Hi guys, interested in DAB+, how does signal get from station to transmitters? Say ABC national programs (overnights for example),
Does signal leave Sydney and run on fibre too each transmitter site around country or would it be broadcast via satellite to each cap city then microwaved to transmitter in that capital city , Say Brisbane (Southbank studios too Mt Cootha),
then from each capital city the stream would be forwarded too the regional transmitters via fibre in its respective states to save on the long distance fibre hauls between states?
But then when shows are local it would be a whole diff setup im guessing to have local streams. say sunshine coast abc or rockhampton abc for example would the local studios streams be aggregated back in Brisbane for sending back to transmitters for broadcast to their towers?
Why is there a sometimes 2/3 second delay between am/fm stream and digital streams…triple m brisbane is a good 7/8 seconds or so delay
That explains why I lost all the stations randomly the other night! Didn’t realise they were doing works. And have noticed the reception has been a bit patchy in places it never used to be so it’s good to know it’s not my radio.
Keen to see how good reception is once the notch is removed and new transmitters are installed.
One of the good things about analog radio and TV broadcasting is it happens in real time - digital radio and TV always has some signal processing latency, anything from a fraction of a second to 3 seconds for digital TV. Once digital came along the talent could not use foldback into their headphones or earpiece from off-air because of the delay.
Each broadcaster has their own program distribution setup usually a mix of fibre, satellite and microwave or telco links. Satellite of course has the 1/4 second distance delay but most of the others have negligible delay. The main culprit for digital is the encode/decode process.
Some good questions there, the DAB+ transmission chain & networks are extremely complex, so much more than AM/FM & even DTV, I’ll put things in basic terms though here.
If we’re talking ABC DAB+ I’m not sure if ABC send programs individually from each Metro Capital City studio to Sydney first, or directly to the Telstra Broadcast Centre via fibre connection? At the Telstra Broadcast Centre, all the programs are multiplexed together with the SBS programs & then distributed out to the required transmission site over the Telstra DVN2 Fibre network.
The commercial stations are done differently, each Metro Capital City studio has a Studio multiplexer, where all the programs are multiplexed together (local sourced direct), (national stations such as Coles Radio for Nova or CADA for ARN will be sent over fibre from the source studio to each metro station over their internal Fibre WAN). After being multiplexed at each studio, that’s then sent to each local DAB+ transmitter site over a fibre connection, (most networks use either a Telstra, Vocus variant or Pipe Networks/TPG variant), where it then goes to another multiplexer & is multiplexed together with all the other commercial networks & community stations & then sent through the local transmitter.
Most DAB+ translator sites are OCR’s (On Channel Repeaters), that get their signal from the main site transmitter over the air, then re-transmit it, Sydney & Melbourne do have a couple of SFN DAB+ sites, the 2 in Sydney are fed via microwave from Artarmon then transmitted on the same frequency as the other sites, 1 SFN site in Melbourne is fed via microwave & the other is fed via fibre from Ornata Rd Mt Dandenong, in Sydney over the next couple/few years we are looking to convert a few more OCR sites to SFN Fibre or microwave fed.
Community stations send their audio to the CBAA via whatever means they choose, fibre or general NBN internet stream, where the CBAA then send it all to the local transmitter site via fibre & multiplex it together, then it’s joined with the commercial multiplex & sent to the local transmitter & out to the listeners.
The digital delay between AM/FM & DAB+ is due to how long it takes the DAB+ data to get out to the radio receiver, individual networks may delay/buffer audio/data longer than others, then each radio receiver will buffer audio before playing it out, AM/FM doesn’t have this digital delay or only a little bit as it goes through the audio processor. Most DAB+ delay is the buffer in the radio receiver to cover error correction.
Thankyou RFBurns, Interesting reading, So much thought and time goes into setting up a network like a radio network (or any network in that fact) its pretty time consuming for some.
I noticed last night all the dab radio stations went dark around midnight in Brisbane, tho u did post about the abc being down for a lill while. Its great to have some different channels to choose from nowdays instead of the staples on fm/am.
cheers
I ended up retuning one radio when I lost stations a couple of nights ago as well in Brisbane. Not sure if it was necessary as it didn’t impact other radios. The signal strength for me now is down about 3dB according to the signal meter on the DAB App.
Imagine if it was part of the Hit Network… “Get That Fog Horn Feeling” or KIIS “100% Foghorns from Kiistory to Now” Nova - “Turn Up The Foghorn Feel Good”
