As many of you know, I run the GB7KH multimode digital voice repeater on the north east side of London. The project is based around the MMDVM project. When installing the RF hardware, I ensured that the repeater had a calibrated RSSI (received signal strength indicator) output, which I did using a communications test-set. When the MMDVM host program is running, it also output’s an average BER (bit error rate) at the end of each reception. Since the repeater had been operational with the RSSI output for some time, I decided plot some graphs showing how the RSSI effects BER. These graphs appear below:
I also decided to look at the average transmission length on the repeater. Most of the transmissions are for less than 1 second. This is typical of “kerchunking” (to key up the repeater to see if it is there and the user is in range). Speaking with other repeater keepers, it seems this behavior is quite common.-
Some simple Perl scripts running on the repeater controller are able to provide user information. These homebrew scrips consider use since new year’s day 2017.
- D-STAR: A total of 2115 transmissions were made by 38 callsigns.
- DMR: A total of 525 transmissions were made by 23 callsigns.
- YSF: A total of 1294 transmissions were made by 14 callsigns.
- P25: A total of 0 transmissions were made by 0 callsigns.
Today I met with Ian of Icom UK over lunch who presented me my D-Star QSO Party prize! It was good to have an in depth chat with Ian, and hopefully many more to come. Makes a change from me bending Don’s ear! See the official Icom UK tweet here.
The D-STAR repeater project GB7KH is well under-way with the repeater on soak test at my home. See the repeater project website for more information.
Over the past week or so, I have been playing around with DStarRepeater and ircDDBGateway to learn a bit about DSTAR repeaters, given the progress GB7KH‘s NoV is making. I have made a simplex hotspot with my FT817 and a soundcard interface, although I can see that there is certainly room for improvement. I have ordered a DVRPTR_V1 GMSK interface which has been dispatched so that will replace the soundcard, lowering the CPU load. I am to have the system set up on a Raspberry Pi 2 B, which was released yesterday (maybe today actually). I think I now understand how to tune up those Chinese notch filters, too.
Today I finished my 4 month stint at ARM Ltd. During my time I haven’t done much with the website, but I have been working on my implementation of a fully KISS compliant Arduino TNC as well as using DSD 1.7 to decode digital modulation such as D-STAR and DMR (and others) using my FunCube and RTL-SDR receivers.