'Qute DAB feed

Posted by: Anthony Dunn on 24 August 2011

My 'Qute has been doing something odd over the past few days: the DAB feed is indicating that there is no signal. The FM/DAB aerial is connected, the FM signal is strong and I have tried switching off and rebooting the device but to no effect. Any ideas anyone?

Posted on: 24 August 2011 by Bruce Woodhouse

Got any other DAB radios? Checked it is not a locality issue?

I only ask because we live in an area very marginal for DAB reception and if they ever do anything to one or other transmitter then we lose it entirely for a day or two at a time-or at least I assume that is the explanation. For the last 3-4 weeks our reception has dipped greatly, making a kitchen DAB unusable and the Qute marginal despite being attached to a big roof aerial. Bit cross, I thought DAB ccoverage was going to improve over time!

Bruce

Posted on: 25 August 2011 by Simon-in-Suffolk

As mentioned, have you tried other dab radios? Do you use the same antenna for FM as DAB?.
Is it no signal, or low quality but reasonable signal? If it's the latter it might be interference. One possible menace is gigabit Poweline adapters etc which are known to knock out DAB, especially if signals are weak or internal antennas are used.
Simon

Posted on: 25 August 2011 by Simon-in-Suffolk

Bruce, I know the BBC has been restructuring DAB transmission to try and improve coverage, but because of limitations with DAB multiplexes it's not always a case of them turning the wick up on the transmitter.
You mention you have a roof top dab antenna, the same as I. It's a 6 element vertically polarised Yagi which is great gain but is directional. It might be worth checking to see if you dab transmitter has now changed and therefore your rooftop antenna might need to be repointed to get a good signal again.
Simon

Posted on: 25 August 2011 by Bruce Woodhouse

Originally Posted by Simon-in-Suffolk:

Thanks for that. The aerial is a bog standard FM one (I have no idea what sort), and I had not realised it may be directional. I might have a tweak. For now the house portable radio seems useless, it only ever worked in a few locations in the building even when the signal was at its best!

The advent of iRadio on Qute and now HDX is making DAB almost redundant for me in truth.

Bruce

Posted on: 25 August 2011 by Simon-in-Suffolk

Bruce, ok I agree dab is hardly worth bothering about, but it's worth noting that dab is all vertically polarised in the uk, where as Fm is usually horizontal and vertical. Roof top aerials on fm favour horizontal polarisation (ie the elements lay flat rather than upright) as reduces susceptibility of interference from domestic electrical sources and it is eadier to mount, however portable and car whips are vertically polarised. However if you are using a horizontal antenna to pick up a vertical polarisation you are going to only pickup a tiny proportion of the transmitted signal.
The higher the gain an antenna, ie the more elements it has has the more directional it is, imagine it's like a lens focussing light in a particular direction, the narrower the beam the stronger the light rather than a single lightbulb shining all around. Finally the gain is centred around a spot frequency, with FM thats around 98MHz, and the higher the gain the quicker the gain falls away as you deviate from that frequency. DAB (from memory) is around 160 to 180 MHz, and so you quite outside the optimum gain of an FM aerial. The upside is the more you are outside the antennas resonant point, the less directional it becomes... :-).
Perhaps Internet radio is easier...... ;-) it's easier to mash things up.

Simon