APRS DX

Sunday was a fine day - though there was a bit of a cold breeze from the east - and my wife Olga and I decided to take a picnic lunch and my VX-8E for a stroll to the top of Ling Fell, one of the lower Lake District hills that is 205th in height seniority out of the 214 Wainwrights.

I only made two contacts on 2m FM using 5W to a Comet SMA-24 antenna. The first was with Gordon, G0EWN/P who was on the summit of Skiddaw in clear sight of me (the summit, not Gordon!) I couldn't raise anyone else after that so we had lunch and then I called CQ again, to raise Tony G1OAE in Workington.

Although Ling Fell is not all that high - about 375m according to the GPS in the VX-8E - I could hear on 144.8MHz the frequent "brrrap" sounds of APRS signals which I never hear at my home station. Most of them were too noisy to copy, but the VX-8E decoded a position report from EI2MLP at a distance of 319km, which I later found was on the summit of Leinster in south east Ireland. I also received a status report from MB7UND apparently in Taunton, Somerset, listing EI5GRB as DX heard. So clearly there was some tropo about.

Obviously a better antenna would have helped to make more contacts, and dedicated Summits On The Air (SOTA) activators would probably say that it is a waste of time going up a hill without one. However, my objective is primarily to have a nice walk and a picnic lunch with a nice view, unencumbered with kilos of aluminium. I also feel that it is wrong to spoil other people's enjoyment of the summit they've spent time and energy to get to by erecting antennas. Even this minor summit had half a dozen visitors in the hour or so we were up there. How people get away with putting up beams and HF dipoles on the more well-known and popular tops I can't imagine. I guess you need a thick skin and a willingness to ignore adverse comments.

Receiving these DX APRS packets made me think that APRS could be a useful tool to detect openings on 2 metres. It's too late for the Sporadic-E this year, but I'd be interested to hear from anyone who has used APRS as a propagation detector.

Ultimate APRS tracker?

I just stumbled across this. It's an APRS tracker app for the iPhone, called iBCNU. It uses the phone's built-in GPS to send out position reports periodically using the 3G network or wi-fi. Since it isn't using ham radio it is a bit like cheating, but considering the problems I've discovered with lack of ham radio APRS coverage in rural areas it seems like the best solution.

The display is really cool. It even shows your current Maidenhead locator, which would be great for VHF "rover" activity. Even the VX-8 can't do that. Besides position reporting it also supports APRS text messaging.

It's a shame the iPhone is so expensive, and is only available here in the UK from O2 at the moment. Mind you, the VX-8 wasn't cheap. Since I already had a 2m HT, getting one of these would probably have been a better way to get the APRS functionality I wanted.

Gate closed

Although the technical hurdles in establishing an APRS gateway in the North Lake District have more or less been overcome, the final stumbling block has proved to be licensing issues. A comment received in a forum a few days ago prompted me eventually to research the matter. It seems that in order to permit unattended operation of an Internet connected station I would have to apply for a Notice of Variation to obtain a GB7 call. To be granted this I would have to specify a minimum of three licensed operators who would be able to access and close down the station within 30 minutes.

I don't know even one licensed operator who could fulfil that requirement for me! It isn't entirely true that, like Tony Hancock in the famous sketch, I have friends all over the world but none in this country. But there is no other radio amateur in the town where I live at all! There is one who lives in a village a few miles away that I have encountered on the air a couple of times, but that's all. Besides which, giving the keys to the house to three or more strangers is not something I or my wife would wish to entertain. So the North Lakes IGate is dead in the water as an idea. A receive-only gateway presumably wouldn't be a problem. But without the ability to support two-way text messaging the whole project loses its appeal.

What is really needed in an area like this is a gateway on a mountain-top site covering a wide area, managed by a repeater group with the resources to meet the licensing requirements. But there does not seem to be enough interest in APRS for this to happen.

A new 2m voice repeater has recently opened across the water in Scotland, GB3LA, which is a strong signal here. This supplements the two other 2m repeaters accessible from here, GB3AS and GB3DG. Neither of those were heavily used. In fact you can leave a receiver scanning for hours and hear nothing except the occasional periodic identification. So why we needed yet another 2m voice repeater I have no idea.

If it had been an APRS gateway instead then it could have provided coverage over a wide, sparsely populated area popular with hikers for whom APRS could be a useful, not to mention safety-enhancing service.

Success, finally (I think)

I hope I'm not speaking too soon, but I think I finally have a working APRS IGate running on the Eee PC! After recompiling soundmodem to cure an apparent problem with the audio, as I wrote yesterday, I ended up with a worse problem: the diagnostic 'scope display froze when I used it. I was on the point of giving up, but on the basis of "nothing ventured, nothing gained" I ran the soundmodem software anyway, started Xastir and lo and behold, received a position beacon from my VX-8E!

There was still a lot of Googling, tinkering and tearing out of hair to get from there to where I am now, and I probably can't even remember half of it. I won't even start to describe my abortive attempt to set up aprsd to work as a gateway without the mapping interface of xastir which I don't like very much. If any aprsd wizards read this and would like to offer their advice I'd still like to try it, though.

One problem I noticed when using soundmodem as a kernel mode driver (which isn't necessary for xastir, but is for aprsd) was that at start-up it spewed out a long burst of what sounded like packet but actually wasn't. Google (however did we manage without it?) turned up a few snippets about this, with the generic advice that soundmodem was being treated as a network device and you needed to stop your network daemons binding with address 0.0.0.0. This was Greek to me. I was hoping for help along the lines of "click here, uncheck that check box" and so on. Eventually I discovered that the rogue daemon was the avahi-daemon service. In Ubuntu you can disable it from System / Administration / Services, then restart and no long transmission when soundmodem starts. It's simple when you know how!

Next I found that APRS messages addressed to my VX-8E (G4ILO-7) and received by xastir were not being transmitted over the air so it could receive them. I had made all the necessary settings, or so it appeared, but there is an additional step: you have to create a file in $HOME/.xastir/data called nws-stations.txt containing a list of calls whose messages you wish to send over the air. The first time I tried it, it didn't seem to work, and I posted a question about this on the xastir mailing list. The post was spotted by John, EI7IG, who sent me an APRS message that appeared on the VX-8E! Why it didn't work the first time I have no idea.

I think everything is now working as it should be. I'm using my FT-817ND on the RF side, for the simple reason that I already have the cabling for it. I'll probably try using my TH-F7E later on, but I don't have the necessary cabling for it.

So now I can be tracked as I move about the local area, and can send and receive text messages via amateur radio. I've already had a few exchanges with EI7IG and I can tell you, I wish Yaesu had implemented predictive text on the VX-8E! If you have APRS too please send a message to G4ILO-7 to say hello. But check my current location page first to see if G4ILO-7 is shown, because APRS text messages aren't stored and sent later if the recipient's current location isn't known.

Eee I'm getting nowhere

Developments on the APRS front have been moving on faster than I can write about them. A couple of days ago I had an email from someone who was running an APRS IGate on an Asus router. I thought this was a good idea - better and more economical than leaving a PC on all the time - but one to consider for some time in the future. Then I remembered that I had an Asus Eee PC 2G Surf sitting unused on a shelf. If I could install the Linux equivalent of UI-View, Xastir, on this, I would have a standalone low power consumption APRS IGate at no extra cost!

The first thing I did was install Xastir-Eebuntu 3.0 from the live CD available in the Xastir Wiki to the Eee PC. It was time to vape the Xandros OS that came with the Eee PC as it was too old to run the latest ham software and failed with errors when many of them tried to use the soundcard anyway.

Because I don't have a TNC I needed soundmodem, which is the Linux equivalent of the SV2AGW Packet Engine. I downloaded that from the Ubuntu repository and then configured it according to the excellent HowTo: SoundModem instructions in the Xastir wiki. Xastir worked just fine, and I could even hear what sounded like packet coming out of the speaker. But no matter how I adjusted the input audio levels I could not decode a single packet transmitted by my VX-8 radio.

Eventually I found that the soundmodem configuration utility has a diagnostic tool. When using the oscilloscope I saw horizontal lines in the waveform - exactly the problem described here and shown in the screenshot on the right.

While wondering what to do about that I had an email from Gareth, GW4KJW, who suggested running UI-View32 under wine, the Linux Windows emulator. This seemed like a good idea, so I installed wine from the Ubuntu reporitory and then extracted the AGWPE archive into a folder and ran it. This appeared to work OK. I then installed UI-View32 from its installer. Ui-View ran, but the map display went black a fraction of a second after the map was displayed. I also got a run-time error message when trying to load a different map.

After more Googling I found that this problem had been encountered before. I tried the recommended solution of downloading and running the winetricks script. This worked, after installing some CAB extractor utility it needed, and UI-View looked fine. But it still did not decode any packets.

Using the AGWPE soundcard test utility I found that audio was being received by the software. However there was a delay of a few seconds between changing the audio level and seeing a response on the oscilloscope display. Presumably some delay was occuring getting the audio from Linux to wine to AGWPE. Perhaps the Eee PC is just too underpowered for this application. The audio looked normal - no horizontal lines - but I could not get anything to decode, so I decided to give Xastir one more try.

First I had to fix the problem with the breaks in the audio. I downloaded the source code for soundmodem (version 0.14), and after downloading and installing a couple of libraries I was able to compile the source code. However when running the diagnostic tool I noticed that the oscilloscope display froze after a second or two. Thinking it was just a glitch, I went ahead anyway and made the changes mentioned in the linux.hams posting mentioned above. This changes the sample rate from 9600Hz (which soundmodem tries to use and which is probably not supported by the Eee PC hardware) to 11025Hz. I then recompiled and tried again. Unfortunately the display still freezes, so I am no further forward.

If you ever wondered why hams who use Linux are hardly ever on the air, I think you have here a very good example of the reason! I suppose the next stage is to try and find some appropriate groups to post the above findings to in the hope that someone more knowledgeable than me will have the answer. But it's all so time-consuming and frustrating that I'm running out of enthusiasm.