Tag Archives: Alexander von Obert DL4NO

75 years ago today, VOA started German broadcasts

Voice of America Bethany Relay Station, May 2015

Many thanks to SWLing Post contributor, Alexander (DL4NO), who writes:

Hello Thomas,

I just heard a short feature on Deutschlandfunk: 75 years ago today VoA started transmitting – in German.

vy 73

Many thanks for the tip, Alexander!

The Deutschlandfunk article, of course, is in German. I found, that Google Translate did an acceptable job translating it into English.


Cold War radio treasure trove: The CIA Freedom of Information Act Reading room

Many thanks to SWLing Post contributor, Alexander (DL4NO), who writes:

I just found a German reference to the CIA Freedom of Information Act Reading room


As a first test I searched for “radio design”. A few of the documents found:


This could be an amazing source, especially of historical information from the Eastern Block. But expect any search to be real work: Only the title and some classification of the documents are searchable. The rest is scanned documents.

Very cool–thanks for sharing, Alexander. I spent a little time this morning browsing the results using various radio-related search strings. It is a very deep archive.

Click here to search the CIA reading room.

Alexander’s report from Ham Radio Friedrichshafen


The Friedrichshafen exhibition grounds. (Photo: Ham Radio Friedrichshafen)

Many thanks to SWLing Post contributor, Alexander (DL4NO), who shared a few notes with me from his visit at the Friedrichshafen Ham Radio convention. Alexander has kindly allowed me to post his notes here on the SWLing Post. Alexander writes:

The first booth I visited was of Dokufunk (http://www.dokufunk.org/). They collect QSLs and other information about wireless history for scientific evaluation. Its head Wolf, OE1WHC, was a moderator for the Austrian shortwave service which does not exist anymore. But ORF still supports Dokufunk. They have a large archive and even the equipment to digitize large quantities if information. I brought them a package of ham radio periodicals, mostly issues of DL-QTC, the predecessor of cqDL, and got some QSPs (magazine of OEVSV) back. I collect those periodicals to gain and provide access. Seehttp://www.dl4no.de/thema/amateurfunk-zeitschriftenarchiv.htm, catalog at the bottom.

The flea market filled three exhibit halls. If you needed a tube heating for your shack you had a wide choice, from radios to ham equipment to scopes. On the newer side you could get Windows XP packages with the appropriate hardware.

Flea Market Photos Courtesy of Ham Radio Friedrichshafen

A3: Stand mit historischem Radiogeräten (Photo: Ham Radio Friedrichshafen)

A3: Stand mit historischem Radiogeräten

A3: Stand mit Empfängern und Messgeräten

A3: Stand mit Empfängern und Messgeräten (Photo: Ham Radio Friedrichshafen)

A3: Stand mit Empfängern und Messgeräten, hier zwei Schweizer an einer historischen Feld-Telefonzentrale

A3: Stand mit Empfängern und Messgeräten, hier zwei Schweizer an einer historischen Feld-Telefonzentrale (Photo: Ham Radio Friedrichshafen)

A3: Koffer mit Ham-Radio-Aufklebern aus mehreren Jahrzehnten

A3: Koffer mit Ham-Radio-Aufklebern aus mehreren Jahrzehnten (Photo: Ham Radio Friedrichshafen)

A3: Alte Radiogeräte

A3: Alte Radiogeräte (Photo: Ham Radio Friedrichshafen)

A3: Alte Empfänger und Radios

A3: Alte Empfänger und Radios (Photo: Ham Radio Friedrichshafen)

A3: Stand mit Empfängern und Messgeräten

A3: Stand mit Empfängern und Messgeräten (Photo: Ham Radio Friedrichshafen)

Yaesu, Icom & Co where there, of course. A large part of Hall 1 had booths for most of the European ham radio societies and other entities. Several attractions for the youths were there: A fox hunt around the hall, possibilities to solder simple circuits and more. The exhibit center even provides a kindergarden.

A1: Hilberling PT 8000A

A1: Hilberling PT 8000A (Photo: Ham Radio Friedrichshafen)


A1: ICOM (Photo: Ham Radio Friedrichshafen)

A1: Wimo, BABY Loop

A1: Wimo, BABY Loop (Photo: Ham Radio Friedrichshafen)

A1: YAESU Funkgeräte

A1: YAESU Funkgeräte (Photo: Ham Radio Friedrichshafen)

Hamradio had lots of presentations. The “SDR Academy” run all over Saturday – completely in English. See http://www.sdra-2016.de. Last year’s presentations are on Youtube. Search for “SDRA-2015”.

My presentation was titled “HAMNET On 70 cm – Possibilities and Limitations”. I should explain that HAMNET is our way to use the TCP address space reserved for Ham Radio use. Starting in Germany and especially Austria we use more or less standard WLAN equipment to build a ham radio intranet. User access is mostly on 2.3 GHz and links on 5 GHz. Where we have gaps in the wireless coverage we use Internet wormholes. This way you can access for example packet radio sites in Canada. See http://hamnetdb.net.

2,3 GHz and up means exclusively line-of sight connections. Quite some OMs cannot reach access points this way. The only alternative up to now has been VPN connections through the Internet. I think we could provide relatively fast access on 70 cm. Here in Germany we have two 200-kHz channels for such uses. They were defined in the 1980s for packet radio access up to 76 kbps. This technology is next to dead.

Theoretical calculations show that we could provide up to 1 Mbps and cover up to 50 km if we use modern modulation schemes. You could even improve throughput by making TCP/IP less gossipy. I proposed to use SDR blocks like HackRF or LimeSDR and combine them with a RF frontend (filter, preamp, PA, fast switching). The hardware is more or less readily available, but this is mostly a software topic. While HAMNET relies on standard WLAN equipment with all its limitations for ham radio usage, this system could be completely open. We could it adapt to all our needs and ideas. In the end we could port it back to the microwave bands.

Even if we only work on the lowest protocol levels this will pose quite some challenges. We would need programmers with quite varied expertise from TCP/IP protocols to SDR technology. My presentation was to attract such people. Personally I will not program anything. As a technical writer with a quite wide expertise I might be a bracket for the project and write documentation for it.


A “Peltier Lamp”: The candle heats one side of the Peltier element while the other is cooled by the heat sink. This produces enough electricity to light a LED. (Photo: Alexander DL4NO)

At the opposite end of the exhibit center another fair went on, called Maker Faire. In former times you would have called it “make it yourself”. The exhibits there went from computer modding to 3D printing, knitting and also ham radio. For this I modified my presentation a bit: “WLAN Below 1 GHz – Do You Want To Program For It?” The technology I talked about is near hot topics like Internet of Things or traffic telematics.

Booth of a high school showing the robots they built. (Photo: Alexander DL4NO)

Booth of a high school showing the robots they built. (Photo: Alexander DL4NO)


Booth of a high school showing the robots they built. (Photo: Alexander DL4NO)

vy 73

Thanks so much for sharing your notes from Friedrichshafen, Alexander. I look forward to attending one year myself!  I’m fascinated with the fact that the bulk of the event is indoors–what an incredible venue.

Any other Post readers attend Ham Radio Friedrichshafen? Please comment!

Alexander reviews the Avion AV-DR-1410 DRM receiver


Many thanks to SWLing Post contributor, Alexander (DL4NO), for the following review of the new Avion DRM receiver:

A review of the Avion DRM receiver

by Alexander von Obert (DL4NO)

The Avion AV-DR-1401 DRM receiver has appeared on the SWLing Post before in a previous review.

Amazon India does not sell the Avion outside of India. As it happens, I found someone who was willing to buy it for me and bring it with him from India to Germany.

The first impressions were quite disappointing. This feels more like a prototype, not a polished product:

  • The power supply produces lots of interference and runs quite hot. Unless I find another power supply, I can either charge the battery or listen to the radio.
  • The handle rattles. Such things often are symptoms for the whole product.
  • The firmware fails in many ways: update errors of the display, very confusing user interface.
  • No acceptable field strength indicator, especially in DRM until a signal is decoded. If you have a selective antenna you need to switch to AM to tune it. And then you tune it by ear or by numbers. No bar of any kind.
Avion AV-DR-1410 DRM

Radio Romania

Radio Romania produced very good signals this evening in southern Germany on 41m. But with the built-in antenna, DRM reception was impossible even in my shack directly under the roof. A Degen 31MS selective active antenna indoors enabled sketchy reception of Radio Romania and All India Radio on 41m. Reasonable reception was only possible with my external antenna.

All India Radio

All India Radio

Just imagine why I took the trouble to get the receiver! It is a far cry from what I really wanted: a modern replacement of my trusty Sony ICF7600D from the 1980s. I had to retire it for mechanical reasons after it travelled with me for 20 years.

In India, they might not have the industrial infrastructure they have in China or Japan, but an intensive firmware update is urgently needed. Software is something they are good at in India. Many problems could be solved that way:

  • The volume knob has no stop and must be pressed for a few seconds to turn the radio on or off. A short press could be used to switch it between volume and tuning.
  • A reasonable field strength indicator should be introduced.
  • The remote control does not work reliably.
  • With the “mode” switch I can select AM, FM, or DRM. But I have not found anything that the “band” switch could be doing.
  • The “scan” switch works on FM and puts all transmitters found into the favorites. But neither is that the function I would expect it to do nor does it work on other bands.

From my preliminary tests I fear the unit has massive large-signal problems. For example, I heard distorted signals of Radio Romania on bands where they were not transmitting at all. I use an active antenna but this is the same I use for the DX Patrol or SDRplay RSP, therefore I know that my antenna is not to blame. I also see this as an indicator about the DRM signal of Radio Romania.

I could not help but open the Avion receiver: [the internal antenna worked so poorly, I wanted to investigate].

I must say that the rattling handle was an accurate indicator of production quality.

Inside the Avion

Inside the Avion

See “Inside the Avion” image above (click to enlarge). The back side on the left was originally covered by an aluminum shield. I had to remove it as the wires are quite short–one cannot put the two parts flat on the bench otherwise. You see that they tried to improve the shielding on the right.

AVION internal antenna preamp

Avion internal antenna preamp

See “Avion internal antenna preamp” above (click to enlarge). The circuit board at the lower left corner of the first picture is the preamp for the internal antennas. In the lower left corner is the telescopic antenna connection. The wire here was extremely short–either it broke before and made contact by chance or I broke it when I dismounted the circuit board. At least I did not force it (still a bad manufacturing practice).

If you examine the circuitry, you see very bad practices: C2 directly connects the antenna to the base of Q2. It must be a bipolar transistor considering R3/R4. At least there is DN1 which seems to be protection diodes. On the whole board I can find no inductivities at all. There is absolutely no band limiting.

AVION broken shilding wire

Avion broken shilding wire

See “Avion broken shielding wire” above. The shielding wire had broken from the soldering. That was definitely not my fault. At the yellow isolation, a second wire is connected. That is the wire routed around the backside without any connection. This doesn’t make sense to me.

Avion crushed battery holder

Avion crushed battery holder

See “Avion crushed battery holder” above. The battery holder is fixed together with the aluminum shielding. The worker crushed the lug of the battery holder while mounting the shield. A few other threads were torn, too. A typical case of too much strength.

Avion seems to know about the inherent RFI problems of this receiver, but could not solve them. No wonder I have to use an external antenna.

Perhaps I will replace the antenna preamp with something reasonable.

Otherwise this radio will gather dust here.

Thank you for your report, Alexander–I’m sorry to hear about your experiences with the Avion, especially after the trouble you went to obtaining it.

So far, I’ve heard no truly positive reviews of the Avion AV-DR-1410. Sadly, it sounds like a radio to avoid.

Listener Post: Alexander von Obert

Analog Radio DialShortly after posting my plea for your radio stories, I received several replies, including this excellent story from SWLing Post reader, Alexander von Obert, who lives in Germany.

I have created a new series called Listener Posts, where I will place all of your personal radio histories. If you would like to add your story to the mix, simply send your story by email!

In the meantime, many thanks to Alexander for sharing his personal radio history:

Alexander von Obert (DL4NO)

My fate was sealed on my 12th birthday: As a present I got a redio experimenting kit (Kosmos Radiomann for the Germans among the readers). I could build a diode receiver (AKA detector receiver with a Germanium diode) from it. Adding an EF98 pentode (anode voltage 12 V) I could even build a tube audion, a 0V1 for the hams among the readers.

rbfjWithin a few months I outgrew it. My father, an engineer himself but completely absorbed by his job, showed me where a soldering iron gets hot. I managed to get hold of old radio and TV sets including Audions from the 3rd Reich area (“Volksempfänger”). First I simply dismantled them out of curiosity. Then I discovered the public library of my home town. The author of the time was Heinz Richter with titles like “Radiobasteln für Jungen”(radio building for boys).

Naturally I even tried to use these radios – especially those I managed to repair. I even listened to shortwave stations. In these times you found quite some German transmissions, notably from the BBC and Radio Sweden. Later, when my English knowledge blossomed, I discovered an even wider universe out there.

Then came the time where I wished to transmit myself. I never considered to do a radio program, I enjoyed experimenting with my equipment to much. Here in Germany transmitting without proper license was a criminal offence so my tests were few. CB had not been introduced here in Germany at that time, but I learned about ham radio. Somehow I found out about my local club and their license course. So I got the proud owner of the call DB1NO, a VHF/UHF license without Morse code test.

A short time later started my military service. I had to do quite some night shifts, a good opportunity to train Morse code hearing. When my comrades saw my cassette recorder they disappeared knowing about the “music” I would be listening to over the next half hour. After two years I did the code test. I have been DL4NO ever since.

No question about it: After my military service I got an electronics engineer. What I learned at the university I quite often considered as the theoretical background of things that I had known before. In that time I discovered microprocessors. You had to build your machines by yourself. My first computer used a regular cassette tape recorder as “mass storage”. Only the fourth homemade machine had a floppy disk drive – of the 8″ form factor variety, with about 1 MB of capacity per medium. I could only laugh about the first IBM PC with its 320 kB floppies.

During that time ham radio was mostly a social activity for me. I held contact with the OMs around on 2m FM and had no shortwave station at all. Microprocessors, studies, and later my first job, occupied most of my time. OK, I even had discovered girls 🙂

Now, as my job slowly settles down, I have upgraded my ham radio activities. I have built a mobile station that can operate from 7 to 440 MHz. My most important objective is to reduce the effort as far as possible and to stay within the traffic regulatory. For example I have proven that you can operate a 100W SSB station from a standard 12V outlet. Down to 14 MHz you can even use magmounts without really bad effects.

vy 73

Alexander also adds this note:

How I operate my station from a standard 12 V outlet in my car is described at http://www.dl4no.de/thema/mobil-st.htm. The picture and the circuit diagram  at the bottom of the page should be clear enough even if you don’t understand German. At http://www.dl4no.de/thema/mobilbe0.htm you see how a magmount antenna works on 20 m. The magmount has 200-300 pF to the roof of the car. This is an impedance of about 50 Ohms, that can be compensated. The magmount moves the resonance frequency a bit higher as you can see in the SWR diagram.

Many thanks, Alexander, for sharing your story! Readers, be sure to check out Alexander’s ham radio website at http://www.dl4no.de.

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