Over the last few days I've been getting the 'bubbling mud' syndrome on R4
from CP. Although not a continuous boiling - more like a mic being tapped
occasionally. I have two different make tuners fed off the same aerial -
via a DA - and it's more or less the same on both. Signal strength showing
is 13 thingies out of 16. If I unplug the aerial from the DA the signal
level drops considerably but the 'mud' remains constant. 
 I have a second system using a different aerial - actually the FM one -
and that's clean.
It's not there at the moment.

Can reception conditions cause this effect? The DAB aerial is a plain
dipole as CP is close by.

-- 
*Shin: a device for finding furniture in the dark *

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

Dave Plowman (News) wrote:
> Over the last few days I've been getting the 'bubbling mud' syndrome on R4
> from CP. Although not a continuous boiling - more like a mic being tapped
> occasionally. I have two different make tuners fed off the same aerial -
> via a DA - and it's more or less the same on both. Signal strength showing
> is 13 thingies out of 16. If I unplug the aerial from the DA the signal
> level drops considerably but the 'mud' remains constant. 
>  I have a second system using a different aerial - actually the FM one -
> and that's clean.
> It's not there at the moment.
> 
> Can reception conditions cause this effect? The DAB aerial is a plain
> dipole as CP is close by.

The problem with DAB is that despite multiple transmitters all carrying 
the same service in an SFN, if one of the transmissions arrives outside 
the guard band of your primary local signal, then the resultant received 
data becomes corrupted.

ISTR that the mimimum separation of transmitters for this happen is only 
about 80km.

It's likely that during this settled weather, 'lift' conditions are 
bringing in the BBC mux at high signal levels from distant transmitters.
However, if that were to happen, you'd have all BBC services on the mux 
affected, not just R4 ?

For the record, I get a thumping great DAB signal from Hannington, but I 
do lose reception completely during some lift periods. I use a roof top 
aerial, counterintuitively, if I stick a paper clip in the aerial 
socket, that normally restores reception !

In article , Mark Carver
<mark.carver@invalid.invalid> scribeth thus
>Dave Plowman (News) wrote:
>> Over the last few days I've been getting the 'bubbling mud' syndrome on R4
>> from CP. Although not a continuous boiling - more like a mic being tapped
>> occasionally. I have two different make tuners fed off the same aerial -
>> via a DA - and it's more or less the same on both. Signal strength showing
>> is 13 thingies out of 16. If I unplug the aerial from the DA the signal
>> level drops considerably but the 'mud' remains constant. 
>>  I have a second system using a different aerial - actually the FM one -
>> and that's clean.
>> It's not there at the moment.
>> 
>> Can reception conditions cause this effect? The DAB aerial is a plain
>> dipole as CP is close by.
>
>The problem with DAB is that despite multiple transmitters all carrying 
>the same service in an SFN, if one of the transmissions arrives outside 
>the guard band of your primary local signal, then the resultant received 
>data becomes corrupted.
>
>ISTR that the mimimum separation of transmitters for this happen is only 
>about 80km.
>
>It's likely that during this settled weather, 'lift' conditions are 
>bringing in the BBC mux at high signal levels from distant transmitters.
>However, if that were to happen, you'd have all BBC services on the mux 
>affected, not just R4 ?
>
>For the record, I get a thumping great DAB signal from Hannington, but I 
>do lose reception completely during some lift periods. I use a roof top 
>aerial, counterintuitively, if I stick a paper clip in the aerial 
>socket, that normally restores reception !

And this old Dabble radio promised all this perfick reception eh?..
-- 
Tony Sayer

In article , Dave Plowman (News)
 scribeth thus
>Over the last few days I've been getting the 'bubbling mud' syndrome on R4
>from CP. Although not a continuous boiling - more like a mic being tapped
>occasionally. I have two different make tuners fed off the same aerial -
>via a DA - and it's more or less the same on both. Signal strength showing
>is 13 thingies out of 16. If I unplug the aerial from the DA the signal
>level drops considerably but the 'mud' remains constant. 

> I have a second system using a different aerial - actually the FM one -
>and that's clean.

I couldn't possibly comment;)..

>It's not there at the moment.
>
>Can reception conditions cause this effect? The DAB aerial is a plain
>dipole as CP is close by.
>

It seems it happens from time to time even under supposed good reception
conditions.

It might be a fault that no ones noticed or reported...

Try a post over on alt.radio.digital


-- 
Tony Sayer

In article <$ZIsIJE$CWJIFw0W@bancom.co.uk>,
   tony sayer  wrote:
> And this old Dabble radio promised all this perfick reception eh?..

Thought you, as an engineer, would know nothing can ever be perfect? And
also know to differentiate between spin and reality?

-- 
*Corduroy pillows are making headlines.  

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

In article ,
   Mark Carver <mark.carver@invalid.invalid> wrote:
> It's likely that during this settled weather, 'lift' conditions are 
> bringing in the BBC mux at high signal levels from distant transmitters.
> However, if that were to happen, you'd have all BBC services on the mux 
> affected, not just R4 ?

Dunno - it's R4 I listen to most. I doubt you'd hear the effect on a pop
channel, though. Must remember to try R3 when it happens again. It's clean
at the moment. 

> For the record, I get a thumping great DAB signal from Hannington, but I 
> do lose reception completely during some lift periods. I use a roof top 
> aerial, counterintuitively, if I stick a paper clip in the aerial 
> socket, that normally restores reception !

The trouble is these tuners are sort of preset feeding several
destinations - and are not that easy to get at.

 I wonder if a directional aerial would help?

-- 
*I went to school to become a wit, only got halfway through.

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

In article , Dave Plowman (News)
 scribeth thus
>In article <$ZIsIJE$CWJIFw0W@bancom.co.uk>,
>   tony sayer  wrote:
>> And this old Dabble radio promised all this perfick reception eh?..
>
>Thought you, as an engineer, would know nothing can ever be perfect? And
>also know to differentiate between spin and reality?
>

Perhaps I should have included one of these  ;)....

-- 
Tony Sayer

In article , Dave Plowman (News)
 scribeth thus
>In article ,
>   Mark Carver <mark.carver@invalid.invalid> wrote:
>> It's likely that during this settled weather, 'lift' conditions are 
>> bringing in the BBC mux at high signal levels from distant transmitters.
>> However, if that were to happen, you'd have all BBC services on the mux 
>> affected, not just R4 ?
>
>Dunno - it's R4 I listen to most. I doubt you'd hear the effect on a pop
>channel, though. Must remember to try R3 when it happens again. It's clean
>at the moment. 
>
>> For the record, I get a thumping great DAB signal from Hannington, but I 
>> do lose reception completely during some lift periods. I use a roof top 
>> aerial, counterintuitively, if I stick a paper clip in the aerial 
>> socket, that normally restores reception !
>
>The trouble is these tuners are sort of preset feeding several
>destinations - and are not that easy to get at.
>
> I wonder if a directional aerial would help?
>

Very much doubt it Dave.. where's the local DAB TX, Xtal palace is it?..

-- 
Tony Sayer

In article ,
   tony sayer  wrote:
> In article , Dave Plowman (News)
>  scribeth thus
> >In article <$ZIsIJE$CWJIFw0W@bancom.co.uk>,
> >   tony sayer  wrote:
> >> And this old Dabble radio promised all this perfick reception eh?..
> >
> >Thought you, as an engineer, would know nothing can ever be perfect? And
> >also know to differentiate between spin and reality?
> >

> Perhaps I should have included one of these  ;)....

That's why I left off mine too...

-- 
*Corduroy pillows are making headlines.  

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

On May 9, 1:41 pm, Mark Carver <mark.car...@invalid.invalid> wrote:

> The problem with DAB is that despite multiple transmitters all carrying
> the same service in an SFN, if one of the transmissions arrives outside
> the guard band of your primary local signal, then the resultant received
> data becomes corrupted.

Does DAB support RDS-style automatic frequency switching between
relays and, if so, could they abandon the SFN idea without people
having to change their receivers?

In article ,
   tony sayer  wrote:
> > I wonder if a directional aerial would help?
> >

> Very much doubt it Dave.. where's the local DAB TX, Xtal palace is it?..

Yes - and my aerial sort of points south east to it. Or rather a
directional one would. In other words I don't know which other transmitter
would be causing the problem - on the front or back of a directional
aerial.

Other point which may help is the problem is worst at approx midday. It's
clean at the moment (1600) while I have my break from gardening. ;-)

-- 
*Corduroy pillows are making headlines.  

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

On Sun, 11 May 2008 06:39:28 -0700 (PDT), jamie_p84@excite.com wrote:

>On May 9, 1:41 pm, Mark Carver <mark.car...@invalid.invalid> wrote:
>
>> The problem with DAB is that despite multiple transmitters all carrying
>> the same service in an SFN, if one of the transmissions arrives outside
>> the guard band of your primary local signal, then the resultant received
>> data becomes corrupted.
>
>Does DAB support RDS-style automatic frequency switching between
>relays and, if so, could they abandon the SFN idea without people
>having to change their receivers?

No it doesn't.  Two tuners would be needed for that to work, and so
far no one has made a DAB radio with two tuners.  DAB does switch to
FM & back though.

Marky P.

Marky P wrote:
> 
> DAB does switch to FM & back though.
> 

Would you mind explaining that a little further?  I thought DAB used OFDM.

Andy

In message , Marky P 
 writes
>On Sun, 11 May 2008 06:39:28 -0700 (PDT), jamie_p84@excite.com wrote:
>
>>On May 9, 1:41 pm, Mark Carver <mark.car...@invalid.invalid> wrote:
>>
>>> The problem with DAB is that despite multiple transmitters all carrying
>>> the same service in an SFN, if one of the transmissions arrives outside
>>> the guard band of your primary local signal, then the resultant received
>>> data becomes corrupted.
>>
>>Does DAB support RDS-style automatic frequency switching between
>>relays and, if so, could they abandon the SFN idea without people
>>having to change their receivers?
>
>No it doesn't.  Two tuners would be needed for that to work, and so
>far no one has made a DAB radio with two tuners.  DAB does switch to
>FM & back though.

Neither of my DAB radios, which are in almost daily use, has an analogue 
tuner ... I'm now intrigued about how it switches. Hopefully you'll 
explain.
-- 
Give a man a fish and you feed him for a day; give him a freshly-charged
Electric Eel and chances are he won't bother you for anything ever again.

"Tony Quinn"  wrote in message 
news:KE9XhzDBr1JIFwiK@tqvideo.co.uk...
> In message , Marky P Neither 
> of my DAB radios, which are in almost daily use, has an analogue tuner ... 
> I'm now intrigued about how it switches. Hopefully you'll explain.

I think he's talking about the facility to switch automatically between FM 
and DAB depending on which has the best reception at any given moment, for 
the desired station. I have two radios that do this. It's a mixed blessing.

Bill

In article , Dave Plowman (News)
 scribeth thus
>In article ,
>   tony sayer  wrote:
>> > I wonder if a directional aerial would help?
>> >
>
>> Very much doubt it Dave.. where's the local DAB TX, Xtal palace is it?..
>
>Yes - and my aerial sort of points south east to it. Or rather a
>directional one would. In other words I don't know which other transmitter
>would be causing the problem - on the front or back of a directional
>aerial.
>
>Other point which may help is the problem is worst at approx midday. It's
>clean at the moment (1600) while I have my break from gardening. ;-)
>

Somehow doubt its CCI possibly due to the amount of reflections round
your way there might be very long delays which are causing it grief but
I may not be right on that one..

A directional aerial may help possibly may add too much signal and
clobber the tuner;!..

Why not convert to Freeview or Freesat for Radio 4 listening now?..
-- 
Tony Sayer

In article <RBhne7AYg$JIFwhK@bancom.co.uk>,
   tony sayer  wrote:
> In article , Dave Plowman (News)
>  scribeth thus
> >In article ,
> >   tony sayer  wrote:
> >> > I wonder if a directional aerial would help?
> >> >
> >
> >> Very much doubt it Dave.. where's the local DAB TX, Xtal palace is
> >> it?..
> >
> >Yes - and my aerial sort of points south east to it. Or rather a
> >directional one would. In other words I don't know which other
> >transmitter would be causing the problem - on the front or back of a
> >directional aerial.
> >
> >Other point which may help is the problem is worst at approx midday.
> >It's clean at the moment (1600) while I have my break from gardening.
> >;-)
> >

> Somehow doubt its CCI possibly due to the amount of reflections round
> your way there might be very long delays which are causing it grief but
> I may not be right on that one..

Any other possible explanations? If it happened on just one tuner I'd
suspect that. 

> A directional aerial may help possibly may add too much signal and
> clobber the tuner;!..

Could always attenuate it, I suppose. 

> Why not convert to Freeview or Freesat for Radio 4 listening now?..

I've thought of that, but it would mean sorting out a UHF feed to that
area. Not impossible but would need some work. More than simply changing
the aerial.

-- 
*If you don't like the news, go out and make some.

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

On May 11, 9:04 pm, Marky P  wrote:
> On Sun, 11 May 2008 06:39:28 -0700 (PDT), jamie_...@excite.com wrote:

> >Does DAB support RDS-style automatic frequency switching between
> >relays and, if so, could they abandon the SFN idea without people
> >having to change their receivers?
>
> No it doesn't.  Two tuners would be needed for that to work, and so
> far no one has made a DAB radio with two tuners.

They are? I thought it could be done using RDS with a single tuner -
each transmitter broadcasts a list of alternate frequencies for
adjacent regions, and I understood that the FM tuner momentarily
switches to one of them to test the signal strength and then back
again if it's worse, hence those annoying momentary dropouts one hears
while driving in fringe areas.
On a digital system using TDM, this could theoretically be done
without any dropouts, depending on the length of the timeslots.

In article , Dave Plowman (News)
 scribeth thus
>In article <RBhne7AYg$JIFwhK@bancom.co.uk>,
>   tony sayer  wrote:
>> In article , Dave Plowman (News)
>>  scribeth thus
>> >In article ,
>> >   tony sayer  wrote:
>> >> > I wonder if a directional aerial would help?
>> >> >
>> >
>> >> Very much doubt it Dave.. where's the local DAB TX, Xtal palace is
>> >> it?..
>> >
>> >Yes - and my aerial sort of points south east to it. Or rather a
>> >directional one would. In other words I don't know which other
>> >transmitter would be causing the problem - on the front or back of a
>> >directional aerial.
>> >
>> >Other point which may help is the problem is worst at approx midday.
>> >It's clean at the moment (1600) while I have my break from gardening.
>> >;-)
>> >
>
>> Somehow doubt its CCI possibly due to the amount of reflections round
>> your way there might be very long delays which are causing it grief but
>> I may not be right on that one..
>
>Any other possible explanations? If it happened on just one tuner I'd
>suspect that. 

If its happening on both then I would suspect that, just for clarity is
this one or Both tuners affected?..
>
>> A directional aerial may help possibly may add too much signal and
>> clobber the tuner;!..
>
>Could always attenuate it, I suppose. 

Yes..
>
>> Why not convert to Freeview or Freesat for Radio 4 listening now?..
>
>I've thought of that, but it would mean sorting out a UHF feed to that
>area. Not impossible but would need some work. More than simply changing
>the aerial.
>
Right..
-- 
Tony Sayer

In article ,
   tony sayer  wrote:
> >> Somehow doubt its CCI possibly due to the amount of reflections round
> >> your way there might be very long delays which are causing it grief
> >> but I may not be right on that one..
> >
> >Any other possible explanations? If it happened on just one tuner I'd
> >suspect that. 

> If its happening on both then I would suspect that, just for clarity is
> this one or Both tuners affected?..

Both - I can set them to the same station and swop between the audio. One
is slightly worse than the other. They seem to decode the nasties rather
differently. 

I could record the effect, I suppose. I can pick them up on this computer.

-- 
*If at first you don't succeed, then skydiving definitely isn't for you *

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

In article , Bill Wright wrote:
> "Tony Quinn"  wrote in message 
> news:KE9XhzDBr1JIFwiK@tqvideo.co.uk...
> > In message , Marky P Neither 
> > of my DAB radios, which are in almost daily use, has an analogue tuner ... 
> > I'm now intrigued about how it switches. Hopefully you'll explain.
> 
> I think he's talking about the facility to switch automatically between FM 
> and DAB depending on which has the best reception at any given moment, for 
> the desired station. I have two radios that do this. It's a mixed blessing.

I have a tuner that can switch between DAB and FM. It switches by means of a 
button on the front panel, yet it always outputs my preferred system. I just 
leave it switched to FM and never press the button.

Rod.

jamie_p84@excite.com wrote:
> On May 11, 9:04 pm, Marky P  wrote:
>> On Sun, 11 May 2008 06:39:28 -0700 (PDT), jamie_...@excite.com wrote:
> 
>>> Does DAB support RDS-style automatic frequency switching between
>>> relays and, if so, could they abandon the SFN idea without people
>>> having to change their receivers?
>> No it doesn't.  Two tuners would be needed for that to work, and so
>> far no one has made a DAB radio with two tuners.
> 
> They are? I thought it could be done using RDS with a single tuner -
> each transmitter broadcasts a list of alternate frequencies for
> adjacent regions, and I understood that the FM tuner momentarily
> switches to one of them to test the signal strength and then back
> again if it's worse, hence those annoying momentary dropouts one hears
> while driving in fringe areas.
> On a digital system using TDM, this could theoretically be done
> without any dropouts, depending on the length of the timeslots.

I suspect it's not technically, or at least economically possible for a 
DAB tuner to be agile enough to take a sniff of another Transport Stream 
on another frequency, and jump back to where it was without quite a long 
mute.

It's bad enough with analogue FM and RDS. As it is, all that is verified 
on an RDS AF 'sniff' is the four digit hex PI code, along with the 
signal strength and multipath (aka AM) content. The PI is transmitted 
several times a second. That's why you often get the half second pause 
in the audio. Most DAB tuners take *seconds* not milliseconds to relock 
to a new mux.

In article , Dave Plowman (News)
 scribeth thus
>In article ,
>   tony sayer  wrote:
>> >> Somehow doubt its CCI possibly due to the amount of reflections round
>> >> your way there might be very long delays which are causing it grief
>> >> but I may not be right on that one..
>> >
>> >Any other possible explanations? If it happened on just one tuner I'd
>> >suspect that. 
>
>> If its happening on both then I would suspect that, just for clarity is
>> this one or Both tuners affected?..
>
>Both - I can set them to the same station and swop between the audio. One
>is slightly worse than the other. They seem to decode the nasties rather
>differently. 
>
>I could record the effect, I suppose. I can pick them up on this computer.
>
Lets hear it then!...
-- 
Tony Sayer

In article ,
   tony sayer  wrote:
> >I could record the effect, I suppose. I can pick them up on this
> >computer.
> >
> Lets hear it then!...

Will do. Of course it's clean at the moment...

-- 
*Time is fun when you're having flies... Kermit  

    Dave Plowman        dave@davenoise.co.uk           London SW
                  To e-mail, change noise into sound.

On Mon, 12 May 2008 02:10:31 -0700 (PDT), jamie_p84@excite.com wrote:

>On May 11, 9:04 pm, Marky P  wrote:
>> On Sun, 11 May 2008 06:39:28 -0700 (PDT), jamie_...@excite.com wrote:
>
>> >Does DAB support RDS-style automatic frequency switching between
>> >relays and, if so, could they abandon the SFN idea without people
>> >having to change their receivers?
>>
>> No it doesn't.  Two tuners would be needed for that to work, and so
>> far no one has made a DAB radio with two tuners.
>
>They are? I thought it could be done using RDS with a single tuner -
>each transmitter broadcasts a list of alternate frequencies for
>adjacent regions, and I understood that the FM tuner momentarily
>switches to one of them to test the signal strength and then back
>again if it's worse, hence those annoying momentary dropouts one hears
>while driving in fringe areas.
>On a digital system using TDM, this could theoretically be done
>without any dropouts, depending on the length of the timeslots.

I always believed that RDS worked using a twin tuner method with one
tuner monitoring the airwaves whilst listening to the other.  I
thought hat's how it changed so seamlessly.  Of course, I may be
wrong.

Marky P.

In article ,
   Marky P  wrote:
> On Mon, 12 May 2008 02:10:31 -0700 (PDT), jamie_p84@excite.com wrote:

> >On May 11, 9:04 pm, Marky P  wrote:
> >> On Sun, 11 May 2008 06:39:28 -0700 (PDT), jamie_...@excite.com wrote:
> >
> >> >Does DAB support RDS-style automatic frequency switching between
> >> >relays and, if so, could they abandon the SFN idea without people
> >> >having to change their receivers?
> >>
> >> No it doesn't.  Two tuners would be needed for that to work, and so
> >> far no one has made a DAB radio with two tuners.
> >
> >They are? I thought it could be done using RDS with a single tuner -
> >each transmitter broadcasts a list of alternate frequencies for
> >adjacent regions, and I understood that the FM tuner momentarily
> >switches to one of them to test the signal strength and then back
> >again if it's worse, hence those annoying momentary dropouts one hears
> >while driving in fringe areas.
> >On a digital system using TDM, this could theoretically be done
> >without any dropouts, depending on the length of the timeslots.

> I always believed that RDS worked using a twin tuner method with one
> tuner monitoring the airwaves whilst listening to the other.  I
> thought hat's how it changed so seamlessly.  Of course, I may be
> wrong.

some makes have twin tuners, others don't.

-- 
From KT24 - in "Leafy Surrey"

Using a RISC OS computer running v5.11

charles wrote:
> In article ,
>    Marky P  wrote:

>> I always believed that RDS worked using a twin tuner method with one
>> tuner monitoring the airwaves whilst listening to the other.  I
>> thought hat's how it changed so seamlessly.  Of course, I may be
>> wrong.
> 
> some makes have twin tuners, others don't.

Indeed.

The RDS spec is designed for only one tuner in mind. The Clarion in my 2001 
406 only has a single tuner, or at least it behaves as if it does !


-- 
Mark
Please replace invalid and invalid with gmx and net to reply.