Category Archives: AREN

TH-D72 Battery Life

So EI4HQ and I were discussing “toys” and presents in general, and he inquired about the TH-D72 and battery life. I purchased mine in November 2010 (G0HWW twisted my arm) and have used it for various things from AREN events, listening to aircraft, DTN Experiments (PDF), silly IP over AX.25 tunnels, the usual.

Anyway, I said to EI4HQ that I though it was about 8 hours, but I would check.

The radio has a setting to allow it to transmit the position of the radio, automatically at fixed intervals (beacon interval). So, I did three experiments.  I left the radio in the car for the day on all three occasions. Setting the beacon interval to 5 minutes the first day, 10 minutes the second, 20 minutes the third while the second side (transceiver) of the radio was monitoring the local voice repeater(EI7WDR). This was done just to see what the difference was in battery life, and I (and WE7U) was making the assumption that with the longer intervals, that the battery life would be better.

Day 1, first beacon recorded on at 08:50, last at 18:06, total operational time of 9h 16 minutes. Day 2, first beacon recorded at 08:21, last at 17:41, total operational time of 9h 20 minutes. Day 3, first beacon recorded at 08:18, last at 17:18, total operational time of 9h.

Now, today I had to drop down to WIT, so the onboard GPS had to come out of its power save mode for that short journey, which may account for the reduced battery life. Also there could have been more activity on the repeater, actually there was, I had a brief conversation for a few minutes with EI2HI in Cork on the way into work this morning.

However, the results are pretty clear I think (and I would love to see someone else’s results to compare), that the once every few minutes position beacon is not the biggest load on the battery with everything else running.

So what is the battery life?  Without more experimentation, i would guess about 6 hours if I was out walking with it. That, I think, will have to be the next experiment.

Sean Kelly Tour – a different view

And this is it…


What has this got to do with the Sean Kelly Tour? well, the Sean Kelly Tour took place last Sunday (August 30th), and from all accounts it was quite successful with roughly 2700 hardy cyclists taking to the roads.

The above screenshot (covering an area of roughly 900 square kilometers) is taken from the xastir window of my home Ubuntu desktop after I got home from the event. It shows the trails left from the APRS equipment in several vehicles (including some of these, these, one of these and one of these), several objects and a few home stations. As the screenshot is from the end of the day, it is quite confused looking.

AREN was at the event to assist Civil Defence in maintaining an accurate location of as many of the three different sub-events (50k, 100k and 160k) as we could, allowing them to more cleverly deploy their own medical resources around the course. Great use was made of the SEARG APRS digi-peater network, and it definitely (as can be almost seen) proved it’s usefulness on the day, allowing the guys in Net Control Tim, EI2KA and Bernard, EI8FDB (see below) to keep both the the Civil Defence and event organisers updated as to the locations of various items almost in real time, throughout the day.


It was a good days exercise for AREN, and best of all I wasn’t manning Net Control!

Delay Tolerant Networking over AX.25 & QSLs

I wrote in January that I had done some testing of Darren, G0HWW’s DTN over AX25 (also know as Packet Radio) Implementation. At the time we really only wanted to see if it worked. Since then I have been quite busy in my day job, and not had a chance to really do any more testing up until recently.

In the last few weeks had some free evenings and devoted it to testing the Darren’t DTN implementation against ‘raw’ AX25 connections with different AX25 window sizes from 1 – 7. I used a test file size of 9744 bytes (a NASA format keplerian element set that was handy) over at 1200bps AX25 link.

For the raw AX25 test, I connected from one node to another over and had the test file waiting for me in an email (using axmail). I recorded the wall clock time from when I pressed return until the command prompt was returned.

For the DTN test, I used the dtncp command to send the file and I started recording from when I pressed return on the command line. Obviously there is a problem there in that the AX25 test has to transmit the command before it can receive anything, whereas dtncp immediately starts transmitting, but as I only wanted to get a ‘feel’ for the figures, I think it will suffice. Several runs of each later (to get average figures) we have:

Window Size “Raw” AX25 (seconds) DTN over AX25 (seconds) Delta (seconds)
1 110.67 121.33 10.67
2 90.33 106 15.67
3 84.67 101 16.33
4 81.67 97.67 16
5 79 95.67 16.67
6 78 91.67 13.67
7 77 108.33 31.33

I’m not an AX25 expert by any stretch of the imagination, so we had several false starts trying to get working settings for the various timers that are part of the AX25 implementation. None of them were set to ‘optimum’ but really I just increased T1 and T2 in line with the Window parameter until it worked reliably.

Several things surprised us. Firstly, Darren’s implementation is not as bad, performance wise, as we thought it would be. At the moment, no effort been made to streamline the implementation but it is designed to be highly robust in the event of data transmission errors. Secondly, all data was transferred successfully on every occasion, always good :). Also, on average, the overhead (if we ignore the window of 1 and window of 7), is between approximately 17% and 21%. The figures for the Window set to 1 (above) is a special case in that it forces an almost ’round-robin’ transmit cycle on the two participating stations. Setting it to 7 seemed to trigger a bug, but we don’t know where exactly. In fact the picture is much worse than that. 1 in every three runs took almost 5 minutes to complete as the two stations got completely out of sync AND it looks like Darren’s code (or the kernel) wasn’t honouring the window of 7. In reality though, it would be seldom that one would attempt to use a window size of 5-7 on a shared frequency due to the likelihood of being ‘trod on’ by another station.

All that said, it’s pretty reliable. If your are interested in giving it a try, email Darren, his details are at the bottom of this page, describing his implementation.

Now, back to writing QSL Cards. Shamefully, I’m several years behind.

DTN over AX25 – Update.

Dissapointingly it has taken far to long to get back to this (see my earlier post), but recently Darren and I managed to be both online over the same few days to organise some testing. The infrastructure has changed slightly, in that the testing is now taking place through an AX25 Digipeater on a 1200bps Packet Channel, with the nodes being approximately 32Km distant from one another.

Both machines were Ubuntu 8.04, with kernel 2.6.17 on my end, 2.6.24 on the far end, latest ax25 utilities and tools.

My end was used to bring up the link every time (The far end has no /proc/ax25, so I can’t sent the ax25 parameters remotely, I’ve to change/rebuild the kernel afaik)

Through the digi we used the following settings when setting up the kiss ports. Txdelay of 150ms, paclen of 255, maxframe set to 1.

We quite quickly identified a problem with ‘chattyness’ (the locals got upset), and Darren did some re-work. Since then its performing much better, and the locals are much happier. I was away for a bit and Darren has updated the code some more, so more testing for me I think.

Given that I’m looking at this from an Emcomm/AREN point of view, I’m really pleased with how its progressed so far, and I think Darren may even be considering sending the code ‘upstream’.

./configure ; make; sudo make install

Airmail2000 on Linux.

Airmail is “a message program specifically designed for connectioto a HF radio mailbox station.” it is “a 32-bit program which runs under Windows-95, 98, NT, 2000 or XP”. For the last few weeks I’ve been testing it on Ubuntu using Wine. My Linux laptop is re-cycled, so it didn’t come with an OS. So I installed Ubuntu 8.04 LTS Desktop Edition. After installing my APRS application of choice, Xastir (from source of course). I happened to read somewhere that Airmail seemed to work reasonably well with Wine. So I tried that as well.

After installing Wine (apt-get install wine), I downloaded airmail, and one double click later it was installing. Better than that, I’ve had it running since (needed no reboots!) I’ve tested the VHF Packet Module, POP/SMTP Client, POP/SMTP server, Telnet Client, and all seems to be working as it should. There is one quirk I’ve found.

There is an option in the mail client to “Check Spelling as you type” and this is enabled by default. With this enabled, text in the ‘body’ of a message appears white on a white background (and is thus invisible). Once disabled it works fine. It took me a while to find the solution and this question has appeared a few times on the airmail list, and the simple fix is to select “Tools” then “Options”, then the “Spelling” tab which is the 8th from the left, and make sure there is no ‘tic’ in the  “Check Spelling as you type” box.

If this works for you, send me a mail, ei7ig at winlink dot org

Hams Called to Action!

From the ARRL NEWS:

“On Monday, May 12 at 0628 UTC, a magnitude 7.8 earthquake hit Sichuan, China. The Chinese Radio Sports Association, the Chinese IARU Member-Society, has designated the following frequencies for emergency services involved in the rescue: 14.270, 7.050 and 7.060 MHz. The ARRL encourages US amateurs to be aware of the emergency operations on those three frequencies.”

World Amateur Radio Day, how was yours?

Mine was cold, very cold. Friday morning I posted to a mailing list in work that I was going to set up a station in the car-park, a few colleagues braved the elements and helped me set up a station (thanks lads).

I decided to do it the hard way and enlist help in putting an 80m dipole together, while I put the VHF/UHF antenna together and on the pole. When we got the pole up, my radio, the FT-857 was not happy with a very high reflected power level (SWR).

It turned out that the antenna was about 30 feet to short. So down it came. All was well on the second attempt and I was happy when John, EI9JO returned to my call. I worked several other stations nationally (on 80meters using Near Vertical Incidence Skywave Techniques) some through the South East Repeater Network (part of which is maintained by SEARG), and some stations in Europe using PSK on 30meters.

It was cold, but it was fun.

Geosynchronous Birds.

At the Symposium AMSAT President Rick Hambly, W2GPS, along with Vice President of Engineering Bob McGwier, N4HY, were able to make public the results of their recent work, which will change the face of Amateur Radio going forward. AMSAT has been in consultation with Intelsat regarding an application of Intelsat communications satellites carrying our Amateur Radio satellites into geosynchronous orbit.

Bob described changes in Department of Defense (DoD) policies that will require DoD-subsidized launches to allow secondary payloads to fill in excess launch capacity of the primary mission. During his talk, “Where’s the Launch,” Lee McLamb, KU4OS, explained that factors such as the increased size and efficiency of launch vehicles results in excess lift capacity. Gone are the days where adding a pound to the payload meant removing a pound of fuel from the booster. Lee described how current missions on the schedule have 1000 to 1500 pounds of excess capability. These are slots AMSAT can fit into.

Bob, N4HY, made the following observation about the Phase IV Lite project, “There is enough in place at this time that AMSAT needs to begin planning engineering work and possible construction of a geosynchronous payload so we are ready if Intelsat says they have a ride for us.”

This is a fantastic opportunity for the hobby, read the full article here.

DTN and AX.25

Almost 12 months ago Darren, G0HWW sent this post to the linux-hams mailing list. We exchanged some emails discussing how Delay Tolerant Networks (DTNs) could be used for Emergency Communications (being a classic store and forward network). In a DTN network, each sub-net or point-to-point link can operate over whatever stack is available, in this case it is AX25. In August Darren became aware of some work done in Helsinki University of Technology (under Joerg Ott) specifically a paper entitled Opportunistic Email Distribution and Access in Challenged Heterogeneous Environments. Joerg forwarded Darren their DTN Mail Proxy and we started experimenting with it.

Last weekend, we went a step further. Darren sent me on patches to the DTN2 reference implementation that implement an AX25 Convergence Layer. As I had a working 9600 baud AX25 connection we were eager to test it. After some patching, head scratching and recompiling we were able to successfully pass email from my Laptop over AX25 (439.850MHz) to my Linux server, then over the Internet to Darren’s server and on to his mailbox. All using the DTN bundling protocols. Very cool!

TM-D710 Kiss mode/EMCpup

Reports on mailing lists seem to indicate that the new Kenwood TM-D710 has a properly working KISS mode and works fine with Airmail. So it should work for TCP/IP as well. Not everyone likes all the new ‘features’, however, as the radio is firmware upgradeable it should get ‘better’ over time.

Much as I would have liked to see smart-beaconing, I have finally given in to temptation, so to make room, the PCR-1000 is departing (no need to learn Python now), with a new TM-D710E on order.

After the Radio Rally, Conor, EI4JN, took away a few copies of the Puppy Linux EMCpup CD and I suggested to him that he try it out himself given he had never used Linux.

He let me know during the week that he had used it for to complete some PSK31 contacts. This is impressive, not that he was able to make the contact, but because he had no experience of Linux before (and ‘afraid’ of it by his own admission) and was able configure the software to suit his specific station with no external help. I’ve suggested to him that he next make his own CD (from the existing one) customised for his own station.

I’m looking forward to getting back home to try it out myself as I’m currently travelling on behalf of WIT/TSSG.