1C to link REF001C, try DTMF tones D14B to link Aussie reflector DCS014B or DTMF tones 44B to link XRF044B.  Unlink by sending DTMF tone #

If you prefer, setting the URCALL to eg REF001C also works.  If you want to record and playback your audio, set URCALL to "       E" (seven spaces with E in the 8th position).

Try the CCS system to connect to a particular station

The CCS system permits use of a 4 digit DTMF tone sequence to link to a particular callsign, wherever they are, whether on a repeater, through their own hotspot or via a dongle.  It will connect to any kind of reflector including DPlus, DCS or XReflector.

To use the CCS system follow these steps 1) go to www.xreflector.net click on CCS System, User Register, answer the questions and get your own 4 digit DTMF code. 2) Look up your counterparty's DTMF code by clicking on User Register, DTMF list 3) OK now dial the 4 digit DTMF tones on your transceiver keypad and the system will find that person.  The zCCS system is similar to setting the URcall to your counterparty's call, but is more real time and lets you hear both sides of the QSO that may already be active.  All you need to do then is wait for a pause and make your call.   By the way, my CCS code is 3987.

To disconnect the CCS system send the DTMF tone "A".

What is this "BERI" Displayed on Screen??

The BERI is the BIT ERROR RATE INCOMING and is an indicator of how well signals are getting in to the repeater.  Typically any signal with less than 1 or 2% BERI will be Q5 audio.

Repeater Coverage

Anecdotal repeater coverage data is accumulating daily with Q5 coverage to base stations running 50watts north 27km and east up to and including the scarp.  Mobile coverage is patchy beyond about 10km, but useful audio is available all the way along the Mitchell Freeway from South St to Warwick exit.  Received VK6ROX B while mobile in Ellenbrook - would be interested to hear if a base station could work into the repeater from there.

Future Development Plans

Implement SoundCardRepeater in a Linux environment running on the RaspberryPI microcomputer.  This work is underway, but not able to progress further without full ALSA support for USB sound FOBs on the RPi.  Results with the RPi + sound FOB were somewhat marginal.  The software GMSK implementation running on the RPi used too much computing power and prevented use of the graphics interface.

I have ordered a DVRPTR-V1 GMSK modem board (North America version) and expect to have VK6ROX B running with a RPi + DVRPTR controller by Feb 2014 if all goes well.

Once the RPi version is implemented, stable and fitted into the 19inch rack enclosure (already in place waiting), the repeater will be moved to a more permanent steel 19inch rack.  (The temporary wooden rack provides easy access to all sides of the equipment, but takes up valuable real estate in the radio shack)

Way down the track I may experiment with a dual mode version of the repeater that listens to the mode being received (either FM analogue or DStar) and re-transmits in the appropriate form.

Proposals for a Better Repeater Site

I would like to locate the repeater at a better, elevated site that has a robust ethernet connection available.  If you have a suitable location and are willing to host the repeater - please contact me.

ACKNOWLEDGEMENTS

According to my way of thinking I have done all the work and deserve all the credit.

HOWEVER, THE REALITY IS DIFFERENT!   MANY PEOPLE HAVE CONTRIBUTED TO THE SUCCESS OF THIS HOMEBREW DSTAR REPEATER AND I WILL ATTEMPT TO LIST THEM:

Paul N1PA was pivotal in taking the time to make me aware of the Homebrew DStar Repeater technology and for providing ongoing support.  Also right in there was Dave N1FCC.

Reg VK6BQQ for providing the bulk of the hardware and much professional expertise to get the original FM analogue repeater operational.

Rich VK6HRC for offering encouragement and support during the long periods when the repeater's performance was rubbish.  Also thanks for various computing equipment which helped debugging generally and was used to work on the RPi specifically (which he also donated).  Also the LDF4-50!

My dear XYL Joanne VK6FASO.  Without her support VK6ROX B would be in the landfill.

Jonathan Naylor G4KLX for writing and developing the brilliant SoundCardRepeater and ircDDBGateway software

Peter VK6AIF, Steve VK6ST, Martin VK6ZMS and Jim VK6JIM for being early adopters, trying out the system and offering feedback and ideas.  Also Peter  VK6FUN for helpful RPi ideas.  And Barry VK6WF for daily offerings of "DStar is @#&% and it'll never catch on".

Steve VK6ST donated a Windows XP laptop for the repeater - thank you!

Rick VK6XLR donated a mini-ITX motherboard to use as the controller - thank you!

Anyone I forgot to thank - here is yours - THANK YOU!