A Quick RoIP Experiment

RoIP stands for Radio over the Internet Protocol and you can use this technology to connect remote radios over any distance, easily.

There are, of course, very complicated and elegant communications systems that do this already such as Echolink, D-STAR, Allstar, IRLP, Tetra and DMR/Mototrbo, but tonight I homebrewed my very own, modest private link in half an hour – and you can too!

If you have a rig with a packet data port and an external sound interface, such as a Signalink USB, then all you need is some software and a mobile phone, for example.

Signalink USB Interface with FT-817 set to 2m FM calling

Zello app with PTT

I used a fantastic free app called Zello. Zello is a walkie talkie emulator for your smartphone but also has a PC programme counterpart. The clever bit is that it has a VOX function with several adjustments for sensitivity and delay. My project enabled me to talk remotely over 2m using my smartphone!

So, by pressing ‘PTT’ on my smartphone and making a direct call to my computer, the VOX switch was activated on my Signalink USB interface and my FT-817 transmitted. When the squelch was opened on my ‘817 by the station I was talking to (and this is the clever bit) the Zello programme on my computer used its VOX feature to transmit back to my smartphone.

Zello GUI on Windows XP

Zello VOX settings

Now I know that Ham Radio Deluxe can be established to give full remote control over my rig, but that’s for another day. This is one solution to automatically link two radios that anyone can do.

More of a Shout than a Whisper…..

The key to converting your treasured and incredibly versatile FT-817 or similar into a digital powerhouse seems to be an A. computer and B. a sound card interface.

So, armed with a tidy little Signalink USB interface, I’ve been attacking digital modes with vigour, starting with WSPR (Weak Signal Propagation Reporting). The Signalink USB is basically a remote sound card in a box, powered by your computer’s USB. This solution allows controlled audio isolation between your rig and transceiver. Level adjustment is available on the front panel too which means you don’t have to navigate clumsily through several windows on your PC and adjust sliders with your mouse to optimise levels.

FT-817 and Signalink USB Interface

The interface connects directly to the data port of my FT-817 and provides a PTT function, if required. However, I’m also using a CAT interface which provides PTT (Push To Talk) as well as frequency configuration from the WSPR program that I’ve started with.

So, straightforward then? Nearly but not quite. There are a few small pitfalls to be aware of. Firstly, the ‘817 needs to be put into DIG mode as opposed to USB mode. This routes the input and output signal to the data port on the rear panel. The data port is inactive in SSB modes. Secondly, the correct data mode needs to be selected in the second-level menu, namely USER-U. This means that it will be operating in USB mode and the passband will be adequate. If this were to be set to RTTY or PSK, then the filtering for WSPR would be too narrow. WSPR signals are individually narrow, but several occupy the given passband. Finally you need to follow the instructions on Windows setup that comes with the Signalink box to the letter. One unchecked box or misplaced slider will drive you to madness.

WSPR Control Software

Apart from that, it seems to be ‘plug and play’! My first play on 40m with a random wire of some 20m in the back garden pulled in a VK straight away. I was heard up in the Norwegian Arctic Circle with 1W. Elation. Simply tuning to 472kHz pulled in a Dutch station with absolutely no special equipment.

For one whole day I exercised near-military discipline. I stayed on the 30m band all day long without jumping to other bands. 1W into my rear-garden wire antenna reached Israel and the Arctic Circle again. East Coast US stations starting to come in at 20.00 GMT and I was reaching the Mid-West by late evening. Within ten minutes this morning on 17m I was heard in New South Wales and Iceland.

10 mins on 17m!

10 mins on 20m!

I finally unleashed my single Watt on the 20m band for the first time this afternoon, immediately yielding a nice path to the Philippines as well as Europe and the East US.

No wonder this aspect of the hobby is so absorbing. I’m absolutely addicted. Did the developer, Joe Taylor, K1JT, realise what he was unleashing on us? A ‘big shout’ goes out to the man who invented WSPR!