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Old 19-02-2020, 00:38   #1
AF4MP
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VOA Radio Marti DRM 7345 kHz

Today was able to decode the xHE-AAC mode transmitted by Radio Marti 7345 kHz from the VOA transmitter site near Greenville, North Carolina.

The receiver was the Ten-Tec RX320D running the latest Dream 2.2.1 Linux software (that I finished compiling this morning). The antenna was the long wire lying on the ground and snapped in two pieces by a recent heavy storm.

Signals were strong with the SNR peaking over 21 dB!

I was going to attach a reception log but the DRM Log plotter apparently does not like the output from the xHE-AAC decoder.

Attached are the received station ID and the DRM constellation.
Attached Images
File Type: png Radio Marti 18-feb-20.png (26.9 KB, 99 views)
File Type: png Radio Marti Constellation 18-feb-20.png (21.2 KB, 94 views)
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Old 20-02-2020, 21:52   #2
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VOA Radio Marti DRM 7345 kHz

This afternoon's reception - Audio/SNR graph (15 minute duration) from the evaluation screen starting at 2122z (attachment 1).

There is a multi-media slide show also transmitted. Although they show the number as four slides, there only two, repeated as 3 and 4 (Attachment 2 shows the first slide).

The receiver is my Kenwood R-1000 modified with a Sat-Schneider crystal controlled mixer/convertor.

The antenna is a about 3 meters of wire lying on the ground (the remains of the long wire that was torn apart by recent storms)!

Please notice that there is audio decoding at a low SNR of about 12 dB.
Attached Images
File Type: png Radio Marti SNR-Audio 20-Feb-20.png (18.3 KB, 86 views)
File Type: png Radio Marti MOT 1 20-Feb-20.png (18.6 KB, 86 views)
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Last edited by AF4MP : 21-02-2020 at 03:23. Reason: low SNR typo: changed 20 db to 12 dB
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Old 21-02-2020, 01:29   #3
tpreitzel
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Codec +
Modulation +
Frequency +

Excellent configuration and production by VoA which should be emulated by most other digital broadcasters via shortwave. VoA might experiment with Mode A or stereo. but otherwise the broadcast is still excellent... with just 10 kbps data rate. Bravo!

VoA is my generic reference for any broadcast from their site in NC.

Last edited by tpreitzel : 21-02-2020 at 01:36.
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Old 23-02-2020, 10:20   #4
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VoA's production and configuration are good enough to clearly reveal a flawed performance of female announcer who was too close to the microphone...


The xHE-AAC codec is wonderful and 16 QAM enables the listener to enjoy the broadcast...great stuff.
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Old 23-02-2020, 16:27   #5
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VOA Radio Marti DRM 7345 kHz

The audio spectrum from this afternoon's transmission.
Attached Images
File Type: png Radio Marti Audio Spectrum 23Feb20.png (12.2 KB, 93 views)
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Old 28-02-2020, 23:17   #6
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Hi,

I'll just post something here so I can get the notifications! ;-)
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Old 01-03-2020, 05:13   #7
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Some signal here in Germany,
but most probably using xHE-AAC mode it didn't make it to the MSC.
They were using mode B/ 9kHz.
Attached Images
File Type: png 7345_200229_2156_DK6QI.png (39.6 KB, 72 views)
File Type: png 7345_200229_2240_DK6QI.png (9.6 KB, 67 views)
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Last edited by FritzWue : 01-03-2020 at 05:18.
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Old 03-03-2020, 13:09   #8
AF4MP
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VOA Radio Marti DRM 7345 kHz

Terje has been working on enabling the DRM Log Plotter to plot the xHE-AAC mode. He has kindly permitted me to use his Beta version to plot yesterday's reception report.

Radio Marti commenced its broadcast earlier than scheduled. The latest Dream 2.2.1 still crashes but yesterday was able to log 4 hours and 33 minutes of the transmission uninterrupted (Attachment 1).

As night time approaches this receive location the SNR starts to drop (Attachment 2) and the signal gradually fades out.
Attached Images
File Type: png 7345-200302-1648-2121-Zyg.png (44.6 KB, 71 views)
File Type: png 7345-200302-2234-2302-Zyg.png (42.4 KB, 66 views)
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Old 04-03-2020, 01:49   #9
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VOA Radio Marti DRM 7345 kHz

Today's reception report choosing the longest period in between DreaM crashes (attachment 1).

The 2nd attachment shows the interesting sudden signal drop-out at 0010z.

Observing the received signal over the last few days at 2330z, local sunset, the signal strength and SNR gradually drop down and fade out. As the propagation changes to a long skip.

This evening after the SNR dropped slighty it then went up as did the signal strength. Finally at 0010z the signal and SNR suddenly dropped.

I monitored a KiwiSDR web receiver located in Alabama, about 300km south and a little west of my location, go through the same sequence, and ending with an identical signal drop, about half an hour later!
Attached Images
File Type: png 7345-200303-2012-2208-Zyg.png (44.7 KB, 55 views)
File Type: png 7345-200303-2345-0047-Zyg.png (39.2 KB, 62 views)
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Old 04-03-2020, 23:28   #10
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VOA Radio Marti DRM 7345 kHz

Today's reception report.

Attachment 1 shows the longest uninterrupted period between DReaM crashes. The xHE-AAC audio still being decoded at deep SNR fades!

Attachment 2 shows the last part of the received transmission when the signal drops out for the evening at 2343z (earlier than yesterday's 0010z).
Attached Images
File Type: png 7345-200304-1652-1858-Zyg.png (43.2 KB, 53 views)
File Type: png 7345-200304-2322-0008-Zyg.png (40.3 KB, 58 views)
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Old 06-03-2020, 00:32   #11
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VOA Radio Marti DRM 7345 kHz

Today's reception report.

Attachment 1 - 1h39m longest audio period not interrupted by a DRreaM crash.

Attachment 2 - Rather than a sudden signal drop-out as happened in previous days, this was a slower movement starting at 2350z (not shown) and audio decoding going off and on until final drop-out starting at 0036z.
Attached Images
File Type: png 7345-200305-1746-1925-Zyg.png (42.7 KB, 55 views)
File Type: png 7345-200306-0032-0049-Zyg.png (44.8 KB, 54 views)
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Old 09-03-2020, 00:28   #12
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VOA Radio Marti DRM 7345 kHz

Friday's reception report (6-March-20).

Signal loss due to propagation change at 0024z!
Attached Images
File Type: png 7345-200306-2351-0107-Zyg.png (39.2 KB, 47 views)
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Old 09-03-2020, 00:31   #13
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VOA Radio Marti DRM 7345 kHz

Saturday's reception report (7-March-20).

Longest audio period (2 H 12 min) not interrupted by a DRreaM crash.
Attached Images
File Type: png 7345-200307-1846-2057-Zyg.png (43.8 KB, 42 views)
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Old 09-03-2020, 00:40   #14
AF4MP
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VOA Radio Marti DRM 7345 kHz

Today's reception report.

This was the only uninterrupted log recorded today. Didn't have time to check the computer this afternoon.
Attached Images
File Type: png 7345-200308-2020-2142-Zyg.png (42.3 KB, 47 views)
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Old 09-03-2020, 23:54   #15
AF4MP
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VOA Radio Marti DRM 7345 kHz

Today's reception report.

Attachment 1: Longest audio period (1 H 18 min) not interrupted by a DRreaM crash.

Attachment 2: Decoding termination at 0006z.
Attached Images
File Type: png 7345-200309-1929-2047-Zyg.png (42.9 KB, 46 views)
File Type: png 7345-200309-2247-0042-Zyg.png (42.0 KB, 54 views)
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