Unexpected radio behaviour

[hdhondt]

Here's a puzzle that completely baffles me.

My AMG A35 supports both FM and DAB+. In Australia, where I live, the station "ABC Classic" is on both. Both stations broadcast the exact same program. I normally tune the radio to Classic DAB+ (206.4 MHz). Unfortunately, that signal is lost in my garage (a large apartment bock), but FM is fine. When I first had the car, the radio would either drop out completely in the garage, or it would switch to some random other station.

Now for the puzzle. For the last few weeks, it has been reliably and automatically switching between "ABC Classic" DAB+ and "ABC Classic" FM (92.9 MHz) . It selects FM when entering the garage, and DAB+ when exciting.

My questions are:

1. Why has it only been doing this recently, and not from the beginning? I guess there may have been a firmware upgrade at the last service, in August.
2. How does it know those 2 frequencies broadcast the same programme? All I can think of is that the radio just grabs 2 stations with the same name.
3. Now for the real puzzle: there is NO audible break when it switches stations. Yet, the digital signal should have a delay of several seconds, depending on both the transmitter and the receiver. I have 2 DAB+ radios at home, and they are not in sync; it's clear that one is ahead of the other. Again, I can imagine that the radio, after having found 2 identical stations. delays one of them to bring them in sync. But, is it worth the effort to add that to the firmware? How many people would want this feature?

Any guesses?
Thanks

 

[hdhondt]

I finally called Mercedes. The service guy I spoke to knew what I was talking about. He said that there has indeed been a firmware update to the radio which, among other things, makes the radio switch between similar stations on FM and DAB+. However, he expected the 2 signals to be out of sync with each other, and was very surprised when I told him they are not.

 

[Botus]

In Europe DAB+ services came on-line in Feb 2016. It is a totally different transmission signal and compression standard, DAB is an older and very different, totally incompatible system. (of course with FM being even older and an analogue wave signal - instead of compressed noughts and ones digital trash)

The idea of DAB+ taking over from DAB was touted way back in 2012, and some manufacturers started to build the kit with the capability to receive either DAB or DAB+ from that era. But on most Mercedes models DAB+ it was not enabled. With it off in software prior to 2014 (as nothing was there to receive, this era's tuners don't play up). I believe 2015 model year cars had both its DAB and DAB+ chips enabled in software and sprung in to action during that 2016 "switch over event"

To avoid issues Germany just stopped broadcasting DAB overnight - moving the whole country to DAB+ services only
The UK moved to dual broadcasting of DAB and DAB+ services in Feb 2016. Overnight in major cities with significant reception of DAB and DAB+ channels (aka London) it saw many owners immediately notice the Merc DAB tuners all keeled over and kept rebooting.

Luckily the tuner on these is a separate unit, so you could revert back to FM and the car radio and comand unit carried on working normally. It was just DAB / DAB+ that was dead or playing up. What muddled most owners heads, was it would work at times, especially on longer trips away from major city centers.

The reason it was crashing was bad software. They had never anticipated the car would ever see >99 Digital channels. Once DAB+ came on alongside DAB, it was easy to find that many in major cities and the tuner went "now what - crash"... in a nasty loop.

Merc released two software updates in 2016 attempting to fix it. But the first one in June was wrong - they hadn't understood the fault correctly. Oct 2016 saw them release a fix for >99 channel bug. But its wasn't the full fix. As the antenna amp isn't really suitable for DAB+ services (not much surprise it was never fit for DAB either). So there is later better hardware (an antenna module) and correct software fix out there.

On Ford's and Peugeot, many owners claim cars that display the channel logo's on screen have found another round of bugs. With the BBC National mulitplex killing their tuners when the BBC enabled logo's circa 2018. I suspect that's similar software fun, where too much or new data it didn't expect is causing the tuners to have a headache.

Of course I'm not in Oz, but I'd be straight round to the dealership for a software update on the DAB module - until you have verified the car's tuner and rest of the comand system is on the latest iteration of software, I would bother stressing about what next... (we all know its firmware, but Merc like to call is software)

 

[hdhondt]

Hi Botus

You seem to have misunderstood my question. There is nothing wrong with the radio. In fact, I posted my question because it works better than expected.

Australia has never had DAB, we went straight to DAB+ in 2005. As I said in my last post, the dealer confirmed my first 2 questions: there has been a firmware upgrade. The 3rd question he was not aware of; he was very surprised when I told him FM and DAB+ are perfectly sync'ed. That's a pretty complicated bit of processing for what seems to be a very minimal gain in function.

 

[sonic]

Only having FM & DAB+ the set up would have been much easier. In Europe having FM, DAB, & DAB+ must have been a software nightmare. Particularly as Germany just switched DAB off.

 

[Botus]

Hi Botus

You seem to have misunderstood my question. There is nothing wrong with the radio. In fact, I posted my question because it works better than expected.

Australia has never had DAB, we went straight to DAB+ in 2005. As I said in my last post, the dealer confirmed my first 2 questions: there has been a firmware upgrade. The 3rd question he was not aware of; he was very surprised when I told him FM and DAB+ are perfectly sync'ed. That's a pretty complicated bit of processing for what seems to be a very minimal gain in function.

That's quite interesting. DAB+ Services mostly started out in 2016 / 17. I presume with Oz not getting messed up with the bad idea of original DAB, you had more freedom to start early. It says Oz thought about it in 2005 and went DAB+ earlier than Europe in 2009 - commencing a staged roll-out of commercial DAB+ services during May 2009 with Perth launching on 4 May 2009; Melbourne on 11 May 2009; Adelaide on 20 May 2009; Brisbane on 25 May 2009; and Sydney on 15 June 2009 (sydney delayed due to bad weather) trial multiplexes for Canberra commenced broadcasting on 14 July 2010 and Darwin 13 August 2010. With nothing to this day in Ballarat. https://en.wikipedia.org/wiki/Digital_radio_in_Australia

However with Australia's vast distances and low population density it not suited to the propagation characteristics of DAB+ and it is therefore likely that a standard other than DAB+ will be adopted for serving areas outside the major cities - so you should have used the USA Sat radio sirius idea instead ! https://en.wikipedia.org/wiki/Sirius_XM

Asking a Dealership how it works will never be a good idea, they know nothing about anything, never did never will.

The idea of dropping back and forth from DAB to FM is not new, most do it nowadays and its sort of seamless. But of course the car DAB, DAB+ and FM tuners need to align the set up or it would be more irritating than helpful, I guess they do this by delaying you hearing the FM signal. But of course the broadcasters need to do it right their end or it would be all wrong.

We see delays in transmission of services in the UK. If you toggle Std Def Digital TV to HD TV services, its like pressing rewind for 2 seconds. Uncompressing higher bit depth digital signals takes longer, what they should do is broadcast it earlier. Maybe Oz broadcasting updated what they are doing or dropped the bit rate (to squeeze in more channels) and the delays in transmission now fit Mercs idea of the maths?

One of the biggest changes from DAB to DAB+ (much like video from MPEG 2 to MPEG4) was a better compression standard - better info yet less to transmit - alongside better error handling to try and cover up the terrible reception digital radio tends to have