Remote Operation
G3YXM


The new UK licence which came into force in 2007 allows for remote operation of an amateur station so long as certain conditions are met.

The station must not be accesible to all, and must be secure against misuse. I decided to set up a remote base at the my parents' home in Galloway.

This is an ideal location as the noise level is low and there is adequate space to erect some useful topband aerials in the trees.

I arranged for broadband internet to be available via Plusnet (who were very efficient), bought a Netgear router and started experimenting with a remote-control solution.

The basic building blocks are, at the remote end:


basic block diagram


At the operator end you need:

The system works like this:

The two computers are linked by a Virtual Private Network (VPN) over the internet. This ensures that you, and only you, can access your radio. Very important to comply with licence conditions (doesn't matter if it's just a receiver of course).

On the remote computer you run a serial-port server program which allows the rig to be controlled over the VPN as if it were on your home network. You must also run a VOIP program which sets up a two-way audio link between the operator and the radio. Additional remote control facilities for switching aerials etc can be added as desired.

The most convenient VPN software is Hamachi from Logmein. The basic version is free and does everything you want.

The obvious software for rig-control was HRD (Ham Radio Deluxe) which is free and has the ability to control almost any modern radio. I initially decided to use my old IC735 and set about building the necessary interfaces to control it and feed audio to and from the computer. You install HRD on the remote computer but just run the server app, not the whole program.

G4ZLP has a great range of control cables and interfaces to connect your radio to your computer if you don't want to build your own.

The VOIP program of choice is IP Sound written by SM5VXC, or you can use SJ Phone which has a few more facilities. Both are free.

If you want to switch aerials, power etc you can use a parallel-port remote program like Lalim's Chcport. It's a bit fiddly but once again it's free! Using this, you can connect relays to the parallel port of the remote computer and switch them from the shack. Interface details come with the software.

Setting up

The IRB under test

The Original version of the IRB under test in the shack.


For my remote PC I used an old 850MHz P3 laptop running Windows 2000. I did a clean install, updated it to the latest spec and turned off all Windows updates, I didn't want my remote computer re-booting and failing to re-start after one of Bill's updates..
I set up the BIOS to remove any annoying boot funnies and added a remote control to the on-off button on the laptop using a switching transistor across the contacts. This was then connected to a DTMF decoder board which was plugged into the audio from the GSM phone. Using this I can re-boot the PC if it should lock up (a 5 second burst of the appropriate tone will shut it down even if locked solid, then another short dab starts it up again). Another output of the DTMF decoder will cut the router power so that I can re-boot that too.

logic boards

The IRB logic, power relay on the left, DTMF decoder on the right.


I installed, Hamachi, IP sound, SJ Phone, HRD, VNC, a webcam, an FTP server and chcport. The free version of Hamachi is hard to set up as a service so I also installed Logmein which allows secure remote access to the PC via a browser, whether a user is logged in or not (more belt & braces). I set up all the essential programs to start at login (there's a useful program called Starter which makes this easy) e.g. HRD remote server, chcport, IP sound and Hamachi.

The laptop PSU was fitted into a screened case an filters added to the mains and DC leads, I didn't want my PC to interfere with the nice quiet location!

My audio interface was built with a pair of audio transformers and a some resistors to match the rig's input and output levels to the PC. I used the rig's mike input so that I can use the processor, so the PC headphone output had to be padded down; similarly, the laptop only has a mike input so the rig's output had to be padded down too. If using a modern radio (I now use an FT897) PTT is via the serial link, for the old IC735 I had to build an interface. G4ZLP can supply the hardware if required.
The radio was then connected to the PC with the appropriate control lead between its CAT port and the PC's serial port. Some PCs don't have an RS232 serial port but USB convertors work fine. See 'ZLP again!

An auto ATU (cheapo CG3000 from Martin Lynch) was connected to the aerial and housed in a stacking box in the garden. This would enable me to transmit on any band from topband up to 10m. I also installed a VHF/UHF colinear in th garden and connected that to the VHF/UHF socket on the FT897.

The ADSL micro-filter was fitted at the master socket where the phone line entered the house and an extended RJ11 lead fed from there to the router which was fitted in the "shack" (utility room). I wrapped this lead around a large toroid as many time as possible to try and reduce RF interference to and from the overhead telephone line. As it happened, I didn't get any interference from the ADSL on the receiver, but I did get problems with my transmission dropping the ADSL line. To cut a long-story short, I solved it by disconnecting the Sky box from the telephone system and fitting a topband series-tuned cct across the feed between the micro-filter and the router. This forced the ADSL carrier speed to drop to 1MHz (it was 2 before) and the problem went away. The speed is still plenty for this application.

In use

The IRB in operation

The IRB as it is now, in operation in Scotland.


With the remote system shut down I have to go through the following procedure to get it all up and running:

Dial up on the GSM phone and send the "boot" tone. The remote PC boots up and sits at its login screen, no software running.

Go onto the Logmein web-site and log in as the Windows user. The PC starts all the software automatically (but I could start anything I wanted manually through Logmein).

I check that the remote PC has appeared on Hamachi, then I can log out of the Logmein web-site. I can then run VNC to do any administration, listen to the rig via IP sound, twiddle the knobs with HRD and switch aerials with chcport. It's almost as good as being there...

Normally I just leave the remote PC running. With no Windows updates or rogue software to mess it up it's been superbly reliable for over a year now. If you hear GM3YXM "remote" then that's the station.

I hope to add more to this page soon, diagrams, pictures etc, but I'm off for a cuppa now..


© G3YXM 2008

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