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Old 16-08-2005, 19:24   #1
dk8cb
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1296 kHz BBC WS from Orfordness

Hi,

not so good over here mainly due to fading.

Roland
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Old 16-08-2005, 19:37   #2
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Effect on AM signal on 1305 kHz

Hi,

during the last few minutes of this increased-bandwidth transmission, I tuned my receiver to the adjacent channel, 9 kHz higher. The station transmitting on 1305 kHz calls itself "Pure FM" and belongs to RTBF from Belgium, not even far away from Orfordness. I have verified the origin of this programme by listening to the live stream on the internet.

Listen to the attached MP3 recording. For the first part, I used an IF bandwidth of about 8 kHz, reception was quite ok then, but as soon as I increased the receiver's bandwidth to 9 kHz, interference became very strong and made reception in double sideband AM mode quite difficult.

Roland
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Old 16-08-2005, 21:01   #3
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Hi James,
I was surprised that you were using mode B tonight with the 10 kHz signal. The past days I always got 100% at least from 1830, but today a few dropouts although the SNR was higher
(BTW the version of DreaM I was using is not supporting UEP)
No problems due to the 10 kHz wide signal, no interference from adjacent channels.
Audio bitrate was nearly the same, so why use mode B which would require a higher SNR on a transmission where co-channel interferers and fading always cause problems?
It will be interesting to see how results on the night transmission compare to the lately excellent results.
But nice to see some experiments on DRM transmissions again
73, Simone
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Old 16-08-2005, 22:52   #4
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Side effects

Hi,

unfortunately, the switch to the other mode and bitrate seems to have brought back unwanted effects that were thought to have been overcome.
I noticed an interruption shortly after the start of the late night transmission at 21:08 UTC and I also noticed a repetition which sounded like "the Israeli army geared up geared up ...".
See the attached cut-out from the waterfall plot which shows the interrruption.

Roland
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Old 17-08-2005, 00:06   #5
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Late night test transmission, August 16

Hi,

mode B with its higher SNR requirements seems to have lessened the overall decoding success.
See attached screenshot which includes results from both DRMSWR and Dream.

Roland
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Old 17-08-2005, 06:09   #6
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mode B, 20.14 kbps, UEP

Hi all,
I also noticed the interruption at 2108, maybe just a coincidence and not related to yesterdays changes. But maybe these changes also caused the problems on the Russian transmission?
As usual on UEP transmissions the audio light on the FhG decoder often was red but audio was OK for listening.
The old configuration worked a lot better, hope it was only a test for one night with this configuration.

73, Simone
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Old 17-08-2005, 08:22   #7
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The main aim of the tests is to see if we can have the same DRM signal on HF & MF, this means we are operating an MFN and therefore receivers will have no trouble to switch between Orfordness and the HF transmission. Thanks for the comments so far. Maybe Mode A on HF is possible, we will look into this.
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Old 17-08-2005, 19:30   #8
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Thumbs up mode A, 22.14 kbps, EEP

Hi all,
better results back in mode A and with increased bitrate this evening
Again no problems with adjacent channels due to the 10 kHz bandwidth.
If the conditions of the corresponding HF transmission(s) would allow for mode A this would be a great configuration also for this MF transmission. Otherwise an MFN of MF and HF transmissions would always be a (bad) compromise.
@James: Thanks for explaining the purpose of these 10 kHz tests.
The attachment shows the comparison with yesterdays results.
73, Simone
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Old 17-08-2005, 20:07   #9
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Good audio, now we still need stereo.
The spanish interference started very early from 17:20 UTC this evening, so I switched to the shielded loop at 18:20 UTC and tried different positions for some time. That caused the two dropouts.
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Old 17-08-2005, 20:38   #10
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Tonight I also recorded the identification of the spanish interferer on 1296kHz when Orfordness was off between 19:15 and 19:30 UTC.
It is indeed Cadena COPE Valencia:
http://www.cope.es/paginas/emisoras.asp?p=1&id=33

I've zipped the short mp3 64kbps file:
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Old 17-08-2005, 21:39   #11
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Hi James and all,
this evening interruptions occured again at the beginning of the night transmission, I noticed them at 2109 and twice at 2116
73, Simone
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Old 18-08-2005, 00:13   #12
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Evening transmission in mode A, 10 kHz

Hi,

here is my report, logged partly unattended.

Not very good.

Roland
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Old 18-08-2005, 00:16   #13
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Late night transmission, mode A, 10 kHz

Hi,

my unattended log, so no comment on interruptions or repetitions.

Roland
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Old 18-08-2005, 05:02   #14
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Good audio at start, then unattended log with dropouts:
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Old 18-08-2005, 06:22   #15
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Thumbs up

Hi all,
as I already mentioned above, the cold start problem occured again last night, also the 4 dropouts between 2215- 2250 seem to be Tx related. Besides this the new configuration works better and also gives great audio quality.
73, Simone
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