AmateurRadio.com

Part 2 of 2 

If you purchase the DHAP with the Raspberry Pi, it includes a factory image of the OS and software. Configuration is easy enough. The DVAP software is set to auto-boot so you need only configure it once. If you connect the device to a wired network connection the Pi will boot up and obtain a connection. If you want to use the device with Wi-Fi, then you have to launch the WiFi configuration tool and set up the connection.

This is only slightly tricky because it would be handy to plug in a keyboard, mouse, and the network dongle — three USB connections while the Pi only offers two. A USB hub handles the multiple connections and you’re underway. After setting it all up once, there’s no need for reconfiguration as it all just boots up and obtains a network connection without the need for additional interface.

In other words, connection to a monitor, mouse and keyboard is only required for the initial configuration. After that, the DHAP can be operated “headless”.

Unless of course you’re thinking of taking this on the road with you and would like to connect it to a hotel’s Wi-Fi. Then you’re going to need to carry the input peripherals and a monitor, or use the TV in your hotel room if that’s possible.

This is all much more than I like to carry on out of town trips which is why I tether the DHAP to my cellphone. Carrying Wi-Fi in my pocket simplifies things considerably though this brings me to a tip I’d like to pass along when using it this way.

Wi-Fi and Tethering

If you set your home Wi-Fi and your tethered connection to have the same SSID, password, and encryption method, then there is never a need to reconfigure the Raspberry Pi. One of my home wireless networks (WPA PSK2) is called ‘GUEST’ and the password is ‘lemonade’ and I’ve made those settings identical on my phone.

When I’m away from home, I tether to my phone. When I’m home, the Pi auto connects to my home Wi-Fi. Simple. Easy. Clean.

It takes about 15-20 seconds for the Pi to boot up and another 20-30 seconds for the networking to kick-in, negotiate a connection, and begin working. When you power up the DHAP, give yourself a full minute before trying to connect to it with your radio.

Powering the DHAP

The DHAP comes with a brick charger that has an LED indicator. When it’s red, the batteries are charging and when it’s green the charge cycle is complete. Silly me. I plugged it in and started using it right away. The charger went through the cycle, the LED turned green and the voltage began to drop. Though I wasn’t paying attention and several hours later my D-STAR connection was dead. When I checked on the DHAP the voltage display showed 2.2 volts — not enough to keep the Pi or the DVAP alive.

This seemed odd. The battery voltage was low but the charger LED was green. There was no charging going on for some reason and I thought I had a defective unit.

Then I discovered that the charger is fairly “dumb”. It provides one charge cycle then stops. Removing power resets it for the next charge. This works well if you charge the DHAP, then unhook it and take it in the field. If, on the other hand, you want it to just sit on the shelf at home and provide a hot-spot, you should provide power via the USB Power socket on the front panel.

This bypasses the batteries altogether and directly powers the Raspberry Pi and the DVAP. By the way, *don’t turn the unit on in this mode* — and the voltage display will show the power being supplied via a USB power supply — probably something a little less than 5 volts.

A one amp USB power supply should do the trick nicely.

Odds and Ends

It makes sense to get things working with your DVAP connected to your desktop (or laptop) computer before installing it in the DHAP. It will operate exactly the same once it’s tucked away in the enclosure.

There is a small slot in the top of the DHAP that permits you to see the activity LED’s on the DVAP. You will find this quite useful.

The tiny antenna on the DVAP works well enough but it can be replaced with a more efficient “ducky” style antenna. The DHAP comes equipped with a built-in cable that can “remote” the antenna connection to the back panel. Don’t be tempted to try and interface the DVAP to a full-sized, outdoor antenna. Internet Labs has reported hardware failures that they attribute to doing just that.

Have Fun

D-STAR is not worth the bits it’s built upon if you don’t enjoy it. If you’re considering joining the growing crowd in this unique mode of operation let me first ask you one simple question: do you enjoy repeater operation?

Because at its core, that’s what D-STAR is. A global collection of repeaters and individual users who have the ability to communicate with each other using this digital technology. If you’re answer is “YES” and you enjoy rapid learning, then you will no doubt enjoy digging in and exploring this evolving mode of operation.

But if you’re answer is “NO”, well, then this facet of amateur radio is probably not for you. Don’t waste your time — or your treasure. Move on and find something you really enjoy. After all, amateur radio is a hobby with endless things to do, people to meet, and fun to be had.

[miss part one?]

Part 1 of 2

I’m traveling this week with a DHAP and the Icom ID-51A dual-band handheld. This combination of hardware permits me to stay connected with my friends on the D-STAR network from wherever I happen to roam – no local digital repeater required. The DHAP is a custom-built enclosure and battery supply for a Raspberry Pi and DV Access Point – a DVAP.

If all this sounds like too much alphabet soup (it is!) let’s first break it down in pieces.

The DVAP is a small USB powered D-STAR transceiver that runs about 10mW of power on UHF. VHF is also available. It’s manufactured by Internet Labs. The concept here is that you plug the DVAP into a USB port on your Windows, Mac or Linux computer, running the proper software and connected to the Internet, and it looks a lot like a D-STAR repeater to your radio — albeit a micro-repeater with only about 100 yards of coverage.

With this arrangement, a user can connect to other repeaters and reflectors on the network. While it’s an effective solution, it’s not elegant or efficient to keep a desktop or laptop computer running all the time just to maintain that connection.

Enter the Raspberry Pi, a single board computer that’s smaller than a pack of cigarettes, costs $35, supports networking, and runs Linux. It didn’t take long for users to see the advantages of this arrangement over the desktop PC and the rapid migration was underway.

You can put all this together for the price of the DVAP and another $50-100 for a Raspberry Pi, memory, associated cables, power brick, and all that jazz. It will work perfectly well setting on your desk or workbench like that, but if you want to take it outside with you, an enclosure to house and organize it all is a really good idea.

Which gets us to the DHAP. Manufactured by Hardened Power Systems, this contraption is a robust enclosure for the DVAP and the Pi that conveniently brings all of the on-board connections out to the front and back panels. NiMH batteries run the show for several hours between charges while a front panel display shows the battery level.

It’s not waterproof, and I suppose you could break it if you tried. But it is a hardened, machined case that’s slightly smaller than a football. Once it’s configured and charged, you just pick it up and carry it with you wherever you go.

Of course, it requires a network connection that can be provided from a hardwired Ethernet cable or via a Wi-Fi network. That Wi-Fi link means it can be easily tethered to your cell phone, which is how I use it on the road, when I bring it home, it automatically connects to my home Wi-Fi.

It’s the ultimate in convenience and portability for the D-STAR enthusiast though it’s not cheap. $300 [US] for the unit with a Raspberry Pi, a little less if you’re bringing your own Pi. And that doesn’t include the DVAP…

More about how I use all this on the road, and a few tips about the DHAP in the next post.