Forth Estuary Experimental Data Network
Most of what can be achieved via FEEDNET is courtesy of open source software. The sheer hard work, altruism and inventiveness of all open source authors is gratefully acknowledged here.
USBtran - RoIP Remote VHF (UHF) Base Station.
Bernie McIntosh, GM4WZG - March 2016.
What is USBtran ?
USBtran is a VHF FM transceiver that has a USB port which plugs into a computer, such as a Raspberry PI or a PC. Using the Asterisk VoIP system, the VHF channel can be linked to other similar units on the other end of a network connection. This connection could be an independent one implemented by radio amateurs such as FEEDNET or it could be a standard Internet connection point.
VHF users can talk to other VHF users or to VoIP telephone users.
USBtran provides, in one unit, a replacement for both the standard soundcard/PTT interface and the transceiver itself in a typical Allstar Node. It partly came about because the supply of the commonest hardware interface for these nodes has dried up and partly because the DRA818V module looks pretty neat and is worth trying out. I am not disappointed with the results.
What does it do ?
It is possible to substitute the VHF module for a UHF module in this transceiver. The Low Pass filter would need to be substituted also.
Are these boards available for sale ?
I've already been asked if these transceivers are available for others to purchase. It kind of looks like a "product". Right now the answer is no. This was a fun project and I happen to like making things look like a decent product - nothing more!
But if enough folk really were interested I could get a local PCB assembler to to make up a batch of boards - maybe 100 or so, with a view to folk paying cost price plus a small amount for contingency. An alternative could be to just make some bare PCBs available. Write to me if you are interested in either option. There are other products out there and its quite easy to modify a soundcard, or even make a board like this, but if there is sufficient interest I will let you know and put an update here.
How do I find out about the software ?
I thoroughly recommend Doug Crompton's web site. Doug, and many others, have given huge amounts of their time and effort in the production of software and images that are easy to use just by following instructions. Inspirational, and a perfect demonstration of the true spirit of Ham Radio.
This allows you to connect a mobile telephone, for example, to the PI to operate Asterisk and the USBtran. I'm not too familiar with ArchLinux but after figuring a few things out and going down a few blind alleys this wasn't too hard. Maybe I can make someone else's journey a little quicker. I used Doug's v1.02
First login as root.
Make sure you do a full system back up using whatever method you prefer and have confidence in. Your system may be different to mine and you may lose any or all of your working system.
There are a few packages need to be installed:
First - iw, a tool to show / manipulate wireless devices and their configuration
# pacman -S iw
Now wpa_supplicant - a tool that allows you to use authentication on wifi networks
# pacman -S wpa_supplicant
hostapd is a software access point daemon
# pacman -S hostapd
We use dnsmasq to provide dhcp services to the access point. Without this you can't issue a device connecting to your access point with an ip address/.
# pacman -S dnsmasq
Nettle seems to be needed. I don't know much about it - seems to be a cryptographic library.
# pacman -S nettle
Here is a wonderful access point tool that can save you hours of configuration work. Download and install it.
# git clone https://github.com/oblique/create_ap
# cd create_ap
# make install
That's it. A reboot might be sensible although probably not needed.
To create an access point once, from the command line
# create_ap -n wlan0 myaccesspoint mypassword
If you check with a wifi enable device you should see the wifi ssid myaccesspoint. Connect to it and give it the password mypassword.
Any error messages will appear on the screen.
Read the documentation for create_ap at https://github.com/oblique/create_ap
You can use systemctl to enable your access point on every reboot. First edit your service file to configure it the way you want it.
# vi create_ap.service
#systemctl start create_ap
# systemctl enable create_ap
Things to do
When we make a few more of these I will be including a small 20mm x 20mm fan on the Dorj module. The rear heatsink of the module is soldered onto the board which helps to dissipate heat. I think for long term continuous duty cycle use it might be reassuring to have just a touch of air movement to help with cooling.
Folk often say that SMD work requires too much specialist equipment and are dissuaded from trying it. Don't be! This board was created using free Designspark PCB software. Etched by Eurocircuits. Assembled by hand with nothing but a Weller soldering iron that I have had since 1979, and a cheap Atten 858D hot air station. I do use a hot plate at times made from a slab of aluminum which is handy for keeping the board at 100 deg C. This makes the final reflow with the hot air happen very quickly. But really, just the iron and the hot air is more than enough.
© 2016 - GM4WZG
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