AmateurRadio.com

I know that one of the purposes of my website is meant to be to demonstrate that you can play ham radio even if you can’t have outside antennas. But sometimes the frustrations of not quite being able to achieve what you want to make become almost too much.

On Tuesday I replaced my home made ribbon cable Slim Jim 2m antenna with a commercial dual band colinear from Moonraker. I wasn’t sure the home made antenna was working as well as it possibly could. Originally I planned to replace the Slim Jim with a single band 5/8 wave Sirio, but after a month waiting for Radioworld to deliver it I cancelled the order and gave up. Then I got the Kenwood TM-D710 which is a dual band transceiver, so I decided I should have a dual band antenna to give me the option of running a public Echolink node on 70cm.

During the last few days I have been searching for signs of improvement in my 2m receive capability, but the signs haven’t been good. I’m hearing a frustrating number of APRS “braaps” that are just not strong enough to decode.

The antenna certainly works. I’m getting almost end-stop signals from the repeaters GB3DG and GB3LA, whilst GB3AS is about S5 with a bit of noise on it. I have had a couple of solid contacts using the antenna but nothing to form a basis for comparison until today, when Noel G4PEW drove past.

On the left of the screengrab you can see his track on Monday, when I was still using the Slim Jim. On the right you can see today’s track, received using the new antenna. It’s a lot shorter. I certainly heard a lot of packets after the last one shown by the grey blob, but none were strong enough to decode.

If only I could have the antenna outside the attic, up above the apex of the roof, I’m sure that extra little bit of height would make all the difference.

Steve WG0AT, Rich, AC7MA and Guy, N7UN recently returned from their expedition to activate Huron Peak in the Sawatch Range in Colorado, USA, for Summits On The Air (SOTA). Together with their “sherpa” goats Rooster and Peanut, they took a GPS-equipped Yaesu VX-8R so people could track their progress.

You can see a slide show of the expedition here.

I rather like the idea of using goats to carry the heavy equipment but I think you’d get some funny looks in the hills around here. This has made me wonder what has been the highest SOTA activation to date. Has anyone activated Mount Everest yet? I bet that would create a pile-up!

Hot off the press. An APRS client for Blackberry smartphones is being developed. More information about it can be found here.

I was surfing around looking at information about robust digital modes, as you do, and stumbled across something called the WINMOR Sound Card TNC. WINMOR is a free, open and documented protocol intended for reliable HF data communications. Originally developed as a low cost alternative to Pactor for emergency communications systems such as Winlink, it has been made available as a virtual TNC for other developers to incorporate in their products. I started to wonder if this is the solution people are looking for to make APRS over HF more reliable, rather than trying to use digital modes such as PSK63 or GMSK that weren’t designed for this type of application, as is being tried by G4HYG in APRS Messenger.

The documentation for the software is somewhat over my head, but from what I can deduce the Sound Card TNC (shown above) does not provide an interface like a regular packet TNC. However there is a module called BPQ32 that appears (from the description) to implement a TNC-like interface. I’ve probably misunderstood something – in which case hopefully someone will point this out to me – but it doesn’t seem beyond the bounds of possibility to connect an APRS client like APRSISCE to this TNC and then you would be able to send APRS using the reliable WINMOR protocol with forward error correction (FEC).

The only problem would be finding a place to operate, since SCS’s proprietary Robust Packet protocol seems to have already established itself below the FSK300 APRS channel on 30m.

I haven’t had time since I got back from holiday to read every post of every blog that I follow, but I was glad that I caught the post about HFDL in Adam, M6RDP’s blog.

 HFDL stands for High Frequency Data Link. It is also known as HF ACARS, which gives the game away as to what it is about, for ACARS stands for Aircraft Communications Addressing and Reporting System. In other words, it’s like APRS but for aircraft.

HFDL uses a proprietary protocol. Transmissions use USB with a symbol speed of 1800 baud. The modulation is 2-PSK, 4-PSK or 8-PSK with effective bit rates of 300, 600, 1200 or 1800 bits/sec. Aircraft log on to a ground station, of which there are currently 17 located around the world, each of which receives on several different and unique frequencies. The ground station assigns the aircraft a sequence ID number which is used in subsequent communications with it. HFDL is used by over 1200 aircraft operated by more than 60 airlines and allows pilots to always be able to communicate with the ground, no matter where they are located.

I downloaded the PC-HFDL software from the author G4GUO’s web page which unfortunately contains no information about the program itself. I also downloaded and installed Google Earth which is used to display the positions of the aircraft. I tuned my receiver to the frequency 6532kHz mentioned by Adam, which is one of the frequencies used by the ground station at Shannon. After a minute or so I received a loud signal that was obviously a burst of quite rapidly modulated data.

After a few minutes of head scratching when the program did not decode anything I found that it apparently sets the input level from the sound card to zero at start-up. PC-HFDL is “shareware” and this is presumably one of the annoyances authors of such programs put in to encourage users to pay up. It is more likely to encourage me to uninstall the software, but that’s another subject.

Once the program is receiving the audio from the radio, each burst results in a decoded message being displayed by the PC-HFDL program, while the aircraft position is plotted on Google Earth. You can see the results of about 10 minutes of listening on the 6532kHz frequency in the screen grab.

After 10 minutes or so of receiving the program shuts down, another limitation of using it without purchasing a registration. But 10 minutes is probably enough for most people to realize that, whilst the technology is interesting, as a pastime it would quickly get boring. Perhaps it would be possible to receive signals from more distant aircraft, but that’s about it. There’s a lot more happening on HF APRS, plus as a licensed amateur you can actively participate.

It doesn’t appear to be possible to submit position reports from PC-HFDL to a site like flightradar24.com (which I discovered from a comment to Adam’s post) which aggregates aircraft positions received by amateur enthusiasts to display a real-time radar map of all the commercial aircraft in Europe. Those position reports are sent using ADS-B (Automatic Dependent Surveillance – Broadcast) which uses a frequency of 978MHz and requires a dedicated receiver costing around £500.

As regular readers will have realized from my previous post, I have been on holiday in Prague, capital of the Czech Republic. I won’t bore you with details of where I went or what I did, though I have made a few comments about the holiday over on my other blog. So I will just describe my ham radio experiences over there.

Prague is quite a hilly city. The picture above was taken from the Botanical Gardens to the north of the city, looking towards the famous Zizkov TV Tower. This building, looking from a distance like an Atlas rocket waiting to take an Apollo mission to the Moon, is widely regarded as the ugliest building in Prague. But from a radio point of view it would be a good QTH. I quite like it. Apparently you can go up it to see the view, but that is something we have yet to do.

I took with me on my travels my Yaesu VX-8GR dual band APRS hand-held. Due to the language difficulty (I don’t speak Czech) I didn’t anticipate having many contacts with locals but I could see from aprs.fi that there was quite a lot of APRS activity in the city and I was interested to experience it first hand. I was not disappointed.

From the moment the VX-8GR was first switched on the APRS channel on 144.800MHz began receiving packets. The station list, able to hold the 50 most recently received APRS packets, filled up in about ten minutes. I was receiving position reports from fixed stations and mobiles, not only in the Czech Republic but also sometimes from Germany, Poland and Austria. I also received local weather reports, including the position of lightning strikes over a more than 300km radius and weather bulletins sent out by OK1COM. Coming from West Cumbria where you can often go a whole day without receiving anything on VHF it was quite a revelation.

I sent a greeting using APRS to Colin, 2E0XSD. By checking aprs.fi I discovered that he received it, but I didn’t receive any of the acks his client sent back, nor his reply. It appears that no-one sets up their gateways to gate messages and acks for locally heard stations from the internet to RF, so the much-vaunted APRS messaging capability is essentially useless except between stations in direct radio contact.

Later in my stay I did have a messaging QSO with OK1RQ on foot in Prague with a Kenwood hand-held. Unfortunately he was busy so I never got to meet him or any other local hams. I also received greetings via APRS from a couple of other local stations.

We needed to make some local phone calls so I purchased a pre-paid SIM card from O2 for my smartphone. This included 3G data so I was able to try the APRSISCE client from Prague. I had several messaging conversations over the internet with Lynn, KJ4ERJ, the program’s author. We also had our first voice QSO via OK0BNA, the Prague repeater, which Lynn was able to access through Echolink as it is connected to OK1OGA-L. I monitored OK0BNA on many evenings and heard only two other contacts take place on it. I did not hear any other FM contacts on either 2m or 70cm the whole time I was in Prague.

APRS works well in Prague because there is a network of several digipeaters and gateways within a radius of a few kilometres of the centre. The apartment where we were staying was just a few hundred metres from the QTH of OK1ALX who runs a digipeater and Igate, so most of the APRS signals I heard on my VX-8GR inside the apartment with the stock rubber duck were S9+.

The map on the right shows the tracks of some of our outings in the seven days before our return, tracked using the VX-8GR. Although aprs.fi reportedly stores position reports for a year, it doesn’t appear to be possible to display tracks for specific periods retrospectively, and as I didn’t have a computer with me (this was supposed to be a holiday) I couldn’t capture my tracks at the time. But you can see at the top one day’s walk in the Botanical Gardens, at the bottom a walk around Vysehrad, and in the middle a circular walk we made into the city centre and back along the river one evening.

Tracking an outing from start to finish wasn’t very convenient, or even possible, because the GPS wouldn’t pick up a fix inside the apartment and I couldn’t be bothered to stand around for 3 or 4 minutes on the street outside waiting for it to get a fix before we started. Hence the big jumps from where we were staying to where we started walking.

We were on foot or using public transport and you would lose a fix whenever you got on the metro or a tram or went inside a building, and then have to wait to regain a fix when you came out. It was too much hassle. But when we were planning to just walk, it was interesting to see where my beacons were picked up, both from higher ground and from street level within the city.

I didn’t use the Windows Mobile client for tracking much at all (apart for one short evening stroll along by the river) because using the GPS reduced the phone’s battery life to an unacceptable couple of hours. However I was impressed by the battery endurance of the VX-8GR. After reducing the beacon frequency to no more than one every two minutes and using the 2.5W power setting, it lasted all day with enough power left for a couple of hours receiving in the evening. This is particularly noteworthy considering that the power saver was disabled (as it needs to be for APRS usage) and the receiver was constantly receiving and displaying APRS data. If only the GPS was quicker at finding its position after switch-on it would be just about perfect.

Like most hams, I guess, I always keep an eye open for antennas wherever I’m travelling. Antenna-spotting in Prague is quite difficult as every building has comprehensive lightning protection consisting of tall lightning conductors looking like VHF collinears, usually connected together along the ridge of the roof. I have never seen this anywhere else.

Close to where we were staying, in a street called Vysehradska, I noticed a shop window displaying a few old radios, some vacuum tubes, what looked like a tube tester and some other electronic bits and pieces. On the roof of the building next door I spotted an MFJ multiband HF vertical antenna. I was sure that the owner of the shop must be a ham, so we decided to go in and introduce ourselves.

Inside, the place looked more like somebody’s untidy workshop than a shop. There were three elderly gentlemen, one of whom was presumably the owner. Another was leafing through a dog-eared book while the third was inspecting a vintage broadcast radio he had taken down from a shelf. They looked at us expectantly. I said “ham radio?”, anticipating that someone would understand at least that English phrase, but was met with blank stares and something we couldn’t understand in Czech.

Older people in the Czech Republic speak Russian, a legacy of the Russian occupation, so Olga then explained in Russian that I was a ham radio enthusiast and was interested in what they had in the shop. No-one introduced themselves as a licensed amateur, however. Instead, they told us that it was not a ham radio shop, but that there was one a few blocks away. Unfortunately Czech street names are confusing to non-native speakers, even to Olga. We didn’t find it. Perhaps we will on our next visit.

The web is a great way to get information about subjects like ham radio that you might never find if you had to rely on books. Unfortunately it’s also a good way to get wrong or obsolete information. For example, people looking for advice on how to make their first contacts via amateur satellites will find many articles that explain in great detail how to work through satellites that have long been defunct – even on the Amsat website!

There are numerous websites that explain about SSIDs used for APRS. (An SSID is the numeric suffix to the call, for example G4ILO-7, which is used to distinguish an operator’s APRS devices and also to give an idea of what type of device it is.) They are all wrong! Bob Bruninga, WB4APR, the inventor and ultimate authority on APRS, released an updated set of recommendations on 9 June this year to provide more flexibility for current usage.

The new recommendations are:

-0 Your primary station, usually fixed and message capable.
-1 Additional station, digi, mobile, weather station etc.
-2 Additional station, digi, mobile, weather station etc.
-3 Additional station, digi, mobile, weather station etc.
-4 Additional station, digi, mobile, weather station etc.
-5 Network sources (smartphones etc.)
-6 Special activity, e.g. satellite operations, camping, 50MHz etc.
-7 Handheld radios and other human portables.
-8 Boats, RVs or second mobile.
-9 Primary mobile.
-10 Internet gateways, Echolink, Winlink, AVRS, APRN, etc.
-11 Balloons, aircraft, spacecraft, etc.
-12 APRStt, DTMF, RFID devices, trackers etc.
-13 Weather stations.
-14 Truckers or other full time drivers.
-15 Additional station, digi, mobile, weather station etc.

These are recommendations and not set in stone, but they are intended to help people know what type of device or application is being used, particularly in situations where someone doesn’t have a graphical map display and can’t see an icon.

Due to these recommendations I am now using G4ILO-5 for my Windows smartphone running APRSISCE. My VX-8GR remains G4ILO-7. My main 2m station is G4ILO-0 or just plain G4ILO, and my HF station is G4ILO-1.

Of course, this page could also become out of date in the future so I am including this link back to the original document in case Bob should make any further changes.