Commenting on digital radio | radioinfo

Commenting on digital radio

Wednesday 14 August, 2019

If you are not a regular reader of our comments section  you may have missed a learned and well informed debate has been raging (well perhaps ‘raging’ is an overstatement) about DAB+ in response to a recent article on ten years since Australia's digital radio launch.
 
It has built up a good cross section of opinions about the success of DAB+ in Australia and about the audio quality of transmission.
 
Here’s your summary of the debate so far:
 
Anthony the Koala, a regular contributor to various topics we report on, started it all by posting a response to this article about ten years of digital radio:
 

DAB+ is certainly the level playing field. While FM stations had the advantage since the auctioning of parts of the FM spectrum 30 years ago, and indeed successful bidders paying exorbitant fees to occupy a certain VHF frequency, it gives the opportunity for AM stations who could not afford to bid to participate in transmitting CD-quality sound.

The DAB+ system is an improvement on the test transmissions conducted in the early 2000s using MP3 streaming instead of HE-AAC streaming. The latter system permits more stations to be broadcast for a given 'fidelity'.

However, while the DAB+ has a superior sound, some of the 'permanent' auxiliary stations associated with the main FM or AM station are transmitting on 32kbs stereo. I don't count Macquarie's NTS which is mainly broadcasting speech in mono. Nevertheless, 32kbs stereo streams have a "metallic sound". The sound is acceptable at rates of 48kbs in stereo. ABC-FM, RN and Metropolitan ABC (in Sydney 702 (2BL)) broadcast at 70kbs. In Sydney the best signal is 2GB and 2CH at 128kbs stereo.

 
He also raised the issue of transmission bands (currently the VHF Band in Australia) and alternative transmission systems for regional areas.
 
Raymond responded that he was worried that DAB+ has not expanded across the whole Australian continent yet:
 

So 10 years on, regional centres apart from Darwin, Canberra and Hobart, still don't have digital radio.

That in itself is a worry about the real commitment of the industry to adopt the medium in the way it trumpeted on launch day a whole decade ago.

He also drew attention to New Zealand’s approach to DAB and why NZ won’t be introducing it any time soon. “It's a revealing read,” says Rayond, linking to this document

Christer then weighed into the debate saying: “After 30 years still few countries are on the DAB trail. The unique national FM switch-off in Norway is a fiasco.”
 
GerardW proposed that community radio should move off the FM band to make more space:
 

Free up the FM Band by moving Community Radio completely to DAB+ and establish a proper FM band populated by Commercial Stations.
 

A few days later StJohn responded to Anthony, taking issue with his belief that the sound is tinny, and raising the DRM question for large coverage areas:
 

Anthony, Perth has a 32 kbit/s station and it’s sound is not tiny and the centre of the sound stage is normal volume. At this data rate DAB+ makes a mono signal which is steered around. It sounds as if there has been a reversal of the phase of the left vs right signals prior to encoding. You can simulate this by reversing the connections to one speaker.

Don’t convert the country to FM, the coverage areas become smaller than AM. Use DRM which can sound as good over larger coverage areas, but also transmit pictures and multipage indexed text as well.

That led to a few back and forth comments from both Anthony and StJohn, politely differing from each other’s opinions and adding other interesting technical points.
 
Anthony has just added a further comment today about India’s DRM transmissions and more about the quality of transmission (Read more about radio in India in our sister publication AsiaRadioToday). One of the questions raised in that post is about Indian commercial radio transmitting in DRM, the answer is that only the national broadcaster AIR currently has some transmissions in DRM, there are no commercial stations broadcasting in digital.
 
We are delighted that our site stimulates informed, polite debate from all viewpoints. We don’t necessarily agree with all the points made, but we are pleased that readers feel that our publication is the place to have a sensible discussion about issues.
 
We verify people who post, but we never reveal their identities and we allow them to post under pseudonyms if they wish.
 
We always moderate comments, based on our policies, and read and sometimes edit them before we make them live.
 

If you have something to add to the discussion, read the full comments from each of our contributors first, then feel free to post your thoughts in that story, or at the bottom of this report. You only need to register for a free account to do so (we never spam you or sell your data).

 
When you register, you can opt in or out of our three newsletters: twice weekly, daily or job alerts, just tick the appropriate boxes.
 
 
 

 
 
 

Advertisement

 

Post a Comment

2 Comments

Log InYou must be logged in to post comments.
StJohn
15 August 2019 - 11:39pm
Anthony,
Many AM stations use processors to try and sound like FM by boosting the high frequency audio because of the very poor high frequency response of AM receivers. This will particularly affect the SBR signal. X Digital in Perth only transmits music and some advertising but not much speech. There is plenty of bass.
The problem for broadcasters is that they can preview MP2, MP4 files and they sound fine, but once transmitted are poor sounding regardless of the bit rate.
As far as India goes, India does not have its population evenly distributed. The Government is trying to cover the whole of the country because it’s All India Radio is the only broadcaster allowed to transmit news and current affairs. They do separate the networks like the ABC local radio does. There FM commercial broadcast industry is tiny. http://www.asiaradiotoday.com/news/drm-association-radio-operators-india’s-agm shows that DRM+ is likely because it can transmit 3 programs on one transmitter. Two DRM+ transmitters can fit into a single FM channel. A main driver for DRM in India is the Emergency Warning System will save millions of lives from the floods of the dual monsoons per year.
As far as cars goes, they have only just started installing DRM in cars and have done it to 1.5 million cars in 18 months and they have only just started. An app has been written for the FM tuner in most Android phones which are much more popular than iphones.
The ACMA has already stated that they are only converting the remote and a few country AM licences to FM as the band is too crowded elsewhere. You can fit 6 DRM+ audio programs onto one FM transmission channel.
As far as Australia goes the cost difference between FM and DRM+ is no where as big as you claim as the single transmitter is used for both of each broadcasters’ programs. The only difference is the modulator and a content server to combine their pair of audio programs to fit into one digital stream. They can add coloured pictures for advertising and could also radiate an electronic text “newspaper” using Jounaline.
So, the cost is reduced because the AM transmitter is switched off as well as the FM transmitter. It can be replaced with a DRM+ transmitter of 1/ 10th of the power for the same coverage area. In remote areas such AM transmitters can be modified to DRM, however there is currently one commercial station on High Frequency (Short Wave) which can economically cover large remote areas. Converting it to DRM will give good stereo sound and it is easily tuned.
Your comment about tuning ranges is exaggerated. FM radios tuning below 87.5 MHz Lower FM frequencies were only used in Japan and the USSR. USSR is now testing DRM+ at a frequency around our analog TV channel 2. All digitally tuned AM receivers are selectable for 9 kHz spacing for 531 – 1602 kHz or is 530 – 1700 on 10 kHz spacing which is only used in the Americas. Much of Europe has no AM at all. No mobile phones virtually no DAB+ radios will receive AM at all.
Over 67% - 100 % of the power of an AM signal is wasted in the carrier. DRM does not have a carrier resulting in drop in electricity consumption. It uses COFDM just like our digital TV.

St John
Anthony The Koala
16 August 2019 - 9:57pm
Dear StJohn,
Thank you for your reply.

You have confirmed what I said about using lossy compression files in the transmission/reception chain sounding poor.

Thank you for elucidating on the number of 'services' on one DRM channel being three. If two DRM channels can fit onto one FM frequency, given one FM frequency occupies 200kHz, then one DRM channel is 100kHz. It follows that in the AM band typically 1602 to 522 khz has a bandwidth of 1122kHz can fit approximately 10 DRM services. On the FM channels, 108MHz-88MHz = 20Mhz, which gives approximately 20/0.1 = 200 theoretical DRM transmitters. With 3 services per DRM transmitters, that's the equivalent to 600 DRM services. Theoretical because that does not take account of any co-channel interference whether it's on MW or VHF.

HOWEVER, I do note that with DRM and DAB+ transmissions, the same frequency can be used in different areas PROVIDED that all DRM and DAB+ are synchronized using accurate clocks. Synchronization shouldn't be hard because atomic clocks have been used in broadcasting for decades.

My calculations were based on the third paragraph of three programs on one transmitter, NOT the fifth paragraph, where you say that one can fit 6 DRM channels on one FM channel. Please clarify the 3 channels and 6 channels distinction.

Nevertheless, that does not account what for what is final government policy on spectral allocation of DRM services.

One question I would like to ask you is when the DRM signal is on MW or SW bands and due to the properties of the ionosphere such that MW and SW signals skipping long distances is: what is the quality of the received signal over long distances? In addition is there enough error correction information sent with the DRM signal that the recovered signal at the receiver is 'perfect'?

I noted in your previous answers (plural) that DRM has the facility to transmit pictures and text. The questions about pictures and text services raises non-engineering questions but economic: will the radio stations be able to afford providing pictures and text services OR will the radio stations want to monetise and and let other parties pay to use the text and pictures services. A corollary to auxiliary text services is the teletext service, text services on analogue tv as well as DVB. Teletext services providing news, weather, market information was abandoned by the Seven network nearly 20 years ago. The justification for the abandoning of teletext services was that such information was available on the web! Similarly the potential of DRM to provide text and picture services, one asks will it be utilized when the information is available on the web, especially the radio station's web page.

REGARDLESS of technology: whether DRM or DAB+ or web pages, it is an issue for the broadcaster to keep information up-to-date. For example, a former 2UE personality who left 2UE nearly three years ago is still publicised on a rural radio station's web page http://www.hayfm.org/wp/show/stuart-bocking/ . Nevertheless, I do note that DRM's capability to send pictures and text - regardless of DRM or WEB technology, the information needs to be up-to-date.

I must disagree with you about the alleged 'exaggeration' of the use of the FM band. My description of the FM band is EXACT. Yes I am aware for example that VHF FM bands are not the same world wide. For example Japan's VHF FM band is between 75MHz and 95MHz. I was talking about the 88MHz to 108MHz band as used in the Australian market place. All my 88MHz to 108MHz FM receivers can receive frequencies beyond this band. There are services used below 88MHz for example in Sydney for multicultural languages such as Campbelltown's Spanish language station "Radio Austral" 87.6MHz, dance tracks on "Raw FM" to name a few. Source, https://www.acma.gov.au/-/media/Licence-Issue-and-Allocation/Information/Word-Document/High-power-and-low-power-radio-open-narrowcasters-programming-and-broadcasting-data.doc?la=en - definitely not an exaggeration.

In addition, though the MW AM band is officially 522kHz-1602kHz, there are radios sold and marketed in Australia that have its AM band go to 1701kHz. Pioneer A/V receivers, for example VSX-932 and Toyota Camry's radio goes to 1701kHZ to name a few. You can receive in Sydney "The Voice Of Charity" on 1701kHz.

An observation, this is not numerology. Nevertheless, without mathematical proofs, adding the digits of the frequency of a radio station, if divisible by 9 is indicative of a 9kHz-spaced radio frequency. To illustrate for Sydney frequencies, RN on 576 kHz, adding the digits 5+7+6 =18 is divisible by 9. Another example 1701kHz, add the digits, 1 + 7 + 1 = 9, is divisible by 9. One final example 2GB at 873kHz, 8 + 7 + 3 = 18 which is divisible by 9.

One final point. I agree with about the carrier in an AM mode being wasted. I already stated that the carrier remains at a constant level regardless of the amplitude of its side bands.

I thank you for enriching the public at large about the capability of DRM. Please clarify whether a DRM transmitter can carry 3 or 6 signals on one tx, and the quality of a decoded DRM signal over long distances especially on the MW and SW bands.

Thank you,
Anthony of exciting Belfield


radioinfo ABN: 87 004 005 109  P O Box 6430 North Ryde NSW 2113 Australia.  |  All content © 2012. All Rights Reserved.