h4cking, ham radio, fire fighting and m0re

How to Identify a Genuine #MMDVM_HS_Hat

Since DB9MAT an me came up with a selfmade MMDVM_HS board called the MMDVM_HS_Hat there is a number of Chinese copies out there which we belive are bad quality rip-offs. We published our sources under Creative Commons Attribution-NonCommercial-ShareAlike 3.0 (CC-BY-NC-SA 3.0) license which explicitely forbids commercial use (unless authorized by us). Of course these Chinese copies are not authorized and thus just a clone of our work.

To help distinguish between an orginal #MMDVM_HS_Hat and a clone have a look at the two pics below. The first one is an original board revision 1.2 manufactured by us. It has the name “MMDVM_HS_Hat” on it in the upper right part. The silkscreen is properly placed and our callsigns are clearly readable. In addition to that there is the Open Source Hardware (OSHW) logo on the lower left.

Modification of T-962 Reflow Oven

For the latest MMDVM_HS_Hat project by me and Mathis, DB9MAT I arranged for a reflow oven model T-962 which is a good assistant for SMD soldering work. As per Toufik, F0DEI there were some interesting modifications to make in order to improve the results as well as to get rid of smelly evaporations.

There is a famous article on hackaday (See [1]). It was the reason to open up the unit and get some improvements done. In order to support this there is a nice YT video [2] describing the mods in detail.

Homemade Data Cable for Yaesu FT-2D

A while ago I bought a Yaesu FT-2D in order to try some YSF with MMDVMs. I discovered that German shops sell the data cable for nearly 90€ which seems quite expensive - especially after discovering that I just contains a pl2303 USB-RS232 adapter and a MAX3232 or similar level coverter. So the only difficulty left to clone this cable was the connector on the radio side. There is a longer thread on Twitter about this (see [1]). Sources for the plug seem to be [2] and [3].

Excluding FT-232 From Ftdi_sio Driver

For the upcoming AMBEd daemon needed by XLX reflector software there is a need to connect an FTDI USB-serial adapter without using the default ftdi_sio kernel module. Instead the software makes use of the D2XX drivers by FTDI. This driver is available as binary only from FTDI’s website.

The problem with Linux operating systems is that it loads the ftdi_sio driver by default. One option is to blacklist that module. The drawback is that also all other FT232 based USB-serial adapters will also not work anymore. In my case I had some other devices that had to use the ftdi_sio driver while the AMBE device should not. So blacklisting the whole driver is not an option.

Make SVXlink Tell 24h Time / UTC

After re-setting up my SVXlink node I encoutered the problem that the time announced was using German spelling but English time format. That lead to very strange time announcements during the long identification transmission. Also the 24h time format was missing. After reading around on [1] and [2] I found that this can be overridden locally. The best local.tcl settings were found on a German forum (see [2]). Andi, DL1HRC made a nice local.tcl that just needs to be installed under /usr/share/svxlink/events.d/local. The sub directory has to be created if not existent. So the last issue was to let listeners know that the time ist UTC.

Interfacing Motorola GM1200

I had an unused GM1200 that should be interfaced to a SVXlink node. Turns out that it is not as easy as I thought. I wanted to use the CTCSS decoder and a hardware squelch signal. The CPS offers different options that can be programmed per FM channel. The essence is the option “Data Channel”. That enabled unfiltered raw output on pin 25 of the accessory connector. The audio input can be connected to pin 24. The hardware squelch can be used on pin 8. It carries +4.5V if the squelch is closed and drops to GND if the squelch opens.

Headless Building MMDVM Firmware

A while ago I was looking for a way to build the MMDVM firmware on a bare Debian Jessie system running on a Raspberry Pi. It has no X installed and thus I need a way to build the Arduino Due firmware without installing tons of GUI packages. I copied parts of a Makefile for the Arduino IDE as it is just executing command line binaries under the hood.

I added some support for building the MMDVM firmware using a Makefile to the github project a while ago. The only problem left was finding a way to “install” the Arduino IDE in command line mode.

Interfacing Tait TB7100 and MMDVM

The other day I got hold of a Tait TB7100 1U repeater. I thought I might make a good basis for a MMDVM HotSpot or even repeater. Apparently the RX had a sort of a problem. Using the service manual I discovered that the TCXO for the RX was missing its power supply due to a removed resistor. After fitting in a replacement the unit worked ok with a testing configuration for a FM repeater.

So that would make a good hardware for a MMDVM HotSpot now. Some research on the Yahoo group revealed that you need to directly wire RX and TX audio directly to the two modules on the inside.

Monitor a DAPNET Transmitter With Nagios

After describing how to get notified of system criticalities via pager I wanted to have my DAPNET transmitters monitored via Nagios. A basic description can be found under [1]. Firstly you need to set up the plugin check_http_json. The source and installation hints can be found on [2]. That enables Nagios to query the DAPNET master using a JSON request and process the result.

A little different to the manual by RWTH Aachen I also configured the hostname of the master in /etc/nagios3/resource.cfg in order to have it not depend on the hostname of the Nagios host.


After settinp up a DAPNET client for the POCSAG Amateur Radio paging network I was looking for some good source for interesting information to be sent to my pager. I already had a Nagios monitoring solution set up in order to monitor several D-Star service and repeaters in my area. So I wanted to get Nagios to inform me as soon as one of these services changes state to critical.

The solution is to implement a second method for nagios to send a notification. The original method to send an alarm via email was left as it is.