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Old 02-06-2018, 02:14   #16
PhilipOneL
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Good point about RFI producing the RFI.

Also about this being a good spot for a web SDR. Ahh, if I were a rich man. . .

Thanks for the map of signal strength. It seems an odd distribution with many of the best reception areas being totally unpopulated.

Philip
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Old 02-06-2018, 02:33   #17
AF4MP
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Quote:
Originally Posted by PhilipOneL
It seems an odd distribution with many of the best reception areas being totally unpopulated.

That was the reason for my comments. Their 9265 kHz frequency is definitely the better choice!

To WINB's defense they only have one rhombic antenna and a limited number of transmitters and frequencies. I certainly support their DRM experimentation and I wish them all the success!
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Old 04-06-2018, 18:41   #18
Cumbredx
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VOACAP, WINB, and DRM

I don't believe that VOACAP can plug in various DRM parameters such as mode, bit rate, QAM, protection levels, etc.

If VOACAP can, please share with us how this map would look if WINB was at
16 QAM instead of 64. Or Mode A or C instead of B.
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Old 04-06-2018, 20:24   #19
AF4MP
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Quote:
Originally Posted by Cumbredx
I don't believe that VOACAP can plug in various DRM parameters such as mode, bit rate, QAM, protection levels, etc.

You are correct it does not have an option for DRM.

Quote:
Originally Posted by Cumbredx
If VOACAP can, please share with us how this map would look if WINB was at 16 QAM instead of 64. Or Mode A or C instead of B.

VOACAP can, however, show you the received signal level in dBw (or equivalent S-meter reading).

Since it is DRM the RF signal level does not change with the DRM parameter (provided it is transmitted in a 10 kHz bandwidth). The S-meter reading will not change whether you go 16 or 64 QAM, or whatever Mode you choose.

So the VOACAP plot would remain the same.
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Old 04-06-2018, 21:53   #20
Cumbredx
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DRM

The S meter reading stays the same no matter what changes.

But irrespective of this, wouldn't the readability change based on whether one
chooses 16 or 64 QAM?

Mode A is for local reception, B typical service, C long distance, D NIVS, so you are saying that a VOACAP map will look the same in dBw at a 10 kHz bandwidth?
If this is the case, then how could a broadcaster us VOACAP to determine which mode he should use if his map will always look the same?

Hans
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Old 05-06-2018, 00:30   #21
AF4MP
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Hans,

Please let me refer you to the DRM Organization "DRM Introduction and Implementation Guide, Revision 3, October 2017"

Specifically to:

1. Page 26


ii. Modulation parameters

In addition to the basic transmission Modes, there is also a choice of modulation (QAM constellation) and coding (Viterbi) rates for the main service channel. Normally, provided the broadcaster has selected the transmission mode correctly, the service area achieved should be defined predominantly by the received signal-to-noise ratio.

This allows the use of simple analogue planning tools (see Section 10).

In all DRM30 Modes the option exists to choose either 64-QAM or 16-QAM for the Main Service Channel, and this choice will be largely influenced by the signal-to-noise + interference ratio (SNR) that can be achieved in the
target area. The more robust 16-QAM option is normally chosen where the SNR is expected to be too low to support 64-QAM.

2. Page 89

Table 10.5.2.2d shows the range for minimum usable field strength needed to achieve the BER target on HF channels using robustness mode B. This range arises from varying propagation channel conditions. Mode A is
not applicable to HF transmission because of the lack of robustness in the OFDM parameters (length of the guard interval and frequency spacing of the subcarriers).

Here is the table (with the average field strength calculated from the range shown in the original table)

MOD PROT dBuV dBW

16-QAM 0 20.8 -116
16-QAM 1 23.75 -113

64-QAM 0 26.2 -110.7
64-QAM 1 28.55 -108.4

I calculated the corresponding dBuV to dBW conversion.

3. Page 85

10.4 Planning tools

At the time of writing there are no planning tools available which have been specifically designed to calculate coverage and availability for DRM transmissions.

However, provided that the broadcaster uses a transmission mode appropriate to the channel being used, the more esoteric aspects of digital transmission and reception (delay spread, channel impulse response etc.) are automatically catered for within the various DRM-mode parameters.

This then leaves only the received field-strength (and predicted interference levels from other broadcasts) to be determined by the planning tool in precisely the same manner as when planning an analogue service. In other words, given the additional knowledge of the receiver performance and the relevant local noise-floor, the overall received c/n ratio can be calculated in the normal way.

Hence, current ‘analogue’ planning tools capable of predicting mean and standard deviation of field-strength can be used to plan DRM services, provided the appropriate target s/n figure for the relevant DRM mode is used.

--------------------------------------------------------------------------------------

My comments on the difference between 16-QAM and 64-QAM.

From the above table:

a 64-QAM signal with protection level 0 is better than one with level 1 by 2.3 dB which is less than half of an S-point.

a 16-QAM signal with protection level 0 is better than one with level 1 by 3 dB which is exactly half of an S-point.


a 16-QAM signal with protection level 1 is better than 64-QAM with level 0 by 2.3 dB which is less than half of an S-point (e.g. RRI 11650 kHz).


a 16-QAM signal with protection level 0 is better than 64-QAM with level 0 by 5.3 dB which is less than than one S-point.
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Last edited by AF4MP : 05-06-2018 at 00:55. Reason: corrected arithmetic..
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Old 05-06-2018, 02:24   #22
zfyoung
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I'm afraid whether VOACAP can predict various DRM transmission coverage is moot here. Even the field strength at receiver site is NOT the determinate factor of a successful DRM reception.

From my observation through kiwiSDR, their signal seems suffer from poor linearity in PA link. For a properly calibrated DRM signal of the same signal strength, it should register much higher SNR on the receiver side. All I can say is that their engineers haven't done their homework adequately.
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Any kind of audio drop-out is worse than any kind of low quality audio: No audio, No log report.

My Rx location: GuangXi Province @ E106°36′ N23°55′
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Old 05-06-2018, 03:19   #23
AF4MP
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Originally Posted by zfyoung
I'm afraid whether VOACAP can predict various DRM transmission coverage is moot here. Even the field strength at receiver site is NOT the determinate factor of a successful DRM reception.

Totally agree! Although VOACAP can provide a reasonable indication as to whether a signal has a chance to be heard provided the transmitter is correctly adjusted and can handle the DRM load.
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Old 05-06-2018, 18:40   #24
tpreitzel
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Jun 5th, 2018 partial log ...

Frequency: +
Codec: -
Modulation: -

Please switch to 16 QAM modulation with the xHE-AAC codec. Statistically, there aren't too many DRM receivers, DReaM or dedicated hardware, anyway so there's little loss in switching to the xHE-AAC codec as well. Yeah, I'd have to switch to my GR-216 receiver with its software bugs, but it'll do for awhile.
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Old 05-06-2018, 19:18   #25
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Quote:
Originally Posted by tpreitzel
Jun 5th, 2018 partial log ...

Frequency: +
Codec: -
Modulation: -

Please switch to 16 QAM modulation with the xHE-AAC codec. Statistically, there aren't too many DRM receivers, DReaM or dedicated hardware, anyway so there's little loss in switching to the xHE-AAC codec as well. Yeah, I'd have to switch to my GR-216 receiver with its software bugs, but it'll do for awhile.
In addition, despite not arriving in Brazil, sound very muffled, with a rate of 8.28 kbps, despite the use of 64-QAM mode. It is regrettable that the DRM transmitter parameters are not used correctly: https://alokeshgupta.blogspot.com/20...-drm-mode.html
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Old 05-06-2018, 19:23   #26
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In addition, despite not arriving in Brazil, sound very muffled, with a bitrate of 8.28 kbps on 64-QAM mode . It is regrettable that the DRM transmitter parameters are not used correctly: https://alokeshgupta.blogspot.com/20...-drm-mode.html
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Old 06-06-2018, 00:16   #27
tpreitzel
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Quote:
Originally Posted by Braccini
In addition, despite not arriving in Brazil, sound very muffled, with a bitrate of 8.28 kbps on 64-QAM mode . It is regrettable that the DRM transmitter parameters are not used correctly: https://alokeshgupta.blogspot.com/20...-drm-mode.html

Unfortunately, people learn best when making errors... I sincerely wish DRM SW broadcasters would closely review the posted logs on these forums, both current and historical. Despite this hopefully constructive criticism, I wish WINB the best in their effort to bring DRM to shortwave.

Terje,

Is it a good idea to add 15670 kHz to your log plotter or not? WINB doesn't normally use this frequency.

Last edited by tpreitzel : 06-06-2018 at 01:00.
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Old 06-06-2018, 03:17   #28
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Quote:
Originally Posted by tpreitzel
Terje,
. . . add 15670 kHz to your log plotter . . .

Done!

(Finally I'm getting closer to a completed hobby room!!!)
The propagation is terrible - - - not much to hear at all . . .
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Old 06-06-2018, 07:28   #29
Braccini
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Quote:
Originally Posted by Digger
Done!

(Finally I'm getting closer to a completed hobby room!!!)
The propagation is terrible - - - not much to hear at all . . .
I think it's hard not to pick up some DRM station in Japan ... Even in Brazil it is getting right to RRI at 11650 kHz DRM at 21h UTC. Although the spread is also low here, RRI has been a spectacle. I suggested the frequency, maybe that's why it's cool and the modulation in 16-QAM was phenomenal 😊📻

Clint 73 from South of Brazil!
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Old 07-06-2018, 01:30   #30
tpreitzel
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Quote:
Originally Posted by Digger
Done!

(Finally I'm getting closer to a completed hobby room!!!)
The propagation is terrible - - - not much to hear at all . . .

I appreciate it. Yeah, propagation has been, well strange. On some early mornings, I can receive the BBC from Meyerton on 15400 kHz fairly well and on other days the frequency is just static.

We're looking forward to your logs as time permits so it's great that the setup of your radio gear is proceeding nicely.
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