In reply to G4YTD:
You can do APRS quite cheaply but in order for it to be any good you need the network infrastructure. You need to have that network running 24hrs/day to hear the posits you send. And, of course, you need the gear you will carry.
The easy bit is the carried gear. You need a GPS receiver (filth cheap now), an 1200bps APRS encoder and a transmiter. You could buy a 2nd hand Kenwood TH-D7 which has everything for APRS except the GPS or you can make your own tracker. Making the tracker appeals to me and if you build on Veroboard you should be able to build the GPS interface/packet encoder for around £15 (less depending on your junk box contents). You could use the GPS many of us carry when walking or use a small embeddable GPS which cost around £30 in small quantities. Finally you need a transmitter. Again most of have a handy with us when walking or you could use the main activation rig. Personally and from a convenience point of view, a tracker comprising a small GPS module, the encoder and a link to the handy would be the most convenient. Irrespective of what is used you need to ensure you have sufficient batteries for the activation if some of the activation equipment is used to send APRS information when walking to and from the startpoint.
That’s the easy bit because designs exist and are available on the net or kits/ready built gizmos can be bought. The only downsides are how much it weighs, how much it costs and how many more batteries (cost and weight) you need.
Oh and a network to connect to!
The network is the APRS problem. In the UK it’s, at best, patchy. Sure there are people doing APRS in the UK but you may find that you can only get your APRS packets into the network when you get to the top of the hill and that rather defeats the point of being tracked as you climb! If you want to be trackable from the base of a remote mountain to the summit then you have an APRS network that can hear you. Thin of how amazing the mobile phone network coverage is in the UK. Even in remote parts of Scotland the coverage is pretty damn fantastic. Now just how many cell towers are there in the UK? 5000? 10000? So it’s a reasonable assumption that we’re never going to get an amateur network that big. You could use the mobile phone networks to carry the APRS messages to a gateway but that’s a naff solution because it costs money for each byte sent. I don’t want to pay!
The alternative is to use the free repeater in the sky to get the APRS info from the base of any hill into the APRS network. Yes use the ionosphere. Now I’m not suggesting we get into Sean’s interest and run HF pedestrian mobile APRS systems but we could. No the obvious solution to me is to use 2m/70cms from the walker and place a 2m/HF gateway in your car in the car park. Most of use never walk that far from the carpark and I can think of loads of activations I’ve done where I could see the carpark from the summit. From the car, 30m will be ideal to get to the gateways that exist in mainland Europe. Once at a gateway you can be sent into the internet connected APRS systems and then pop back out locally in the UK on RF if needed.
The equipment needed is a 2m/70cms receiver and HF transmitter, a TNC to receive the APRS transmissions from the walker and another encoder to drive the HF transmitter at 300bps rather than 1200bps used on VHF. The newly revised licence in the UK allows you to remote control a station so there’s no problem having an HF transmitter running from your car. You do need to ensure that only you can control the remote system and that’s done by having it only retransmit APRS messages that contain your own callsign.
So some ballpark costs assuming buying everything new, cases, leads etc. £70 for the tracker+GPS+batteries. On top of that you need a 2m/70cms radio (handy) and rucksack mounted antenna (cue Richard G3CWI). In the car for the VHF>HF gateway you’re looking at £30 for the 1200bps APRS decoder/300bps APRS encoder and you need a VHF receiver and HF transmitter, aerials and a battery. These don’t need to be expensive, FT290s change hands for often less than £50 at rallies and you only need it to RX. The HF transmitter won’t cost the earth either. I picked up a brand new Codan 2-18MHz 125W SSB set for £80 on eBay and there are lots of beat up rigs about cheap because they don’t do all the modern magic.
So it’s possible and legal in the UK to run a remote VHF>HF gateway and use that to get APRS spots out to the network. Have gateway, can connect!