DRM Software Radio Forums  

Go Back   DRM Software Radio Forums > DRM Software Radio - User Forums > General Topics
User Name
Password
FAQ Members List Calendar Search Today's Posts Mark Forums Read

Reply
 
Thread Tools Search this Thread Display Modes
Old 09-02-2017, 08:41   #1
Per
Registered User
 
Per's Avatar
 
Join Date: Nov 2002
Location: Stockholm - Sweden
Posts: 676
DRM Trial in South Africa

There is an article in the magazine "Bizcommunity" of the DRM MW-trial that took place in South Africa from Sept. 2014 until Oct. 2015:
http://www.bizcommunity.com/Article/196/59/157354.html

Did anyone here on the forum actually hear it? Or was it just one of many trials?
"Listeners can look forward to excellent audio quality (CD quality) with stereo and 5.1 surround sound."...
__________________
73's Per - SM0ITS
Per is offline   Reply With Quote
Old 10-02-2017, 08:01   #2
Aetheradio
Registered User
 
Join Date: Aug 2012
Location: New Zealand
Posts: 61
I read the report which although encouraging I must observe inaccurate parameters for the comparison to AM coverage

When changing an existing MW service to DRM30 the new transmitter is required to have power reduced in accordance with the interference protection ratio. The DRM consortium website contains the technical handbook which references to this document, https://tech.ebu.ch/docs/tech/tech3330.pdf


This means the example 10 kW AM transmission in the trial needs to be running with a DRM30 transmission of 2 kW average power (7 dB lower) for the comparison.

With those parameters the DRM performance would surely result in poorer coverage than the AM test

If we ignore the regulatory aspect - say its a new clear channel - so if the same powers can be used:

The 10 kW AM transmitter could be run with the MDCL enabled resulting in the same electricity consumption as the 10 kW DRM30 example, with no change to coverage. New AM transmitters have this as standard.

The DRM30 transmitter for 10 kW output would need to be a 25 kW rated transmitter, as was used in the trial. These transmitters cost more than a 10 kW model.



below is an extract from the EBU document - I have not studied this further there may be other considerations making the -7 dB figure higher or lower

5.1.3.4 Decisions of the RRB - Dec. 2002
The RRB (Radio Regulatory Board) approved the Rules of Procedure as proposed with the following
amendments:
Amend the fourth paragraph of the Rule relating to Resolution 8 (Annex 1 to CCRR/20) and the
ninth paragraph of the Rule relating to Annex 2 (Annex 2 to CCRR/20) as follows: "After
consideration of the relevant ITU-R studies, the Board decided that any frequency assignment
for AM broadcasting in the Plan may provisionally be used with digital modulation (transmission
types DRM* A2 or B2), provided the radiation is reduced by at least 7dB in all directions,
compared to the radiation of the AM modulated frequency assignment in the Plan".
*The DRM system is described in Recommendation ITU-R BS-1514
Aetheradio is offline   Reply With Quote
Old 10-02-2017, 11:28   #3
zfyoung
Registered User
 
Join Date: Aug 2006
Location: BaiSe, P.R. China @E10636′ N2355′
Posts: 245
Cool

Quote:
The 10 kW AM transmitter could be run with the MDCL enabled resulting in the same electricity consumption as the 10 kW DRM30 example, with no change to coverage.
So I can infer from your comment that 'The 10 kW AM transmitter with the MDCL enabled has the same coverage as the 10 kW DRM30'? Well, that is a direct contradictory to what past field test results have shown(at least in the formal official report).

Did I miss something here or someone(s) is misleading public opinion intentionally??

zfyoung
__________________
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 @ E10636′ N2355′
zfyoung is offline   Reply With Quote
Old 10-02-2017, 19:51   #4
Aetheradio
Registered User
 
Join Date: Aug 2012
Location: New Zealand
Posts: 61
sorry - to clarify - I am saying a 10 kW AM transmitter running MDCL at the usual -6 dB setting will consume about the same electricity as a 10 kW transmitter running DRM30. There is no efficiency gain using DRM over similarly set up AM using modern and approved power saving techniques.

secondly, the transmitter model required for 10 kW DRM transmission is a 25 kW transmitter. This is a much more expensive transmitter to buy also the antenna coupling components are more costly.


thirdly, in most countries the regulations for setting transmission power levels are tightly controlled by international agreement to prevent interference to stations operating on same channel or adjacent channel.
In the case of a DRM service, that would be required to operate at a power reduction 7 dB than the AM service was allowed. In my country several AM services every night must reduce power 7 dB to protect the reception area of another station which may be another country
These stations are currently 5 kW day and reduce to 1 kW each night. If the broadcaster wished to go DRM, his day power would be 1 kW and the night power would be 200 Watts.

The first broadcaster on a frequency gets the licence for full power. Any broadcaster setting up on that frequency in a different area only gets a lower power that will not interfere with the encumbent.

The most logical way to establish DRM service in MW is to add new channels above 1620 kHz, or use the tropical bands starting at 2.3 MHz. All DRM receivers can do this range.


I agree with your tagline: bad audio is much better than dropouts and no audio

regards, Ralph
http://radioalchem.blogspot.co.nz/







Quote:
Originally Posted by zfyoung
So I can infer from your comment that 'The 10 kW AM transmitter with the MDCL enabled has the same coverage as the 10 kW DRM30'? Well, that is a direct contradictory to what past field test results have shown(at least in the formal official report).

Did I miss something here or someone(s) is misleading public opinion intentionally??

zfyoung
Aetheradio is offline   Reply With Quote
Old 11-02-2017, 00:52   #5
zfyoung
Registered User
 
Join Date: Aug 2006
Location: BaiSe, P.R. China @E10636′ N2355′
Posts: 245
Ralph, since I'm from the background of electrical signal and processing system, I am really interested in the power efficiency of both (AM/DRM) systems, theoretically and practically.

So, assuming both system consuming equal power at the Tx side (with/without MDCL ... energy saving and others known/unknown optimization technique), signals from both systems should give the same dBuV/m strength at the Rx side? If that is the case, which system give the better audio quality or equivalently has better coverage?

About the your second point: I think the fairer question should be: In the whole service time of each Tx equipment (20, 30+years), with electrical bill, antenna and cooling system... maintenance cost included, which system is cheaper?

And your third point about the night time power back-off, I agree with your principle: the late comer should not affect the encumbent negatively. And I want to throw in a few words: In the AM world, the ONLY way to avoid night time interference is power back-off. With DRM, we can also re-configure the signal parameter(code rate..) at the Tx side. And I should emphasize we under-estimate the resilience of DRM signal to noise interference, even the pioneering BBC trial in Devon. With DRM signal, there is myriad of method to combat noise and recover the original data. With AM signal, once the noise is there, it is there. The harder you try, the more damaged the signal would be.

So, my point is: DRM is not perfect, but it is the step at the right direction and given time could be near perfection, while AM is beyond redemption.


zfyoung
__________________
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 @ E10636′ N2355′

Last edited by zfyoung : 11-02-2017 at 00:59.
zfyoung is offline   Reply With Quote
Old 11-02-2017, 04:14   #6
Aetheradio
Registered User
 
Join Date: Aug 2012
Location: New Zealand
Posts: 61
The easiest article for MDCL is here
http://www.nautel.com/resources/arti...-transmitters/

AMC algorithm at 6dB is used on a 50 kW AM and I listen to this station at night from 400 km away its interesting to watch the field strength vary with modulation gaps - but the audio is not noticeably affected. they did the MDCL for power saving.

of course the MDCL power saving is considerable at 50 kW but less dramatic for a 5 kW station however the lower stress on components

I dont know how a field strength reading on the typical meter would read for a DRM signal, as there is the overall bandwidth to consider the Potomac FIM 41 etc will only look at the carrier +- 2 kHz so a DRM signal would read incorrectly
some of this is coverd in the EBU article

Once AIR starts using their fleet of DRM / AM transmitters we shall have the opportunity to see how it all works out. I do hope for the best. In the tests I did here (equal average power level for AM - DRM30 - ssb - P25 and finally AMstereo) I got a better result with the AM overall. And the test gave a 4 dB advantage to DRM. I would like to re run the test with He-AAC coding and parametric stereo which wasnt available to me on the DReaM transmitter.

I wish there were more car radios with AMstereo here - there are 2 stations with CQAM modulators here and a third coming soon. but they are not turned on (STL is mono too)
Aetheradio is offline   Reply With Quote
Old 11-02-2017, 11:51   #7
zfyoung
Registered User
 
Join Date: Aug 2006
Location: BaiSe, P.R. China @E10636′ N2355′
Posts: 245
Thanks, Ralph. I'm fully aware of the 'AMC' and other power saving technique. One way or another, they achieve their goal through manipulation of carrier and side band power. In DRM, the counterpart is called 'pilot cells' which is scattered all over the nominal 9/10KHz bandwidth periodically while the AM carrier center on the middle carrier(well, that is obvious). Just from this respect, DRM should stand at a better position to cope with noise interference and other anomaly in channel condition.

Anyway, it would be greatly appreciated if you could share the trial data esp. digitized IF signal record for public scrutiny in the future side-by-side test. And I think only a standard that withstands public critics could possibly be a good standard.

Regards
zfyoung
__________________
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 @ E10636′ N2355′

Last edited by zfyoung : 11-02-2017 at 13:17.
zfyoung is offline   Reply With Quote
Old 04-10-2018, 21:01   #8
G4TMV
Registered User
 
G4TMV's Avatar
 
Join Date: Feb 2015
Location: East Lancashire, north west England
Posts: 215
There was a piece in the Southgate ARC Daily News yesterday about South Africa possibly going to broadcast DRM+ in VHF Band One, you can find it here, with links to the various sources:

http://www.southgatearc.org/news/2018/october/south-africa-considers-band-I-drm-broadcasting.htm?utm_source=feedburner&utm_medium=email&utm_campaign=Feed%3A+AmateurRadioNews+%28Southgate +Amateur+Radio+News%29
__________________
Alan.

Modified NRD-525G with
Radiokit DRM Decoder Board,
SDRplay RSP-1A, SDR Console v3

Lancashire, UK
53:39.18N 02:10.28W
IO83vp

https://www.ndblist.info
G4TMV is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

vB code is On
Smilies are On
[IMG] code is Off
HTML code is On
Forum Jump


All times are GMT. The time now is 17:40.


Powered by vBulletin Version 3.5.3
Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.