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-   -   DRM trial on Sottens by amateur radio (http://www.drmrx.org/forum/showthread.php?t=2307)

mathias 11-02-2011 12:40

DRM trial on Sottens by amateur radio

Recently the Sottens 600kW AM Mediumwave transmitter has been phased out in Switzerland and a local amateur radio club has been able to get the right to use the huge antenna (188m) for a month for amateur radio transmission (More info and antenna pictures on
http://www.hb9mm.com/sottens/ )

There will be DRM transmission trial done by amateur radio on this transmitter using Spark software, a USRP and amateur radio linear amplifier.

We will use the narrowest band so 4.5kHz and high robustness to transmit slides.

So if you are interested, you are more than welcome to try to receive our signal and send us back reception report.

The tests will happen on the 2 next Sunday, on 13th February 2011 and 20th
February with 15 minutes periods on the following times (same for both sundays):
- 20h-20h15 CET (19h-19h15 UTC) TX on 7.180 MHz
- 21h-21h15 CET (20h-20h15 UTC) on 3.780 MHz

UPDATE: TODAY 20th Feb, We will transmit at the same times but during 30 minutes periods. Just after the transmission is finished we will be ready for QSO (conversation) for reports on the same frequency in SSB.

Any questions or suggestions are welcome.


f1tay 13-02-2011 18:19

No signal on 7180 kHz this evening here in Paris.

drmdab 13-02-2011 19:02

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3780 kHz, sometimes the label appears, heard a second of audio

tradio99 13-02-2011 19:25

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HE3OM here in Latvia was on 7180 kHz only, nothing on 3780 kHz

drmdab 13-02-2011 19:50

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Managed to receive about one minute of audio, did not receive any slides unfortunatly. One or two breaks in transmission, probably for loading the new configuration (I think the slideshow was not on air when the transmission started).

Merci, guys! :)

By the way, nothing 7180 kHz here.

f1tay 13-02-2011 19:51

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Reception at Paris.

simone 13-02-2011 20:36

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Dear Mathias,

what a nice experiment, I had setup two receivers here in Hessen Germany to record the RSCI stream, sorry unfortunately I did not set the correct DRM frequency for this mode, so it did not work. Luckily transmission lasted longer than scheduled so I had a chance to look at the signal, MER was about 16- 20 dB, good enough for audio decoding, I also received one slide. At the beginning transmitted time was wrong, around 2025 it had been corrected. Will send a report to the address given in the text messages.


DL1SAX 13-02-2011 21:38

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Hello Matthias,

many thanks for the very interesting transmission - i was a little too late for getting the complete transmission on 3780 kHz - but from 20:16h UTC to 20:42h UTC i had good reception of audio and i got 6 pictures of the slideshow.

In the attachment you will find a screenshot from the reception situation in Heilbronn - the S-Meter is set to Peak-Mode so the DRM-signal should have a more precise value.

In the attachment there is a screenshot of your transmission and a DRM-Log-plot please notice that the time in the plot is wrong it was generated in the "playback-mode" so the real time is from 20.16-20.42 UTC.

More info via E-Mail direkt to your E-Mail.

Greetings from Jürgen

mathias 13-02-2011 22:27


A big thank you to all for your reports. Without you, the experience wouldn't be so great. We were very surprised to see that you could receive it so far, given the low power and the fact that the antenna is designed for 765kHz. We will now try to analyse and see what we can enhance for the next trial on next Sunday (same times, same frequencies).

We extended a bit the transmission time as we saw that the power amplifier could cope with the DRM signal as it is normally designed for SSB (we first thought that it would overheat). We will probably do the same on next week. We had some linearity problems and had to reduce a bit the power.

You may have had interruptions too because we changed the mode in the middle. We started transmission with 16QAM and so only with audio (no space left for slides) which is the most robust and then switched to 64QAM where you had slides too. Sorry, the time was effectively wrong.

Please don't hesitate at any time to give proposal of what could be enhanced for the next trial.

You can also follow the latest updates on our page: http://www.opendigitalradio.org/inde..._II_in_Sottens

Don't forget to check it before the next trial in case we would have to change something.

Credits also to Yves HB9DTX, Stan from Maxxima, the HB9MM amateur radio club and Swisscom for lending them for a month such a great antenna. At least Sottens will have gone digital before dying. It shows also that DRM transmission can be done with limited equipment (apart from antenna), an interesting thing for local or community radio.

A warm thank you again,

Mathias Coinchon

stef 15-02-2011 21:02

@simone is it possible to send é mail to the members when such experiments take place so everyone how can set up his receiver.
I am always to late.
greetings stefaan.

Digger 19-02-2011 11:48

I live around 130 km from Sottens and I will try to listen tomorrow, Sunday. I also added the coordinates for the TX in the TX data file on my DRM page.

Per 20-02-2011 18:12

Feb 20
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Clearly visible here in Stockholm Sweden, February 20, 2011 on 7180 kHz.
But no sync, no audio.

Digger 20-02-2011 18:17

No trace of signal here in Biberstein (Aarau) around 1915 UTC, only a lot of aggressive local QRM. :mad:

I am probably too near, about 130 km from the TX.

stef 20-02-2011 18:18

Here in brussels also lot of qrm and no signal.:(

F10300 20-02-2011 18:27

Nothing in Bourges (Centre France) just noise on 7180 kHz

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