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Old 10-05-2015, 16:07   #1
benravin
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DRM-Bangalore AIR 0621KHz

Please find the attached results of new DRM AIR transmission MW from Bangalore.

AAC+, 23.62 kbps UEP P-Stereo

-ben
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File Type: jpg DRM-BGL.jpg (98.0 KB, 472 views)
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Old 10-05-2015, 18:58   #2
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DRM-Bangalore AIR 0621 kHz

Hi,

Hm, another impossible DRM configuration... I think I'll mention this to AIR's Spectrum Manager and hear what he thinks.


PS: 621 is not possible to search in the forum, please use 0621 kHz (separated by one space) to make it easier to find.
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Old 11-05-2015, 03:26   #3
benravin
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Hi,

Just curious to know, why it is impossible with this configuration. Could you please give me the details.

-ben

Quote:
Originally Posted by Digger
Hi,

Hm, another impossible DRM configuration... I think I'll mention this to AIR's Spectrum Manager and hear what he thinks.


PS: 621 is not possible to search in the forum, please use 0621 kHz (separated by one space) to make it easier to find.
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Old 12-05-2015, 20:53   #4
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Hi Ben,

Judging from listening experience on MW some years ago in Europe I think the bitrate chosen is too high. It is possible to use SBR and P-Stereo with much less bps and still get excellent results and nice sounding audio. At least in Europe the second biggest problem was interference from AM stations on the same frequency. It would be interesting to know how you hear this station from your location. I dare to say that you probably did not hear much with 8 dB SNR?

Please keep reporting. Unfortunately I never lived near enough to a medium-wave DRM station.
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Old 12-05-2015, 23:10   #5
F1BJB
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I think a good idea for MW would be to reduce the bitrate during
night time.
Anyway 23.62Kbps seems too high even for daytime on a 9 Khz channel
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Old 13-05-2015, 17:21   #6
benravin
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Hi Terje,

Today they changed into Stereo AAC+ 26.48 kbps. Forget about bitrate I can't even hear a drop of audio so far. SNR has to be > 20dB for anything audible.

Please find the attached snapshot of todays reception.

-ben

Quote:
Originally Posted by Digger
Hi Ben,

Judging from listening experience on MW some years ago in Europe I think the bitrate chosen is too high. It is possible to use SBR and P-Stereo with much less bps and still get excellent results and nice sounding audio. At least in Europe the second biggest problem was interference from AM stations on the same frequency. It would be interesting to know how you hear this station from your location. I dare to say that you probably did not hear much with 8 dB SNR?

Please keep reporting. Unfortunately I never lived near enough to a medium-wave DRM station.
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File Type: jpg DRM-BGLR-0621.jpg (97.7 KB, 437 views)
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Old 13-05-2015, 20:11   #7
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Quote:
Originally Posted by benravin
Hi Terje,
Today they changed into Stereo AAC+ 26.48 kbps...
-ben

Hi Ben (and all),

26 kbps... even more problematic. And P2/1. I wonder why you get only 9 dB SNR? How many km are you from the TX? Could you make a screenshot of the Input Spectrum in DReaM? And sometimes I wonder what the engineers are thinking when they set the parameters. But again, I never lived in an area where there was ground wave coverage. And I agree with F1BJB on nighttime bitrate reduction.
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Old 14-05-2015, 16:03   #8
UA3ARI
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Hi Terje and all!
Some results of our old DRM MW measurements near Moscow:
http://www.drm.org/wp-content/upload...0228MSW-E1.pdf
Good receivers (DT-700 or AR-7030) + good external ferrite antenna + rural area = more than 100 km with 34680 kbit/s (or to 260 km with 10980 kbit/s) at daytime.
Himalaya with external ferrite antenna have same results.

Oleg
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Old 14-05-2015, 16:31   #9
benravin
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Hi Terje,

I stay 27km away from DRM transmission, but it covers more than 30km. Please find the attached SNR spectrum captured today.

I guess the MSC channel is always having CRC errors and is always in red. FAC and SDC channels it is able to decode without CRC errors.

Please find the attached screen shots of Dream SNR spectrum and Waterfall

-ben


[quote=Digger]Hi Ben (and all),

How many km are you from the TX? Could you make a screenshot of the Input Spectrum in DReaM?
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Old 14-05-2015, 16:41   #10
benravin
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not able to attach any images....
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Old 14-05-2015, 18:33   #11
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Hi Oleg,

Nice to hear from you again. I remember that document, which is very interesting. I got it from you on 5th June 2013 together with the e-QSL after the SFN tests you were involved with. There are many factors to consider using MW for DRM. I learned today that this 621 kHz transmission is a 200 kW TX in simulcast. What that means receptionwise I cannot judge from my location. We need logs from people like Ben to find out more.

All the best from a rainy and cold Stockholm!
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Old 15-05-2015, 10:15   #12
UA3ARI
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Hi Terje,
I remember well our excellent cooperation on the SFN tests. But I forgot that sent this document for you. I think it might be useful for Ben.
You're right that a lot of factors for MW should be taken into account. If they use 200 kW simulcast, and the standard ratio of the analog and digital is 16 dB, then the DRM power is 5 kW.
Ground conductivity at Bangalore ia 3 ms/m (ITU Rec-P.832). Maksimum atmospheric noise at Bangalore on 600 kHz may be about 40 dBuV/m (I did not calculate for sure, it is long).
So, my express prediction is about 70...80 km daytime radius for 20 dB SNR.
Download full text of my new article on this topic from:

https://www.researchgate.net/publica...RENT_REGI ONS

In any case, Ben must to receive well - if all goes well with the equipment and it does not put the receiver close to switching power supply.

73!
Oleg
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Old 15-05-2015, 15:17   #13
benravin
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Somehow the attachments are not working for me...it gives error wrong image extension, though everything is correct
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Old 15-05-2015, 15:41   #14
benravin
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Today they reverted to P-Stereo AAC+ 23.62 kbps UEP

MSC WMER - 13dB, still no audio and MSC channel is always having CRC errors (red )

-ben
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Old 15-05-2015, 15:42   #15
oh2bfo
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For the curious, here's a 2-minute I/Q recording of this transmission:
http://rms-upload.appspot.com/files/..._00615_24k.wav (11 MB)

The center frequency is 615 kHz so the 'DC frequency' of DRM signal will be +6 kHz. Use the following command line options to play back this file with Dream.
Code:
dream -c 4 -f BGLR_20150515_141959_00615_24k.wav
Now here's the fun part. The I/Q file also contains the analog portion of the simulcast, so you can switch Dream to analog mode and listen! But the AM carrier is 9 kHz below the DRM (-3 kHz), so first you need to adjust the '-c' command line option to access the 'negative' frequencies.
Code:
dream -c 5 -f BGLR_20150515_141959_00615_24k.wav
For comparison, here's also the Delhi simulcast (828 kHz DRM, 819 kHz AM):
http://rms-upload.appspot.com/files/..._00822_24k.wav

This transmission also includes Journaline with very high bitrate (10 kbps). So although the audio service is only 20 kbps, the combined transmission is over 30 kbps. No problems with decoding.
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