AmateurRadio.com

I’m suffering from a severe case of Android envy. I was just checking the latest post in Jeff KE9V’s excellent blog (glad you haven’t forsaken the blogosphere in favour of podcasts, Jeff) which mentions in passing that Google has just released AppInventor, a free simple application builder for the Android platform.

What piques my interest particularly is that AppInventor includes building blocks that allow you to talk to things like the GPS, so you can write location-aware apps, perhaps even apps that are APRS related.

I own a Windows Mobile smartphone. I also own a currently uninstalled copy of Microsoft Visual Studio, which can create apps for the phone. I once wrote an app to sync the clock to an internet time server. But like everything to do with Windows it’s all just too darn complicated and my ageing brain doesn’t feel like getting to grips with it.

The AppInventor approach looks much easier and more fun. I see an Android in my life before too long.

I noticed today that Richard G1JTD had a GPS-equipped VX-8R with him on his activation of several Wainwright summits in the Fairfield round. I spoke to Richard on his VX-8R a fortnight or so ago when I was out with my VX-8GR and he mentioned that he might get the GPS option so as to do some APRS. It’s good to see more APRS activity from the Lakeland fells.

You can see Richard’s track captured from aprs.fi. As you can see, his position reports were only received when he was on the summits and a few other points on the highest parts of the ridge. This is inevitable given that the only digipeaters and iGates are situated around the edge of the mountains located at the homes of amateurs and not at any great height.

From my experience it’s quite common to lose cellular data coverage once you get off the beaten track so smartphone based APRS isn’t really much better in this situation. Running the GPS drastically shortens the phone’s battery life so you are also likely to end up with a dead phone just when you might need it. I think RF based tracking is the best solution for taking APRS into the wilds.

It’s a pity that the power requirement and antenna size for HF operation would make it impractical to use HF for portable APRS operation.

The last couple of days I’ve been wasting way too much time tracking mobiles using the new Google Street View feature of aprs.fi, which since I wrote about it last is now live on the production server. I have been running a second instance of APRSIS32 linked to my K3 on 30m using the AGWPE soundcard modem. Surprisingly, I have found quite a few mobile stations beaconing their position on 30m and even more surprisingly they are often being picked up direct by my attic mounted MFJ magnetic loop. It’s fun to follow these mobiles and see what they are seeing as they drive along, but I get a bit of a thrill when I see my station displayed as the one that gated their position report to the internet. I suppose it’s a bit like reverse WSPR.

Yesterday and today I have been following Bernd DF8HL and his XYL Karin DF8HY who are touring Scandinavia an an old VW camper van festooned with antennas, as you can see from their website. It must be great to just tour in your mobile shack, going from one place to another, yet in touch with your friends by amateur radio. But Olga wouldn’t agree, so instead I must content myself to do it virtually with the help of APRS and Google Maps.

Steve, GW7AAV, spotted a news item on the NZART web page which states that the authorities in New Zealand have become concerned about IRLP, D-Star, Echolink, APRS and similar modes as they do not appear to fit within the New Zealand license conditions. Their concerns include the use of unattended transmitters and unlicensed digipeaters for APRS and amateurs based overseas operating a NZ amateur station via the internet.

It’s easy to forget that other countries don’t have such liberal licensing conditions as we do in the UK, although I would point out that operating an Echolink, D-Star, IRLP or packet radio (including APRS) node is not within the standard license conditions here either – you are supposed to apply for special permission. I know there are many who feel that is a good thing, and even that internet linking is not amateur radio and should not be allowed anywhere in the world, at all, but my opinion is that prohibiting it devalues amateur radio.

This policy is probably one of the main reasons why the APRS RF network is broken for messaging as many people (myself included) who are unwilling or unable to comply with the requirements for obtaining permission avoid the problem by operating receive-only gateways. Consequently we have the situation where smartphone-based APRS using mobile internet connections are more useful than APRS over radio.

I certainly believe that the point of our hobby is to use radio wherever possible, but where the internet makes possible something that could not practically be achieved using RF alone I think that we should be permitted to use it.

I’ve just been for a pleasant afternoon drive down to the coast with Lynn, KJ4ERJ, developer of the APRSISCE software, currently on holiday in Spain. No, I didn’t nip down on EasyJet for the day. Actually I was following him on APRS using the Google Street View feature in the beta version of aprs.fi.

With the new software, when you click on a station you get the option to Track in Street View. If you do then the browser window splits in two, with the top half showing the view the person you are tracking sees, facing the direction he is going, and the bottom half showing the track on the map. It works pretty well. You just have to remind yourself that you are viewing images previously taken by Google, not live images!

This is beta software, so you won’t find it on the regular aprs.fi just yet. But it’s a pretty cool application, I think you’ll agree!

As I wrote yesterday, I have been experimenting with APRS on the HF bands (30 metres.) This morning I spotted a couple of mobile stations beaconing position reports, or more likely I was receiving the digipeated copies of them. I can see that position reporting on HF could be useful if you want to be tracked and are out of range of any VHF digipeaters or gateways, but HF stations with their much larger capture area and four times slower data rate really couldn’t sustain many fast-moving mobiles sending position updates every minute or so.

APRS is meant to be more than just a system for capturing position reports using radio and I find the facility to exchange messages with ham friends and know that they received them (even if they aren’t immediately able to respond) to be very useful. It isn’t a substitute for conventional digital contacts, it’s an additional way of communicating. However, unlike on VHF where you probably know the people whose calls you see on your screen, on HF there is no way of knowing whether someone wants to chat, or even if a particular station is attended. Unless the intention is to chat direct by radio, using HF seems to me to be an inefficient way of reaching the APRS-IS internet backbone. So apart from giving someone in the middle of nowhere an extra chance that their packets will be received – which would be a rather boring use of an expensive HF radio – I’m still unsure of the value to me personally of running an HF APRS station. The technology is interesting but the practical use eludes me.

Despite this I was still keen to try APRS over HF. As I didn’t know whom to contact I decided to send a greeting to Lynn, KJ4ERJ, currently holidaying in Spain, who I knew (from checking aprs.fi) was online at that moment. I disconnected my APRSIS32 client from the internet so I would know that if my message was received, it would have been picked up on the radio.

The message went out on 30m, and was repeated several times as no acknowledgements were received by my station. In the meantime I decided to send a second greeting message to Colin, 2E0XSD. No acks were received for that message either. Eventually I checked aprs.fi and sure enough my messages had made it to APRS-IS through various gateways in Switzerland and France. They had even made it to their destinations and Lynn and Colin had both sent replies. But I never received their replies over the radio, either.

The screengrab shows a section of the raw messages list from aprs.fi which includes the paths of my messages as they were received on the internet. It appears that nearly all were received and digipeated by HB9MM-4. I’m not sure if that station also gated my messages to the internet.

The way I understand APRS to work, any messages sent to me (and any acknowledgements of messages sent by me) should be relayed back to me over RF by any stations that have heard me on RF. The acknowledgements and replies from Lynn and Colin were on APRS-IS and could be received by the HF stations that were hearing me. But they were not transmitted. I was receiving a strong signal from HB9MM-4 so it is very unlikely that the packets were sent and none of them were decoded.

What’s the use of a system for messaging if it can’t be relied on to work as intended? It seems to me that APRS is broken and is really only useful for collecting position reports where the traffic is all one way – to the internet.

A post about the French ban on D-Star on QRZ.com has predictably become a platform for everyone who dislikes D-Star to reiterate their views on why it should be banned altogether, not just in France. These reasons boil down either to its use of a proprietary codec or the fact that it involves linking radios using the internet.

I admit to toying with the idea of making a post on the lines of “what if internet linking of radios was banned worldwide? Wouldn’t that be a real catalyst for innovation, to try to replicate internet facilities using entirely amateur radio RF based methods.?” But further thought as to what would be the effect on APRS if it were denied the use of the APRS-IS internet backbone made me realize that the effect would be catastrophic. The amount of traffic would be far too great to be carried over any HF network, while the number of hops needed using a VHF network to achieve worldwide coverage would also be far too many and far too slow. You might be able to do something using a sophisticated network of amateur satellites, but that would be far too expensive. While some uses of the internet do devalue the use of radio itself, in my opinion, many of them make possible things that could not otherwise be achieved. The internet is an integral part of APRS just as it is probably an integral part of whatever D-Star is meant to achieve.

Which led me to the question of what exactly is the point of APRS over HF radio? I understand the purpose of the VHF APRS infrastructure, which is to capture the messages from local APRS stations and pass them to APRS-IS. But given that it would be impractical for messages from one side of the world to be conveyed reliably to the other using RF, what is the point of APRS networks on HF?

I started off the day trying the latest version of Cross Country Wireless’s APRS Messenger software. This is an interesting product in itself, in that it enables APRS traffic to use various PSK data modes, which are arguably more reliable on HF than the 300baud packet most people use. Unfortunately there are not many users. I switched to using 300baud packet and my screen quickly filled up with callsigns from all over Europe. But when I looked at aprs.fi to see its map of stations received by my station I saw only one.

The reason, I surmised (since I am far from being an expert on this) is that my client software, APRSIS32, is doing “the right thing” and not forwarding most of the messages I received as they had already propagated by the maximum number of hops. The one station whose messages I did pass on, F6KPH-4, had against it the note “Seriously bad path.” Following this was the explanation: “This station is transmitting packets with a configured path of over 3 digipeaters. This causes serious congestion in the APRS network and errors when plotting the station’s route on a map. Please consider using a path of WIDE1-1,WIDE2-1 or WIDE2-2, or even WIDE1-1,WIDE2-2 if you are moving very far away from an iGATE.”

I don’t really understand this WIDEx-x business, I just do what I am told. But I think I get the gist, which is that APRS messages sent over HF should be configured to take no more than three hops. If they don’t reach a gateway by then, they will be lost, which is just tough luck, because the HF channels can’t handle the congestion that would be caused by messages being rebroadcast more than three times.

Which brings me back to the question of what exactly is the point of APRS over HF for the average amateur? It is certainly interesting to see what you can hear using your own equipment. But if it is impractical for an RF based network to ensure that a message could get from Sydney, Australia to New York, New York without touching the internet, what useful purpose is achieved by transmitting and receiving APRS on the HF bands?