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Old 04-12-2004, 13:51   #151
arniek
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Hi,

i just compiled the new CVS today and didn't notice any difference with the new feature enabled either.

However right now i'm listening to RTL on 6095kHz and there is a weak carrier on 6100kHz. With Mod. Metric enabled the SNR seems to be a very little bit higher. But maybe the feature only affects SNR calculation in this case, not the stability of reception...

73
Arne
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Old 04-12-2004, 15:24   #152
dk8cb
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Comparison reports

Hi,

today, I conducted a few tests with the penultimate and the latest version of Dream 1.1.6cvs with "Mod Metric" enabled on the latter.

There seems to be a very small gain on the new version. Here are my comparison plots:

VoR, 15780 kHz, Bouquet Flevo NL, 7240 kHz and VT Digital, 9875 kHz, on which there was the strongest interference (from MOI Kuwait's DRM signal on 9880 kHz) encountered in my test series.

Only a slightly better performance with the new feature enabled.

Roland
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Old 04-12-2004, 16:29   #153
df9rb
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Hello,

today I did the following test to find out the possible improvements of Mod. Metric in the latest Dream version 1.1.6.
I started Dream two times on my computer one time with Mod. Metric SET, not SET in the second started Dream, and observed the SNRs and the MSC CRC LEDs.
Results:
no differenece on strong DW from Sines
up to 0.4 dB better with Mod. Metric set at RTL in the afternoon
no decoding of any DRM station in the 49 m band in the evening
no difference on BBC on 1296 (with interfering carrier!)

The little improvement on RTL in the afternoon was reproducible by
changing the Mod. Metric setting.

I think these results should encourage us to support the developers to go on analyzing this method and find a better algorithm.

Bernd, DF9RB
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Old 04-12-2004, 16:51   #154
simone
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Hi all,
I just did a 30 min test the same way as Bernd did it (running the latest version twice, one with the new Mod. Metric feature and the other one not using it) on 1296 kHz with the interferences present, SNR was exactly the same on both, but 0.3 % less decoded audio when using the new feature, I would say there is not really a difference that I could hear.
73, Simone
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Old 04-12-2004, 18:39   #155
dk8cb
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Another comparison

Hi,

here is another comparison report (mode A, 1296 kHz), in which the result with "Mod Metric" is slightly worse.

Roland
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Old 05-12-2004, 14:02   #156
dk8cb
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Hi,

here is an about 11 minutes long comparison plot of the result with respect to correctly decoded audio with "Mod. Metric" switched on and off in two instances of Dream running in parallel.
I have cut off the part of the plot during which only the left instance of Dream was running.

This was recorded during reception of 7320 kHz, it stops at the end of transmission. The sudden drop in SNR at the end was caused by someone else starting AM transmissions on 7325 kHz about a minute before DRM on 7320 kHz ended.

Roland
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Old 30-12-2004, 16:38   #157
dk8cb
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Multiple Windows

Hi all,

the current CVS version of Dream has a nice new feature:
All the evaluation plots that are selectable from the evaluation window may now be opened as individual windows and may be displayed simultaneously which allows to monitor different parameters at the same time.
See attached screenshot for an example.

There is also a new noise reduction feature available for AM demodulation.

Very nice. Thanks, Volker!

Roland
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Old 03-01-2005, 20:49   #158
VE3MEO
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Re: Multiple Windows

Hear, Hear! and here's my sample from RNWB at 12MHz today.

Tom

Quote:
Originally posted by dk8cb
Hi all,

the current CVS version of Dream has a nice new feature:
All the evaluation plots that are selectable from the evaluation window may now be opened as individual windows and may be displayed simultaneously which allows to monitor different parameters at the same time.
See attached screenshot for an example.

There is also a new noise reduction feature available for AM demodulation.

Very nice. Thanks, Volker!

Roland
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Old 03-01-2005, 21:45   #159
dk8cb
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Re: Re: Multiple Windows

Quote:
Originally posted by VE3MEO
Hear, Hear! and here's my sample from RNWB at 12MHz today.

Hi Tom,

so many windows but where is the input spectrum - in my view the most important of them all?
I wanted to check why your WMER plot shows low values at the edges, but for that, the input spectrum is required.
Is there interference or is your IF filter a bit too narrow? From the Input PSD it rather looks like the latter.

Roland
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Old 03-01-2005, 22:02   #160
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Re: Re: Re: Multiple Windows

Quote:
Originally posted by dk8cb


Hi Tom,

but where is the input spectrum - in my view the most important of them all?
I wanted to check why your WMER plot shows low values at the edges, but for that, the input spectrum is required.
Is there interference or is your IF filter a bit too narrow? From the Input PSD it rather looks like the latter.

Roland

Hi Roland,

I find the Input Power Spectral Density plot to be more useful than the Input Spectrum - it shows the essentials without the visual 'noise'. Maybe that's why Volker put it first.

Yes, I am using a nominal 10kHz bw filter with steep skirts - it's a LF-D6 15-element ceramic, and not especially flat across the passband, also affected by the loading of the subsequent, stock 7kHz IF filter.

One of the problems with a steep-skirted 10 kHz filter is that noise looks like a DRM signal in the spectral plots! A 20kHz filter is better - a real DRM signal then jumps out of the noise.

73, Tom
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Old 03-01-2005, 22:17   #161
dk8cb
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Re: Re: Re: Re: Multiple Windows

Quote:
Originally posted by VE3MEO
Yes, I am using a nominal 10kHz bw filter with steep skirts - it's a LF-D6 15-element ceramic, and not especially flat across the passband, also affected by the loading of the subsequent, stock 7kHz IF filter.

It looks more like an 8 kHz wide filter, the outer carriers seem to be strongly attenuated, especially at the upper end. I think that you could obtain better reception with a wider filter in some cases.

Roland
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Old 06-01-2005, 12:47   #162
dk8cb
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Hi,

in case of UEP (unequal error protection) transmissions, Dream's latest CVS now also displays the percentage of the data stream's part that has a higher degree of protection with respect to the total data block length.
See attached screenshot for an example.

Roland
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Old 08-01-2005, 02:02   #163
VE3MEO
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Re: Multiple Windows

And now the extra windows are saved on closing so that they re-appear in the next session. That's nice - saves a lot of keystrokes and resizing. I was going to suggest that

73, Tom
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Old 09-01-2005, 17:06   #164
FritzWue
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noise problems

My main problem when listening to drm on mediumave at daytime are switches: Light switches, the burner of the heating system, refrigerator, etc..

Everytime a switch is actuated the snr drops for several seconds sometimes causing audio dropouts, see attached screenshot.
In my case I need a proper grounding system for my outdoor antenna, but what will happen when we want to listen to drm in the car etc. where electrical noise is a common problem?

As the crackling of a switch is a very short event I wonder if it is possible to include something like a software noise blanker into the decoding software.
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Old 09-01-2005, 18:16   #165
simone
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Re: noise problems

Hi Fritz,
Quote:
Originally posted by FritzWue
My main problem when listening to drm on mediumave at daytime are switches: Light switches, the burner of the heating system, refrigerator, etc..
but what will happen when we want to listen to drm in the car etc. where electrical noise is a common problem?

I would not be worried about receiving DRM on MW in the car, see these results as an example, see also mobile reports but those are mostly results on SW, often better than at home, I think I also posted some mobile results in the 1296 kHz BBC WS thread.
73, Simone
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