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Old 10-06-2007, 17:17   #256
simone
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Similar results as yesterday, SNR still limited, good decoding again.
Simone
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Old 10-06-2007, 17:19   #257
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Hi all!

Similar results here at my place: Low SNR with rates between 15 and 16 dB, but overall good decoding with 99.92% from 05.00 UTC to 06.00 UTC.

I've made a waterfall screenshot from the hcjb-transmission some weeks ago and shot a new one yesterday for comparison:

At normal days the 4 kW Transmitter produces some little bit wider footprint than the pure DRM-Signal. It's about 2-3 kHz wider. You can see it at days with good reception-conditions in the waterfall-diagramm through the "selective Fading mosaic" (you can see it at the PSD-Input window, too, but in this window it just looks better ;-) ) . But this 13 kHz wide "base" is very low in comparision to the 10 kHz "DRM-Pay-Load". I think thats quite normal for that kind of transmitter.

These days the "footprint" of the transmitter looks kind of different: The base is much wider than it used to be. You can see the "selective Fading Mosaic" from about 5 to 20 kHz in the spectrum. But the "Main DRM Signal" isn't as high (colored) as it has been.

Even as very good reception conditions can cause the fact that we can see the base of the signal getting wider, that can't explain why the Main DRM Signal is that weak: It should be much higher in that case, too.

So i think there could be something wrong (or just not optimal) with the exiter or the Amp-Stage of the transmitter.

(I hope everyone can understand what i ment to say. There are a lot of technical terms that i don't know in the english language...)

Stephan
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Last edited by maxpower : 10-06-2007 at 17:27.
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Old 11-06-2007, 06:25   #258
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June 11

Hi all,

Here is the result this morning. A nearly excellent result when the broadband strong QRM is not present. Look at the log file.
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Old 11-06-2007, 07:43   #259
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11th June

A mostly unattended log. So I missed that QRM which seems to have been even worse in my place.

Looked for a waterfall screenshot here, but unfortunately I have none. I'll try to have a look tomorrow morning. Something is not right. I think Stephan's thinking might be in the right direction.
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Old 11-06-2007, 11:39   #260
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11th June

Hi all.

This morning I start 0500UTC signal stringth was very good S9+10db under 60min. But propagation for DRM brake down totaly from 0535 to 0554UTC . ?????
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Old 11-06-2007, 12:19   #261
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Hi all,

Regarding my post #258. This is the first time I have noticed this kind of QRM (?). Can anybody explain what is it?. It had a BW more than 20 kHz, very strong, with carriers (?) evenly spaced and it sounded in AM like rather a high pitched hum. Here are the WF and PSD graphs in full size.
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Last edited by mitajohn : 11-06-2007 at 12:24.
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Old 11-06-2007, 12:56   #262
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Here's my log for today:

Transmitter started a little bit late at 05.02 or 05.03 UTC. Good decoding with still limited SNR.

There has been a "signal valley" between 05.30 UTC and 06.00 UTC here at my place, too. But it wasn't as deep as at the other places and so decoding went on: 99.92% correct decoded audio from 05.04 UTC to 06.02 UTC.

@John: Hmm, never saw something like that before. hundreds of carrieres at about 400 - 500 hz space!?! A defect maschine somewhere in your neigbourhood? Or is the UDSSR back with digital jamming?

Stephan
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Last edited by maxpower : 11-06-2007 at 13:30.
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Old 11-06-2007, 14:35   #263
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Stephan,

Thanks for the analysis on our DRM signal. We checked out the Txer last week after the SNR dropped and it seemed OK. However, I have forwarded your comments out to our engineers in Pifo so they can look at the DRM spectrum as well. I don't think they did that last week.

By the way, as many of you have noticed, we are only programming audio from 0500 to 0600 UTC. However the transmitter is usually on longer than that. I just wanted to clarify that for you. We don't have enough programming in German to sustain a longer transmission than 1 hour.

These reports are really great. Keep up the good work.

Doug
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Old 11-06-2007, 18:47   #264
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Doug, I am sure your European DRM audience would not mind receiving e.g. some nice Ecuadorian music after 06:00 UTC. (For me your transmission time is very comfortable, you start 08:00 AM local time, but for most of Europeans it is an hour or two earlier.)
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Old 11-06-2007, 21:17   #265
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A late start, bad results for about 20 minutes and still limited SNR, time is a few minutes wrong.
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Old 12-06-2007, 06:10   #266
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June 12

Hi all,

A late log start. No QRM today and a rather very good result. Some instantaneous sound breaks noticed.
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Old 12-06-2007, 06:51   #267
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two antennas, two receivers, one result
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Old 12-06-2007, 07:11   #268
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12th June

Generally a very good result, except for a few audio drop-outs around 0547. The label also disappeared for a short while at that time, but the DRM stream was intact. The decoding was a bit shaky around 0553 for a couple of minutes; the last 5 minutes were perfect. I cannot see this problem in Mitajohns log.
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Old 12-06-2007, 07:11   #269
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Hmmm, thats a strange log that I have today:

First thing: SNR isn't limited any more to 15/16 dB! It went up to max 28 dB at my place today.

But many ups and downs in SNR (min 14 and max 28) over the period from 05.00 UTC to 06.00 UTC and major dropouts at the last quarter of hour.
With only 96% correct decoded audio it's the worst reception of the HCJB european test-transmission I got within the last weeks.

AM Reception now at 07.00 UTC on 9740 kHz is quite ok so I don't know if it's maybe a problem with my receiver or propagation or some try outs at the TX?


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Last edited by maxpower : 12-06-2007 at 07:21.
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Old 12-06-2007, 15:06   #270
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Signal stringth very strog and stabile S9+10db , and SNR very good today.

SNR MAX 27.8db and CDA 99.87% ok . QRN give short brake in DRM.

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