Ham Radio Clock for Raspberry Pi

In a previous post I discussed building a clock to display the grey line and times zones on a large screen. Thanks to this project I've been able to improve the display as well as reducing the cost by a further $65.

The finished clock running on a 5 Inch LCD screen on the Raspberry Pi3

This clock originally appeared in a QST article in October 2017 but it took me a while to get around to it.  Whilst trying to get some "shacksessories" organised for my wife, KM4WSK's new radio shack I remembered it. I also happened to have a RPi3 connected to the Official Raspberry Pi 7" LCD and associated enclosure so I installed the software onto that.

The clock application installed into Official Raspberry Pi 7" LCD

As you can see, the clock displays not only the greyline but also solar weather data, sunspots, local weather data, UTC time and the current state of the HF Beacon transmissions. It's also able to display the path of a few satellites too.

Whilst I had all the parts for my wife's clock I was lacking an enclosure for my 5" LCD screen. A quick search on Thingiverse.com revealed a case that I could print on my 3D printer and then mount onto the wall. 

First boot of the clock. Note the lightning bolt

At first boot of the 5" display I was confronted with the dreaded lightning bolt. This is an indication that there is insufficient current available to properly drive the RPi and associated hardware. It's a simple fix requiring a bigger PSU. KM4WSK was able to supply a larger one from her seemingly bottomless "junque" box.

I've decided to revisit my large clock on the LCD TV (the one from the previous article). To this end I've temporarily mounted my 5" version on the wall. With a few crontab entries I can turn the display on and off so as to save energy overnight.

MMDVM based digital modes hotspot

Now that there are so many different digital modes around for the V/UHF bands I decided that it was time I had a hotspot that could cover all the modes at the same time.

I've been following G4KLX's MMDVM project since it's initial inception and have even donated one of my NQSMHS modems to the project (it started out as a D-STAR project). Today the project has gained quite some momentum and is now able to run on a Raspberry Pi Zero W along with other hardware addons such as screens and buttons etc. Significant work has also gone into creating a RPi distro explicitly for the MMDVM.

My hotspot is based on the RPI0W and ZumSPOT hotspot board that you can get from HRO here in the US. I followed this HowTo which said to download the latest image from the PiSTAR site and transfer it to an SD Card (just like any other RPi distro).

And this is the finished result. The 3D printed case is by George, M1GEO and is available from Thingiverse. It only supports a 3.5" Nextion LCD display but having also tried a 2.8" display I can tell you that you want the bigger screen! I have asked George to knock up some designs for other screen sizes and also to add some cooling holes into the box as it can get quite hot in there after a good round table QSO!

The Nextion screen is quite clever in that you upload a handful of screen images to it when setting it up. These images also have various text fields that will be populated with data every time the MMDVM host sends some info to the screen (eg, which screen image to display, what frequency, RX Callsign etc). Below is a selection of the screens that mine does.

The bootup screen. I decided to abandon this particular one as I couldn't really see it properly.

Traffic arriving from the Internet. This will be broadcast via the built in 20mW TRX. Note the RPi3 mounted next to it on the left. That's an Echolink system.

It's listening for my local input. It'll do this for 10 seconds. If I do not respond in YSF (in this case) it'll drop back to listening for any mode.

Receiving my YSF signal from my HT in the shack. Note the BER. This is quite high and can be attributed to overload in the RX. When I'm on the other side of the room the BER is down to almost 0%.

Raspberry Pi/Echolink using a USB-RIM Lite

I built an Echolink interface for the W4FCV repeater in Floyd, VA. This page is not so much to brag about it but rather to write down some notes for later reference.

The repeater in Floyd is a System Fusion capable machine with an Arcom RC210 repeater controller attached. The Echolink system will connect to one of the 3 "radio" ports on the controller. A look at the Repeater builder website shows a number of sound card interfaces that will directly connect to the back of a number of different radio's and repeater controllers. I bought one that fit the RC210 directly.

I shall not be explaining how the various steps are performed. They are well documented on their respective websites.

Things I used:

• Raspberry Pi 3 single board computer https://www.amazon.com/
• USB-RIM Lite sound card interface http://www.repeater-builder.com/products/usb-rim-lite.html
• 8GB MicroSD card https://www.amazon.com
• 3D printed 19" rack mount case https://www.thingiverse.com/thing:794695
• USB power supply https://www.amazon.com

What I did:

1) Install latest Raspian Lite image onto the SD card. Make sure to enable SSH.
2) Install SD card into the RPi. Attach an Ethernet cable and power.
3) Log in to the RPi and set up the environment with "sudo rasp-config".
4) Disable the WiFi and Bluetooth radio's as we'll be using Ethernet. Edit /boot/config.txt 

# Free up some memory by allocating less RAM to the graphics

gpu_mem=16

# Increase current to USB ports

max_usb_current=1

# Turn off WiFi and Bluetooth

dtoverlay=pi3-disable-wifi

dtoverlay=pi3-disable-bt 

5) Install SVXLink per the instructions https://github.com/sm0svx/svxlink/wiki/InstallSrcHwRpi

6) Configure the SVXLink config file http://www.svxlink.org/doc/man/man5/svxlink.conf.5.html. The USB-RIM interface required HID_RAW settings and the HID_PTT on GPIO3 also.

7) Configure the Echolink config file http://svxlink.sourceforge.net/man/man5/ModuleEchoLink.conf.5.html.

Raspberry Pi ST-4 compatible Autoguider

I'm working on a project to add a Raspberry Pi to my telescope setup. In the end it will do everything from plate solving to photography and also allow me to do it from the warmth of my armchair rather than standing out in the cold all night.

I'm not the first one to have thought of this and there are many ideas as to how to do it. Presented below is my take on an ST-4 compatible autoguiding interface. It plugs into the Pi's 40 pin I/O connector and sticks out of the case so as to allow the cable to connect from the guide port on your mount to the Pi. I've also added a DSLR trigger too.

I've uploaded the board to Oshpark so that you can order one (well, 3 really). The BOM is trivial and the opto chips are nothing special.



Below are the Eagle files.

RPi_ST-4_Opto_Interface.brd
RPi_ST-4_Opto_Interface.sch