DRM trial II in Sottens

Revision as of 00:37, 17 January 2012

Introduction

Following the amateur radio DRM trial on the phased out shortwave antenna in Sottens in 2004, it has been decided to make another amateur radio DRM trial but this time on the 188m MW antenna that has just been phased out on 31.12.2010.

Transmission schedule

The tests happened on 13th February 2011 and 20th February 2011 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

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

Please send your reception reports to sottens@hb9mm.com

Original audio loop transmitted

Setup

Video of a short tour of the room

• Spark software (free full license gracefully offered by Michael Feilen)
• USRP with LFTX daughterboard
• Mini-circuits Gali74+ amplifier
• Preamplifier recycled from the bin by Yves HB9DTX: ENI modell-300, 40 dB from 40 kHz to 110 Mhz, 1-2W max output power
• Amateur radio linear amplifier.

Mode used:

• 4.5kHz, Mode B, MSC 16QAM, EEP code rate 0.5, AAC audio at 4.8kbit/s
• 4.5kHz, Mode B, MSC 64QAM, EEP code rate 0.5, AAC Audio, MOT Slideshow at 2.56 kbits/s

Report

The signal has been received in various places in Europe and even in Sweden and Latvia. It is impressive considering the low transmitted power compared to normal broadcast DRM transmission that use normally kilowatts and also considering the antenna that is not designed for such frequencies.

See also:

• Reports on DRM RX forum: http://www.drmrx.org/forum/showthread.php?t=2307
• Pictures by HB9HLI
• Article by HB9HLI (in french)

Credits

Credits to Yves HB9DTX, Stan from Maxxima, the HB9MM amateur radio club and Swisscom for lending 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. Mathias HB9UFQ

See also

• HB9MM special operation in Sottens: http://www.hb9mm.com/sottens
• Receiver modification to catch DRM transmissions using Dream or Diorama or SODIRA or any other commercial software radio receiver.