Tuesday, June 29, 2010

Plug-n-play APRS (not!) and lack of APRS documentation

Gary Hoffman, KB0H writes on the ARRL web site (The Amateur Amateur: APRS, the Beginning):
"I was still interested enough in APRS that I Googled it the next day. There were a great many sites dedicated to the field, so I skimmed a random sampling of them. Wow! Everything I read seemed highly technical, and none of it described what APRS actually was. The only solid piece of information I was able to garner was that if you called it Automatic Position Reporting System, the APRS Police would come knocking at your door. But just what was APRS? I still didn’t know.

Skip forward a few years.

The term APRS caught my notice from time to time, so I periodically went back to the Internet to see if I could figure it out. I didn’t have much luck. I did find a commercial Web site, byonics.com that sold APRS equipment, but all of the products seemed to be geared toward hams who already had a pretty good grasp of the subject."
I have to agree with him – the obvious places to find documentation for beginners (the Wikipedia page and, especially, aprs.org) do not have it. The wiki page goes quickly pretty deep into a technical network and protocol overview right after the introduction. aprs.org is a mess – it spends a lot of time complaining how APRS really isn't what most people are using it for, and doesn't really have any starting points. And there are broken links. The APRS Wiki has something, but it isn't very strong or up-to-date either.

G4ILO has written an article, APRS - Putting ham radio on the map, which I find pretty good – probably not the least because he says aprs.fi is "the best". It would be good to have this on the APRS Wiki.

If you manage to actually buy some hardware to use APRS, the configuration programs and menus are also very hard to use. I heard or read somewhere that some amateur clubs now have monthly meetings on the topic of programming radios (which actually means going through the menus to get settings right). The Byonics and Argent configuration tools show an awful lot of settings to start with. Most of the defaults are OK and you only need to fix your callsign and the audio levels, but it's way too easy to make configurations which break things for yourself (for example, by selecting invalid symbol codes instead of picking the symbol image from a table). Many misconfigurations actually break the network by transmitting way too often, or with abusive long paths.

I strongly think that the configuration programs should be improved to not accept any abusive or broken configurations. Also, they should initially only show the settings you really, really need to change (your callsign, comment text, TX audio level, and "pick a symbol image from this graphic table of images"). Most other settings should go to an "advanced settings" menu of some sort. Think Apple and the iPhone – to get regular users started it needs to be simple and lean. Path setting should, even in the Advanced menu, consist of a drop-down selection of "1 hop", "2 hops", or "3 hops" which would translate to something like WIDE1-1,WIDE2-2 somewhere behind the scene (with maybe a checkbox for "use TRACE instead of WIDE"). Free-form path entry should be in the Very-Super-Advanced configuration file, and even then the tracker firmware should refuse a WIDE3-7,TRACE9-9 path.

If you're looking for a little programming project, I'd guess Scott wouldn't mind if someone would improve the OpenTracker Windows config program a bit. It's Open Source, after all.

I suppose I should look at my software, too. aprs.fi doesn't have a proper beginner's guide, either. Or an user's manual. There are only 4 tooltips, and 14 help links (which are not localised). Awful.

theborg989 has uploaded a nice introductory aprs.fi video on Youtube. It could use a sequel which would describe things like tracking multiple stations and using the tools in the top right corner of the display.

Friday, June 4, 2010

Tooltips, center map here, quick refresh, and some bugfixes

Here are a few improvements from the past couple days which were installed this evening:

The top right corner buttons of the real-time map now have hover-on tooltips. The right-click context menu of the real-time map now has a 'center map here' option.

The station info balloon will only pop up automatically in the real-time (and embedded) maps, if the map is at least 300 pixels wide and 260 pixels high. This should keep the tracked station in view even on a small view.

The directional PHG cardioids on the real-time map were fixed, they were broken for a while due to a little bug. Same goes for clicking on the Google Earth KML tracking link when tracking a single station.

The static map positioning was fixed on the info pages with Internet Explorer.

The real-time map refreshes quickly after panning the map, instead of waiting for the regular update timer.

AIS ship callsign display is now more correct in the info balloon (no separate tracking link for the callsign).

Thursday, May 27, 2010

APRS track export tool

Please try out the new data APRS export tool. There are no links to it from the web site yet. User account and login required. Feedback welcome, as usual!

It can export to KMZ (zip'ed KML + embedded symbol graphics in the same file, for Google Earth), CSV (opens up nicely in Excel, but seems to require some tricks in OpenOffice), JSON and XML (for the programmers out there).

This feature is aimed at people who wish to download their balloon's track afterwards, or their path to Dayton and back.

It's not aimed at people who wish to download the whole aprs.fi database, so it's rate limited quite heavily. Also, it's not an API. I'll probably set the limit to 3 downloads per day per user, although for the beta test, it's currently set to 10 downloads per day per user.

Map on info page, with symbols, and other small things

The info pages now have a little static map showing the station's position. I hope you like it this way. The static maps have also been upgraded to show proper APRS symbol graphics! For example: http://aprs.fi/info/SP3WBX-9

Some of the pages now have an "add this" button which allows you to easily share the page on your favourite social networks.

The raw packet display was fixed to be really, really binary clean. It used to choke on some high binary values.

Weather packets with an unrealistic high or low temperature are now ignored.

Thursday, May 20, 2010

Ham::APRS::FAP 1.16 released

Version 1.16 of the APRS packet parser was uploaded to CPAN last night, and according to the first few CPAN tester reports it seems to be working as expected. Here's a list of changes:
  • Added a couple of test cases
  • Added an example script to parse a whole file of timestamped APRS-IS packets
  • Fixed peet WX packet parsing for Perl 5.8 and older, which don't support n! packing
  • Minor speedups by reducing amount of regular expressions, extra variables, reordering things to catch the most common case first, and tightening a loop
  • Put '' around hash key strings (style issue)
The main change was the Perl 5.8 wx parsing fix. I couldn't have noticed it without the CPAN testers and the unit tests included with the module, since I don't run on 5.8 myself any more.

Thursday, May 6, 2010

KP4AO Arecibo Observatory EME reception using a 10-element yagi

This is old news, but anyway... I've just forgotten to upload the videos from my iphone.

On Sunday, 24th of April, I received CW and JT65B transmissions from the Arecibo Observatory in Puerto Rico. Reflected via the moon (EME, Earth-Moon-Earth). Using a very small directional antenna - a 10-element yagi, a scanner-type receiver (Icom IC-R2500) and a small but good preamplifier at the antenna.

To get a good view of the moon we drove to the side of a nearby field with OH2GEK. He even tried to get a two-way contact with the Arecibo station using his TS-2000 and a longer yagi.

Here's a video of the KP4AO CW reception:



And here's one of the JT65B digital signals:

Problem and Solution

This, my friends, is a problem.


And here, my friends, arrives the solution:


Well packaged.


4 units of 1 terabytes each. After RAID10, that's a nice 2 TB of storage for aprs.fi.


This is just for the backups. I'll need to get 4 more of these within a couple of months to upgrade the live servers.

Thanks go to an anonymous Finnish site user for the donation of 2 disks (and organizing delivery in 26 hours), and all other donors for the other two!