Author Archive
Overmodulated JT65 on HF?
April 19th, 2013 | 
Author: Sometimes it is crowded on JT65 on HF due to too little bandwidth. When only 2 kHz is available and each signal needs 175 Hz that’s understandable. But then others seem to complain that some overmodulate their transmitters so that they occupy more than the 175 Hz, making it even harder to fit an extra signal in the band.
My first impression from using the new JT9 mode is that the problem is much smaller there than for JT65, so maybe something like what I am discussing here has been done in the decoder software. But as far as I know, the source code has not been releasted into the public domain yet by K1JT, so I cannot verify it now.
But it seems clear to me that what looks like splatter has much less to do with overdriving and overmodulating transmitters than one may think, and more to do with the particular way that the spectral estimate is found in the JT65 decoder software. Combined with the variable propagation which is an intrinsic feature of HF and which may create a highly variable signal strength, this is what seems to create the spillover.
QOD7 – Can you communicate with me in Norwegian?
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| The Oseberg viking ship, 820 AD |
Not so many nationalities are included in the exclusive group of countries with their own Q-code. I mean of course the QOD-code. I have never heard it used by radio amateurs, but it must have played a role some time ago in shipping.
The Q-codes date back to 1912 and were meant to be a short-hand for use in telegraphy. According to the list of Q-codes which Ralf D. Kloth (DL4TA) has on his web page, the meaning of QOD with a number added is: “Can you communicate with me in … 0 Dutch, 1 English, 2 French, 3 German, 4 Greek, 5 Italian, 6 Japanese, 7 Norwegian, 8 Russian, 9 Spanish?” As a response to the question the meaning was “I can communicate with you in …“
The reason for a separate code for Norwegian must be the historically large shipping fleet in Norway. This is still the case as graphically depicted in this overview of the Top 20 Ship Owning Countries, where we seem to rank as number seven – so QOD7 is appropriate!
But today all of them will QOD1.
Image from Wikipedia, user Karamell
Why do Norwegian callsigns end in A?
Well actually not all end in A, but almost all of the recent ones do. Amateur callsigns in Norway are not so well documented on the web, so here is a short explanation.
Norwegian callsigns are used in these territories:
- LA-LN for use in mainland Norway
- JW is used on Svalbard and close-by islands Hopen and Bjørnøya
- JX is used on Jan Mayen
- 3Y is used on Bouvet Island, Peter I Island, and in Antarctica (Queen Maud Land)
Usually the callsign starts with LA, but why do so many of the LA callsigns end in A?
The callsigns have been distributed with the last letter as the most significant letter, e.g. in this order for the two letter series: LA1AA, LA1BA, LA1CA, …, LA9ZZ. In the 80’s it was necessary to add a third letter and that series started like this: LA1AAA, LA1BAA, LA1CAA, …, LA1ABA, LA1BBA, … As an example LA9KTA was issued last year. With the ‘TA’ we are getting closer to the last one, LA9ZZA, in the series ending in ‘A’ now. Therefore in some years all new radio amateurs will get callsigns ending in B.
We also had an LC license at the same time. That was a no-code VHF/UHF-license. All those callsigns ended with -T for Technician license, e.g. LC3SAT. That series is no longer used and it is not possible to get the old LC callsign back.
There is no vanity callsign system in Norway, but club stations were allowed by the Norwegian Post and Telecommunications Authority to get one of the rare single-letter callsigns that were issued to the very first radio amateurs (up to about the time of the second world war). There are only 26*9 = 234 of these callsigns and one example is LA4O for the Oslo group. But this practice seems to have ended now. It is also possible to inherit a callsign from family as I have done.
There are also a few special callsign series:
- LD: Packet radio repeater nodes for VHF and UHF, e.g. for APRS. An example is LD3GT
- LF: License issued to a company, e.g. LF2E
- LG: Only Norwegian-Swedish station LG5LG in Morokulien
- LN: Club stations may switch to this in some of the major contests, e.g. LA8W – LN8W
Long Delayed Echo on VOA Chinese Service
Thierry, F4EOB from Paris is still hearing strange echoes on the VOA Chinese service broadcasts. There isn’t really any good explanation for this phenomenon.
Now during winter he is hearing it both on 13650 kHz from 9 to 12 UTC and on 21590 kHz from 9 to 11 UTC. The 21590 kHz transmission has been heard by him for a long time and I mentioned it here last year also. As then the echo is about 2 seconds. Thierry also made a youtube video of it with a recording.
The transmitter locations are in Asia. The 19 m band site is on the Mariana Island (Tinian) and the 13 m band transmitter is in Tinang in the Philipines.
In my blog last year I discussed possible explanations such as multiple transmitters or multiple round-the-world travel. But since the delay is so consistent and has had the same delay for such a long time, the probability that it is man-made is rather large.
Thierry tells me that this LDE can easily be heard with the WebSDR at the University of Twente in the Netherlands also. I would be curious to hear from people outside Europe who could compare the Dutch WebSDR with their own local reception and see if the same echoes are heard everywhere.
1 Volt/2 Volt Transceivers
Transceivers with a power supply of 1 and 2 Volts, how much can one achieve with that? Well, actually quite a lot according to DL2AVH, Helmut, who together with DL4ALJ, Gero, wrote two articles about that in the German QRP-Report in 2011. I am impressed by the output power, up to 200 mW with one battery cell (1.5 Volts) and 0.5 Watts with two cells.
I wrote about this in April last year where I also mentioned that the 1 Volt design from 2000 later had been corrected. Those corrections can be found in the article in QRP-Report 3/2011: “Niederspannungs-Schaltungtechnik – der 1-V- und der 2-V-transceiver” (Low voltage circuit technology – the 1 Volt and the 2 Volt transceivers). The improvements are concerned with better input filtering at 14 MHz with a quartz crystal in the front-end filter and better efficiency in the mixer and removal of an audio stage in the direct conversion receiver. This design only uses bipolar transistors and no ICs.
This is different in the newer 2 or 3 Volt transceiver for 7 MHz. Here an impressive figure of only 5 mA power consumption for the receiver is achieved. The transmitter consumes about 250 mA. Several MC1496P balanced modulator/demodulator ICs are used for the mixers in the transmitter and the superhet receiver, and for the product detector of the receiver. They seem to run quite comfortably on only 1.8 Volts as supplied by a low-droput regulator from the battery supply. The TDA7050 is used for the audio output stage. This is a low voltage audio amplifier for headphones which can operate with a supply voltage down to 1.6 V.
The design is said to benefit from low voltage technology of mobile phones. This is the case for circuitry like that of the output stage of the transmitter which consists of a pair of BFG21W transistors. However, both of the ICs have been around for many years.
I think this was a very inspiring read, and the final comment about power consumption from the second article is interesting. They say that with two AA-batteries, the receiver will last for 285 hours, which is the same as 70 days of listening of 4 hours per day. With transmission for 10% of the time, the set of batteries will last for 4 weeks!
- Related post: Whatever happened to the 1 Volt QRP Transceivers?
My grandfather’s Blaupunkt radio
As I was clearing out my childhood home I came across an old radio that my father had tucked away in the basement. It was a German Blaupunkt radio, and what a historic dial it had!
It turned out that my father had himself found it as he was clearing out his childhood home many years before and that it had belonged to my grandfather who died in 1959.
It covers longwave, medium wave and three shortwave bands from 5.5 to 21 MHz. I had never before seen a radio with a dial given in meters rather than kHz or MHz, but I have later understood that that was not uncommon for pre world war II radios.
Since the back was missing, I had no information about age or type. The tubes which were all in the 11-series suggested the end of the thirties, but here it turned out that the dial had valuable information.
The medium wave part of the dial had a separate side on the left hand for German stations and here one can find cities that are no longer in Germany such as Königsberg on 223 m and 291 m (1348 and 1031 kHz). Today this is Kaliningrad in Russia. The dial also showed Danzig on 230 m (1303 kHz), ”Schles. G. W.” (Schlesische Gleichwelle – a single frequency net with stations in Gleiwitz and Reichenbach/Oberlausitz) on 244 m (1231 kHz), and Breslau (315 m – 950 kHz). Today these are the cities of Gdansk, Gliwice and Wroclaw in Western Poland, an area which was in Germany until the end of the war. At least the radio must have been from before the end of WW2.
But there were a couple of more names with a lot of history in them. Troppau can be found on a wavelength of 249 m (1204 kHz), a frequency which it had until September 1939. Today Troppau is called Opava and lies in the Czech Republic. Troppau lies in the Sudetenland which Germany annexed on 30. September 1938. Finally one can find Memel on 531 m (565 kHz). This city is today called Klaipeda and lies in Lithuania. It was occupied on 22. March 1939 as the last German annexation before the outbreak of the war on 1. September 1939.
Thus the conclusion of this historic search across the dial is that the radio dates from some time between March and September 1939.
With some cleaning the exterior turned out to be quite nice. I thought to myself that I cannot give up now, so on inspection I could see that a couple of electrolytic capacitor had been replaced, probably by my father. It had the following tubes: ECH11 as mixer/oscillator, EBF11 and EF11 for the intermediate frequency stages, and EFM11 for the magic eye and the first low frequency amplifier.
The output tube and the rectifier were missing, and it was natural to look for tubes in the same 11-series. I was not able to find this particular radio in the large archives of the Norwegian Radio History Society, but there was documentation for a few other Blaupunkts there. From their descriptions I could guess EL11 for the output tube. Measuring the filament voltage for the rectifier gave 4 Volts, so then AZ11 was a good choice.
With some excitement I turned on the voltage for the first time, and to be on the safe side I connected it in series with a 60 W light bulb to reduce the voltage. No explosion! As incredible as it sounds, with full voltage it actually produced sound. But unfortunately after a few seconds everything disappeared. One evening with diagnosis of the radio and I could isolate the problem to the beginning of the audio section and two rotten shielded cables connecting audio in and out of the pentode in the magic eye. Not everything is as new after 60 years! After having replaced the cables the radio was perfect, and even the magic eye and the dial lamps functioned. In my experience the magic eye is often weak and in the Oslo region the dial lamps for the longwave band may have burnt out as the local station used to be on 218 kHz.
Some weeks later as I was about to clean the dial for dust I disassembled the glass in the front and found an inscription saying Blaupunkt 7W79 and the date 28.3.39. So the result of my detective search wasn’t too bad! In fact the dial was produced with an updated name just 6 days after the occupation of Memel/Klaipeda.
This radio cannot have been more than a couple years old when all radios were confiscated in Norway in 1941. Imagine how sad it must have been to give up such a nice and costly radio at that time! This must also have been one of the few radios that actually were returned to their rightful owners in 1945.
Now the radio has a prominent place in my house and every time it is turned on it is a reminder of both the history of my family and of a turbulent era in the history of Central Europe.
First published as “Min farfars Blaupunkt radio” in Hallo Hallo of the Norwegian Radio History Society, September 2001, updated in 2013. © Sverre Holm
Twine “Internet of Things” Monitor
My children know what kind of gifts that please their father, so they gave me a Supermechanical Twine for Christmas. It is described in this way:
Want to monitor things and environments remotely without a nerd degree? Maybe you want to get a tweet when your laundry’s done, an email when the basement floods, or a text message when you left the garage door open.
I am presently using it to monitor the temperature in the outer part of the basement, where there is a chance of freezing when the outside temperature drops below about -15 C (5 F). I can continuously read the status such as the temperature on any web browser on my computer or mobile phone. I can also set threshold values that trigger an email message.
The Twine is easy as a breeze to program, by using simple rules as shown below.
The only catch is that right now the conversion to centigrades is not fully debugged, so I had to enter the strange world, to me, of Fahrenheit degrees close to freezing temperatures to get the rules to work.
I just couldn’t let go of my curiosity as to what’s inside, so here’s a picure. Links to the datasheet for the processor and the Wifi-module can be found on the Supermechanical Community site.
The Twine comes with a temperature sensor and an orientation sensor built in. As options one can connect an external humidity sensor or a magnetic switch. Alternatively one may use a breakout board for inputs from one’s own binary sensor.
Other interesting applications are:
- Garage door monitoring and alarm when it has been open for a certain time period
- Monitoring the temperature of a turkey thawing
- Use of the magnetic switch in a pet door to track when your pet comes and goes.
- Christmas tree water level monitoring
- Temperature logging
There is a Supermechanical Community forum with discussions and lots of ideas as well as a Supermechanical Support page for users who need assistance. I think we will soon see many more similar devices – we are at the threshold of the era of the Internet of Things.
Update 29. Jan 2013: Yesterday, the Twine got software upgrade 1.2 and now it does Celcius properly, I have just tested it. So what I wrote about having to use Fahrenheit is no longer needed – and now that I was about to get familiar with Fahrenheit! In addition some new functionality was added such as vibration sensing, I’m looking forward to testing that too.
