petersw wrote:

Is it always in the same location ? If so it could be where the Dab switches to a different receiving station

It happens anywhere in the country and at random but infrequently - once in a couple of weeks.

It cannot be due to "switching frequency" because DAB technology is a Single Frequency Network - all radio sites transmit the same signal on the same frequency with high precision timing:

http://en.wikipedia.org/wiki/Digital_Audio...y_networks

hence there is no retuning... which leads to a second issue with the Disco 4 radio... that is sometimes it says "Searching ..." as it it is scanning around for another frequency which is meaningless as the BBC National DAB Multiplex (12B) is a single, national, frequency and it does not transmit an "alternate frequency" (AF) list like traditional FM+RDS.

My hunch is this is a bug in the radio firmware and is due to some sort of timing issue (time slip) in the buffering that gets gradually worse until it runs off the end of the buffer and then snaps back in to step and plays the same part out twice in the process.

It happens so infrequently that the first time or two you notice it you think "was I dreaming or did they just say that bit twice" and its not until you've noticed it five or six times over as many months that you start to realise your not going mad


Mike

Not sure if this enlightens

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Signal delay

The nature of a SFN is such that the transmitters in a network must broadcast the same signal at the same time. To achieve synchronization, the broadcaster must counter any differences in propagation time incurred by the different methods and distances involved in carrying the signal from the multiplexer to the different transmitters. This is done by applying a delay to the incoming signal at the transmitter based on a timestamp generated at the multiplexer, created taking into account the maximum likely propagation time, with a generous added margin for safety. Delays in the receiver due to digital processing (e.g. deinterleaving) add to the overall delay perceived by the listener.[19] The signal is delayed by 2–4 seconds depending on the decoding circuitry used. This has disadvantages:

DAB radios are out of step with live events, so the experience of listening to live commentaries on events being watched is impaired; Listeners using a combination of analogue (AM or FM) and DAB radios (e.g. in different rooms of a house) will hear a confusing mixture when both receivers are within earshot.

Time signals, on the contrary, are not a problem in a well-defined network with a fixed delay. The DAB multiplexer adds the proper offset to the distributed time information. The time information is also independent from the (possibly varying) audio decoding delay in receivers since the time is not embedded inside the audio frames. This means that built in clocks in receivers will be spot on.

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Only if there is DAB software to update Confused .

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network that's not perfect Smile

i have stick on highway device and not an issue with it

(external aerial though)